Towards Oxide-Based Electronics: growth and applications of oxide thin films and heterost

Resume : Control at silicon-oxide interfaces is of great importance since it enables high-quality integration of oxide materials with Si platform and thus provides versatile additional functionalities to semiconductor industry. However, the ability to control such interfaces is hindered by the intense reaction of constituents. Therefore Si has to be passivized, which is normally performed by the formation of an appropriate buffer layer that is chemically stable in the oxygen rich environment, as well as structurally compatible with silicon and the oxide. In our study pulsed laser deposition (PLD) was used to prepare Sr- and SrO-based buffer layers, which have been so far prepared successfully only using molecular beam epitaxy method. By optimization of deposition conditions we were able to monitor Si surface reconstructions during PLD of Sr and SrO using the reflection high-energy electron diffraction (RHEED) technique. In case of Sr we observed characteristic two-domain (2×3)+(3×2) pattern at 1/6 ML Sr coverage and (1×2)+(2×1) pattern at ½ ML Sr coverage. This enabled us to control the surface coverage at the atomic level, which is needed for proper Si passivization. Subsequently, epitaxial layer of SrTiO3 with STO(001)║Si(001) and STO[110]║Si[100] was grown on as-prepared buffer layers and analyzed using different analytical techniques. Results of our study revealed new PLD-based path towards epitaxial integration of SrTiO3 and other functional oxides with Si.

Resume : Pyroelectric materials, in which a change in polarization occurs in response to a change in temperature, can provide thermal energy harvesting for electrical generation in compact systems with temporal temperature variation and can be used for cooling applications via the electrocaloric effect [1]. According to the structural dependence of electric properties and to recent reports, single-crystalline pyroelectric films should provide an enhanced conversion energy efficiency with respect to bulk or polycrystalline materials [2]. In this communication, we will show the impact of the domain-orientation on the ferroelectric and pyroelectric properties of epitaxial PbZr0.52Ti0.48O3 films tuned by the thermal expansion mismatch with the substrate. SrTiO3(001) and Si(001) substrates are used to generate different orientations of the ferroelectric domains. The intrinsic pyroelectric coefficient is revealed to be much larger along the polarization axis and it can reach -450 µC/m2K in c-oriented films, compared to -320 µC/m2K in a-oriented films [3]. The corresponding harvested pyroelectric energy can be beyond 10 mJ/cm3 per cycle for temperature variations of 10°C, and temperature changes of more than 10°C can be reached close to room temperature under high electric field, that could provide cooling solutions for electronic components. [1] S.B. Lang, Phys. Today 58, 31 (2005) [2] G. Sebald et al., Smart Mater. Struct. 18, 125006 (2009) [3] R. Moalla et al., submitted

Resume : Pulsed Laser Deposition (PLD) has been established in recent years as a versatile thin film deposition technique for the near stoichiometric synthesis of materials including complex transition metal oxide thin films. These oxides offer a variety of exploitable properties and, when combined, new functionalities due to electronic reconstruction at interfaces. Despite this rich potential for use in electronics, actual applications are relatively few as they rely on full control of thin film growth on atomic scale with substrate materials at sizes suitable for industrial applications. We present the latest results on optimized growth and characterisation of ferromagnetic LSMO on YsZ/(CeO2)/(SRO) on 4” silicon wafers utilizing a TSST developed large-area PLD system. X-ray diffraction measurements show a high degree of (buffer layer dependent) epitaxy and crystallinity over the full wafer comparable to small scale PLD grown films. Furthermore, it is shown that growth parameters do not trivially scale from small area deposition settings. For LSMO, at typical ‘small-area’ temperature settings of up to 700°C, no epitaxy is observed, where at elevated temperature, a high degree of epitaxy is obtained. This is understood by recent improved understanding on the composition of the plasma, in which the oxidation of species in the plasma is suggested to be a crucial mechanism in the stoichiometric reconstruction of the synthesized oxide thin films1. 1. R. Groenen et al. Subm. APL mat.

