Novel Mechanism-Based Descriptors for Extreme Ultraviolet-Induced Photoacid Generation: Key Factors Affecting Extreme Ultraviolet Sensitivity.

Predicting photolithography performance in silico for a given materials combination is essential for developing better patterning processes. However, it is still an extremely daunting task because of the entangled chemistry with multiple reactions among many material components. Herein, we investigated the EUV-induced photochemical reaction mechanism of a model photoacid generator (PAG), triphenylsulfonium cation, using atomiC-Scale materials modeling to elucidate that the acid generation yield strongly depends on two main factors: the lowest unoccupied molecular orbital (LUMO) of PAG cation associated with the electron-trap efficiency 'before C-S bond dissociation' and the overall oxidation energy change of rearranged PAG associated with the proton-generation efficiency 'after C-S bond dissociation'. Furthermore, by considering stepwise reactions accordingly, we developed a two-parameter-based prediction model predicting the exposure dose of the resist, which outperformed the traditional LUMO-based prediction model. Our model suggests that one should not focus only on the LUMO energies but also on the energy change during the rearrangement process of the activated triphenylsulfonium (TPS) species. We also believe that the model is well suited for computational materials screening and/or inverse design of novel PAG materials with high lithographic performances.

Surface-Conformal Triboelectric Nanopores via Supramolecular Ternary Polymer Assembly.

A triboelectric nanogenerator (TENG) is of tremendous interest owing to its high energy efficiency with a simple device architecture and applicability to various materials. Most previous topological surface modifications introduced for further improving the performance of a TENG are detrimental because they require expensive and/or harsh (e.g., high temperature and acidity) postetching processes, which limit the material choice and design of its components. Herein, we demonstrate an one-step route for developing rapid wet-processable surface-conformal triboelectric nanoporous films (STENFs). Our method is based on a simple supramolecular assembly of a ternary polymer blend suitable for various conventional solution processes such as spin-, bar-, spray-, and dip-coating. The one-step wet process of a ternary solution produces thin large-area films in which self-assembled, ordered nanopores of approximately 33 nm in diameter are developed even without an additional etching process. The study reveals that the small amount of amine-terminated poly(ethylene oxide) added to the binary blend of sulfonic-acid-terminated poly(styrene) and poly(2-vinylpyridine) efficiently activates the formation of spontaneous nanopores as a pore-generating agent. Our STENF significantly enhances the open-circuit voltage up to 1.5 times higher than that of a planar one, leading to an improved power density of approximately 77 µW/cm2. The suitability for diverse conventional coating processes offers a convenient approach for fabricating high-performance STENFs not only on flat substrates such as metals, polymers, and oxides but also on topological ones including wrinkled, roughened surfaces, textile fibers, natural leaves, and fabrics over a large area.

Surface functionalized nanostructures via position registered supramolecular polymer assembly.

Versatile control of cylindrical nanostructures formed by supramolecular assembly of end-functionalized polymer blends is demonstrated not only in their orientation over large areas but also in their surface chemical functionalities. Two binary blends consisting of supramolecular analogues of diblock copolymers with complementary end-sulfonated and aminated groups are investigated, viz., mono-end-functionalized polymers of (i) one-end-sulfonated polystyrene (SPS) and one-end-aminated poly(butadiene) (APBD) and (ii) one end-aminated polystyrene (APS) and one end-sulfonated poly(butadiene) (SPBD). The orientation of the cylinders with respect to the substrate surface depends on the solvent annealing time; either hexagonally ordered vertical cylinders or in-plane ones are readily obtained by controlling the solvent annealing time. Selective chemical etching of one of the polymers provides four different chemically modified nanostructures, viz., hexagonally ordered cylindrical holes and cylindrical posts with either sulfonate or amine surface functional groups. Additional supramolecular assembly is successfully achieved by solution coating either polymers or organic dyes that complementarily interact with the functional groups on the nanostructures. Furthermore, the supramolecularly assembled nanostructures are controlled by confining them to topographically pre-patterned Si substrates with pattern geometries of various shapes and sizes to produce globally ordered vertical or in-plane cylinders with chemical functionalities on their surfaces.

