Block-copolymer self-assembly: fundamentals and applications

Resume : Achieving sub-10 nm high-aspect-ratio patterns from block copolymer (BCP) self-assembly requires both a high interaction parameter and a perpendicular orientation of microdomains. However, these conditions are difficult to achieve simultaneously because the blocks in a high-? copolymer typically have very different surface energies, favoring in-plane microdomain orientations. We introduce top coat for the control of orientation, alignment and morphology of BCP thin films. Using partially hydrolyzed PVA top coats with a solvent annealing, perpendicular orientation of PS-b-PDMS can be obtained despite the large surface energy differences between PS and PDMS. Extremely straight and laterally aligned cylindrical microdomain of BCP films were prepared by simply covering the BCP films with a top coat and dewetting the latter via thermal annealing to generate shear flow in the BCP underlayer. We also observed the gyriod-cylinder phase transition using interfacial-energy-tailored top-coat. At the optimized top-coat composition, gyroid nanostructures with sub-10 nm strut width were achieved down to ?125 nm. Secondly, for the superior thermoelectric properties of graphene and conducting polymers, we also briefly introduce sub-10 nm graphene nanomesh structures and in-situ vapor phase polymerization of PEDOT:Tos on highly ordered lamellar, cylindrical and disordered nanostructures from block copolymer/oxidant blended films.

Resume : Diblock copolymer self-assembly has been a subject of active studies with considerable progress made in understanding the principles of equilibrium self-assembly. Kinetics of self-assembly or chain exchange are influenced by different factors starting from hydrophobicity and chain length to chain architecture. Computer simulations can provide molecular level insights which are often difficult to access experimentally. We’ll discuss different factors influencing chain exchange kinetics based on results of dissipative particle dynamics simulations and compare the finding to experimental data. In particular, the effect of chain architecture and conformation will be considered with the example of diblock copolymers with a ring-shaped core or corona block in comparison with their linear diblock copolymer counterpart. We found a striking difference in both the equilibrium micelle size and kinetics of chain exchange in these systems. Furthermore, mixed micelles containing block copolymers of both types while having similar size and shape to linear diblock copolymers, possess different chain exchange kinetics, which exhibit synergism of chain exchange. The origin of this effect and its implication for micelle self-assembly and practical applications of self-assembled nanostructures will be discussed.

Resume : Random copolymer brushes have been widely used to control the wetting behaviors of block copolymers (BCPs), but random copolymerization is only limited to a few monomer pairs. Here we demonstrate the use of homopolymer brushes to modify the substrate to form a chemically homogeneous surface. The surface affinity is tuned by changing the monomer substituent, and a variety of wetting behaviors are obtained in BCP films on homopolymer brushes. Three series of hydroxyl-terminated or crosslinkable homopolymers, including polymethacrylate, polyacrylate and polystyrene derivatives, are prepared for controlling the BCP-substrate interaction. Both preferential and non-preferential wetting behaviors of PS-b-PMMA, PS-b-PLA and PS-b-PPC films are obtained as the homopolymer structures change in terms of the carbon contents. Moreover, homopolymer brushes can also substitute random copolymer brushes in directed self-assembly of BCP films with density multiplication on chemical pattern. The use of homopolymer brushes may have advantages over random copolymer brushes in terms of reproducibility and uniformity of brush formation, reduction of defect density and increase of assembly kinetics.

Resume : The self-assembly of block copolymers is a cost-effective method for large-scale, high-resolution nanopattern fabrication. Typical patterns include hexagonal dots and parallel lines, but through additional of chemical and/or topological features, more complex patterns can be produced. In this work, we describe an entirely bottom-up approach that yields Moiré superstructures through a two-step process involving two sequential self-assembly steps of incommensurate block copolymer dot arrays. Preferential orientation of the two hexagonal arrays is observed due to a registration force exerted by the first layer on the second, leading to the large-area Moiré patterns. Statistically meaningful data, derived from helium ion microscopy imaging, revealed specific size regimes where interlayer registration forces can induce long-range preferential alignment of these incommensurate block copolymer dot array patterns. As is typically the case with block copolymer self-assembly, subtle effects can play critical roles, including factors such as dot size, grain boundaries between dot domains, and the annealing process - the potential, and limitations, of this approach for making higher order nanoscale patterns will be described.

Resume : Gyroid terpolymer films can serve as templates for the fabrication of a range of 3D functional nanostructures including optical metamaterials. These plasmonic materials can show interesting optical properties - a nanostructured gold gyroid, for example, was demonstrated to exhibit a linear dichroism. However, these anisotropic optical properties can only be observed in materials that were fabricated using gyroid terpolymer templates with long-range order, the generation of which still remains challenging. In this work, we show that gyroid structures with grains of about 5-15 µm in size can be generated by means of controlled solvent vapor annealing of a polyisoprene-b-polystyrene-b-poly(glycidyl methacrylate) (ISG) triblock terpolymer film. In situ grazing-incidence small-angle x-ray scattering (GISAXS) was employed to identify the order-disorder transition in terpolymer films during annealing in the vapor of tetrahydrofuran. Gyroids with long-range order were produced by slowly removing the solvent from swollen ISG films in the ordered state. Interestingly, these terpolymer films exhibit alternating gyroid morphology with a previously unreported out-of-plane orientation along the [111] direction. Gold gyroids replicated from ordered ISG terpolymer films feature interesting optical properties relevant for future design strategies of optical metamaterials.

Resume : The all-organic polystyrene-block-poly (methyl methacrylate) (PS-b-PMMA) BCP thin films have been widely investigated for advanced lithographic applications, due to possibility to promote perpendicular orientation of the nanodomains by easy neutralization of the surface with the appropriate poly(styrene-random-methyl methacrylate) P(S-r-MMA) random copolymer. Because the XS-MMA parameter is weakly dependent on T, fundamental studies on the self-assembly and grain coarsening processes can be performed modulating the segregation strength XN by simply changing the degree of polymerization N. In this work the grain coarsening process in thin films of asymmetric cylinder forming PS-b-PMMA BCP with degree of polymerization, N, ranging from 461 to 1281 (molecular weight: 48-132 kg/mol) was accomplished by fine tuning of the annealing temperature (TANN = 140-290 °C) and time (tANN = 1-900 s) in a rapid thermal processing machine. Hexagonally packed PMMA cylinders perpendicularly oriented with respect to the substrate with different level of lateral order were obtained. The evaluation of the correlation length allows determining the growth exponent f and the activation enthalpy HA for each N. For the lowest N, f saturates at ?1/3. This value equals that of systems that coarsen with a diffusion-limited mechanism. Increasing XN, both f and HA decrease following an exponential decay as a function of N with exponent ?XS-MMA. This dependence exactly mimics that of the chain diffusivity.

