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Previously, a photoanode composed of nanostructured SnO2 coated with the perylene diimide dye N,N′-bis(phosphonomethyl)-3,4,9,10-perylenediimide (PMPDI) plus photoelectrochemically deposited cobalt oxide (CoOy) was shown to photoelectrochemically oxidize water at 31 ± 7% faradaic efficiency. A non-ideal part of that prior system is that the addition of the known CoOy water oxidation catalyst (WOC) resulted in a reduction of the total photocurrent rather than the anticipated increase, due to an increase in charge-carrier recombination. Herein, we show deposition of an ultrathin alumina overlayer applied by atomic layer deposition (ALD) on the SnO2/PMPDI photoanode can improve the photoactivity and catalytic activity of the system; the addition a ca. 1 nm-thick AlOx layer deposited on a 4000 nm (i.e., 4 micron) thick mesoporous anode system can and does have a positive, 2.5-fold improvement in the steady-state photocurrent with 29 ± 9% faradaic efficiency vs. the control anode without alumina passivation by reducing charge-carrier recombination. Moreover, ALD-deposited AlOx layer does help support the understanding of the “anti-catalysis” of co-depositing a CoOy WOC on the SnO2/PMPDI DS-PECs—specifically the picture of direct CoOy–SnO2 contact-mediated recombination—but that AlOx layer was unable to improve the photocurrent in a net SnO2/PMPDI/AlOx(/CoOy) system. We attribute the lack of a performance enhancement by CoOy WOC to incomplete coverage of each SnO2 nanoparticle by the AlOx. Overall, we find the addition of an optimized ultrathin AlOx layer (0.6 nm thick; deposited at 85 °C) improves the SnO2/PMPDI/AlOx system's photoactivity by a factor of up to ca. 3-fold with reduced recombination. These results document that metal-oxide passivation by low-temperature ALD can be an effective strategy for improving the water oxidation performance of even nanostructured dye sensitized-photoelectrochemical cell.

Organic-inorganic hybrids featuring tunable material properties can be readily generated by applying vapor- or liquid-phase infiltration (VPI or LPI) of inorganic materials into organic templates, with resulting properties controlled by type and quantity of infiltrated inorganics. While LPI offers more diverse choices of infiltratable elements, it tends to yield smaller infiltration amount than VPI, but the attempt to address the issue has been rarely reported. Here, we demonstrate a facile temperature-enhanced LPI method to control and drastically increase the quantity and kinetics of Pt infiltration into self-assembled polystyrene

We here report that adsorbed chains composed of one of the constituent blocks can be used as a new surface modification approach to induce perpendicularly oriented lamellar microdomains in block copolymer thin films. A nearly symmetric polystyrene-block-poly(methyl methacrylate) (PS-block-PMMA) diblock copolymer was used as a model. Densely packed PS- or PMMA-adsorbed chains of about 2–3 nm in thickness (“polymer nanocoatings”) were deposited on silicon (Si) substrates using a solvent-rinsing approach. Spin-cast films of 40 or 60 nm-thick PS-block-PMMA (equivalent to two or three interdomain spacings) were subsequently deposited onto the PS or PMMA nanocoatings. Grazing incidence small-angle X-ray scattering experiments revealed the formation of perpendicularly oriented lamellar microdomains within the entire films at 200 °C, where balanced interfacial interactions at the polymer–air interface were achieved. Additionally, X-ray photon correlation spectroscopy studies demonstrated the dynamics of the fully...

A novel atomic layer method for encapsulating individual micro- and nano-particles with thin (sub-10-nm) dielectric films is presented. This method leverages the diffusion of vapor-phase precursors through an underlying inert polymer film to achieve growth of a metal oxide film on all sides of the particle simultaneously; even on the side that is in contact with the substrate. Crucially, the deposition is performed on stationary particles and does not require an agitation mechanism or a special reaction chamber. Here, conformal coatings of alumina are shown to improve stability in aqueous environments for two optically-relevant particles: compound semiconductor laser microparticles and lead halide perovskite nanocrystals.

