Materials for nanoelectronics and nanophotonics

Resume : Amorphous azopolymer thin films exhibit the formation of photoinduced surface reliefs as result of a macroscopic mass migration phenomenon, originated at molecular level by the UV-visible light-induced isomerization cycles of the azobenzene molecules embedded in the polymeric chain. Relief formation occurs below the glass transition temperature of the azopolymer and produces surface patterns that are stable over time. Their geometry is strongly dependent on the intensity distribution, polarization and wavefront of the incident light. This property has made them highly interesting in many research fields of photonics and material science. Additionally, as the structuring process is intrinsically reversible, the pristine state of the surface can be restored both thermally or optically, without destroying or altering the polymeric chain. For this reason, this class of materials can be used to replace common photoresists in order to obtain a single step all-optical reversible lithographic structuration. Full control on the tridimensional shape of photoinduced surface structures on azopolymer films can be obtained by tailoring the spatiotemporal distribution of light intensity on the free surface of the polymer. Here, I will overview recent advances in the design and fabrication of azopolymer light-induced reliefs obtained with an illumination scheme based on computer generated holograms. This technique allows the generation of grayscale intensity patterns on the azopolymer surface by phase modulating a laser beam through a computer controllable spatial light modulator. Almost arbitrary geometries in the light distribution can be achieved in this way, enabling accurate and fast control over all the lithographic parameters needed for the realization of reversible diffractive optical elements (DOEs) on the azopolymer. With this versatile optical scheme, flat optical components, modulating incident light wavefront within thickness comparable with the light wavelength, are realized and dynamically tuned by accurately engineering the azopolymer surface according to the desired optical functionality. In addition, the possibility to in-place erase and rewrite the polymer surface with completely different geometry is here used to design dynamical optical systems based on shapeshifting diffractive gratings, lenses and holograms that represent a valid prospective for the realization of next generation optical systems, where flat and dynamic optical devices will needed.

Resume : Chemical (pigmentary) coloration of butterflies is often supplemented by physical color generated by photonic nanostructures. These nanoarchitectures (often complex 3D structures) - characteristic for a given species - are located in the lumen of the wing scales and exhibit wavelength ranges in which light propagation is forbidden. It is crucial to establish well-defined measurement methods for the unambiguous characterization and comparison of colors generated in such a complex manner. Owing to the intricate architecture ordered at multiple levels (from centimeters to tens of nanometers), the precise quantitative determination of butterfly wing coloration is not trivial. We present an overview of several optical spectroscopy measurement methods and illustrate techniques for processing the obtained data, using the species Polyommatus bellargus as a test case, the males of which exhibit a variation in their blue structural color. The benefits and drawbacks of these optical methods are discussed and compared [1]. Furthermore, the origin of the color differences is explained in relation to differences in the wing scale nanomorphology revealed by electron microscopy. As the photonic crystal structure determines the wing color, by induced alteration of size or refractive index of the building materials, it is possible to tune the resulting color. In order to obtain information on multiple types of structures, single crystalline, polycrystalline, thin film, and pepper-pot-type photonic nanoarchitectures of different butterflies were investigated, and also a bioinspired multilayer of silica spheres as a purely physical model. By atomic layer deposition (ALD) (additive) the color of all nanoarchitectures was red shifted and by plasma etching (subtractive) was blue shifted in a controllable way. It was demonstrated on butterfly wing scales with open 3D nanostructures that two structural modification methods offer fine and controllable tuning of the reflected light spectrum, using completely different principles and instrumentation [2]. In terms of surface chemistry, one builds up the substrate with a conformal, chemically inert/or chemically active coating, and the other removes the original superhydrophobic superficial layer. Both methods keep the benefit of these structures possessing large surface area. They open new routes to potential applications [3]. This research was funded by the Priority Project of the Centre for Energy Research and by the TKP2021-NKTA-05. [1] Kertész, K. et.al., Multi-instrumental techniques for evaluating butterfly structural colors: A case study on Polyommatus bellargus (Rottemburg, 1775) (Lepidoptera: Lycaenidae: Polyommatinae) Arthropod Struct. Dev. 61 (2021) [2] Kertész, K. et.al., Additive and subtractive modification of butterfly wing structural colors Colloids Interface Sci. Commun. 40 (2021) [3] Piszter, G. et.al., Spectral tuning of biotemplated ZnO photonic nanoarchitectures for photocatalytic applications, submitted

Resume : Rare-earth phosphors are the materials in which solid-state lighting technology is based. Nevertheless, their large crystal size hinders the control over the emitted light. The synthesis of nanoparticles made of such materials and the processing of them into transparent thin films open new routes to manipulate the way the light is generated. In this talk, we show that the integration of nanophosphor-based transparent films into photonic structures lead to a precise control over the chromaticity and directionality of these nanosources avoiding chemical modification in the synthesis route and thus maintaining the stability of the nanoparticles. To do so, we start with the optimization of efficient and bright transparent films processed through wet methods. [1,2] Then, we carry out different approaches to modify their optical properties. In particular, nanophosphors films are embedded in systems based on one dimensional photonic crystals. Intense red emission at targeted directions and particular colors are attained when nanophosphor light emission is coupled to resonant modes supported by the photonic structures. [3,4] Furthermore, we explore the outcoupling of the emitted light when the surface of nanophosphor films is periodically patterned via soft-lithography. As a result, the direct nanoimprint of the films leads to an enhanced emission at selected directions employing inexpensive procedures.[5] References: [1] Geng, D., Lozano, G., Calvo, M. E., Núñez, N. O., Becerro, A. I., Ocaña, M., & Míguez, H. (2017). Photonic tuning of the emission color of nanophosphor films processed at high temperature. Advanced Optical Materials, 5(13), 1700099. [2] Geng, D., Lozano, G., & Míguez, H. (2018). Highly efficient transparent nanophosphor films for tunable white-light-emitting layered coatings. ACS applied materials & interfaces, 11(4), 4219-4225. [3] Geng, D., Lozano, G., Calvo, M. E., Núñez, N. O., Becerro, A. I., Ocaña, M., & Míguez, H. (2017). Photonic tuning of the emission color of nanophosphor films processed at high temperature. Advanced Optical Materials, 5(13), 1700099. [4] Geng, D., Cabello-Olmo, E., Lozano, G., & Míguez, H. (2019). Tamm plasmons directionally enhance rare-earth nanophosphor emission. ACS photonics, 6(3), 634-641. [5] Cabello‐Olmo, E., Molet, P., Mihi, A., Lozano, G., & Míguez, H. (2021). Enhanced Directional Light Extraction from Patterned Rare‐Earth Phosphor Films. Advanced Optical Materials, 9(2), 2001611.

Resume : High-quality monocrystalline materials and nanostructures are key to high-efficiency optoelectronic devices (Polman et al., Science, 2016), plasmonic materials (Wu et al., Adv Mater, 2014) and metasurfaces (Koenderink et al., Science 2015). A large variety of materials can be synthesized at low temperature in solution as colloidal single crystals, combining the advantages of high-quality material, low-cost fabrication, and potential for large area integration into nanophotonic and plasmonic devices. Unfortunately, they have so far been limited to Platonic solid shapes. This is in stark contrast to nanostructures obtained by top-down methods, that offer almost unlimited capability for plasmon resonance engineering, but present poor material quality and have doubtful perspectives for scalability, limiting nanostructured monocrystalline materials to niche applications. It has been demonstrated that single-crystal silver nanocubes, grown in solution phase, could be used as building blocks for the fabrication of continuous monocrystalline 1D nanostructures through epitaxial welding of adjacent nanocubes (Sciacca et al, Adv Mater., 2017). We show that this approach can be used as a general method to fabricate 1D and 2D monocrystalline gold (Au) plasmonic arrays of arbitrary shapes for the first time, combining the best of different worlds (highest material quality, arbitrary geometry, bottom-up, low cost). Monodisperse Au single-crystal nanocubes are first synthesized in solution at room temperature. Next, using capillary forces they are self-assembled in a polydimethylsiloxane (PDMS) mould containing pre-defined 1D and 2D nanoscale patterns, in a closely packed configuration, with individual nanocube subunits lying face-to-face. Then, using a novel approach of simultaneous oxidative dissolution and growth, assemblies of nanocubes are epitaxially connected and transformed into continuous monocrystalline nanostructures in the time scale of a few minutes at low temperature. The chemical framework for nanocube epitaxy is thoroughly investigated with a set of control experiments and operando optical characterization on a nanocube dimer model system is used to unveil the mechanism with atomic scale resolution. This enables us to control morphology and faceting of the monocrystalline nanostructures. We use high-resolution transmission electron microscopy and electron diffraction to provide evidence for epitaxy, and compare optical spectra of individual nanoantennas and arrays to FDTD simulations to show that materials of the highest quality are obtained. Finally, we show that such complex continuous Au nanostructures of arbitrary shapes can be transferred from PDMS to various substrate by contact printing. This paves the way for swift integration of nanophotonic surfaces of the highest quality in optical and optoelectronic devices and architectures that are incompatible with classic nanopatterning strategies such as perovskite layers.

Resume : Nowadays needs necessitate thinking beyond conventional rigid and planar lighting and paving the way for bendable lighting, such as light-emitting devices on substrates that can be bent, flexed or even stretched like polyethylene terephthalate (PET), other plastic-like materials and even textiles. In the past decade, there has been dramatic progress in the field of solution-processed organic light-emitting diodes (OLEDs). Along these lines of research in both academia and industry, there is still a great demand to develop blue-light emitting polymers on the path toward white emission and full-color polymer displays. While a stable blue Polymer LED (PLED) is still a challenge for polymer scientists, it is hard to achieve a balanced charge injection because of the large bandgap between the HOMO and LUMO energy levels. In this study, we compared promising lab-scale blue-emitting polymer bearing Carbazole moiety with commercially available Polyfluorene derivatives in terms of film-forming ability, emission characteristics and color purity. The spin coating technique was implemented to produce functional layers, including the hole transport layer and emitting layer. The optical and photophysical properties of the solution-processable thin films were thoroughly studied via NIR-Vis-far UV Spectroscopic Ellipsometry (SE) and Photoluminescence (PL) respectively, whereas the structural characteristics were examined by Atomic Force Microscopy (AFM). Subsequently, blue light OLED devices were fabricated, and they were evaluated using Electroluminescence (EL). From the analysis of the electrical data, valuable information was obtained for the different current-density characteristics under different bias voltage regimes. Emission bandwidths, color coordinates and luminance were also derived in order to evaluate the devices’ stability. Finally, the printability of the polymer films to flexible substrates was investigated using slot-die coating processes. Acknowledgments This research has been co‐financed by the European Regional Development Fund of the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH – CREATE – INNOVATE (project code: T1EDK-01039).