Resume : Directed self-assembly (DSA) of block copolymers (BCP) is considered by the semiconductor industry as one of the main alternative for next generation technological nodes. Further advances towards the incorporation of DSA-based technologies require a deep understanding of the self-assembly mechanism to find optimal process conditions (i.e. kinetics of self-assembly) and decrease the defect density. In order to evaluate the potential of BCP-based technologies, new metrology methods with sufficient spatial resolution and capable to probe large analysis areas for statistical studies must be applied. In this scenario, grazing incidence small-angle X-ray scattering (GISAXS) is a reliable method for its high spatial resolution and fast temporal response over large scanning areas. In this contribution, we show the characterization of dynamics of thin film BCP self-assembly processes by GISAXS. First, the self-assembly of different PS-b-PMMA systems has been studied in real time by thermal annealing while GISAXS data is recorded (i.e. in-situ testing). Different annealing conditions have been analyzed, allowing us to monitor the order-disorder transition of the BCP films. Furthermore, this technique has been also used for the characterization of sequential infiltration synthesis (SIS). An evolution of the maxima at Yoneda band was observed in the samples attributed to the incorporation of aluminium oxide into the PMMA block, as a function of number of cycles and process conditions.

Resume : Video-rate atomic force microscopy (AFM) provides a new paradigm for studying the evolution of block copolymer (BCP) self-assembly during the thermal annealing process. We use real-time, environmentally controlled AFM to examine the dynamics of BCP patterns on the time scale of individual microdomain connections to achieve direct visualization of defect healing mechanisms. This highly general technique has been applied to several systems fundamental to understanding polymer dynamics. First, we have tracked defect healing and pattern alignment of BCP thin films on chemically templated substrates. We observe that pattern evolution is mediated by the presence of a novel, metastable BCP superstructure. Strikingly, the chemical template caused alignment of these films to occur irreversibly. Second, we have monitored spatial fluctuations of BCP domains during thermal annealing. Such fluctuations give rise to line-edge roughness and line-width roughness which currently limit the applicability of BCP templates for device fabrication. We find that fluctuations also play an intrinsic role in controlling the defect rates of patterned films.

Resume : The directed self-assembly (DSA) of block-copolymers (BCP) is now established to be a straightforward technology to further decrease limits currently achievable by conventional lithographic tools. Indeed, the capabilities of these materials to form homogeneous self-assembled structures of different shapes of small sizes over large areas make them attractive for sub-10nm patterning.1 In this contribution, we will first highlight the patterning performances for the two strategies specifically developed to improve self-assembly defectivity and kinetic, illustrated on the basis of PS-b-PMMA systems. These approaches, namely blended-materials2 and Special3 BCPs, will be benchmarked through the key DSA material properties (film-thicknesses, defectivity, CDU, …) versus regular PS-b-PMMA BCPs of same dimensions, in order to evidence their improved characteristics and the potential benefits of using such approaches in microelectronic applications. Then, we will present the properties of various materials developed to further reduce the dimensions achievable with PS-b-PMMA BCPs. These high-χ silicon-containing BCPs, based on PDMSB-b-PS architecture,4 can be self-assembled under a standard thermal bake to form perpendicular features, either on neutral free-surfaces or once guided in templates. Thanks to the silicon contained in one phase of the BCP, the features obtained can be transferred into the substrate with high aspect-ratios, rendering thus these materials attractive for patterning applications. References: 1. H.-C. Kim &al., Chem. Rev. 2010, 110, 146. 2. X. Chevalier &al., Proc. SPIE 9049, Alternative Lithographic Technologies VI, 90490T (March 27, 2014). 3. X. Chevalier &al., Proc. SPIE 9779, Advances in Patterning Materials and Processes XXXIII, 977913 (March 25, 2016) 4. A. Legrain &al., ACS Appl. Mater. Interfaces 2017, 9, 43043.

Resume : Single electron transistors (SETs) operating at room temperature (RT) are promising candidates for low power electronics needed for Internet of Things. The IONS­4SET project aims to realize SETs on the basis of single Si nanodots (Si NDs) in the centre of thin SiO2 layers, which are part of vertical nanopillars etched out of a Si/SiO2/Si layer stack. For RT operation, tiny Si NDs (< 3 nm) with high Coulomb blockade energy are necessary. Moreover, to ensure enough current by quantum mechanical tunneling, the Si NCs have to be exactly loca­ted in the oxide at distances to source and drain of ~ 1…2 nm. We employed self-assembly of Si NDs where ion beam mixing transfers SiO2 to SiOx and subsequent phase separation forms the Si NC in the c-Si/SiO2/a-Si nanopillar. Predictive com­puter simulations and energy-filtered transmission electron microscopy demonstrate the self-assembly of Si NDs with targeted dimensions. Formation of single Si NDs requires mixing/phase separation to be per­for­med in nanopillars with volume < 1.000 nm³. Experimentally two different approaches are currently under investigation to fabricate these tiny structures. A conventional top-down approach based on e-beam lithography is tested together with a bottom-up solution based on directed self-assembly of block copolymers. An overview of current achievements of the project will be presented. This activity is funded by the European Union’s Horizon 2020 research and innovation program under grant agreement No 688072.