We have developed an organic-inorganic hybrid resist platform featuring versatile ex-situ control of its performance by incorporating inorganic elements using vapor-phase infiltration (VPI) into standard organic resists. With poly(methyl methacrylate) (PMMA)-AlOx hybrid as a model composition we unveiled controllability of the critical exposure dose, contrast (as high as ~30), and etch resistance; estimated Si etch selectivity over ~300, demonstrating high aspect ratio ~17 with ~30 nm resolution Si fin-structures. Building upon the demonstration of PMMA-AlOx hybrid resist, we expanded our material portfolio to a high sensitivity resist and other inorganic moieties. We present preliminary results obtained from the extreme ultraviolet (EUV) lithography dose tests conducted on corresponding infiltrated hybrids and optimization of infiltration with the help of transmission electron microscopy (TEM).

Recently, ultrathin metal-oxide thin film transistors (TFTs) have shown very high on-off ratio and ultra-sharp subthreshold swing, making them promising candidates for applications beyond conventional large-area electronics. While the on-off operation in typical TFTs results primarily from the modulation of charge carrier density by gate voltage, the high on-off ratio in ultrathin oxide TFTs can be associated with a large carrier mobility modulation, whose origin remains unknown. We investigate 3.5 nm-thick TiOx-based ultrathin TFTs exhibiting on-off ratio of ~106, predominantly driven by ~6-decade gate-induced mobility modulation. The power law behavior of the mobility features two regimes, with a very high exponent at low gate voltages, unprecedented for oxide TFTs. We find that this phenomenon is well explained by the presence of high-density tail states near the conduction band edge, which supports carrier transport via variable range hopping. The observed two-exponent regimes reflect the bi-exponential distribution of the density of band-tail states. This improved understanding would be significant in fabricating high-performance ultrathin oxide devices. The origin of large mobility modulation in ultrathin oxide transistors, promising for their high on-off ratio, remains mostly unknown. Here, a 106 gate-induced mobility modulation in 3.5 nm-thick TiOx transistors is explained by a high density of tail states, mediating variable range hopping of carriers.

The spontaneous formation of well-organized three-dimensional (3D) nanostructures from self-assembled block copolymers (BCPs) holds promise for nanofabrication and lithography. The addition of a th...

Organic–inorganic hybrid resists are emerging as an effective way of addressing stringent process requirements for aggressive down-scaling of semiconducting devices. However, hybrid resists generally require complex chemical synthesis while being predominantly negative-tone with high dose requirements. For positive-tone processes and high-aspect-ratio pattern transfers, resist choices are limited to costly, non-hybrid alternatives, whose etch resistance is still inferior compared with hybrid resists. Here, we demonstrate a novel hybrid positive-tone resist platform utilizing simple ex situ vapor-phase inorganic infiltration into standard resist materials. A model system based on poly(methyl methacrylate) (PMMA) thin film hybridized with aluminum oxide has been demonstrated for electron-beam lithography patterning, featuring a fully controllable critical exposure dose, contrast, and etch resistance. The hybrid resist not only achieves contrast as high as ∼30, six-fold enhancement over standard PMMA, but also enables Si nanostructures with resolution down to ∼30 nm and an aspect ratio as high as ∼17, owing to enhancement of the Si etch selectivity to ∼70, with an estimated achievable maximum of ∼300, far exceeding known commercial positive-tone resist systems. The easy implementabilility, combined with versatile ex situ control of resist characteristics, makes this hybrid resist synthesis approach uniquely suited for addressing the resist performance and high throughput required for advanced nanolithography techniques, such as extreme ultraviolet lithography, potentially.

Three-dimensional (3D) nanoarchitectures can offer enhanced material properties, such as large surface areas that amplify the structures' interaction with environments making them useful for various sensing applications. Self-assembled block copolymers (BCPs) can readily generate various 3D nanomorphologies, but their conversion to useful inorganic materials remains one of the critical challenges against the practical application of self-assembled BCPs. This work reports the vapor-phase infiltration synthesis of optoelectrically active, 3D ZnO nanomesh architectures by combining hierarchical successive stacking of self-assembled, lamellar-phase polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) BCP thin films and a modified block-selective vapor-phase material infiltration protocol. The 3D ZnO nanomesh exhibits optoelectrical functionality, featuring stack-layer-number-dependent electrical conductance resembling the percolative transport originating from the intrinsic morphological network connectivity of the lamellar BCP pattern with symmetric block ratio. The results not only illustrate the first demonstration of electrical functionality based on the ZnO nanoarchitecture directly generated by the infiltration synthesis in self-assembled BCP thin films but also present a new, large-area scalable, metal oxide thin film nanoarchitecture fabrication method utilizing industry-compatible polymer solution coating and atomic layer deposition. Given the large surface area, three-dimensional porosity, and readily scalable fabrication procedures, the generated ZnO nanomesh promises potential applications as an efficient active medium in chemical and optical sensors.