Resume : It is vital to enhance solar cell efficiency in order for photovoltaic power generation to be a realistic alternative to the global energy challenge. Photovoltaics (PVs) will be crucial in transitioning to a fully renewable energy economy. Increasing power conversion efficiency (PCE) is critical because it reduces the amount of energy-intensive materials used, such as crystalline silicon (c-Si), and thus decreases energy payback. Enhancing the amount of sunlight that reaches the photo-conversion layer is one approach that could be taken. In recent years, femtosecond lasers have demonstrated promising applications in bio, energy, and aerospace. As previously stated, multiphoton phenomena and nonthermal processes are at the heart of femtosecond laser surface modification. With a minimum of flaws, this type of laser can form extremely uniform periodic structures on the nano- and microscale. On surfaces of various materials, such as titanium, stainless steel, silicon, aluminum alloys, and others, beautiful self-assembled structures are produced. To increase solar cell efficiency, for example, femtosecond lasers are used to alter the surfaces of solar panels [1,2]. Femtosecond lasers are used in Mazur's group to create periodic structures on black silicon with nano- and micro-size features [3,4]. Sub-micron scale three-dimensional microstructures could be formed by influencing the laser beam straightforward trying to focus radiation or interference, and also the scanning rates and routines. To pattern Silicon Nitride (SiNx), various techniques have been developed, such as photolithography with wet etching in acidic solutions [5]. However, this method necessitates a number of process steps, as well as costly equipment and toxic chemicals. To fabricate fine structures with well-defined edges on SiNx thin films, a non-lithographic or direct patterning strategy must be developed. Laser ablation is the expulsion of materials from a substrate by direct absorption of laser energy, which can yield the required combination of narrow and clean patterning due to their advantage in regionalized heating and material expulsion. Research teams studied the interaction of femtosecond laser pulses with various materials such as silicon, Al, and ITO in the presence of air, water, and sulfur hexafluoride (SF6) [4] but no one is not studied direct laser writing on SiNx till now as per my knowledge. The micro/nanostructures over silicon nitride films were created using a femtosecond amplifier laser system (800 nm, 120 fs, 1 kHz). For the micro/nano fabrication procedure, an amplifier that generates a linearly polarized Gaussian beam with pulse energy of 4.0 mJ/pulse and pulse width of 120 fs at a maximum repetition rate of 1 kHz and a central wavelength of 800 nm was used. An x-y galvo was used to focus and scan the laser beam in a line pattern on the film surfaces. The Galvo scanner was designed to travel at a speed of 0.1 mm/s to ensure faster fabrication as well as the stability of silicon nitride over Si substrate during laser pulse interaction with film. During optimization at higher speeds, irregular patterns were observed. The focused spot had a diameter of about 10 m, defined by an intensity drop to 1/e2 of the maximum value. For single pulse energy, pulse repetition rate, laser scanning speed, and line spacing, the laser processing parameters used to fabricate the hyper-hierarchical structure are 75 mW, 1kHz, 0.1 mm s-1, and 100 m, respectively. The current work reveals the fabrication of micro/nanostructures on SiNx over silicon substrates using femtosecond laser writing in an air medium. These micro/nanostructures have a diameter of about 300-400 nm and resemble structures. It has discovered that micro/nanostructures structures form as a result of the interaction of femtosecond pulse-induced plasma with a SiNx/Si substrate. The absorption of intense light in a thin SiNx/silicon layer produces a plasma at the SiNx-air interface. The plasma then equilibrates with the surrounding air and SiNx, resulting in a layer of molten silicon on the surface. Furthermore, these fabricated structures have been characterized using scanning electron microscopy (SEM), Raman spectroscopy, cross-section FESEM, and a UV-VIS spectrophotometer for optoelectronics applications such as Photovoltaic and Surface Enhanced Raman Spectroscopy (SERS). In the wavelength ranges of 400–800 nm, and 200-1000 nm, respectively, average specular reflectance of 2.82 percent, and 5% are attained, with an average absorptance of 95 percent within 0.2–1 m. The material easiness, patterning versatility, boosting capability, structural reliability, and self-cleaning quality can meet the necessary criteria for useful light-harvesting applications. References: [1] McDonald J P, Mistry V R, Ray K E, Yalisove S M, Nees J A and Moody N R 2006 Femtosecond-laser-induced delamination and blister formation in thermal oxide films on silicon (100) Applied Physics Letters 88 153121 [2] Feng T, Chen G, Han H and Qiao J 2021 Femtosecond-Laser-Ablation Dynamics in Silicon Revealed by Transient Reflectivity Change Micromachines 13 14 [3] Dalili A, Tan B and Venkatakrishnan K 2010 Silicon wafer surface patterning using femtosecond laser irradiation below ablation threshold Optics and Lasers in Engineering 48 346–53 [4] Vorobyev A Y and Guo C 2013 Direct femtosecond laser surface nano/microstructuring and its applications Laser & Photonics Reviews 7 385–407 [5] Hoheisel M, Mitwalsky A and Mrotzek C 1991 Microstructure and etching properties of sputtered indium—tin oxide (ITO) Physica Status Solidi (a) 123 461–72 [6] Stratakis E, Zorba V, Barberoglou M, Fotakis C and Shafeev G A 2009 Femtosecond laser writing of nanostructures on bulk Al via its ablation in air and liquids Applied Surface Science 255 5346–50

Resume : Artificial Intelligence (AI) is a concept that has seen many hype cycles arrive and fade as we have become overly impressed by our computing machines and then dismayed by our realization of the complexity of what brains actually do. In recent years, we might believe that the age of AI has finally arrived as algorithms beat human champions at complex games and the champions retire in frustration. However, a look into the backroom reveals that the machines that run these algorithms require kilowatts of power to operate, and the amount of preparation and training of the algorithms is long and extremely costly. When it comes to functions like intelligence, cognition, and decision making, any of today’s best computing systems is outperformed by the brain by orders of magnitude both in terms of energy and space efficiency. The primary reason for our shortcoming is that we are using conventional passive circuit elements to emulate a highly non-linear dynamic operating system of a brain that operates on the verge of chaos. In this talk, I shall introduce a new generation of molecular circuit elements [1-3] that can capture complex, reconfigurable, dynamic logic in nano-scale material properties and can also be poised on the verge of instability. These devices could offer an optimal platform for emulating brain’s functions. [1] Nature, 2021, 597(7874), 51-56 [2] Nature nanotechnology, 2020, 15(5), 380-389 [3] Nature materials, 2017, 16(12), 1216-1224

Resume : Resistive switching (RS) in metal oxides which offer self-compliance, and multiple resistance states without the requirement of any high voltage forming step hold the potential of application in selector less high density resistive random access memory devices. Typically, operation of metal oxide based RS devices require integration of additional oxide layers or circuit elements to achieve current compliance and complicated device architecture for high density memory applications. It is well known that oxygen vacancies (VOs) often play deterministic role in the RS mechanism of metal oxides. An in-depth investigation of the RS properties in VOs engineered WO3-x thin films suggest that optimization of VOs concentration in WO3 holds promise of realising stable bipolar resistive switching. We demonstrate self-compliance, and multi-level RS that does not require high voltage forming in a single layer non-stoichiometric WO3-x. This study suggests VOs in the pristine WO3-x layer leads to its forming-free filamentary switching characteristics, whereas reversible formation and annihilation of an oxygen-rich region in the filament at WO3-x/electrode junction has been envisaged to be responsible for self-compliance set and voltage controlled multiple reset resistance states. Our results demonstrate non-stoichiometric WO3-x with an active metal/oxide interface permeable to reversible oxygen migration can pave the way of producing high density, reliable RRAM devices.

Resume : Two dimensional transition metal carbides/nitrides, MXenes have attracted immense attention in energy storage and optoelectronic device applications, due to their excellent conductivity. The potential use of the compound in nanoelectronic applications like resistive switching is least explored. The utilisation potential of the material is limited by the hazardous HF etching and mixed acid etching routes of synthesis. The alternative milder etching routes fail to convert the MAX phase fully into MXene, hence suppressing the inherent properties of MXene. Attempts to synthesize MXene via temperature assisted routes like hydrothermal synthesis increases the risks of oxidation. The present work synthesizes MXene via milder in situ HF etching technique, with a simple modification using a base in the dilution process, to improve the properties of the material. Liquid phase exfoliated titanium carbide (Ti3C2Tx) MXene synthesized through novel base assisted in situ HF etching technique, exhibiting enhanced structural, electronic and optical properties was used for resistive switching applications. The delaminated stable colloids obtined by sonication of multi-layered MXene were ultrasonic spray coated onto ITO and glass substrates. The structural properties were confirmed by the appearance of characteristic (002) plane diffraction peak of MXene with significant intensity in the XRD patterns of the multilayer powder and MXene thin film. XRD analysis also confirmed successful removal Al, by the disappearance of (104) plane diffraction peak. The morphology was analysed using SEM analysis, to obtain the typical open accordion MXene, even with a milder etching route. The functional groups were identified with XPS analysis and the optical properties were studied using UV Visible absorbance spectrum. The absorbance spectrum of the delaminated MXene colloids exhibited characteristic plasmonic peak in the NIR region and that of the thin film had a transparency of about 50% in the visible rnge. The colloidal stability was studied over a course of 40 days and was further confirmed using DLS to rule out any possibility of aggregation detrimental to colloid stability. ITO/Ti3C2Tx/Cu devices were fabricated and the device exhibited bipolar resistive switching characteristics. The stability of the ON and OFF states of the device were also studied. A simple and scalable synthesis technique has been utilised to fabricate high quality titanium carbide MXene thin film, suitable for memristor applications.

Resume : Due to enormous increase in industrial activities, toxic metallic pollutants such as As, Pb, Cd and Hg have gained worldwide concern due to their deleterious environmental and biological effects. These heavy metals are non-biodegradable and can easily attach with the food chain of the environment which later puts severe threat to human health. Due to fatal consequences of these pollutants in public health, many organizations have determined the maximum permissible amount of the ions in food, drinking water, blood, etc. Based on the Environmental Protection Agency (EPA), the safety limits of mercury, lead, cadmium and arsenic in drinking water are 2, 15, 5 and 10 parts per billion (ppb) respectively. The repletion of Hg2+ in human body can cause ailments in vital organs, disorders in the nucleic acid function, defects in the immune system, and even death. It is a very challenging task to detect As3+ ions in the presence of other contaminants in water. Hence development of accurate and sensitive analytical techniques for effective monitoring and accurate measurement of these toxic ions are getting considerable attention worldwide. Conventional analytical techniques such as AAS/AES, ICP-MS, ASV are time consuming, requires expensive equipment and incur complex measuring procedures. Alternatively, several sensors have been developed for the detection of As3+ ion, such as colorimetric, fluorescent, electrochemical, and surface-enhanced Raman scattering. Despite these advancements, novel sensors with simple operation, low cost, portable analytical platform for user friendly analysis are still needed. In this work, curcumin functionalized zinc oxide nanorods (Cur-ZnO) were used as an electrical sensing platform for highly selective and sensitive As3+ detection. Zinc oxide nanorods were synthesized using solvothermal approach and attachment of curcumin to ZnO nanrods were obtained through an in-situ approach. Field emission scanning electron microscopy (FESEM), High resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) absorbance analysis were done to confirm the attachment of curcumin sheets to ZnO nanorods. The sensing platform was fabricated in a novel staggered gate-field effect transistor (SG-FET) configuration with Cur-ZnO as the sensing layer. A high-k dielectric (hafnium oxide) was used as gate dielectric and aluminium was used as gate metal. The sensor performance towards As3+ was investigated electrically in presence of other competitive contaminants. The sensor was found to be highly selective towards As3+ in presence of Pb2+, Hg2+,Cd2+, Na+ and Cu2+. The interaction of As3+ ions with the sensing layer was also studied using UV-Vis and PL spectrophotometer. The sensitivity of the sensor was seen to improve by tuning the gate voltage. Our work suggests that Cur-ZnO based staggered gate-field effect transistor (SG-FET) are promising towards development of low-cost, portable and real-time room temperature heavy metal ion detectors.