Resume : Block Copolymers (BCPs) are attracting wide interest for advanced lithographic applications due to their ability to self-assemble into well-ordered nanometric size structures. In this work we investigated the influence of interfacial energy and BCP film thickness (hBCP) on the dewetting mechanisms and the self-assembly properties of thin films of asymmetric PS-b-PMMA BCP. In particular, the control over γ was achieved by grafting to the substrate a random copolymer layer with thickness between 2 and 7 nm, while the morphology of the dewetted structures was studied by tuning hBCP. For hBCP < 10 nm the BCP films dewet generating holes, bicontinuous structures or circular droplets. In addition, chemically patterned substrates obtained by laser writer lithography were used direct the ordering of the dewetted droplets, providing a simple route to the fabrication of hierarchically self-assembled nanostructures. The formation of highly ordered self-assembled features inside the dewetted film, organized in single and defectless grains propagating for several micrometers was observed. Respect to other surface-directed dewetting approaches, the present procedure guarantees a significantly higher level of ordering of the nanometric cylinders while maintaining their perpendicular orientation to the substrate.

Resume : New emerging lithography approaches are promising technologies, among which Directed Self-Assembly of block copolymer, also called “DSA”. In order to favour block copolymer orientation with a long range order, one of the widest used technics is the chemo-epitaxy. It orientates the block copolymer thanks to a chemical contrast of predefined periodic patterns based on a difference of the surface energy. Among all the different chemo epitaxy processes developed (Line [1], SMART [2], Lift-Off [3], COOL [4] ) the selective grafting of the guiding material with regards to the background layer remains a key challenge: it has to be fully effective after grafting without modifying the background layer, especially in terms of the surface energy. This paper investigates different materials families for a chemo-epitaxy application, that is to say cross-linked and grafting underlayers of different chemical properties (composition, molecular weight…), and the effect of a grafting material at their surface. In order to illustrate the results obtained, a proof of concept on a new innovative chemo-epitaxy process using spacer patterning lithography is introduced. The latter process has the advantage to integrate high chi block copolymers with the conventional lithography targeting sub-20nm pitch line/space patterns. [1] C.-C. Liu et al., “Fabrication of Lithographically Defined Chemically Patterned Polymer Brushes and Mats,” Macromolecules, vol. 44, no. 7, pp. 1876–1885, Apr. 2011. [2] J. Kim et al., “Toward high-performance quality meeting IC device manufacturing requirements with AZ SMART DSA process,” 2015, p. 94230R. [3] J. Y. Cheng et al., “Simple and Versatile Methods To Integrate Directed Self-Assembly with Optical Lithography Using a Polarity-Switched Photoresist,” ACS Nano, vol. 4, no. 8, pp. 4815–4823, Aug. 2010. [4] Y. Kasahara et al., “Characterization of half-pitch 15-nm metal wire circuit fabricated by directed self-assembly of polystyrene-block-poly(methyl methacrylate),” Microelectron. Eng., vol. 159, pp. 21–26, Jun. 2016.

Resume : Challenges for sub-10 nm patterning can be addressed by the direct self-assembling of block copolymers (BCP) in combination with a volume selective sequential infiltration synthesis (SIS). Selective growth of inorganic materials in one of the BCP domains can be used for enhancing polymer etch resistance for pattern transfer to the substrate. We investigated the infiltration of trimethylaluminum (TMA) in combination with H2O for the synthesis of Al2O3 into polymethylmethacrylate (PMMA) and polysterene (PS) films, being the building blocks of PS-b-PMMA BCPs, by means of dynamic in situ spectroscopic ellipsometry. In particular, swelling of the polymer films is probed during SIS cycle, and observed to be affected by SIS process parameters as TMA dosing and purging, but also by the history of the polymer for SIS cycles following the first one. Investigating the swelling of fresh PMMA films during TMA infiltration at 90°C, the diffusion coefficient of TMA in PMMA has been extracted and shown to be dependent on polymer molecular weight but not on the film thickness, indicating a Fickian behavior for diffusion of TMA in PMMA films. Differently, PS films swelling is almost negligible during TMA exposure and after the first 3 complete SIS cycles reflecting the inertness of PS to TMA molecules, while for many SIS cycle process, swelling increases and some Al2O3 growth is observed also in PS films, attributed to defects in the film, leading to loss of infiltration selectivity.

Resume : Block copolymers (BCPs) which are able to spontaneously self-assemble into discrete nanostructures have been proposed as a promising candidate for next generation nanopatterning technologies, namely directed self-assembly (DSA), enabling high-resolution patterning in thin films over large areas at low cost. Silicon-containing BCPs have garnered significant attention for achieving sub-10 nm feature sizes required for next generation lithography techniques. In addition, the high etching contrast between the hydrocarbon polymer block and the silicon-containing polymer block allows for facile pattern transfers to substrates upon oxygen plasma etching. However, the hydrophobicity and lower surface energy of the silicon-containing polymer block prevents the lamellar structure from forming with a perpendicular orientation that is vital for line patterning lithography. In this study, a series of perpendicular lamellae-forming high-chi block copolymers have been developed based on the bottom-up concept of a simple yet effective material that adjusts the chemical properties and molecular composition of the material. One example is newly designed and successfully synthesized silicon- and fluorine-containing high-chi BCP, poly(polyhedral oligomeric silsesquioxane-block-2,2,2-trifluoroethyl methacrylate) (PMAPOSS-b-PTFEMA) whose surface free energies of the constituents are perfectly balanced. The perpendicularly oriented BCP thin films were fabricated using simple spin-coating and thermal annealing processes under ambient conditions. The thin films displayed a minimum domain size of L0 = 11 nm. The formation of microphase-separated nanostructures were observed in in-situ Atomic Force Microscopy.

Resume : The International Technology Roadmap for Semiconductors ITRS considers the directed self-assembly (DSA) of block copolymers as one of the four next generation lithography techniques. Guiding patterns are required to induce long-range order in a thin film of block copolymers and to enable the use of block copolymers for lithography applications. Extreme ultraviolet interference lithography (EUV-IL) is used to manufacture topographical guiding patterns to direct the self-assembly of block copolymers. High-accuracy silicon oxide-like patterns with trenches ranging from 68 nm to 117 nm width are fabricated by exposing a hydrogen silsesquioxane (HSQ) resist layer using EUV-IL. We investigate how the accuracy, the low line width roughness and the low line edge roughness of the resulting patters allow to achieve DSA line/space patterns of a PS-b-PMMA (polystyrene-block-poly methyl methacrylate) block copolymer of 11 nm half-pitch with low defectivity. We conduct an in-depth study of the dependence of the DSA pattern morphology on the trench width and on how the neutral brush covers the guiding pattern. We identify the relation between trench width and the emergence of defects with nanometer precision. Based on these studies, we develop a model that extends available free energy models by adding the effect of a non-zero defect density, which allows us to predict the patterning process window to achieve a low level of defects.