Resume : Monolithic direct integration of functional oxide nanowires with vertically oriented crystals on a semiconductor platform is challenging due to difficulties on preserving epitaxy, crystalline phase, and composition. Here, we developed a new strategy to produce vertical epitaxial single crystalline manganese oxide based nanowires thin films with tunable composition and enhanced ferromagnetic properties on Si substrates by using a chemical solution deposition approach [1]. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates combined with the controlled growth of quartz thin films at the Si surface, which allowed the epitaxial stabilization and crystallization of the oxide nanowires. α-quartz layers were obtained by thermally activated devitrification of the native amorphous silica surface layer assisted by a heterogeneous catalysis driven by alkaline earth cations (Sr2+, Ba2+ or Ca2+) present in the precursor solution [2]. Therefore, the combination of soft-chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional complex oxides nanomaterials on Si substrates [3]. References [1] A. Carretero-Genevrier et al. Chem.Soc.Rev. 43, 2042 (2014) [2] A. Carretero-Genevrier et al. Science 340, 827 (2013) [3] A. Carretero-Genevrier et al. Chem. Mater. 26, 1019 (2014)

Resume : Interest in thin film transition metal oxides is driven in part by the potential technological application of devices exploiting intriguing phenomena, i.e. oxide electronics, and in part by the novel structures and properties observed in epitaxial oxide films, using phase, strain, and interfacial engineering. However, in spite of the large number of observations and promise of epitaxial oxide thin films, most of the investigations have been focused on films on low-index commercially-available single-crystal substrates, which have limited the scope of the study. Here, we present a novel high-throughput synthesis process (called combinatorial substrate epitaxy) where an oxide film is grown epitaxially on a polycrystalline substrate, and applied it to the growth of Ca2MnO4 or BiFeO3 materials. Using EBSD, we determine the preferred epitaxial orientation relationships, and also show how functional properties could be investigated across the entirety of epitaxial orientation space, and provide a library of physical property observations, that can finally be applied to a wide range of complex functional oxides. Support from ANR, MEDILIGHT and MEET are acknowledged.

Resume : An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in solid electrolyte with low ion mobility and are expect to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.

Resume : During the last 10 years, the quest for a replacement gate dielectric in field effect transistors has been a powerful driver to investigate the deposition of ultra thin oxide thin films. Replacing SiO2?with HfO2?in transistors was a major breakthrough for the microelectronic industry and generated a lot of know-how. This knowledge is today cross-fertilizing research areas beyond traditional CMOS microelectronics. Controlling the interface between the oxide and silicon has for example always been a key issue. This specific research triggered the development of new deposition processes, enabling researchers to grow high quality, crystalline, complex oxide films onto silicon. Such ?functional? oxides have physical properties that make them very attractive to perform functions that will be required in future Information and Communication Systems. In particular, technologies must be developed that enable a performance scale-up of the full system, while having stagnating data processing capabilities at the chip level. Silicon photonics is emerging as one of the technology of choice for this purpose. Electro-optical oxides are therefore an extremely important area of research to enable the integration of new functionalities in advanced silicon photonics. This presentation will deal with the opportunities and challenges to combine silicon microfabrication techniques with the capability to grow crystalline directly on silicon. It will in particular focus on the use of ferroelectric perovskites for photonic circuits in future systems, and how defect chemistries might play a crucial role.?

Resume : The evaluation of the dielectric response in thick films of dielectric materials and in mixtures of dielectric and metals is not as straightforward as in bulk materials, due to the presence of porosity. To simulate the effective dielectric function of these films, porosity and percolation effects should be taken into account in the theoretical models. The case of the mixture of a ferroelectric with a metal, is specially interesting because the dielectric response can be greatly enhanced, and near the percolation threshold the permittivity diverges. This effect is discussed for a set of thick Pb(Zr,Ti)O3 films and composite films Pb(Zr,Ti)O3 −xPb2Ru2O6.5 prepared by screen printing on sapphire substrates. Their homogeneity and phonon response were studied by Raman spectroscopy and Fourier-transform infrared (FTIR) reflectivity. The dielectric response below phonons was measured using time-domain terahertz transmission spectroscopy. The compositions, up to 25 vol% Pb2Ru2O6.5, are below and above the electrical percolation threshold, known to be about 17% in the bulk composites. Using the dielectric functions of bulk PZT ceramics and Pb2Ru2O6.5 single crystals, the effective dielectric functions can be compared with those obtained using the theoretical models. D Nuzhnyy, E Buixaderas J. Petzelt et al, J. Physics D: Appl. Phys 47 (2014) 495301 (2014).