Resume : Printed electronics has emerged as a pathway for large scale, flexible, and wearable devices promising to unlock a transformational change in the electronics as we know it, and enabling applications in high demand such as wearable electronics[1], Internet-of-Things[2] and smart textiles[3]. Graphene and related two-dimensional (2D) materials offer an ideal platform of novel materials for high performance printed electronics [4,5]. Electronic inks from 2D materials with different electronic properties have been developed to print the different elements of a device: semiconducting or semimetallic inks in the active layer, insulating inks for dielectrics, and conducting inks for electrodes. However, the complexity of the ink formulations, the three-dimensional assembly of the 2D flakes and the polycrystalline nature of the resulting thin films, have made it difficult to examine charge transport in such devices so far [6], therefore impeding an accurate and controllable design of electronic devices. In this work, we identify and describe the charge transport mechanisms of surfactant- and solvent-free inkjet-printed thin-film devices of representative few-layer graphene (semi-metal), molybdenum disulphide (MoS2, semiconductor) and titanium carbide MXene (Ti3C2, metal) by investigating the temperature, gate and magnetic field dependencies of their electrical conductivity.[7] We find that charge transport in printed few-layer MXene and MoS2 devices is dominated by the intrinsic transport mechanism of the constituent flakes: MXene exhibits a weakly- localized 2D metallic behaviour at any temperature, whereas MoS2 behaves as an insulator with a crossover from 3D-Mott variable-range hopping to nearest-neighbour hopping around 200 K. Charge transport in printed few-layer graphene devices is dominated by the transport mechanism between different flakes, which exhibit 3D-Mott variable range hopping conduction at any temperature.[7] Our results establish the fundamental mechanisms responsible for charge transport in inkjet-printed devices made of 2D material, enabling the controlled design and engineering of future printed electronics based on 2D materials, and paving the way to new types of flexible electronic devices. [1] Torrisi, F. & Carey, T. ?Graphene, related twodimensional crystals and hybrid systems for printed and wearable electronics? Nano Today 23, 73 (2018). [2] C. Scholten et al. ?Advanced Technologies for Industry ? Product Watch: Flexible and printed electronics?, doi: 10.2826/29513 (2021). [3] Carey, T. et al. ?Fully inkjet-printed two-dimensional material field-effect heterojunctions for wearable and textile Electronics? Nat. Commun. 8, 1202 (2017). [4] Torrisi, F. et al. "Inkjet-printed graphene electronics" ACS Nano 6, 2992{3006 (2012). [5] F. Torrisi & T. Carey ?Printing 2D Materials? in ?Flexible Carbon-based Electronics? Editors P. Samori and V. Palermo, Ed.: Wiley-VCH, Weinheim, Germany, 2018. ISBN: 978-3-527-34191-7. [6] D. Akinwande ?Two-dimensional materials: printing functional atomic layers? Nat. Nanotechnol. 12, 287 (2017). [7] E. Piatti, A. Arbab et al. ?Charge transport mechanisms in inkjet-printed thin-film transistors based on two-dimensional materials? Nature Electronics 4, 893 ? 905 (2021).

Resume : The Terahertz (THz) region is the portion of the electromagnetic (EM) spectrum between 0.1 and 10 THz. Across the past decades, motivated by the strikingly vast range of possible applications of THz radiation, many new terahertz techniques have been investigated and demonstrated [1]. In particular, the development of new THz direct detectors [2] is of paramount importance for the development of future communication systems [3]. Graphene-based Fied-Effect Transistors (GFETs) are attractive for the development of highly sensitive THz detectors. Graphene encapsulated between two sheets of h-BN allows the fabrication of GFETs with excellent values of carrier mobility in the transistor channel enabling the use of GFETs as THz detectors [4]. In the present work we present a study both experimental and theoretical of the impact of the use of an antenna on the THz response of a GFET. A GFET based on a vertical dual heterojunction h-BN/graphene/h-BN was fabricated as described in [4]. Graphene and h-BN sheets were obtained by mechanical exfoliation. The graphene sheet was encapsulated between two layers of h-BN and deposited on a SiO2/Si substrate by using the hotpickup technique [4]. The top gate of the transistor was a metallic asymmetric double-grating dual gate (ADGG) that was connected to a broadband bowtie antenna (with a radius of 500 µm and 90º) monolithically implemented on the transistor epilayer structure. The Silicon doped substrate was used as the back gate. The GFET was characterized as a THz detector at low temperature (4K) under radiation at 150, 300 GHz and 600 GHz. The photoresponse signal obtained at 300 GHz showed the higher intensity with a maximum value of 6 mV for a negative value of the backgate voltage close to -7V. This is attributted to a better coupling of the incoming THz at this frequency that is related to both ADGG layout of the gate electrode and the action of the antenna in agreement with EM simulations. A better coupling of the incident radiation with the channel at this frequency could be the reason for the measured signal. Additionally, it was also experimentally observed that when varying the back gate voltage while the top gates are grounded a modulation of the photoresponse arises that was attributed to the formation of regions of carriers of opposite sign along the channel. This creates the conditions in which the plasmonic ratched effect, that is responsible of the rectification of the terahertz radiation, can take place [5, 6]. This opens the way for the development of a new novel devices based on 2d materials for terahertz technology. References: 1. S. Das, et al. Edits. Advances in Terahertz Technology and its Applications, Springer, (2021). 2. R. A. Lewis J. Phys. D: Appl. Phys. 52, 433001 (2019) 3. J.Xie et al. Nanomaterials; 11(7) 1646 (2021) 4. J. A. Delgado Notario et al., APL Photonics 5, 66102 (2020). 5. D. V. Fateev, et al. Appl. Phys. Lett., 110, 061106 (2017). 6. J. A. Delgado et al., Nanophotonics https://doi.org/10.1515/nanoph-2021-0573 (2022).

Resume : As the future brings continued down-scaling of semiconductor device technology, computational screening for alternative materials with improved electronic properties, and investigating the impact of defects, dopants and material thicknesses with atomistic simulations, have become a crucial step in developing next-generation advanced logic, memory, power electronics, and quantum computing. In this talk, we will demonstrate an efficient method for high-accuracy atomistic ab initio simulations for semiconductor device technology development, such as high-k metal gate stack (HKMG) engineering and investigation of 2D material-based FET performance [1]. The method combines the HSE06 hybrid density functional [2,3] with linear combination of atomic orbitals (LCAO) basis sets, as implemented in the QuantumATK atomic-scale modeling platform [4,5] developed by Synopsys. The HSE06-LCAO methodology can be used as part of the recently developed Design-Technology Co-Optimization (DTCO) multiscale atomistic-TCAD [6] workflow by Synopsys for simulating 2D material-based FET performance. This DTCO workflow enables a comprehensive investigation of the impact of various 2D materials and a number of layers, source/drain materials and orientations, doping concentrations, device architecture and dimensions, and other parameters on the full device electrical characteristics. We will show that the HSE06-LCAO method overcomes limitations of local and semilocal (GGA) density functionals and predict accurate band energies, defect trap levels, band offsets, band diagrams and effective work functions for semiconductor materials, interfaces and stacks comprised of several thousands of atoms. Importantly, such large-scale simulations are performed using relatively modest hardware, for example, a band diagram simulation across the 2992 atom HKMG Si|SiO2|HfO2|TiN stack taking only 45 hours on 40 cores. This can be achieved by using LCAO basis sets as they enable orders of magnitude faster simulations than standard HSE06 Plane-Waves (PW) implementations. HSE06-PW has thus so far been practical only for systems with a relatively small number of atoms, limiting the applicability to a small subset of technologically relevant problems. Finally, we will present how HSE06-LCAO is combined with the nonequilibrium Green’s-function method (NEGF) method for studying electron transport, i.e., IV characteristics, of the 2D material (black phosphorous) based FET. References 1) P. Khomyakov, J. Wellendorff, M. Palsgaard, T. Gunst, H. Miyagi, B. Verstichel, F. Corsetti, V. Arcisauskaite, U. Martinez, A. Blom, and S. Smidstrup, ‘Ab initio LCAO hybrid density-functional method for accurate, large-scale electronic structure simulations of semiconductor materials, interfaces and gate stacks’ SISPAD 2021. 2) J. Heyd, G. E. Scuseria, and M. Ernzerhof, ‘Hybrid functionals based on a screened Coulomb potential’ J. Chem. Phys. 124, 219906 (2006). 3) S. V. Levchenko, X. Ren, J. Wieferink, R. Johanni, P. Rinke, V. Blum, M. Scheffler, ‘Hybrid functionals for large periodic systems in all-electron, numeric atom-centered basis framework’ Comp. Phys. Comm. 192, 60 (2015). 4) S. Smidstrup et al. ‘QuantumATK: An integrated platform of electronic and atomic-scale modelling tools’ J. Phys.: Conden. Matter 32, 015901 (2019). 5) https://www.synopsys.com/silicon/quantumatk.html 6) https://www.synopsys.com/silicon/tcad.html

Resume : Atomically thin two-dimensional (2D) materials have been —and are still currently being— extensively studied due to their desirable mechanical, electronic, and optical properties. These, together with the materials' intrinsic ultra-thin size, have the potential to enable the development of compact devices and innovative, beyond-CMOS, technologies. Here we look at single-layer molybdenum disulphide (MoS2) as the core material in 2D memristors for neuromorphic computing applications [1-3]. 2D memristors based on MoS2 present several advantages with respect to conventional devices based on transition metal oxides: good flexibility, high transparency, and the potential to work when applying low voltages (0.1 - 0.2 V), thus allowing the fabrication of compact and energy-efficient devices. However, there is still much debate regarding the physics of their resistive switch, which is thought to depend on both surface defects and the type of metal-semiconductor junction [4]. Moreover, the metal contact is particularly important when designing such devices, as it can significantly influence the properties of MoS2 at the interface. Indeed, both surface defects, which are intrinsically present in the material following common growing techniques such as CVD, and the nature of the metal contact affect not just the performance but also the working mechanism of 2D memristors. To shed light onto the physics of metal-MoS2 interfaces, we carry out atomistic computer simulations in the framework of density functional theory (DFT). We employ surface calculations based on the Green’s function, in order to construct realistic interfaces and to compute surface properties. To model the metal electrode, we choose Au as it is commonly one of the most popular choices, and it has been successfully used to develop 2D memristors [4]. In this work, we want to bridge the gap between materials’ properties and device physics and to do so, we investigate the impact of both experimentally-observed point defects (i.e., vacancies and substitutions) and extended defects, such as grain boundaries, on the physics and chemistry of Au-MoS2 interfaces. To the best of our knowledge, this is the first attempt to thoroughly model interfaces in the presence of grain boundaries. Ultimately, our study constitutes the first step of a more comprehensive multi-scale modelling approach, in which the aim is to construct a full atomistic-to-device level model that can aid us in elucidating the working mechanism of 2D memristors based on single-layer MoS2. [1] EU H2020 NeurONN Project, www.neuronn.eu. [2] A. Todri-Sanial et al., IEEE Trans. Neural Netw. Learn. Syst., 1-14, 2021. [3] A. Todri-Sanial, MRS Fall Meeting and Exhibit, 2021. [4] R. Ge et al., Nano Lett., 18, 434-441, 2017.