Resume : The capability to control dopant incorporation within semiconductor materials with atomic accuracy represents the major challenge toward further scaling down of electronic devices. In this work, we propose a new bottom-up technology for precisely controlling the amount of dopant atoms tethered on silicon substrates based on the self-assembly of dopant-containing end-functional polymers. Monodisperse polystyrene and poly(methyl methacrylate) polymers with different molar masses, end-terminated with a phosphate containing moiety were prepared and grafted to an activated silica surface by thermal annealing (T=250°C). Subsequent removal of the organic layer by oxygen plasma and capping with SiO2 leads to the formation of a P δ-layer embedded in a SiO2 matrix and spatially separated from the Si substrate. Taking advantage of the self-limiting nature of the “grafting to” process, precise control of the areal dose of dopants in the δ-layer from 3×10^13 to 8×10^13 atoms/cm^2 can be achieved by properly tuning the polymer molar mass. Moreover, repeated cycles of polymer grafting followed by plasma hashing led to a further stepwise increase in the dose of P atoms. P injection in the silicon substrate was promoted and precisely controlled by high temperature thermal treatments. Finally, the combination of this approach with block copolymer lithography is explored to control at the nanoscale the lateral confinement of the dopant atoms.

Resume : The proliferation of advanced portable information and communication technology places substantial demands on current patterning techniques to satisfy future device and data needs. In this context, research on integrating high-performing nanomaterials such as 2D transition metal dichalcogenides (TMDs) with emerging bottom-up patterning methods is critical. In this talk, we will outline our approach for positioning exfoliated layered materials, e.g. MoS2, In2Te3, using PS-b-PxVP (x = 2 or 4) block copolymer templates with sub-10 nm resolution. Block copolymers offer a flexible, low-cost strategy to define nanotemplates over large surface areas1,2 and is a prime candidate for next-generation lithography. Our work assesses the precursor parameters including solution concentration, exposure period, and post-deposition treatment in forming well-defined nanofeatures. Directed self-assembly of few-layer TMDs is demonstrated revealing high-density coverage. We will also detail a more conventional deposition route using metal salt precursors3 to form GaTe, NbSe, and InTe binary nanowires. In summary, we present and discuss an innovative strategy to place inorganic nanomaterials at specific BCP sites that may find use to advance future information technologies owing to superior 2D TMD material properties. 1. M. A. Morris, Microelectronic Engineering 132, 207-217 (2015). 2. R. Lundy, S. P. Flynn, C. Cummins, S. M. Kelleher, M. N. Collins, E. Dalton, S. Daniels, M. A. Morris and R. Enright, Physical Chemistry Chemical Physics 19 (4), 2805-2815 (2017). 3. C. Cummins, T. Ghoshal, J. D. Holmes and M. A. Morris, Advanced Materials 28 (27), 5586-5618 (2016).

Resume : Poly(ethylene oxide) (PEO) is well known for its excellent protein-repelling property. However, it remains challenging to fabricate membrane with uniform and robust coverage of PEO chains in a simple and efficient way. In this work, we fabricated composite membranes with mesoporous amphiphilic block copolymer, polystyrene-block-poly(ethylene oxide) (PS-b-PEO, abbreviated as SEO) as the size-selective layer and a macroporous membrane as the supporting layer. SEO solutions were coated on water-filled substrate membranes, and dried to obtain a dense SEO layer tightly coated on the substrate membranes. The SEO-coated substrates were then immersed in hot ethanol followed by air drying to cativate the SEO layers. Mesopores were generated in the SEO layer by a selective swelling-induced pore-formation process. The pore size in the SEO layer can be tuned simply by varying the swelling durations, which led to membranes with adjustable separation properties. Furthermore, the hydrophilic PEO blocks were selectively enriched on the pore walls in the SEO layer during the swelling process, rendering an intrinsically active surface on the membrane and making the composite membranes possess a superior antifouling property. The antifouling property of the composite membrane was investigated with bovine serum albumin (BSA) solution as the model foulant. The BSA flux decline rate of the membrane was as low as 4.1%, and the water flux recover ratio was up to 100% after multiple cycles of BSA filtration.

Resume : N-doped graphitic carbon submicrorods were synthesized by thermal transformation of zeolite imidazolate framework-8 (ZIF-8) submicrorods. The morphology and pore structure of the carbon submicrorods were readily tuned by using tri-block co-polymer Pluronic F127 as a soft template. The as-synthesized carbon submicrorods with morphology preserved derived from submicrorods of ZIF-8 comprise both micro- and meso-pores with high surface areas of over 1000 m2 g-1. In addition, nitrogen-doping in the carbon submicrorods was achieved as was confirmed by XPS and EELS. The hybrid carbon submicrorods provide pseudo-capacitance that promotes electrochemical performance, rendering a high specific capacitance of up to 297 F g-1 at a current density of 0.5 A g-1 in a three-electrode system. A long cycle life was also demonstrated by recording a 90.26% preservation of capacitance after 104 cycles of charge-discharge at a current density of 4.0 A g-1. Furthermore, a symmetrical supercapacitor is fabricated by employing the carbon submicrorods, which shows good electrochemical performance with respect to energy, power and cycle life.

Resume : Nanotubes have attracted considerable attention due to their unique one-dimensional hollow structure, which are more efficient to capture, store and release nanomaterials. In this work, well-defined nanotubular micelles with uniform diameter and high aspect ratio were successfully prepared via self-assembly of a poly(styrene-b-4-vinyl pyridine-b-ethylene oxide) triblock terpolymer in binary solvent mixtures with assistance of solution thermal annealing. It was found that nanotubular micelles are formed by simultaneous unidirectional growth and solid-to-hollow transition with large solid cylindrical aggregates as precursors, which is distinct from conventional formation pathway. Moreover, the thermal annealing and cooling procedure allows for preparation of a series of novel kinetically frozen morphologies. By virtue of the radially compartmentalized structure, gold nanoparticles are able to be selectively incorporated into different micellar domains of the nanotubes, holding promise for fabrication of nanosensors and bioreactors. Acknowledgments: This work was supported by National Natural Science Foundation of China (Grant 21674112, 21474108).