Resume : Thin film layers of Al2O3 present a clear technological interest in a variety of applications: as surface passivation on top of silicon wafers in photovoltaic technology [1], as a dielectric covering layer for carbon nanotubes or graphene layers [2], as a blocking electrode in organic photovoltaic devices using a conformal deposition of Al2O3 on TiO2 or columnar ZnO [3,4], and, doped with Er, as optical amplifiers or lasers in planar optoelectronic applications [5]. The most common techniques used to grow Al2O3 layers are chemical vapour deposition (CVD) and atomic layer deposition (ALD). The purpose of this work is to study the structural and bonding properties of Al2O3 films obtained with r.f. magnetron sputtering and pulsed laser deposition (PLD). The influence of the different deposition parameters, like substrate temperature or oxygen partial pressure and film thickness, on the properties of the deposited layers will be considered. The samples have been analysed by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results will be discussed to evaluate the suitability of each technique for the different potential applications. [1] B. Hoex et al, Applied Physics Letters 91, 112107 (2007) [2] Steven M. George, Chem. Rev. 2010 (110) 111 [3] E. Palomares et al. J. Am. Chem. Soc. 2003 (125) 475 [4] M. Law et al J. Phys. Chem. B 2006 (110) 22652 [5] Polman A., J. Appl. Phys. 82 (1) 1

Resume : High value of phase boundaries in dispersed systems based on nanopowders is one of advantages compared with coarse-grained analogues. At presence on outer side of border of adsorption ionic atmospheres with work function, different from electron work function of nanoparticles material, nanoparticle has heterojunction properties. Changes of external conditions will change electrical properties of heterojunction. This property can be used as a sensor. The aim was to study electrical properties of porous dispersed system based on ZrO2 nanoparticles by method of impedance spectroscopy in depending from ambient humidity. As the object of investigation compacts from ZrO2+3molY2O3 (700°C) nanopowder were used. Impedance was measured by the Measurer-analyzer of impedance parameters type 2V-1 in the climatic chamber with adjustable humidity over a wide range (40-90%RH). The frequency dependence of imaginary and real components of the complex impedance was recorded. With the use of author's method, contribution of surface and volume components to overall conductivity was estimated. Relationship between air humidity and electrical resistance of samples was established. Increase of humidity from 39 to 94% leads to decrease of total sample resistance by 25 times (from 0.46kOhm to 11.51MOhm). The determining role of the adsorption layer (surface component of impedance) in conductivity was found. These studies provide a base for development of nano-ionic humidity sensor of high sensitivity.

Resume : Rear earth oxycarbonates are potential candidate materials for constructing simple and low cost chemiresistive sensors usable for monitoring level of carbon dioxide (CO2) gas in the living and working environment for personal comfort and health reasons. Also, measurement of CO2 concentrations is needed in many industrial processes. Specifically, Nd and La oxycarbonates in a form of nanoparticles have been studied previously as novel CO2 gas sensor materials. In this paper, pulsed laser deposition of La oxycarbonate (La2O2CO3) thin films was studied and structural properties of obtained thin films were characterized. Also, CO2 gas sensing ability of synthesized films was evaluated. The films deposited under CO2 partial pressure in various conditions were all Raman amorphous. In-situ or ex-situ annealing procedure at high CO2 partial pressure was needed for obtaining crystalline La2O2CO3 films, whereby hexagonal and monoclinic polymorphs were obtained in ex-situ and in-situ processes, respectively. Sensor structure, made using in-situ process, was sensitive to CO2 gas and showed relatively fast response and recovery characteristics.