Resume : Self-powered broadband ultrathin photodetector provides excellent commercial value for a wide range of optoelectronic applications, including neuromorphic functions, safety and security, and many more. We used thermal CVD grown in situ MoS2 embedded in solution-processed copper phthalocyanine (CuPc) thin film to show such a photodetector produced cost-effectively and robustly. Surprisingly, a behaviour comparable to the photogating effect has been identified, which occurs when carriers are trapped at defect sites and the dielectric interface of layered materials. Because carriers are trapped in 2H-MoS2 flakes due to type–II staggered band alignment with CuPc, we called this the spontaneous photogating effect. Estimating the EQE between the spectral regions of 0.3 to 1.1 micron with a maximum of 300% is used to detect the broadband spectral response. We achieved a response speed of 50 ms rise and 60 ms fall time with responsivity and detectivity of roughly 0.7 A/W and 10^11 Jones, respectively. On the other hand, this study suggests that spontaneous photogating has no effect on device reaction time. As a result, the technique described here will expand the use of various TMDs combined with diverse organic materials to create more robust ultrathin self-powered broadband photodetectors with higher figures of merit.

Resume : FEMOCS [1-2] is a unique software that allows multiscale computer simulations, combining atomistic and electromagnetic field analyses together with heat transport calculations for the development of nanoelectronics, nanomaterials and nanoelectromechanical systems (NEMS). The software has been developed to solve materials technology problems of CERN particle accelerator designs, but also has applications in ITER, space applications and high-tech R&D. The functionality of FEMOCS centers on nanostructure changes of materials in severe conditions by providing of a computational framework that combines Finite Element Analysis (FEA), atomistic simulations such asMolecular Dynamics (MD) and kinetic Monte Carlo (KMC), and Particle In Cell models, to investigate the effect of high electric fields on surfaceinteractions. The challenges to be solved include surface electric field calculation accuracy and sensitivity to atom localization, but also electric field influence to the atomic interactions and investigation of the respective corrections in the computational models. Currently, the FEMOCS code can be executed together with PARCAS or LAMMPS molecular dynamics packages. It is also possible to run simulations in conjunction with the KIMOCS KMC code for extended time scales, opening opportunities for investigating the effects of interface composition and material structure (surface roughness, geometry) to the material’s ability to resist the damage over longer time scales (defect localization, surface diffusion). The main features incorporated into FEMOCS code are the atomistic dynamics calculations of bulk and surfaces using molecular dynamics simulations (currently metals ), finite element calculations of near surface electric fields (using open source DEAL.II library). The field emission currents by incorporating state of the art general thermal field models with combined thermionic and field emission, Nottingham heating effects and surface curvature corrections using the GETELEC code [3]. The atomistic dynamics of surfaces are complemented by the space charge formation and screening effects, surface evaporation and initial stages of plasma formation with a capacity for concurrent PIC simulations. Furthermore, future developments are proceeding towards extending the functionality of the code to the semiconductor materials by not only incorporating material in molecular dynamics sub-model but also by incorporating the respective corrections to the electric field calculations and tunneling behavior of electrons into the electron emission models. 1. Veske, Mihkel, et al. "Dynamic coupling of a finite element solver to large-scale atomistic simulations." Journal of Computational Physics 367 (2018): 279-294. 2. FEMOCS source code - https://github.com/veskem/femocs 3. Kyritsakis, Andreas, and Flyura Djurabekova. "A general computational method for electron emission and thermal effects in field emitting nanotips." Computational Materials Science 128 (2017): 15-21.

Resume : Dysnatremia, a disorder in the concentration of sodium levels, possesses a clinical challenge leading to adverse health complications. Using biosensors for online sodium monitoring can be a promising approach to overcome this condition. In this regard, biosensors based on field-effect transistors (FETs) have promising advantages, including high sensitivity, quick response, and easy fabrication. Most of the currently developed FET designs are used only for sensing sweat and in-vitro blood/interstitial fluids (ISF). Using ISF for online detection of biomarkers and long-term health monitoring with FETs has not yet been fully resolved. Herein we proposed an innovative stretchable skin-conformal fast-response microneedle extended-gate FET (MN-EGFET) biosensor for real-time detection of sodium in the ISF for minimally invasive health monitoring along with high sensitivity, low limit of detection, excellent biocompatibility, and on-body mechanical stability. The device relies on a new architecture of FETs whose sensing part and reference electrode rely on extended gate (EG) made of microneedles (MNs) that penetrate the skin to reach the ISF or measuring the sodium therein. The electrical response of the reported sensors over sodium concentration, repeatability and selectivity have been conducted to characterize their performance. The mechanical stability of the platform has also been evaluated by on-body experiments and the response recorded over MNs inserting and peeling-off cycles. In-vitro and in-vivo biocompatibility experiments of the MNs were validated to prove their function in transnational clinical and on-body applications. This platform can, furthermore, be integrated with wireless-data transmitter and the Internet-of-Things (IoT) cloud for real-time monitoring and long-term analysis, showing great potential for home healthcare and clinical diagnosis. This wearable MN-EGFET platform may provide a new fundamental detection technique through further on-body evaluation.

Resume : A main goal of electronics in hybrid materials is to relate device performance to the structure and electronic state of the building components. In particular, nanostructured hybrid materials made by self-assembly of nanoparticles and functional molecules have been proven to be very sensitive to the nature of the molecular components. Among the variety of possibilities that organic, organometallic and coordination chemistries offer to tune the energy levels of these molecular components, spin crossover phenomenon is a perfect candidate for the elaboration of molecular switches. The reorganization of the electronic state population of the molecules associated to the spin crossover can indeed lead to a significant change in conductivity of the hybrid materials. Here, we show that the association of ultra-small 1.2 nm platinum nanoparticles with FeII triazole-based spin crossover coordination polymers leads to self-assemblies, extremely well organized at the sub-5 nm scale. The quasi-perfect alignment of nanoparticles observed by transmission electron microscopy, in addition to specific signature in infrared spectroscopy, demonstrates the coordination of the long-chain molecules with the nanoparticles. Spin crossover is confirmed in such assemblies by X-ray absorption spectroscopic measurements and shows unambiguous characteristics in both magnetic and charge transport measurements. The conductive properties of the materials was governed by Coulomb blockade in the ultra-small nanoparticles, and was shown to depend on the polarizability switch of the molecular components. Spin crossover coordination polymers are therefore ideal candidates for the elaboration of switchable hybrid materials self-assembled with metal nanoparticles, where molecular effects govern the electric responses.

Resume : Nanoscale thermal transport is a key factor limiting the clock speed of computer processors and defining the performance of thermoelectric (TE) materials. While in the former the increase of heat dissipation is essential, in the latter, low thermal conductivity provides a major boost to the TE figure of merit (FoM). The versatility of van der Waals (vdW) materials and their heterostructures provide an extremely useful toolbox for addressing the control of thermal transport in diverse applications. The challenge nevertheless lies in the difficulty of measuring and quantifying the thermal transport within atomically thin and highly anisotropic vdW materials and between these materials and substrates. Here we report a powerful approach of cross-sectional scanning thermal microscopy (xSThM) for studying anisotropic heat transport in nanoscale layered vdW materials. We use beam exit cross-sectional polishing (BEXP) of vdW nanoflakes shaping these into ultra-thin low angle wedges with atomic-scale surface flatness, followed by the xSThM in high vacuum (HV) conditions. By mapping continuously varying sample thickness of the wedge, we eliminate artefacts of through-the-air heat transport and suppress a generally unknown SThM tip-surface interfacial thermal resistance. By comparing experimental results with the finite element analysis (FEA) simulation and analytical models, we can directly evaluate the anisotropy between the in-plane and cross-plane thermal conductance of the vdW materials, the local thermal resistance at the vdW material–substrate interface and the SThM tip-material thermal resistance. We apply this approach to quantify the thermal conductivity of gamma indium selenide (γ-InSe), which has high potential in TE applications due to its advantageous electrical and thermal properties. xSThM allowed us to independently confirm the heat transport anisotropy and anomalous low thermal conductivity values of k‖ = 2.164 W/mK and k⊥ = 0.8897 W/mK for γ-InSe on Si, also extracting the interfacial thermal resistance between γ-InSe and Si (rint = 9.6x10-11 Km2W-1). Our results support the potential of γ-InSe as a high TE efficiency material, where the low thermal conductivity values can be combined with a high power factor, ultimately enhancing the FoM.