Resume : The self-assembly of large molecular weight block copolymers into spatially oriented nanodomains has opened up a range of new possibilities in the manufacture of sub-wavelength optical nanostructures, such as Si nanopillars for anti-reflective coatings (1). Devices have been synthesized thus far using high molecular weight PS-b-P2VP block copolymer on silicon substrates. This work expands this project, examining the formation of these domains on other substrate types - such as glass, Gorilla Glass (TM) and sapphire glass - and characterising feature sizes and optical performance. The synthesis process for nanostructures on amorphous substrates (e.g. glass) is more complex, as the interfacial chemistry varies greatly to Si. This requires the optimisation of parameters including polymer concentration, phase separation process, etch mask deposition, and etch recipes. Additionally, the ability of other large molecular weight BCPs to phase separate, specifically PS-b-PEO, is assessed, with the intention of gaining further insight into the mechanics of their phase-separation. PS-b-PEO has shown strong potential for nanostructure fabrication, however the domain sizes have remained below that required for optical applications in the visible spectrum (2). The fabrication parameters mentioned above are also optimised for large molecular weight PS-b-PEO, and the relative feature spacing, film coverage, diameters and nanostructure characteristics for both block copolymers are extensively compared. 1. Mokarian, P.; Senthamaraikannan, R.; Glynn, C.; Collins, T.; Cummins, C.; et al. Nano Letters 2017, 17, 2973-2978. 2. Cummins, C.; Ghoshal, T.; Holmes, J.; Morris, M.; Advanced Materials, 2016, 28, 5586-5618.

Resume : Nanophotonics explores the possibility of modulating light propagation with very small amount of matter using nanoscale phenomena. The occurrence of plasmons at metal/dielectrics interfaces is one of the very relevant phenomena, which has encouraged, in the recent years, active research efforts towards the fabrication of nanostructured metal-dielectric materials and surfaces. This presentation will show how we used self-assembling block copolymers for the “bottom-up” formulation of original anisotropic plasmonic nanocomposites. In particular, we produce and study periodic cylindrical and lamellar assemblies composed of nanometric domains of pure polymer and domains of composite of polymer loaded with a high density of gold nanoparticles. The spectral variation of their anisotropic effective dielectric permittivity is determined by spectroscopic ellipsometry using appropriate effective medium models. For large gold loading, the lamellar stacks present a frequency domain, in which the ordinary and extraordinary components of the dielectric function are of opposite signs. This peculiar property, called “hyperbolic”, allows for the propagation of large magnitude wavevectors, carrying details finer than half the wavelength, otherwise corresponding to evanescent non-propagative waves in a usual dielectric.

Resume : Arrays of nanopores have widely been used as templates for high-surface area applications, like high-density storage media, catalysis, and ultrafiltration (UF) membranes. Block copolymers (BCPs) can be used as nanopore-generating materials to produce templates and scaffolds for the fabrication of nanostructured materials, since one component can be selectively removed by chemical treatment. Especially, for UF membrane applications, the self-assembly of BCP present an attractive approach for highly size-selective, permeable membranes due to their narrow size distributions and high pore densities. Here, nanoporous ultrafiltration membranes were obtained by the self-assembly of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) where, cylindrical microdomains were oriented normal to the substrate and air interfaces, and in the interior of the films, the microdomains were randomly oriented. Continuous nanopores that penetrated through the film were readily produced by a simple preferential swelling of the PMMA microdomains. The confined swelling and rapid contraction of PMMA microdomains generated well-defined uniform pores with diameters to 17.5 nm. The size selectivity and rejection of Au nanoparticles (NPs) for these ultrafiltration (UF) membranes were demonstrated, suggesting an efficient route to tunable, noncomponent-degradative UF membranes.

Resume : BCPs self-assemble within curved templates has been a question of long-standing interest. BCPs or BCP blends with lamellar or cylindrical microdomains have been templated within 3D spherical or cylindrical pores, leading to a range of microdomain geometries including concentric cylinders or vesicles, stacked tori or disks, helices, or pea-pod structures. Helical structures have also been reported in chiral block copolymers, triblock terpolymers, terpolymer micelles, and BCP globules. There have been reports of concentric ring formation in BCP films confined in circular templates, and from half-onion structures formed in hemispheres, which have applications in the fabrication of sensors based on surface-enhanced Raman scattering. BCPs assembling on a spherical surface are predicted to form spiral structures, and we reported a spiral made from a cylindrical microdomain formed within a hexagonal template. However, there has been little work on the control of the chirality of helical structures or spirals using BCP self-assembly. In this study, we demonstrate that confinement of a cylindrical-morphology BCP in a shallow circular pit can produce either concentric rings or a spiral. A spiral is promoted by the presence of a notch-shaped feature within the template which controls the spiral chirality. The length of the spiral increases with the diameter of the template. Design of the notch geometry enabled double spirals to be formed. A notch of width ≈ L0 promotes spirals even for commensurate pit sizes indicating the critical importance of the inner shape of the template. For smaller notches, spirals formed for incommensurate template diameters and rings for commensurate template diameters. Analogous to using a notch to initiate a spiral in a circular pit, our approach could be extended to guide the chirality of 3D helical spirals formed in cylindrical confinements with a helical ramp template. 2D and 3D chiral nanostructures have a range of potential applications in the sensing of molecular chirality or as chiral metameterials. Chiral nanostructures have so far only been fabricated by top-down lithography or self-assembly of nanoparticles interacted with chiral molecules, and this study provides an effective alternative route to fabricate chiral nanostructures via directed self-assembly.

Resume : Novel ion-conducting polymers with highly sulfonated poly(arylene sulfide sulfone) side block and hydrophobic poly(arylene ether sulfone) backbone have been prepared from the polymer reaction of the hydrophobic backbone containing hydroxyl functional groups with the hydrophilic oligomer with a halogen reactive site at one side of the end group. The graft polymers with different variation of ion exchange capacity (IEC) were obtained by controlling the molecular weights of the side block and the content of hydroxyl groups of the backbone. The structure and the molecular weight of the side chain and the backbone were confirmed by 1H-NMR analysis. The graft polymer membrane exhibited an improved dimensional stability (volume change ~60%) and high proton conductivity (> 30 mS/cm) at a reduced humidity condition (80 degree Celsius, 50%RH).