Resume : Thin-film transistors (TFTs) based on amorphous transparent and conductive oxides (a-TCOs) have been extensively studied in the last decade due to their higher mobility, improved uniformity and stability under bias stress compared to amorphous-silicon based TFTs. In addition, the amorphous layers could be manufactured at low temperatures on inexpensive and flexible substrates, which are also light weight. This opens the possibility for such devices to be used for space applications. There have been very few studies so far on the effect of radiation on a-TCOs structure and properties. We deposited amorphous indium zinc oxide thin films having different In/(In+Zn) compositions by the pulsed laser deposition technique at room temperature. After deposition, the films were submitted to gamma radiation from a 137Cs source up to a dose of 20 kGy (1 Gy = 1 J.kg-1) at a dose rate of 5 Gy/min under argon atmosphere. X-ray reflectivity and diffuse scattering investigations were performed to accurately measure the thickness and estimate changes induced by gamma radiation on the mass density and surface and interface roughness. Once the thickness of the films was known, spectroscopic ellipsometry and optical reflectivity investigations were used to assess changes induced by the irradiation on the optical and electrical properties of the films. Results showed that a-TCOs films could withstand the effect of gamma radiation with minimal changes of their electrical and optical properties.

Resume : Amorphous oxide semiconductors (AOS) based thin-film transistors (TFTs) have been extensively studied in the last decade due to their better optical and electrical properties compared to amorphous-silicon TFTs. There have been very few studies about their performance and reliability after thermal treatments. Amorphous indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) thin films having different cations compositions were obtained by the pulsed laser deposition (PLD) technique at room temperature on glass or Si substrates. The films were measured in-situ by employing spectroscopic ellipsometry and x-ray diffraction and reflectivity up to temperatures of 550° to obtain the optical constants (band gap, refractive index, absorption coefficient) and their dependence on temperature and structure.

Resume : Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. In particular, the existence localized levels at conduction band bottom has been hypothesized to explain the discrepancy between the observed charge carriers density in good quality samples [1] and the one predicted by polar catastrophe model [2] and several indirect evidences of their presence has been collected up to now. We will present the investigation of thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage [3], corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 10^4–10^5 µV/K, oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface. [1] S. Thiel et al, Science 313, 1942 (2006). [2] A. Ohtomo and H. Y. Hwang, Nature 427, 423 (2004). [3] I. Pallecchi et al, Nat. Commun. 6, 6678 (2015).

Resume : High quality lead titanate thin films were deposited using in situ layer-by-layer reactive magnetron sputtering. The optimal parameters were found in order to achieve the best structural quality of perovskite thin films without post annealing. Films were deposited on platinized silicon (Pt/Ti/SiO2/Si) substrates at 450-550 oC temperatures using Ti2O seed layer. It was shown that microstructure strongly depends on deposition temperature. The most dense and flat structures were formed at 550oC deposition temperature. Structural, morphological and ferroelectrical properties of thin films were investigated there. All thin films, deposited using seed layer, are highly texturized and nanocrystalline. Hysteresis measurements show that films exhibit ferroelectric properties with maximum coercive field of Ec=150 kV/cm and of Pr=60 C/cm2. Coercive field dependence on frequency measurements shows that creep regime of domain wall motions dominate till 1kHz frequency. Leakage current investigation shows that films exhibit the space charge limited conduction (SCLC), which in our case was higher due to the large concentration of oxygen vacancies.

Resume : Lithium tantalate is a well-known ferroelectric material, which also possesses piezoelectric, pyroelectric, nonlinear optic and acousto-optic properties. Its high Curie temperature (around 900 K depending on stoichiometry) makes all of its useful properties relatively insensitive to temperature changes. On the other hand, it is possible to use thin layers of the material to make a waveguide, which is controllable by acoustic and/or electric fields. All of this makes investigation of thin films of Lithium Tantalate an important topic with possible future applications. A study of dielectric properties of thin Lithium Tantalate-based films will be presented in this contribution. The films are deposited by pulsed injection chemical vapor deposition technique on a platinum layer on Si substrate. The grains of the films are columnar and make a textured structure. The measurements of the properties were performed in 100 K – 500 K temperature range and 100 Hz – 1 MHz frequency band. Analysis of the data is presented.