Resume : We investigate here how the current flows over a single crystal of SmB6[1] in the presence of an external electric field perpendicularly applied. For this purpose: (i) we calculated the band structure in order to construct the minimal tight-binding type model for the Sm 4f bands of SmB6 based on localized Wannier functions, and (ii) we applied the recursive Green's function method[2] to the computation of electronic transport properties of SmB6 in the linear response regime. Our results show that current flows over the surface, the region of the system with higher charge density, as the bulk conductivity freezes out. This system's charge density polarization opens an energy gap, which the electric field can manipulate. [1] Bulk and surface properties of SmB6, Priscila F. S. Rosa, Zachary Fisk, arXiv:2007.09137, 2020. [2] The recursive Green’s function method for graphene, Caio H. Lewenkopf and Eduardo R. Mucciolo , J Comput Electron 12, 203–231 (2013)

Resume : The dimensional reduction brought by the advent of two-dimensional (2D) materials opened new routes for nanoelectronics and photonics applications [1]. In this framework, the Xenes (artificial graphene-like monoelemental lattices) represented a new forefront because of their peculiar geometric and electronic structure [2]. For years silicene has been considered a good candidate for new applications due to its predicted electronic and optical properties, and intrinsic allotropic affinity for currently used silicon-based technology. Unfortunately, the instability in air and strong hybridization effects with the native substrates limited its use to date. Interface states built up by silicon and the supporting substrate have great impact on the physical properties of the epitaxial silicene and, in the case of silicene on silver, no evidence was found of Si adlayers maintaining freestanding silicene characters [3,4]. In this framework, the Xene-based heterostructure concept takes on a certain relevance for the abovementioned issues. It has recently been shown that silicene-on-silver and stanene on-silver can operate as templates for the epitaxy of the reciprocal Xene single-layer, giving rise to different types of heterostructure [5]. Here, we report on the optical properties of these new Xenes-based configurations made accessible by spectroscopic measurements in the MIR-UV spectral range (from 0.12 to 5.8 eV), in reflection geometry. Our analysis highlights the role of the interlayer in modifying the coupling of the on top Xene and the native substrate, resulting in a different reflectivity spectrum when silicene and stanene are combined. More in detail, we demonstrate that the buffer layer has a dramatic impact on the bandstructure hybridization between the Xene and the substrate, thus resulting in a modification of the optical response of the whole system. Finally, the decoupling effect is studied in terms of the photo-thermal Raman response, revealing stark differences in the heat transport properties of single layer epitaxial Xenes and heterostructures. To conclude, we point out that deepen the knowledge about the building blocks of heterostructures and explore different combinations of them is indeed essential for extending the range of their functionality and applications. References: [1] Grazianetti, C., Martella, The Rise of the Xenes: From the Synthesis to the Integration Processes for Electronics and Photonics. Materials 14, 4170 (2021) [2] Molle, A. et al. Buckled two-dimensional Xene sheets. NATURE MATER VOL PAG(2017) [3] Cinquanta, E. et al. Optical response and ultrafast carrier dynamics of the silicene-silver interface. Phys. Rev. B 92, 165427 (2015) [4] Hogan, C. et al. Optical properties of silicene, Si/Ag(111), and Si/Ag(110). Phys. Rev. B 97, 195407 (2018) [5] Dhungana, D. S. et al. Two-Dimensional Silicene–Stanene Heterostructures by Epitaxy. Adv. Funct. Mater. 31, (2021)

Resume : InP(001) substrates are actively used for growing heterostructures of high-power photodiodes for microwave photonics systems [1]. Pre-epitaxial thermal cleaning of InP substrates in an arsenic flux makes it possible to obtain a sharp layer/substrate heterointerface and avoid uncontrolled incorporation of phosphorus into InAlAs/InGaAs layers lattice-matched with InP(001) substrate. When arsenic interacts with the oxidized InP surface, a solid solution InP1-?Asx is formed, the composition of which depends on the annealing temperature and the arsenic flux [2]. However, the mechanisms of the oxide removal and surface transformation are not fully understood. It is obvious that understanding these processes is important for technologies for the heterostructures growth on InP. In this work, the mechanisms of oxide removal from the surface of an epi-ready InP(001) substrate in arsenic flux are studied in situ by the method of reflection high-energy electron diffraction (RHEED). The studies were carried out in a Compact-21T molecular beam epitaxy system from Riber. We observed a slow increase in the (00) reflex intensity at T>250 °C without an arsenic flux, which indicates thermal removal of the oxide. At the moment of switching on the arsenic flux FAs=6×10-6 Torr at T=300 °C, there are no changes in the dependence of the (00) reflex intensity, i.e. the contribution of interaction with As to oxide thinning is insignificant. At T~350 °C, the nature of the oxide removal process changes sharply, which is associated with the activation of the chemical reaction of the interaction of arsenic with oxide. With a large flux FAs=2×10-5 Torr, a sharp thinning of the oxide layer occurs. This is due to the increased contribution of the chemical reactions of As and oxide, which is proportional to the concentration of As. However, as a result of these reactions, the oxide is not completely removed, and upon further heating, a slow thermal thinning of the oxide occurs. At a temperature of T~410 °C, the maximum intensity of the (00) reflex is reached, which indicates the complete removal of the oxide layer, which no longer scatters the electron beam. The subsequent decrease (00) reflex intensity is associated with an increase in the surface roughness due to desorption of phosphorus and segregation of indium, but with a higher flux of arsenic it occurs more slowly, since the flux increase decreases the desorption of V-group elements from the surface. Thus, the oxide layer is likely to consist of two types of oxides, one of which actively interacts with As, and the other decomposes predominantly thermally. References [1] K. S. Zhuravlev, et al., J. Semicond. 43 (2022) 012302. [2] D.V. Dmitriev, et al. Surface Science 710 (2021) 121861.

Resume : Carbon nanostructures such as carbon nanotubes or graphene are some of the most fascinating materials of the XXI century. Ever since it was discovered that their optical, electrical, mechanical, and thermal properties outperform the characteristics of many traditional materials, the research community has focused on finding ways to deploy them in real life. A myriad of possible applications has been envisioned, but a full realization of these aspirations is still a long way off after three decades of progress in this area. This presentation will present the main challenges that need to be tackled to change this state of affairs, solving of which would greatly increase the technology readiness level of prototypes based on nanocarbon. The main issues are the lack of an appropriate degree of structure control, which governs the properties, as well as the absence of straightforward and scalable methods to make macroscopic networks from individual carbon nanotubes or graphene flakes. The contribution will show how these difficulties can be handled using carbon nanotubes as a model nanocarbon material. The talk will display our advances on the fronts of purification of single-walled carbon nanotubes and their assembly into free-standing networks. Furthermore, the presentation will cover our recent progress in tuning the material's properties by simple chemical or physical treatments. Finally, the broad application opportunities for such nanostructures will be highlighted.

Resume : ?Internet of Things? (IoT) has attracted intensive interest for the field of wireless, portable and monitoring electronics fields. In thise regard, a wearable nanogenerator hold great potential because it can harvest the energy from body movement and surrounding environment to provide sustainable power supply for these electronic devices. Zinc oxide (ZnO) nanostructures have been extensively investigated for harvesting mechanical power owing to its piezoelectric properties combined with low cost, non-toxicity and easy synthesis. [1-3] Carbon fibre has attracted lots of attention due to its unique properties of lightweight, thermally agood conductivity and chemically stability, which is widely applied in the automotive, aerospace and other industrial fields. Herein, a PEDOT:PSS/CuSCN/ZnO energy harvester is successfully fabricated on conductive carbon fibres utilising, combining the advantages of ZnO piezoelectricity and flexibility and electrical conductivity of carbon fibres. PEDOT:PSS/CuSCN structure was fabricated on ZnO nanorods to reduce the rate of screening to achieve higher performance output. The device generates increasing output voltage from 1.4 V to 7.6 V as the impacting acceleration increases from at 0.1 m/s2 to 0.4 m/s2. The device also shows high stability and durability under 26000 cycles test byof impacting testing. In addition, the device is able to harvest energy from biomechanical forces such as impacting, flicking and gentle finger tapping and bending. The output voltage from the device can activate an LCD screen display by finger tapping. In addition, based on carbon fibre itsis used to form the composite, carbon fibre-reinforced plastic (CFRP), A CFRP-based self-powered sensor was also fabricated, of which exhibits the voltage/current output is proportional to the impacting force, therefore it can act as a self-powered impacting sensor with good stability during the 26000 cycles test. The results provides an efficient method to develop energy harvester on carbon fibres, which hold great potential for the future designing of flexible self-powered devices and wearable electronics.

Resume : Reliable molecular electronic and spintronic devices require precise control of the atomic coordinates of both, the molecules and the atoms of the electrodes. The lack of specific chemistry for the efficient bridging of the molecules between the electrodes from one side, and the extremely difficult fabrication of electrodes at the molecular scale from the other, are the principal challenges in the field [1]. In this work, we present the fabrication and characterization of graphene nanogap electrodes embedded in a three-terminal device. We obtain the graphene nanodevices by applying standard and advanced lithography combined to feed-back controlled electro-burning [2,3]. In a second step, the aim is the creation of robust π-π anchoring of ad-hoc synthesized curcuminoid molecules. The viability of the fabricated devices for nanoelectronic applications is corroborated by using different characterization techniques. This work was supported by the project PID2019-108794GB-I00 (AEI/FEDER, UE) and the European Research Council Consolidator Grant Tmol4TRANS (ERC 724981). AGC and RP acknowledge the Ramon y Cajal fellowships program RyC 2017-229210 and RyC 2019-028474I. [1] Amar H. Flood, J. Fraser Stoddart, David W. Steuerman, James R. Heath, Science, 5704 (2004) 2055-2056. [2] Enrique Burzurì, Joshua O. Island, Raúl Díaz-Torres, Alexandra Fursina, Arántzantzu González-Campo, Olivier Roubeau, Simon J. Teat, Núria Aliaga-Alcalde, Eliseo Ruiz and Herre S.J. van der Zant, ACS Nano, 10 (2016) 2521-2527. [3] Cornelia Nef, László Pósa, Peter Makk, Wnagyang Fu, András Halbritter, Christian Schönenberger and Michel Calame, Nanoscale, 6 (2014) 7249-7255.

Resume : Antimicrobial resistance is a major global health issue. Optimised and personalised dosing of antibiotics is one of the routes to target the issue.1,2 Personalized dosing is achievable via real time drug monitoring.3 Current state of the art biosensors can provide continuous monitoring of a prototypical antibiotic, penicillin, in the dermal interstitial fluid.3 However, this biosensor requires expensive materials such as iridium oxide as its pH sensitive layer.3 This work presents an alternative low-cost graphene-based sensing platform for real time measurement of penicillin. The graphene sensing platform is based on selective enzymatic conversion of the antibiotic and the measurement of the resulting pH change. A range of immobilisation methods is investigated to better encapsulate the enzyme. The optimal composition of the hydrogel membranes surrounding the graphene sensor is investigated that enhance the selectivity as well as reducing interference from other molecules. The biosensing device achieved a resolution of 0.05 pH units within the relevant range (pH 7 – 8) and analyte detection sensitivity which is comparable to the current state of the art.3 The results from this graphene-based sensing platform will enable production of low-cost, scalable and versatile, high-performance real time antibiotic sensors. 1 D. G. J. Larsson and C. F. Flach, Nature Reviews Microbiology, 2021. 2 T. M. Rawson, S. A. N. Gowers, D. M. E. Freeman, R. C. Wilson, S. Sharma, M. Gilchrist, A. MacGowan, A. Lovering, M. Bayliss, M. Kyriakides, P. Georgiou, A. E. G. Cass, D. O’Hare and A. H. Holmes, The Lancet Digital Health, 2019, 1, e335–e343. 3 S. A. N. Gowers, D. M. E. Freeman, T. M. Rawson, M. L. Rogers, R. C. Wilson, A. H. Holmes, A. E. Cass and D. O’Hare, ACS Sensors, 2019, 4, 1072–1080.