Resume : In thin films of block polymers composed of more than two blocks, the accurate selective identification of each domain in the film is of prime importance for a clear assignation of the morphologies. We will focus this presentation on the selective identification of poly(isoprene) (PI), poly(vinylpyridine) (PVP), and poly(styrene) (PS) domains in various systems of PI-b-PS-b-PVP (including blends). For this purpose, we have combined AFM, TEM and GISAXS analyses coupled to specific modifications, in order to specifically identify each phases. AFM characterization was performed thanks to a selective elimination of PI by ozonolysis and selective revelation of P2VP by swelling in ethanol. For TEM, thin films were removed from the Si/SiO2 substrate by floatation at the surface of a NaOH solution, carefully collected onto a grid and selectively stained by heavy metals. For GISAXS characterization, we developed an unusual methodology to overcome the weak electronic density contrast in the sample, based on the selective staining of P2VP by I2 or elimination of PI by ozonolysis. The combination of these methods will be exemplified on selected morphologies with gradual complexities.

Resume : Generating the hierarchical nanostructures from various polymers to self-assembled aggregates and discovering the assembling process are important not only to discover the new characteristics of functional nanomaterials but also to improve their physical and chemical properties. Herein, we have fabricated the unique nanostructures including pupa-like and caterpillar-like structures formed by emulsification-induced self-assembly of biocompatible, semicrystalline poly(ε-caprolactone)-block-poly(ethylene oxide) (PCL-b-PEO). The growth mechanism from pupa-like to caterpillar-like structures was confirmed by transmission electron microscopy. It is observed that pupa-like structure was kinetically trapped morphology before being caterpillar-like structure. The caterpillar-like structure with microscale length was generated by end-to-end coupling of short elemental nanostructures to avoid the exposed PCL segment and water. The crystallinity of PCL increased as a function of molecular weight of PCL block, resulting in a driving force for the formation of orthogonal nanostructures. This sophisticated approach would provide a novel nanoplatform for applying the semicrystalline polymer.

Resume : Polycarbosilane-based block copolymers have been designed and evaluated for directed self-assembly applications thanks to their propensity to form well-defined structures of high resolution[1,2]. Following these works, we have studied these materials (both poly(1,1-dimethyl silacyclobutane)?b- poly(styrene) (PDMSB-b-PS) and poly(1,1-dimethyl silacyclobutane)?b-poly(methyl methacrylate) (PDMSB-b-PMMA)) as a platform of morphologies for potential nanotechnological applications. Using industrially-friendly processes, lamellar, cylindrical, spherical and gyroid phases were obtained with sub-20 critical dimension in thin films. We highlight the parameters allowing the control of both the self-assembly and the structure orientation in thin films through the influence of self-assembly kinetics, surface energy and film thickness. Additionally, we show how the commensurability between the gyroid lattice and the film thickness leads to the different plans of the gyroid phase including the (211) G one with a 18.2 nm pitch[3]. 1. Aissou, K.; Mumtaz, M.; Fleury, G.; Portale, G.; Navarro, C.; Cloutet, E.; Brochon, C.; et al. Adv. Mater. 2015, 27, 261?265. 2. Fleury, G.; Aissou, K.; Mumtaz, M.; Chevalier, X.; Nicolet, C.; Navarro, C.; Fernandez-Regulez, M; et al. Proc. SPIE 9425, Advances in Patterning Materials and Processes XXXII. 2015; 94250Z. 3. Aissou, K.; Mumtaz, M.; Portale, G.; Brochon, C.; Cloutet, E.; Fleury, G.; Hadziioannou, G. Small 2017, 13, 1603777.

Resume : Self-assembled vertical-aligned lamellar DiBCP patterns, however, enable a straightforward approach for pattern transfer into the functional material by standard technologies for nanopatterned functional surfaces. The current work focuses on the short-time high-temperature annealing of DiBCPs forming self-assembled lamellar patterns. There are at least two ways to reduce the time for pattern formation: solvent annealing and high temperature annealing. The short time high temperature annealing was investigated in the temperature range from 260 to 300° C and for annealing times between 3 s to 15 min. Within this experimental range a clear phase separation, but with different fidelity, for all temperature- time combinations was observed. SEM images show well-ordered DiBCP films with perpendicular oriented lamellar structures. The best ordering of the lamellar structures were observed at an annealing temperature of 280 °C; higher temperature may cause degradation effects. At a fixed annealing temperature of 280 °C a time series down to 3 s shows gradual reduction of the long range order. Less perfect lamellar ordering is observed for all annealing times.

Resume : In the present work, we used the design of experiment (DOE) to investigate the effect of the process parameters on the self-assembly (S-A) of cylinder forming of poly (styrene-b-Methyl-Methacrylate) (PS-b-PMMA), such as the annealing temperature (T), time (t) and the film thickness (ft). Focusing on the holes defect ratio and the grain boundaries. The Fingerprint Contact Roughness (FCR) metrology was used to analyze the SEM images, collected at each process step. Treatment of experimental data was performed by using Plackett-Burman design. The Pareto chart of effects shows that the most important factor in the block copolymer S-A process is the annealing time (8.9). The annealing temperature has also a positive effect but at lower level (4.9). Otherwise, (ft) has the least effect on the response (2.5). The man effects plot indicates that for both (t and T) the level of influence is higher. This means that, longer annealing time lead to better rearrangement of cylinders into hexagonal phase. However the influence level of (ft) is quite limited in this study. The ANOVA results confirm that all the factors exhibit p-values less than (0.05) indicating that they are significantly different from zero, at 93.16% confident level when the parameters change from level (-1) to level (1). Finally, the DOE allows a mathematical representation of the responses according to all factors. The regression is represented by polynomial equations corresponding to the coded and uncoded parameters.