Resume : Photocatalytic, sensing and light conversion performance of ZnO thin films are strongly affected by materials porous structure. The pores formation, distribution and size are proved to be tailored through films deposition in the presence of doping impurities as well as during post annealing treatments. In this work, thin films of ZnO doped with 5 at. % Mn and Ga have been prepared by sol-gel method starting from acetate and nitrate precursors, and spin coated on Si/SiO2 and glass substrates. The films were sequentially annealed at 500 oC in air for 1 h and at 500 oC in nitrogen or air for 2 h. The films structure, morphology, optical absorption/transmission and the refractive index have been assessed. All the films are polycrystalline, wurtzite type, and show preferential orientation along (002) direction. The crystallites size in the undoped films treated at 500 oC in air is about 22 nm, and decreases to 6 nm in Mn doped films and to 8 nm in Ga doped films. The treatment in nitrogen leads to crystallite size of 17 nm in undoped films, 5 nm and 8 nm in the films doped with Mn and Ga. The effect of thermal treatments on the films porosity have been analysed by spectroscopic ellipsometry. The porosity of the films treated in air is about 11% in the undoped films, 10% in the films doped with Mn and 22% in the films doped with Ga. After the second step of annealing performed in nitrogen, the porosity is 6% in undoped films and increases to 18% and 29% for Mn and Ga films.

Resume : Nanomaterials can be obtained by many different ways: wet chemistry, organometallic reactions, ball milling, electrochemistry, sol-gel reactions, condensation, MBE sputtering, and so on. In many cases the properties of fine materials depend on the manner of fabrication procedure, their crystal structure, size, surface modification, solution composition, etc. [1]. One of the possible wires fabrication is electrodeposition method or thermal decomposition of elements in the anodic aluminum oxide (AAO). The process conditions such as temperature and composition of the used solution as well as current conditions determine matrix parameters (a pore diameter and center to center distance). In this presentation, it will be shown few very effective methods of magnetic nanowires preparation in AAO matrix, with various structure compositions. Such nanowires can possess core-shell, multilayered or alloy-like structure, and can be deposited in the matrix from selected elements. Obtained nanowires will be characterized by SEM. Structure of nanowires will be also examined by TEM and XRD, and magnetic properties will be analyzed by Mössbauer spectroscopy. [1] P. Christian, F. Von der Kammer, M. Baalousha, Th. Hofmann; Ecotoxicology 17 (2008) 326

Resume : Titanium dioxide is one of the most investigated metal oxides, which finds many applications i.a. in photocatalysis, solar cells, water splitting and batteries. In a significant amount of cases, the highly ordered TiO2 nanotube arrays are grown out of Ti metal plate during anodization process carried out in fluoride containing electrolyte. However, for practical some applications: solar cells or electrochromic windows, the semi-transparent TiO2 formed on the semi-transparent, conductive substrate is very much desired. In this work we show the ability to fabricate the semitransparent TiO2 nanotube arrays by varying anodization parameters including concentration and type of electrolyte (organic or inorganic), voltage and the bath temperature. The titanium thin film deposited onto the FTO substrate using gas injection magnetron sputtering (GIMS) method. The fabrication of Ti layer was performed in the vacuum chamber under Ar gas atmosphere (0.16 Pa). The substrate was not intentionally heated or cooled. The thickness of uniform Ti coating was estimated from a linear interface layer/substrate profile using the confocal optical microscope device and was found to be 1.97+/-0.01 um. The morphology of the nanostructured samples were investigated by Schottky field emission scanning electron microscopy and their absorbance ability was characterized using UV-vis spectrometer. Financial support from the National Science Center (2012/07/D/ST5/02269) is gratefully acknowledged.

Resume : Recently, fabrication of nanomaterials attracts attention scientists from various research areas. Therefore, there are elaborated many different techniques of nanostructures preparation. Among others can be listed: MBE, sputtering, laser evaporation, electrochemistry, wet chemistry, etc. But always the easiest and cheapest methods are the best one form the economical point of view. That is why, porous aluminum oxide became very promising and popular, as a matrix to obtain various kind of nanowires by basic electrodeposition process [1]. Simplicity of the preparation of alumina matrixes, allows to obtain nanowires with desired thickness and length. There are few parameters which should be controlled to determine shape and depth of the pore: type of electrolyte, temperature, voltage, and time of anodization process. This way obtained matrixes can be used to deposit nanowires from both organic and inorganic solutions with variable internal structure. In this presentation we would like to show how conditions influences pores ordering and diameter, which reflect in the nanostructures organization and morphology. Techniques used for this studies are mainly SEM, TEM, and Mössbauer spectroscopy. [1] B. Kalska-Szostko, E. Brancewicz, P. Mazalski, J. Szeklo, W. Olszewski, K. Szymański, A. Sidor, Acta Physica Polonica A 119 (2009) 542-544