Multifunctional Woven Structure Operating as Triboelectric Energy Harvester, Capacitive Tactile Sensor Array, and Piezoresistive Strain Sensor Array.

This paper presents a power-generating sensor array in a flexible and stretchable form. The proposed device is composed of resistive strain sensors, capacitive tactile sensors, and a triboelectric energy harvester in a single platform. The device is implemented in a woven textile structure by using proposed functional threads. A single functional thread is composed of a flexible hollow tube coated with silver nanowires on the outer surface and a conductive silver thread inside the tube. The total size of the device is 60 × 60 mm² having a 5 × 5 array of sensor cell. The touch force in the vertical direction can be sensed by measuring the capacitance between the warp and weft functional threads. In addition, because silver nanowire layers provide piezoresistivity, the strain applied in the lateral direction can be detected by measuring the resistance of each thread. Last, with regard to the energy harvester, the maximum power and power density were measured as 201 µW and 0.48 W/m², respectively, when the device was pushed in the vertical direction.

Epitaxial Growth of Thin Ferroelectric Polymer Films on Graphene Layer for Fully Transparent and Flexible Nonvolatile Memory.

Enhancing the device performance of organic memory devices while providing high optical transparency and mechanical flexibility requires an optimized combination of functional materials and smart device architecture design. However, it remains a great challenge to realize fully functional transparent and mechanically durable nonvolatile memory because of the limitations of conventional rigid, opaque metal electrodes. Here, we demonstrate ferroelectric nonvolatile memory devices that use graphene electrodes as the epitaxial growth substrate for crystalline poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) polymer. The strong crystallographic interaction between PVDF-TrFE and graphene results in the orientation of the crystals with distinct symmetry, which is favorable for polarization switching upon the electric field. The epitaxial growth of PVDF-TrFE on a graphene layer thus provides excellent ferroelectric performance with high remnant polarization in metal/ferroelectric polymer/metal devices. Furthermore, a fully transparent and flexible array of ferroelectric field effect transistors was successfully realized by adopting transparent poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] semiconducting polymer.

Controlled Nanopores in Thin Films of Nonstoichiometrically Supramolecularly Assembled Graft Copolymers.

Herein, nanometer-scale morphologies of graft-copolymer-like supramolecular thin films, composed of sulfonic acid terminated polystyrene (SPS) and poly(2-vinylpyridine) (P2VP), and their application to antireflection coatings were investigated. The intermolecular complexes of SPS and P2VP, formed through nonstoichiometric multiple hydrogen bonding between the sulfonic acid group of SPS and the nitrogen atom in pyridine unit of P2VP, occurring in film deposition allowed for the formation of spherical micelles (with SPS and P2VP as the corona and core, respectively) in the thin film. Interestingly, the domain size of the micelles was tunable from approximately 20 to 90 nm on average by controlling either the blend ratio of components or the concentration of polymer solution. Furthermore, nanoporous thin films could be easily prepared by removing the core of micelle-based nanostructures by using a simple solvent etching process, leaving sulfonic acid groups on the surface of nanopores, which can be utilized as potential functional sites. Those resultant nanoporous thin films were conveniently employed as an antireflection layer on a glass substrate, giving a maximum 97.8 % transmittance in the visible wavelength range.

Flexible transition metal dichalcogenide nanosheets for band-selective photodetection.

The photocurrent conversions of transition metal dichalcogenide nanosheets are unprecedentedly impressive, making them great candidates for visible range photodetectors. Here we demonstrate a method for fabricating micron-thick, flexible films consisting of a variety of highly separated transition metal dichalcogenide nanosheets for excellent band-selective photodetection. Our method is based on the non-destructive modification of transition metal dichalcogenide sheets with amine-terminated polymers. The universal interaction between amine and transition metal resulted in scalable, stable and high concentration dispersions of a single to a few layers of numerous transition metal dichalcogenides. Our MoSe2 and MoS2 composites are highly photoconductive even at bending radii as low as 200 µm on illumination of near infrared and visible light, respectively. More interestingly, simple solution mixing of MoSe2 and MoS2 gives rise to blended composite films in which the photodetection properties were controllable. The MoS2/MoSe2 (5:5) film showed broad range photodetection suitable for both visible and near infrared spectra.