Resume : Graphene nanoribbon with width scaling down to nanometers can have bandgap opened and its electrical properties is dominated by the localized electronic states of edge atoms. However, the electron mobility of graphene nanoribbons decreases rapidly with the reduction of the edge width due to the change in the energy band and limited by the increased acoustic and optical phonon scattering. In this study, we explore the graphene nanoribbons with periodic edge structures that can balance the bandgap opening and the disrupt the phonon interaction that limits the electron drifting in the graphene nanoribbons. In this way, graphene nanoribbon with bandgap opened while still maintaining high mobility can be the appealing candidate for the next generation semiconductors. In this study, we focus on the Coved graphene nanoribbons (CGNRs) with edges containing periodic zigzag and armchair nanoribbons. Based on the density function theory(DFT), the electrons and phonons all-energy band of the CGNRs is calculated and considered in mobility calculation. The edge structure leads a big influence of the electron-phonon coupling that effectively limit the influence of phonons on electron mobility. Compared with the same wide zigzag graphene nanoribbons (ZGNRs), the electron mobility of the CGNRs is about 8.6E4 cm2/Vs, which can be an order of magnitude higher. To extend the structure of CGNRs to be compatible the scale of current fabrication facility, we designed the edges of CGNRs have an isosceles triangle with an apex angle of 120 degrees to generate a 120-degree coved shape with edge alignment. We find that the mechanism of bandgap opening of the CGNRs will be the same as the Armchair GNRs: the band gap will be zero in a 3N 2 relationship with the number of atoms. However, as the isosceles triangle of the coved shape gradually increases, the band gap of CGNRs will gradually converge and can expel the zero band gap cases, which is essential for the large-scale circuits level engineering. In this way, moderate fault tolerance of edge condition during the fabrication of the GNRs can be allowed. In our design, CGNRs will have a band gap more than 0.1±0.05eV in a maximum width more than 20nm and a minimum width less than 8nm and a band gap of more than 0.2±0.1eV in a minimum width less than 4nm. The further device simulation is based on quantum transport by means of the Nonequilibrium Green’s Functions (NEGF) and considered about phonon dispersion. The CGNRs structure has a band gap and has better mobility about 1.0E4 cm2/Vs compared to ZGNRs of the same average width. This method can be applied to other semiconductor materials to get IV characteristic and provides important direction for experiments. To integrate our fabrication with the current semiconductor industry, our experimental process utilizes the chemical vapor deposition (CVD) equipment to manufacture a single layer and single crystal graphene film on a germanium substrate. With E-beam lithography (EBL) to pattern the graphene in coved shape, the CGNRs can be defined into sub 10nm dimensions. The edge defect of patterned nanoribbons during the processing can be later repaired through "equilibrium growth conditions", that is tuned with deposition rate of graphene grains close to zero to self-repair the damaged edge during fabrication process. This method reduce defect and enhance edge quality of the CGNRs, that makes mobility increasing while maintaining band gap opened. That the GNRs can become a material that can be used in the semiconductor industry.

Resume : Quantification of hydrogen peroxide (H2O2) in the food industry is a vital step in censoring food safety. The colorimetric detection method has prevailed over other techniques in terms of simplicity to monitor by the naked eye. To date, natural enzymes were used to catalytically convert the substrate into a visually detectable product. Regardless of their high selectivity and specificity, they undergo denaturation resulting in unstable detection. Therefore, nanomaterials with enzyme-like activities are better alternatives for replacing natural enzymes. In this study, Fe species/ZnO@g-carbon composite was prepared with intrinsic peroxidase-like activity via carbothermal reduction using ZnFe-double-layer hydroxide and glucose-derived carbon as precursors. The physicochemical properties of Fe species/ZnO@g-carbon were studied by XRD, XPS, BET, FE-SEM, and TGA analysis. It exhibits excellent peroxidase activity towards the oxidation of 3, 3?, 5, 5?-tetramethylbenzidine (TMB) in the presence of H2O2. The enhanced peroxidase activity is attributed to multiple oxidation states of Fe, quick electron transport ability of porous graphitic carbon. Our results demonstrate that Fe species/ZnO@carbon is a promising candidate for enzyme mimic sensing of H2O2 in food samples.

Resume : In recent years, a range of 0D-2D hybrids with single metal oxides and 2D materials have been exploited for gas sensing due to their synergetic advantages; low-dimensional nature of the 2D materials with interesting electronic properties and highly catalytic reactivity at the oxide interfaces. However, their performance sensitivity, measurement repeatability and certainty (i.e., selectivity) in a mixed gas environment at low power remains inadequate for practical applications. Herein, we address these challenges with a multi-pronged approach consisting of hydrothermal-assisted hybridization of rGO with CuCoOx binary metal oxide to form our sensing material, formulation of a functional rGO/CuCoOx inkjet printable ink for commercially scalable device fabrication, and the novel incorporation of computational techniques and machine-learning algorithms for measurement certainty. Our fabricated chemiresistive devices are fully printed on porous polyethylene terephthalate (PET), the interdigitated electrodes (IDEs) are printed from a commercial silver ink and our sensing material is printed on top of the desired area. The device performance is investigated in both single and mixed gas environments, achieving outstanding sensitivity with 50 ppb of limit-of-detection of NO2 at room temperature. Moreover, we show superior measurement repeatability, stability and excellent signal-to-noise (SNR) of 212.2 at low ppb concentrations. In efforts to achieve greater certainty in our gas measurements we apply principal component analysis (PCA) in tandem with machine learning techniques. Our 10-extracted parameters from transient gas response curves from a single sensor are adequate for utilizing a machine-intelligent classifier, resulting in excellent accuracy for identifying specific gases and predicting their concentration in a mixed atmosphere. A clear decision boundary for 5-different gas species with 98.1% accuracy. Furthermore, our approach of projecting a regression surface onto the classifier plane allows the sensor to predict unseen NO2 and humidity concentrations reliably. We firmly believe that our work represents a breakthrough in the field of 0D-2D material systems for low-temperature machine-intelligent gas recognition platforms in a mixed environment irrespective of ambient humidity.

Resume : Recently, single-walled carbon nanotube (SWNT)/organic semiconductors (OSCs) hybrids have received great attention as thermoelectric (TE) materials due to their characteristics such as flexibility, low toxicity, abundance, light-weight, and robustness. Numerous SWNT/OSCs TE hybrids have been explored to ameliorate electrical properties over the past decade, however, the clear explanation on how the energy level of OSCs affects the TE performance of their hybrids is still elusive. In this presentation, we present a correlation between the electronic levels of OSCs and the TE performance of their hybrids with carbon nanotube by simultaneously modulating the HOMO levels and bandgap of organic small molecules (OSMs). We achieved considerably high ZT for carbon nanotube-based hybrid thermoelectrics via synergistically improved Seebeck coefficient without using conventional dopants. To mechanistically comprehend TE properties of carbon nanotube-based composites at a molecular level, we utilized organic small molecule (OSM) as a hybridizing component as the energy level of OSMs can be easily modulated. The HOMO levels and bandgap of three stilbene-based OSMs (CzS, CzCNS, CzdCNS) were controlled by differentiating the number of cyano (CN) groups on the trans-stilbene backbone. The CzS retaining a larger bandgap (3.03 eV) and having the smallest energy discrepancy to the valence band of SWNT (0.04 eV) among three OSMs enabled its hybrid with SWNT (SWNT/CzS) to have largely enhanced Seebeck coefficient of 108.8 μV K-1 and ZT of 0.058 at room temperature, which are 1.5 and 2.9 times higher than those of SWNT/CzdCNS with a large energy barrier (0.70 eV) and a relatively smaller bandgap of CzdCNS (2.31 eV). Without any additional chemical dopants, we achieved the best ZT value at room temperature among the SWNT and small molecule-based TE materials to date. Measurements of the Seebeck coefficients in OSMs film states provide a rationale that the enhanced TE performance of SWNT/CzS could be attributed to the synergism between the widened bandgap of CzS and the promoted energy filtering in SWNT/CzS. Temperature-dependent resistivity of SWNT/CzS with small barrier energy and relatively homogeneous morphology predominantly follows the variable range hopping conduction model, validating much more efficient carrier transport between SWNT and CzS than between SWNT and CzdCNS. Our transport model is the first systematic elucidation for the conduction mechanism between SWNT and OSMs. We strongly believe that our fundamental, but simple method with energy level control will be applied to other diverse hybrid TE systems as well as carbon nanotube-based hybrid.

Resume : We proposed a highly luminescent and electrically conducting polymer composite material based on polylactide acid (PLA) polymer filled with supramolecular europium complex supported by2D nanoplatelets(graphene oxide or MoS2) as a structure-forming site. Conductivity of the composite film is increased several orders of magnitude as compared to the pure polymer. The simple and reliable proposed procedure is prone to be easily scaled up and open the route for the commercialization of this nanomaterial.The proposed material is suitable for 3D printing technology and wide applications in optoelectronics.

Resume : Water pollution is among one of the major problems, whole world is facing today and building nanomaterials based systems for water purification and recycling could offer potential solutions in this direction. Zinc oxide tetrapod like nanomaterials (1) from metal oxide semiconductor family, are being tested as photocatalysts for the decomposition of various organic dyes. They are excellent candidates for photocatalysis due to their novel properties, affordable production, etc. however, in pure form, the zinc oxide tetrapods exhibit relatively lower photocatalytic activity. Their photocatalytic response can be further enhanced by hybridizing them with certain external nanostructures (2) and, especially using carbon dots due to their attractive properties, like easy synthesis, high biocompatibility, and high photostability, etc. In this work, the surface of zinc oxide tetrapods from flame process (1) was modified with carbon dots to fabricate the hybrid composites and their photocatalytic performance is investigated in detail. Two types of composites are synthesized, i.e., carbon dot-decorated tetrapods and core/shell composites obtained by magnetic stirring and the solvothermal methods. The composites were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), and UV-visible absorption and photoluminescence spectroscopy. The photocatalysis activitiy of hybrid composite was measured against three different types of dyes (Methyl Blue, Methyl Orange, and Methyl Red) and under two irradiation wavelengths (405 nm and 450 nm). The composites demonstrated high photocatalytic efficiency with the possibility of reuseing them upto three cycles. The detailed photocatalytic investigations from the fabricated composites will be presented and discussed here. References: 1. https://www.sciencedirect.com/science/article/pii/S1369702117304443 2. https://www.sciencedirect.com/science/article/abs/pii/S1385894718319727

Resume : Transparent conducting materials are an essential component of optoelectronic devices. It is proven difficult, however, to develop high-performance materials that combine the often incompatible properties of transparency and conductivity, especially for p-type doped materials. In this presentation, I will show our recent work where we have employed a large set of molecular semiconductors extracted from the Cambridge Structural Database to evaluate the likelihood of transparent conducting materials technology based on p-type doped molecular crystals. Candidates are identified imposing the condition of high HOMO energy level (for the material to be easily dopable), high charge carrier mobility (for the material to display large conductivity when doped) and a high threshold for energy absorption (for the material to absorb radiation only in the ultraviolet). The latest condition is found to be the most stringent criterion in a virtual screening protocol on a database composed of structures with sufficiently wide two-dimensional electronic bands. Calculation of excited-state energy is shown to be essential as the HOMO-LUMO gap cannot be reliably used to predict the transparency of this materials class. Molecular semiconductors with desirable mobility are transparent because they display either forbidden electronic transition(s) to the lower excited states or small exchange energy between the frontier orbitals. Both features are difficult to design but can be found in a good number of compounds through virtual screening.