Resume : We propose a direct and fully colloidal route for the preparation of aqueous suspensions of highly stable and poorly aggregated layered double hydroxide (LDH) nanoparticles using hybrid polyion complex micelles (HPIC). HPIC micelles are obtained by complexation between metallic cations and the complexing block of asymmetric poly(acrylic acid)-b-poly(acrylamide) a or poly(vinylphosphonic acid)-b-poly(acrylamide) b (PAA-b-PAm or PVPA-b-PAm) double hydrophilic block copolymers (DHBC). We showed that the LDH colloids are obtained in two steps from mixed solutions of M2+ and Al3+ cations, and DHBC: i) first formation of HPIC micelles constituted almost entirely of Al3+ due to the preferential complexation of the trivalent cations, while the divalent cations remain free in solution; ii) transformation of the DHBC/Al3+ HPIC micelles into DHBC/aluminum hydroxide colloids upon hydroxylation with NaOH. Then the partial dissolution of DHBC/aluminum hydroxide and the progressive incorporation of M2+ ions leads to the precipitation of the LDH phase in the colloid. The formation mechanism depends on the M2+ speciation, e. g. the Cu2+/Al3+ couple is hydroxylated at lower pH than the Mg2+/Al3+ couple and the properties of HPIC micelles depend on the nature of the DHBC complexing block. Indeed Mg and Al yields in the HPIC micelles are higher upon complexation with PVPA than with PAA block of the DHBC. The complexation degree (R) (R = AA or VPA/(Mg + Al)) is a major parameter controlling the colloidal stability of the LDH suspension. It also controlled the hydrodynamic diameter of the DHBC/LDH colloids,, which decreased from 530 nm down to 60 nm, and the growth of the LDH phase with a mean size of the individual particles in the range 50-20 nm when R increased. XRD and TEM results show that the LDH particles are preferentially intercalated by the negatively charged PAA block of the DHBC rather than by chloride anions of the initial salts when R increases. Moreover, the stability of the colloids depends on the asymmetry degree between the anionic block and the acrylamide block and also on the architecture of the DHBC. This colloidal route appears promising for the developpement of biofunctional hybrid nanovectors and for basic catalysis applications. a. Géraldine Layrac, Mathias Destarac, Corine Gérardin and Didier Tichit, Highly Stable Layered Double Hydroxide Colloids: A Direct Aqueous Synthesis Route from Hybrid Polyion Complex Micelles., Langmuir 2014, 30, 9663. b. Géraldine Layrac, Corine Gérardin, Didier Tichit, Simon Harrisson and Mathias Destarac ,Hybrid polyion complex micelles from poly(vinylphosphonic acid)-based double hydrophilic block copolymers and divalent transition metal ions., Polymer, 2015, 72, 292-300

Resume : Directed self-assembly (DSA) of block copolymers (BCPs) is a promising alternative to advance in miniaturization for the semiconductor industry due to its high resolution and process simplification compared with other approaches. In particular, line and space using lamellar BCPs can be used for the definition of nanowire-based devices. However, when BCP materials of very low dimension are used, a high-resolution lithography (such as e-beam or extreme UV) is required for the definition of the guiding pattern, which limits the opportunities for its applicability. In this communication, we propose the fabrication of nanowire-based devices by the combination of conventional optical lithography and DSA of BCPs. The guiding patterns for DSA and contacting lines and pads are defined in a single step by optical lithography. Then, a lamellar PS-b-PMMA block copolymer is aligned perpendicularly to the walls of the topographical guiding patterns. Finally, BCP features are transformed into functional nanowires using two different approaches. In the first approach, PMMA block is selectively removed and PS block is used as an etch mask for the transfer into the silicon under-layer. In the second approach, an organic/inorganic nanocomposite is formed through the selective incorporation of a metal oxide into the PMMA block by means of sequential infiltration synthesis. After the removal of PS, free-standing metal-oxide nanowires are formed.

Resume : The aim of this work is to obtain block copolymer brushes by a combined grafting to and grafting from approach. A new strategy was employed in which the second block re-growths starting from a homopolymer brush layer obtained by the grafting to approach. In detail, several polystyrene samples with molecular weight ranging from 2.5 to 13 kg/mol and narrow molar mass distribution were synthesized by nitroxide-mediated-polymerization (NMP) using N-tert-butyl-N-[1-diethylphosphono(2,2-dimetylpropyl)] nitroxide (SG1/DEPN) as polymerization controller. Such polymers were grafted onto a silicon oxide surface by Rapid Thermal Processing (RTP) at different temperatures. As thermolabile groups deriving from the terminal SG1 are located to the silica surface, they could allow a synthesis of block copolymers via the grafting from approach by surface initiated NMP. Preliminary experiments of regrowth from surface were conducted with deuterated styrene and 4-vinylpyridine. The corresponding block copolymer brushes were obtained and their characteristics discussed as a function of the relevant reaction parameter.

Resume : Boron-terminated polystyrene with molecular weight ranging from 1800 to 18000 g/mol were synthesized for p-type doping of silicon substrates through spin-on technique. Several polymers were prepared using the ARGET-ATRP method using tert-butyl 2-bromoisobutyrate as initiator, changing monomer to initiator ratio and the reaction time. After polymerization, polystyrene samples were functionalized in order to end-cap the chains with a boron-containing molecule. Various polymers were characterized by SEC, to estimate Mn, Mw and PDI, by NMR (1H and 13C) in order to investigate the correct structure of the molecules and by TGA-GC-MS for knowing the thermal behavior and the amount of boron into the polymers.

Resume : Block copolymer (BCP) lithography for self-assembled thin film nanopatterning is known to strongly depend on the interactions between the polymer species of the BCP and the substrate surface. The system of PS-b-PMMA on SiO2 surfaces is investigated by many groups, as one of the most promising applications of BCP lithography lies in semiconductor technology. A silicon oxide surface can, however, only be patterned by BCP lithography if the surface is neutralized, e.g. by a RCP brush, which then allows for pattern orientation control. For many other applications of BCP lithography materials other than SiO2 are of interest. In particular, nanopatterned TiO2 on Ti-6Al-4V alloys can be exploited in biomedicine. Here, we present BCP lithography on different surfaces: smooth and rough Au and Pt are investigated as well as (3D-printed) Ti-6Al-4V (alpha and beta) alloy surfaces. It will be shown that - depending on the polar fraction of surface energy - active surface neutralization is not necessary to obtain ordered arrays of nanopores. An additional influence of surface roughness is analyzed in detail based on automated evaluation of nanopore diameters and shape. The morphology of the BCP PS-b-PMMA on the different material surfaces is investigated by top view SEM, SEM of the BCP thin film backside after its release from the surface and cross-sectional (analytical) TEM.