Self-assembled block copolymer micelles with silver-carbon nanotube hybrid fillers for high performance thermal conduction.

The development of polymer-filled composites with an extremely high thermal conductivity (TC) that is competitive with conventional metals is in great demand due to their cost-effective process, light weight, and easy shape-forming capability. A novel polymer composite with a large thermal conductivity of 153 W m(-1) K(-1) was prepared based on self-assembled block copolymer micelles containing two different fillers of micron-sized silver particles and multi-walled carbon nanotubes. Simple mechanical mixing of the components followed by conventional thermal compression at a low processing temperature of 160 °C produced a novel composite with both structural and thermal stability that is durable for high temperature operation up to 150 °C as well as multiple heating and cooling cycles of ΔT = 100 °C. The high performance in thermal conduction of our composite was mainly attributed to the facile deformation of Ag particles during the mixing in a viscous thermoplastic medium, combined with networked carbon nanotubes uniformly dispersed in the nanoscale structural matrix of block copolymer micelles responsible for its high temperature mechanical stability. Furthermore, micro-imprinting on the composite allowed for topographically periodic surface micropatterns, which offers broader suitability for numerous micro-opto-electronic systems.

Controlled Nanopores by Supramolecular Assembly of End-Functionalized Dendrimer and Homopolymer Blend.

Supramolecular assembly of end-functionalized polymers, forming block copolymer-like supramolecules based on ionic interaction, has been utilized as a simple and facile method for generating functionalized nanoporous thin film. Here, the binary blend film of aminated poly(ethylene oxide) dendrimer (APEO-G) and sulfonated polystyrene (SPS) at a stoichiometric composition after benzene/water solvent vapor annealing exhibits spherical domains in multilayers over a large area. By controlling the number of end-functional arms of dendrimer via divergent ring-opening polymerization of ethylene oxide as well as the molecular weights of SPS, the domain sizes can be controlled ranging from mainly 34 to 54 nm, even to 131 nm. Our supramolecular-assembly system provides an alternative approach to fabricating a functional nanotemplate by easily etching domains with selective solvent treatment and leaving functional groups at the pore surfaces.

Gas-driven ultrafast reversible switching of super-hydrophobic adhesion on palladium-coated silicon nanowires.

A gas-driven ultrafast adhesion switching of water droplets on palladium-coated Si nanowire arrays is demonstrated. By regulating the gas-ambient between the atmosphere and H2 , the super-hydrophobic adhesion is repeatedly switched between water-repellent and water-adhesive. The capability of modulating the super-hydrophobic adhesion on a super-hydrophobic surface with a non-contact mode could be applicable to novel functional lab-on-a-chip platforms.

Functionalized soft nanoporous materials through supramolecular assembly of end-functionalized polymer blends.

Supramolecular assembly through complementary interaction between molecular subgroups belonging to phase-separating polymer species offers a great opportunity, not only for constructing nanoscale soft templates reminiscent of conventional block copolymer morphologies, but also for tailoring surface properties by facile removal of one of the structure components by cleaving complementary interactions. Herein we report the fabrication of a novel, organic, nanoporous film through supramolecular assembly of two complementarily, end-interacting, mono-end-functionalized polymers under solvent annealing. The film of end-functionalized polymer blends under solvent annealing yielded phase-separated nanodomains that resemble nanoscopically ordered structures of block copolymers, but that are more advantageous due to easily cleavable and exchangeable links between the phase-separated domains. The removal of one of the components of the precursor structure formed from the end-functionalized polymers through cleavage of complementary interactions allowed us to fabricate mono- or multilayered nanoporous structures in which the chemically useful end-functionalities of the remnant polymers are rich on the surface of the pores. The resultant, organic, nanoporous films with tailored surface functionality offer a useful platform for various chemical and biological applications.