Resume : There are known the losses due to the spectral distribution of solar radiation, where a significant part of the photons has an energy greater than that required for photogeneration of charge carriers and the residual energy is converted into kinetic energy, that is, into heat. Our main idea is in the combination of photo- and thermo-electrical properties in a single hybrid system to the most efficient conversion of solar energy as well as using the supercapacitor function to increase the energy density of the system and energy storage. We propose concept of the photo-thermoelectric cells - a double (photo- and thermo-) highly efficient convertor of sunlight energy based on transitional metal oxide (Fe2O3 and Cr2O3) nanoscale amorphous films with a thickness of (10 ..100) nm on Si substrates, combined into a hybrid material with organic photo- and thermal - active conjugated polymers (poly-3-hexylthiophene (P3HT), poly (3,4) -ethylene dioxythiophene, polystyrene sulfonate (PEDOT: PSS), namely P3HT/Fe2O3 and PEDOT: PSS/Fe2O3, respectively). The combination of silicon with a layered system of organometallic compounds will make it possible to obtain a new multifunctional structure for solar energy converters. Additional function of the proposed converter is collecting and storing energy by supercapacitors. The concept of energy storage is based on the combination of iron oxide with carbon nanomaterials.

Resume : Composite nanostructures can be efficiently applied for Sunlight detection and conversion and, more in general, for energy harvesting and generation of solar fuels. In most of the applied systems, like photodetectors, excitonic solar cells and (photo)-electrochemical cells to produce solar fuels, nanomaterials can play a critical role in boosting photoconversion efficiency by ameliorating the processes of charge photogeneration, exciton dissociation and charge transport. Critical role in such processes is played by the structure and quality of the interface, which needs to be properly assembled to obtain the desired functionality. Several strategies can be pursued to maximize energy harvesting and storage, including broadening of light absorbance to reduce solar light losses, fastening exciton dissociation and charge injection from the photoactive medium to the charge transporting materials, reducing charge recombination during charge transport and collection at the electrodes. In this lecture, a few examples of application of nanocomposites will be discussed, including all-oxide coaxial p-n junction nanowire photodetectors and solar cells, core-shell quantum dot fluorophores for high-efficiency luminescent solar concentrators, composite sulfides for hydrogen generation, and oriented carbon nanotube forest dispersed in polymer matrix as efficient low-temperature thermoelectric composite. Emphasis will be given to the role of interface engineering in improving the efficiency of energy conversion in different systems, spanning from electric power generation from Sunlight, to chemical fuel production, to conversion of heat lost through thermoelectric materials. Keywords: p-n junction nanowires, quantum dots, interfacial properties, luminescent solar concentrators, solar cells, low temperature thermoelectric composites.

Resume : The spotlight of current research is on the synthesis of nanoparticles with various shapes, sizes, and optical properties as well as on their assembly into three-dimensional structures commonly known as aerogels. Nowadays, the assembly of NPs into meso- or macrostructures is of high interest and the structures can be used in different fields, e.g. photocatalysis, catalysis and sensing.[1] Moreover, inkjet printing is a common technique to deposit nanoparticles on different substrates and enables a lateral structuring. Here, the patterning of 3D nanoparticle-based CdSe/CdS aerogel-like networks on conducting surfaces via inkjet printing of an aqueous nano-ink is presented.[2,3] The main focus is on the implementation of the conventional nanoparticle-based gelation process in a commercial office printing system. By simultaneously printing the aqueous nano-ink and a destabilization agent, an aerogel-like network¬ coated electrode surface can be achieved, which enables the manufacturing of 3D nanoparticle-based network-coated (photo)electrodes for applications in (photo)electrochemistry. Additionally, the charge-carrier mobility within the printed three-dimensional semiconductor nanoparticle based networks was investigated by spectroelectrochemical measurements.[3,4] [1] P. Rusch, D. Zámbó, N. C. Bigall, Acc. Chem. Res., 2020, 53, 10, 2414–2424. [2] F. Lübkemann, R. Anselmann, T. Kodanek, N. C. Bigall, Chemie Ing. Tech. 2017, 89, 807–813. [3] F. Lübkemann, J. F. Miethe, F. Steinbach, P. Rusch, A. Schlosser, D. Zámbó, T. Heinemeyer, D. Natke, D. Zok, D. Dorfs, et al., Small 2019, 15, 1902186. [4] J. F. Miethe, F. Lübkemann, A. Schlosser, D. Dorfs, N. C. Bigall, Langmuir 2020, 36, 4757–4765.

Resume : Harvesting mechanical energy from surroundings has a high potential to act as a power source for micro/nano-devices. The triboelectrification and electrostatic induction are followed by the triboelectric nanogenerator (TENG) to produce an electrical output. The novel materials are needed to investigate the usage in the fabrication of TENG and also extend the conventional triboelectric series. It further improves the performance of a TENG. Herein, a zeolite imidazole framework (ZIF-67) was synthesized using a room temperature solvent-assisted method. The structural and chemical properties are evaluated by the material characterization tools. Further, a simple vertical contact mode S-shaped TENG device (S-TENG) was fabricated by an additive manufacturing approach. The ZIF-67 acted as a positive triboelectric layer while the Kapton/Teflon/PDMS acted as a negative triboelectric layer. The multi-unit S-TENG device was further utilized as self-powered recognition of the various gaits using a digital signal processing approach. The S-TENG (ZIF-67 and Teflon) generates a voltage of 118 V, a current of 1.7 µA, and a power density of 15 µW/cm2 at load resistance of 50 MΩ. The gait analysis and the digital signal processing route could help to shed light upon the various gait patterns for the prevention of falls or injuries among the small kids in playschool. Further, the S-TENG device was utilized to charge a commercial capacitor for powering a wristwatch. The S-TENG was integrated into a robotics gripper and various objects such as foam ball, golf ball, and silicone ball were recognized by the holding and release of the ball by the robotic gripper paves the way to various self-powered object identification.

Resume : On-chip DNA optical mapping is a fast, high throughput and inexpensive alternative for DNA analysis. Currently, optical mapping techniques operate in the 1 kbp resolution range, which could be further improved, for example with more precise control of the transport dynamics at the micro-nano interface. Furthermore, getting the DNA molecules to flow into the nanochannels requires using electrophoresis or pressure. To avoid this, we studied different nanostructured channel inlet and outlet topographies to understand their influence on DNA flow dynamics. By focusing a laser spot on the nanochannel, a length specific DNA fluorescence signal can be detected. Influences of different topographies then result in varied mean signal durations, as DNA molecules get accelerated or decelerated. This leads, on one hand, to spontaneous flow of molecules in the nanochannels. On the other, to an increased throughput of molecules into the nanochannels. Furthermore, slowing down the molecules allows for higher resolution in optical mapping applications. Furthermore, pillar structures were incorporated at channel-openings to facilitate additional decelerating factors on DNA molecules. With the help of these strategies, we were able to significantly slow down the DNA molecules flowing through the nanochannels. In this study we studied the influence of different topographies on the flow and stretching of DNA molecules in nanochannels, for resolution enhancing capabilities through improved control of DNA flow dynamics.The molecules are labeled and read out by a laser, as they flow through a nanochannel. Using 3D funnel inlets, and squared staggered outlets we were able to slow down the molecules by a factor of 3x. By adding nanopillars in the inlets we can slow down the DNA molecules even further.

Resume : With the consumption of fossil fuel and the increasing awareness of environmental protection, more and more efforts are being put into the development of renewable and clean energy. Mechanical energy is the one of the most abundant and accessible energy sources, and has been widely harvested by large-scale technologies such as wind power or tidal stream generators. Piezoelectric nanogenerators (PNGs) provide a potential way to convert small mechanical energy such as body motion or vibration into electricity, which can be used to power small portable electronics, medical bio implants, remote wireless sensors etc.1 P-n junction based ZnO PNGs have attracted interest due to their good flexibility, simple manufacture process and low raw material cost. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS), has been employed in the p-n junction based ZnO nanogenerators owing to its good film-forming properties, high transparency, tunable conductivity, and excellent thermal stability. P-type PEDOT:PSS can form a p-n junction with n-type ZnO nanorods, which slows down the screening of the piezoelectric polarisation to generate the output voltage.2 Therefore, optimizing the conductive property of PEDOT:PSS is a potential way to improve the performance of PNG by controlling screening of piezoelectric polarisation and reducing internal resistance of the device. In this work, ethylene glycol (EG) is doped in to the p-type PEDOT:PSS layer in ZnO PNGs to modify the conductivity of PEDOT:PSS. It is found that modest EG doping can effectively enhance the conductivity of the PEDOT:PSS layer and reduce the internal resistance of PNG device. However, devices without EG doping or using excessed EG doping can result in reduced conductivity and worse performance.

Resume : In the last two decades, ferroelectric polymers have triggered interest in academia and industry due to their flexibility, biocompatibility, facile processibility, high dielectric breakdown strength, and low acoustic impedance. Despite these promising features, lower piezoelectric constant, and dielectric permittivity of ferroelectric polymers in comparison to their inorganic counterparts are the main impediments hindering their application in device fabrication. The mentioned drawbacks led to numerous efforts to enhance the performance of ferroelectric polymers through various strategies. Nanofiller strategy is a method that has shown great promise in improving piezoelectric constant and polarization of PVDF-based polymers. In this work we investigated the influence of amine-functionalized graphene oxide (AGO) on ferroelectric, piezoelectric, and dielectric properties of polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE). It was observed that by incorporation of only 0,1 w% AGO in PVDF-TrFE matrix the remnant polarization increased to 10.92 ?C/cm2 from 8.11 ?C/cm2 for pristine PVDF-TrFE, which is the highest reported value for the polymer with non-piezoelectric filler. Furthermore, the piezoelectric and dielectric constants have increased to -46 nm/V and 17,9 from -33 nm/V and 14,7, respectively.