Resume : Cu2O is an interesting candidate for photovoltaic solar cells due to its suitable band gap, wide abundance, high absorption coefficient above the band gap, non-toxicity and affordability. The maximum theoretical efficiency of 20% is, however, currently far from being realized. There are still many challenges remaining, in particular in connection with the interface of the pn-junction of these solar cells. Defects present at the interface will both act as traps as well as affect the conduction band discontinuity. The highest efficiency cells (>5%) using the Cu2O/AZO (Al-doped ZnO) heterojunction have so far been achieved by inserting an n-type semiconductor material between the Cu2O and the ZnO layers. In this study we have investigated the effect of a buffer layer of TiO2 deposited by atomic layer deposition, between sputter-deposited Cu2O and AZO. Current-voltage (I-V) measurements show significant changes in the electrical behavior with changing TiO2 thickness. The Cu2O/ZnO heterojunction without TiO2 appears purely ohmic in behavior, however, with increasing TiO2 thickness, this behavior changes to an increasingly rectifying behavior. It is thus possible to tune some of the electrical behavior with buffer layer thickness, as will be further discussed in the full contribution.

Resume : Zinc oxide(ZnO) is one of the versatile semiconducting materials due to its chemical and electrical properties such as resistivity control over the range 10-3 to 105 Ωㆍ㎝, transparency in the visible range, high-electrochemical stability, non-toxicity. Zinc oxide is also an attractive material with wide band gap (3.37 eV) and high excitation binding energy (60 meV) at room temperature. It has many potential applications in short-wave device, ultraviolet laser, thin-film gas sensor, solar cell, and wearable devices. In this study, various ZnO nano-structures including flower-like, chrysanthemum-like, tree-like as well as thin films were synthesized by a solution-based deposition method designed by a combination of a continuous flow reactor process and a spin coating method, and then they were characterized to investigate the influences of the processing parameters on the performance of ZnO. XRD, SEM, EDX, UV-vis Spectroscopy, and XPS were employed in the characterization of the prepared structures and films. Based on the characterization, it was found that flow rate, annealing temperature, pH, reaction time, and precursor concentration exerted an effect on the properties of ZnO. We have also fabricated thin film transistors (TFT) using ZnO thin films through the CFR-spin coating process. The Al/ZnO/SiO2/Si/Au structure was used for fabrication of bottom gate metal-insulator-semiconductor-field-effect-transistor (MISFET) device and more in depth investigations are in progress.

Resume : With the use of X-ray Photoelectron Spectroscopy we studied segregation processes occuring in the vicinity of the SrTiO3 (100) single crystal surface induced by low energy Ar+ ion etching. We confirm that selective etching and formation of titanium oxides with lower oxidation states is responsible for the insulator-metal transition. However, photoemission data indicate interesting effect that after exposition of the treated sample to air the SrO insulating complexes are shifted towards the top. In addition, it was shown that the process of conductive layer formation is less effective when ion etching of the crystal is provided at an elevated temperature. It is explained by the enhanced oxygen diffusion rate and the process of self oxidation in the heated sample.

Resume : Understanding the anomalous transport properties of strongly correlated materials in proximity to a quantum phase transition present a significant challenge. For example, in the normal state of unconventional superconductors one encounters deviations from Fermi liquid behavior, longitudinal and Hall scattering rate separation, a pseudogap phase, and bad metal behavior. These properties have been studied extensively in bulk materials. Here we show that oxide heterostructures allow for additional tuning and control, using dimensionality, electrostatic doping, and interface effects to introduce (proximity to) magnetic order. We will discuss emergent phenomena in two-dimensional electron liquids formed at the interface between Mott insulating rare earth titanates and the band insulator SrTiO3. Such interfaces exhibit a high-density, two-dimensional electron liquid, of approximately ½ electron per surface unit cell, providing ~ 3×1014 cm-2 mobile charge. Narrow quantum wells embedded between two such interfaces allow for extremely high mobile carrier densities and the emergence of phenomena typical of strongly correlated systems. We will discuss metal-insulator transitions, the conditions for the appearance of non-Fermi liquid exponents in the temperature dependence of the resistivity, transport lifetime separation, and the relation to the proximity to different types of magnetism and a quantum critical point.