We demonstrate a simple ex-situ inorganic infiltration route for transforming standard organic resists into high-performance positive tone hybrid resist platform. A model thin film PMMA-AlOx hybrid resist system has been synthesized by hybridization of PMMA with AlOx and investigated for electron beam lithography. The approach possesses full controllability of the resist performance in terms of critical does, patterning contrast reaching up to 30 and etch resistance for plasma-based pattern transfer processes. The high selectivity Si etching capability demonstrated using a low-temperature cryo-Si etch process, based on the controlled infiltration outperforms commercial resists and typical hard mask material thermal SiO2, with estimated achievable selectivity in excess of ~300. Si nanostructures down to ~30 nm with aspect ratio up to ~17 are also transferred into the Si substrate. Easy implementation and adaptability for different inorganic infiltrations, this platform is well capable of potentially delivering the resist performance and throughput necessary for EUV lithography.

Polymer–inorganic hybrid nanocomposites exhibit enhanced material properties, combining the advantages of both their organic and inorganic subcomponents. Extensive research is being carried out to functionalize polymers towards various improved physicochemical characteristics such as electrical, optical, and mechanical properties for various applications. Vapor-phase material infiltration is an emerging hybridization route, derived from atomic layer deposition, which facilitates uniform incorporation of inorganic entities into a polymer matrix, leading to novel applications in fields such as microelectronics, energy storage, smart coatings, and smart fabrics. In this article, recent advances in employing vapor-phase material infiltration as a hybridization and nanopatterning technique for various application avenues are reviewed.

Despite successful applications of solution-processed organic–inorganic hybrid perovskites (OIHPs) such as archetypical methylammonium lead iodide (MAPI) in high-performance optoelectronic devices including solar cells and light emitting diodes, their application in field-effect transistors (FETs) remains relatively limited due to the unresolved issues caused by ion migration in OIHPs, such as screening of gate electric fields, lowered device on-off ratios and field-effect mobility, and large hysteresis in the FET transfer characteristics. Here, we report improved performances of the MAPI-based FET via a polymer-additive-based grain boundary (GB) passivation approach that suppresses the ion migration. Polycaprolactone (PCL) was incorporated into the MAPI FET as a GB-passivation additive as confirmed by scanning electron and atomic force microscopies. Unlike the typical n-type behavior and large transfer hysteresis in the starting, pristine MAPI FETs, the GB passivation by PCL led to a drastically reduced hysteresis in FET transfer characteristics, while hinting at an ambipolar transport and slight improvement in mobility, indicating a reduced ion migration in the PCL-incorporated MAPI FET. The effect of PCL GB passivation in suppressing ion migration was directly confirmed by the measured, increased activation energy for ion migration in the PCL-incorporated MAPI. The results not only represent the first report of the polymer-additive-based mitigation of the ion migration in the MAPI FET but also suggest potential utilities of the approach for enabling high-performance OIHP FETs and electronic devices in general.

Owing part of the innovative research concerning the degradation of the chemical industry pollutants was notably focused on photocatalysis process, in order to meet the strict pollution abatement legislation required by environmental protection agencies worldwide. Nanostructured TiO2, ZnO and ZnS as a semiconductor photocatalysts have proved to be effective and more suitable for the widespread environmental application, such as air purification, water disinfection, hazardous waste remediation and water purification. In the present investigation, CuS doped ZnS nanopowders have been synthesized by simple and cost effective sol-gel process. The dried powders have been sintered and the visible photocatalytic property of the pure ZnS and CuS doped in ZnS have been tested for the degradation of standard dyes along with chemical effluent. The samples have been characterized for their structural, chemical and morphological properties by employing X-ray Diffraction (XRD), X-Ray Photoelectron spectroscopy (XPS) and Scanning Electron Microscopy (SEM) techniques, respectively in order to understand the structure–property relationship.