Resume : The measurement of thermal transport on the nanoscale is challenging, and of great importance for many fields of research, such as device and energy technology. Understanding the thermal properties of block copolymers is an inherently interesting question, as block copolymers are used as templates for nano-lithographical processes. Moreover, their controlled nanoscale feature sizes provide a good metrology standard for testing the resolution potential of an imaging method. We present a probe-based thermal imaging technique capable of providing sub-10 nm resolution. We demonstrate this resolution by resolving microphase separated PS-b-PMMA block copolymers with molecular weights ranging from 42 kg/mol to 79 kg/mol, which result in half-pitch widths between 11 nm and 19 nm. At each pixel location, the jump in and out of contact is monitored by recording an entire approach-retract cycle. Electrostatic actuation is used and provides pixel times of ~5 ms and therefore relatively fast scanning speeds. The excellent lateral resolution of the presented technique is enabled by the use of resistively heated tips with apex radii of < 5 nm. We are capable of detecting a heat transport into the sample surface of a few μW. The difference in detected heat transfer between the PS domain and the PMMA domain is in the range of 25 % and therefore in-line with literature values. The presented technique represents a novel way to image complex mixed polymeric systems with high resolution and a good material contrast based on the differences in the material’s thermal conductivity.

Resume : In block copolymer lithography, lithographically defined guiding patterns can be used to induce long-range order in a thin film of block copolymers. We study the directed self-assembly of an 11 nm half-pitch PS-b-PMMA block copolymer in topographical guiding patterns that consist of arrays of silicon oxide lines of sub-10 nm width. The lines have been fabricated by electron-beam lithography using hydrogen silsesquioxane (HSQ) as the resist layer. Detailed analysis of the structures by atomic force microscopy (AFM), scanning electron microscopy (SEM) and grazing incidence small angle X-ray scattering (GISAXS) reveals a self-assembly morphology with long-range order. Unlike it is usually the case in graphoepitaxy, the block copolymer surrounds the guiding pattern features, e.g. block copolymers are deposited not only between the features, but also on top of them. We discuss the implications of this self-assembly mode for a successful guiding pattern design and compare the resulting guiding pattern design rules with those known for topographic guiding patterns with lateral dimensions significantly above 10 nm.

Resume : Selective growth of inorganic materials in one of the domains of block?copolymer (BCP) thin films can be used for enhancing polymer etch resistance for pattern transfer to the substrate. Selective sequential infiltration synthesis (SIS) of self-assembled PS-b-PMMA thin films has been proposed to convert PMMA nanostructures in inorganic Al2O3 using trimethylaluminum (TMA) in combination with H2O as precursors. Perpendicular orientation of the nanodomains with respect to the substrate in PS-b-PMMA films requires the introduction of a grafted random copolymer (RCP) film with tailored composition to neutralize the preferential wettability of PS with respect to the PMMA on the SiO2 surface. However, the RCP film contains MMA monomeric units and consequently is infiltrated during SIS process, with the formation of an Al2O3 continuous layer at the interface between the BCP film and the substrate. A breakthrough process with a specific dry etching chemistry is required to remove this layer and expose the Si substrate. Therefore, detailed knowledge of the infiltration process in this RCP layer is mandatory for the effective exploitation of the infiltrated Al2O3 nanostructures as hard mask for lithographic applications. In this work, we present a detailed investigation of the infiltration of Al2O3 in P(S-r-MMA) thin films with thickness ranging from 8 to 100 nm and variable styrene content ranging from 0 to 100% by means of in situ and ex-situ analysis.

Resume : Block copolymer (BCP) self-assembly (SA) leading to thin films with periodic ordered nanostructures featuring different morphologies has been exploited in a number of technological applications. Among them, polydimethylsiloxane (PDMS) containing BCPs have attracted a great interest because of the possibility to generate high-resolution nanostructures with dimension below 10 nm. The SA of the PDMS-containing BCPs in periodic nanostructures can be achieved by different approaches, but thermal annealing would be highly desirable for easy integration in a product process flow. In this work, we report a systematic study on the SA kinetic and morphological evolution of a cylinder-forming polystyrene-block-poly(dimethylsiloxane-random-vinylmethylsiloxane) PS-b-P(DMS-r-VMS) thin film (Mn = 22 kg/mol). BCP films were deposited on PS or PMMA brushes by spin casting from various solvents. A simple thermal treatment at high temperature was used to promote the formation of PDMS cylinders embedded in a PS matrix and parallel oriented with respect to the substrate. Grain coarsening kinetic of the system was studied considering the time evolution of correlation lenght (?). In most of the cases a power law dependence of ? ~ t^? with ? = 0.21 was obtained irrespective of the combination of brush layer and solvent. For some specific combinations, conversion from parallel cylinders to dots was observed highlighting the important role of residual solvent on the SA process.

Resume : Mesoporous inorganic thin films represent a field of research with growing importance in applications such as sensing, optics, photovoltaic cells and protective coatings. Block copolymers (BCPs) are ideal candidates in the structure-directed assembly of mesoporous inorganic materials. When combined with well-established inorganic sol-gel chemistry methods, BCPs enable solution-processing of mesoporous inorganic architectures with controlled porosity, pore sizes and pore arrangement for a broad materials library. One aspect that hampers the application of porous coatings is their relatively poor mechanical stability and scratch resistance. During this work, we investigate factors that influence the mechanical properties of block copolymer-derived mesoporous aluminosilicate network and identify material strategies to promote their long-term stability. Key parameters such as the porosity, pore size, aluminosilicate content and sol additives are systematically varied and the resulting coatings characterised by a combination of pencil scratch tests, profilometry, spectroscopic ellipsometry, ellipsometric porosimetry and atomic force microscopy.