Resume : The increasing miniaturization of electronic devices and the atomic understanding of physical and chemical phenomena like superconductivity and two-dimensional electron gases are increasing the need for reliable imaging and spectroscopy at the atomic level. Here we present several examples of on-going research in the area of advanced functional materials and interfaces such as (SrCa)CuO2 stacked with SrTiO3, SrRuO3 or BaCuO2 layers, non-crystalline LaAlO3 on SrTiO3 with a (LaSr)MnO3 interlayer and (La,Sr)MnO3 on NdGaO3 (with or without an SrTiO3 buffer layer) to emphasize the key role played by aberration-corrected electron microscopy (EM) in the arsenal of techniques necessary for materials development and characterization. Heavy atoms can be imaged with high-angle annular dark-field Scanning Transmission EM (HAADF-STEM) and light elements such as oxygen can be accessed through annular bright-field imaging (ABF-STEM). Combining these two techniques, atomic displacements and octahedral tilts which have a major influence on the rise of new physical properties in heterostructures can be accessed rather easily. In addition, the electronic structure changes related to strain, orbital and interfacial engineering as well as surface termination are accessible in the fine structure of EELS core-loss edges which can provide bonding and valence states, providing a deep understanding of the electronic structure, at the heart of the fascinating properties observed in these compounds.

Resume : New materials are required in order to meet upcoming technology nodes or to progress ?beyond Moore?. It is well known that Pulsed Laser Deposition (PLD) is a very flexible and versatile technique allowing fast optimization of new thin film materials. Moreover PLD is superior above other deposition technologies for the stabilization of volatile elements and nucleation of complex oxide material systems. However, mainly because of the sample size, the developed materials and processes in PLD research tools only just make it into demonstrator devices. In order to make it into commercial applications, next generation PLD equipment is needed to bridge the gap between demonstrator and the prototype ? pilot ? production stages. The new SolMateS? R&D platform is the next step beyond fundamental (PLD) research. The reliable hardware is flexible for fast process optimization and allows uniform thin film deposition up to 200 mm diameter with high reproducibility. The automated software ensures easy operation and stable performance. The small footprint makes it very easy to attach it to an existing PLD beam path in the research facility. Since process recipes can be transferred directly to SolMateS? PLD production equipment it is the ultimate valorization of thin film research. The PLD R&D platform is the missing link between lab and fab. The first SolMateS? PLD production platform is installed in the field in 2013. This tool is the ultimate proof that PLD has now reached the maturi

Resume : In pulsed laser deposition (PLD) it is often just assumed that thin films will have the same composition (mainly the cations) as the target. However, the widespread use of a background gas, either inert or oxidizing, has important effects in the final film composition as well as on its thickness. We investigate the influence of the background pressure on the deposition of thin film from different multi-element targets. These targets have been specifically selected based on their elemental mass ratios. A quantitative analysis of the thin film composition as well as a semi-quantitative analysis of the plasma plume composition, at different angles and for different pressure regimes is performed. In some targets 18O isotope is used as a tracer to enable an analysis of oxygen, i.e. the origin in the thin films as well as the importance of reactions in the plasma plume and with the background gas. The first results show the influence of the pressure on the film thickness, composition and angular distribution, and how these variations depend on the specific mass ratios of the target material. A homogeneous thickness is challenging at low pressures, while at 1x10-1 mbar a uniform thickness is possible. Depositing films at an intermediate pressure may not work and can result in compositional variations of up to 15%. Analyses using 18O show that the oxygen background pressure is the most important source of oxygen for the as-grown thin films at pressure > 1x10-2 mbar.