Resume : Gallium-based liquid metals (LMs) are recognized as an emerging material due to their unusual combination of metallic and fluidic properties, which could be used in a variety of fields such as flexible electronics, catalysis, soft composites, and biomedicine. Compared to pristine LM, LM-nanoparticles (-NPs) can lower its freezing and melting temperatures, securing facile solution-processability. This superior characteristic expands its applicability in a wide range of operating temperatures for LM-based electronics. Furthermore, LM are easily dispersed in eco-friendly solvents including alcohol and water without any mechanical treatments. However, the fabrication of LM-NPs having a long colloidal stability is still challenging due to the high density and surface energy of LM. Herein, we report the facile and effective fabrication of water-dispersed LM-NPs through emulsification-induced self-assembly of the conjugated polymer. The LM-NPs are generated through the chemical instability occurring at the oil/water interface of emulsion droplet during oil evaporation in water phase. The resultant NPs were encapsulated by conjugated polymers in water (as denoted LM-NP-water ink). This method using chemical instability of droplets allow us to modify the functionalities of LM-NP-water ink by addition of any polymers into droplets. The functional water-inks are successfully generated regardless of the polymer configuration such as rigidity, stability, or planarity. For example, LM-NP-water ink stabilized by catechol-based polymers shows the strong adhesion on any substrates. This research can provide a facile strategy for the preparation of customized LM-NP-water ink that can be applied to soft stretchable electronics with eco-friendly processing.

Resume : Light-emitting electrochemical cells (LECs) are the simplest and cheapest solid-state lighting technology for soft and/or single-use lighting applications, such as decoration, labelling, phototherapy, etc. However, a major concern is the transition towards sustainable devices meeting Green Photonics requirements. To date, huge efforts have been carried out to implement eco-friendly emitters (organometallic complexes, small molecules, etc.),[1] while little consideration has been placed on green electrolytes: i) biodegradable polymers and ii) bio-hybrids based on DNA. Here, bio-electrolyte-based LECs always exhibited moderate performances: 3.2 cd/A@262 cd/m2 and 1 cd/A@1500 cd/m2 for devices with biodegradable and bio-hybrid electrolytes, respectively.[2,3] In addition, they have been restricted to only conjugated polymer emitters. Finally, self-stability with respect to storage under ambient conditions and mechanical/ thermal stress have been neglected. This work shows a fresh approach to overcome these limits. Self-stable, highly efficient, and stable LECs with a novel biogenic cellulose-based electrolyte have been realized.[4] Versatility is confirmed by testing conjugated polymer, organometallic complex, and BN-doped nanographene[5] emitters. Both, the increase of roughness and decrease of photoluminescence response, are limited upon self-stability tests, while the charge injection process is enhanced due to high dielectric constants. Concerning device performance achieved in pulse mode, these LECs featured high luminance and efficacies values (e.g., 15 cd/A@3750 cd/m2 for conjugated polymers) representing an overall ca. 4-fold enhancement with respect to their respective reference devices based on traditional electrolytes. For the first time, a novel biogenic electrolyte has been used without compromising device performance, regardless the type of emitter. What is more, this work reinforces the relevance of carbohydrate-based materials/ electrolytes not only for energy-related applications, but also for lighting purposes. References: 1 E. Fresta et al., J. Mater. Chem. C, 2017, 5, 5643 2 J. Zimmermann, et al., Adv. Funct. Mater., 2018, 28, 1705795 3 S. Tekoglu, et al., Adv. Sustain. Syst., 2021, 5, 2000203 4 L.M. Cavinato, et al., Adv. Funct. Mater., 2022, submitted 5 E. Fresta, et al., Adv. Funct. Mater., 2020, 30, 1906830

Resume : Titanium dioxide (TiO2) is material with diverse applications, from cosmetics and pigments to photovoltaic cells. Many of these applications benefit from TiO2’s large band gap (3.3 eV) and high refractive index. However, their potential in optoelectronic devices and photocatalytic activity are limited by the dynamics of electron-hole recombination and carrier mobility. Some success in decreasing recombination rate has been achieved via nanostructuring and ripening of TiO2 and coupling of metal nanoparticles (NPs) to TiO2, which have also contributed to increased mobility. Still efficient metal NPs-TiO2 coupling is nontrivial, complicated by the defect laden interfaces that are dictated by the formation process. Therein lies the significance of eutectic hybrid composites (e.g. Ni-TiO2) that display several advantages over homogenized nanostructured systems, like high crystallinity of the component and sharp interfaces, opening novel possibilities in materials engineering. Here we explore the optoelectronic properties of Ni–TiO2 eutectics, where high aspect ratio TiO2 nanowires are axially decorated with nodular Ni NPs. The higher work function of Ni (5.01 eV) compared TiO2’s electron affinity (4.21 eV) and the ensuing equilibrium band crossover at the junctions ensures separation of photogenerated carriers. Upon suitable illumination photogenerated electrons migrate from TiO2 to Ni making the NPs electron-rich and TiO2 hole rich. The plasmonic near field amplification by Ni NPs, further aiding the photogeneration efficiency. The enhanced carrier generation efficiency and separation is anticipated to increase the overall efficiency of any ensuing photoactive device. Realization of the above and selective extraction of carriers from the hybrid architecture is the challenge addressed here. Selective extraction of the electrons and holes may be effected using n-type and p-type polymers allowing preferential conduction of holes through the TiO2 nanowire backbone. Photovoltaic characteristics of prototype devices fabricated using PEDOT:PSS and (a)TiO2, (b)NiTiO3 and (c)NiNP-TiO2 eutectic heterostructures show that the UV photoresponse of the devices are ordered as c > b > a. The results not only provide proof-of-concept of the above design, employing the novel eutectic architecture but also provides better understanding of photogeneration of carriers and their control. The architecture effectively exploits the nanostructuring process and opportunistically chosen material properties to increase the efficiency of devices. Overall, charge generation, segregation and transport mechanism are enabled by the novel nanowire-nodule architecture of the hybrid composite that allows co-incidence and exploitation of multi-physics effects i.e. plasmonic enhancement, photogeneration, charge segregation, rectification and controlled transport finally engineering the high-performance device properties that are warranted.

Resume : Hexafluoropropylene copolymer (P(VDF-HFP))-based “active” polymer membranes are prepared by entrapping different extent of pyrrolidinium ionic liquid-based nanofluid (ionanofluid). X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FT-IR) spectroscopy are implemented to characterize the membranes. The study reveals that ionanofluid improves the electroactive phase nucleation of P(VDF-HFP) and suppresses the membranes’ crystallinity. SEM micrographs and butanol absorption study indicate that ionanofluid improves the electrolyte uptake ability and facilitates forming unified ion-conducting channels within the membranes. The 50 wt% ionanofluid (INF) incorporated gel-polymer electrolyte (GPE) exhibits the highest room-temperature ionic conductivity (2.33 × 10−3 S cm−1 at 25 °C), a high lithium-ion transference number (tLi+∼0.6), superior electrochemical stability window up to ~ 5.3 V (vs. Li/Li+) and excellent interfacial compatibility with the lithium electrode. The LiFePO4/Li battery comprising INF-based GPE demonstrates good C-rate performance and excellent cycling stability with a discharge capacity of ~ 156 mAh g−1 and ~ 116 mAh g−1 at C/5 and 2 C rates, respectively, and capacity retention of > 95% after 50 cycles at C/5 rate.

Resume : AlN films were obtained by high-frequency reactive magnetron sputtering of an aluminum target in a gas mixture of Ar and N2 on an upgraded industrial plant ?Katod 1M?. An industrial frequency of 13.56 MHz was used. In order to obtain the more structured film, the power of the high-frequency discharge was about 700 W (target diameter was 16 cm). The thickness of the films was controlled during the covering of the film on the substrate by the deposition rate, which was 1.5-3 nm/min. So, the grown AlN films could be with the thickness of 0.5 - 3 ?m. As the substrate was used n-Si (111) with a resistivity (2 - 3)?10-3 Ohm?cm (electron concentration N was 2.5?1019 cm-3). Before the deposition of the AlN film, the substrate was chemically etched and heated. Clear green rings (? = 510 nm), which alternate with black rings are observed on micro-photos of the surface of the studied samples. They are visualized in specific places on surface of the sample. The diameter of the observed rings varies in the range of 5-10 ?m for different samples. Moreover, depending on the thickness of the AlN film, a different number of the rings is visualized: a larger number at a thin film (~1?m) (5-6 rings) and a smaller number at the thickness of 3 ?m (3-4 rings). Detailed analysis of physical origin of obtained features has shown interference nature of rings. Ellipsometric measurements have showed that for our selected wavelength n?1.6. AFM measurement testifies that places of visualized rings are micro-hills with highs of 500-700 nm. These hills are almost perfectly spherical shape. Such thin AlN film could be applied as effective micro-lenses covering for Si-based solar cells to increase their efficiency.

Resume : Coordination polymers (CP`s, a kind of supramolecular polymers) are highly molecular compounds composed of repeating organic molecules and metal ions linked by intermolecular interactions. One of the strongest types of such interactions is the coordination bond between donor centers in an organic molecule (L) and a metal ion (M). If the ligand contains several donor sites, located in a molecule divergently, then it can participate in the binding of several metal centers into one supermolecule. The translation of such linked (L-M) fragments in one, two or three directions leads to the formation of 1D, 2D or 3D CP. CP`s are functional hybrid materials with original redox, luminescent, nonlinear optical, magnetic, sorption, catalytic, ion exchange, sensory and other properties. [Michael Tran, Katelyn Kline, Ying Qin, et al. / 2D coordination polymers: Design guidelines and materials perspective // Appl. Phys. Rev. 6, 041311 (2019)]. Most of the currently known coordination polymers are constructed using di- and polycarboxylic acids as ligands. Coordination polymers based on di- and three phosphinic acids are currently represented to a large extent compounds containing a flexible spacer between phosphorus atoms, which ensures the conformational mobility of such systems. The complexing properties of arendiyl bisphosphinic acids remain practically unexplored [Gagnon, K.J. Conventional and Unconventional Metal-Organic Frameworks Based on Phosphonate Ligands: MOFs and UMOFs / K.J. Gagnon, H.P. Perry, A. Clear?eld // Chem. Rev.? V. 112, 1034 (2012)]. This work is devoted to the theoretical study, using the methods of electron density functional, ab initio pseudopotential and the author's software [http://sites.google.com/a/kdpu.edu.ua/calculationphysics], of the one-dimensional and two-dimensional coordination polymers based on arendiyl bisphosphinic acids, study of their electronic-structural properties and charge states of donor centers in an organic molecule and a metal ion. The conditions for the formation of a two-dimensional layered structure and one-dimensional chains of coordination polymers are discussed.