Discontinuity‐Enhanced Thin Film Electrocatalytic Oxygen Evolution

Thin film electrocatalysts allow strong binding and intimate electrical contact with electrodes, rapid mass transfer during reaction, and are generally more durable than powder electrocatalysts, which is particularly beneficial for gas evolution reactions. In this work, using cobalt manganese oxyhydroxide, an oxygen evolution reaction (OER) electrocatalyst that can be grown directly on various electrodes as a model system, it is demonstrated that breaking a continuous film into discontinuous patches can significantly enhance the overall OER performance without sacrificing long‐term stability even under elevated electrocatalytic stress. Discontinuous films with higher edge‐to‐area ratios exhibits reduced overpotentials, increased turnover frequency, and more pronounced current increase after electrochemical conditioning. Operando Raman spectroscopy studies during electrocatalysis reveal that the film edges require lower potential barrier for activation. Introducing discontinuity into thin film electrocatalysis can thus lead to the realization of high performance yet highly robust systems for harsh gas evolution reactions.     

Recent Progress in n‐Channel Organic Thin‐Film Transistors

Particular attention has been focused on n‐channel organic thin‐film transistors (OTFTs) during the last few years, and the potentially cost‐effective circuitry‐based applications in flexible electronics, such as flexible radiofrequency identity tags, smart labels, and simple displays, will benefit from this fast development. This article reviews recent progress in performance and molecular design of n‐channel semiconductors in the past five years, and limitations and practicable solutions for n‐channel OTFTs are dealt with from the viewpoint of OTFT constitution and geometry, molecular design, and thin‐film growth conditions. Strategy methodology is especially highlighted with an aim to investigate basic issues in this field.     

Inverse Face‐Centered Cubic Thin Film Photonic Crystals

Recent work on a technique for fabricating inverse fcc photonic crystals from a colloidal system of monodisperse microspheres and titania nanoparticles is described. The technique can be used to produce photonic crystals with other background materials that are available as nanoparticles. The Figure shows the Moiré pattern of a typical photonic crystal sample.     

Characterization of Indium‐Tin‐Oxide Thin Film Microelectrodes for Biomedical Use

Selected properties of indium‐tin‐oxide (ITO) films prepared by r.f. diode sputtering have been investigated in consideration of surface morphology, optical properties, crystal structure and phase formation, electrical resistivity and chemical resistance. The ITO films showed low electrical resistivity (6·10^‐5 Ωm), high optical transmittance (> 80 %) and suitable chemical resistance against selected chemicals during 1 hour.     

A Solution Processable High‐Performance Thermoelectric Copper Selenide Thin Film

A solid‐state thermoelectric device is attractive for diverse technological areas such as cooling, power generation and waste heat recovery with unique advantages of quiet operation, zero hazardous emissions, and long lifetime. With the rapid growth of flexible electronics and miniature sensors, the low‐cost flexible thermoelectric energy harvester is highly desired as a potential power supply. Herein, a flexible thermoelectric copper selenide (Cu₂Se) thin film, consisting of earth‐abundant elements, is reported. The thin film is fabricated by a low‐cost and scalable spin coating process using ink solution with a truly soluble precursor. The Cu₂Se thin film exhibits a power factor of 0.62 mW/(m K²) at 684 K on rigid Al₂O₃ substrate and 0.46 mW/(m K²) at 664 K on flexible polyimide substrate, which is much higher than the values obtained from other solution processed Cu₂Se thin films (<0.1 mW/(m K²)) and among the highest values reported in all flexible thermoelectric films to date (≈0.5 mW/(m K²)). Additionally, the fabricated thin film shows great promise to be integrated with the flexible electronic devices, with negligible performance change after 1000 bending cycles. Together, the study demonstrates a low‐cost and scalable pathway to high‐performance flexible thin film thermoelectric devices from relatively earth‐abundant elements.     

Nanoscale Probing of a Polymer‐Blend Thin Film with Tip‐Enhanced Raman Spectroscopy

Fundamental advances have been made in the spatially resolved chemical analysis of polymer thin films. Tip‐enhanced Raman spectroscopy (TERS) is used to investigate the surface composition of a mixed polyisoprene (PI) and polystyrene (PS) thin film. High‐quality TER spectra are collected from these nonresonant Raman‐active polymers. A wealth of structural information is obtained, some of which cannot be acquired with conventional analytical techniques. PI and PS are identified at the surface and subsurface, respectively. Differences in the band intensities suggest strongly that the polymer layers are not uniformly thick, and that nanopores are present under the film surface. The continuous PS subsurface layer and subsurface nanopores have hitherto not been identified. These data are obtained with nanometer spatial resolution. Confocal far‐field Raman spectroscopy and X‐ray photoelectron spectroscopy are employed to corroborate some of the results. With routine production of highly enhancing TERS tips expected in the near future, it is predicted that TERS will be of great use for the rigorous chemical analysis of polymer and other composite systems with nanometer spatial resolution.     

Highly Uniform Resistive Switching Properties of Solution‐Processed Silver‐Embedded Gelatin Thin Film

The silver‐embedded gelatin (AgG) thin film produced by the solution method of metal salts dissolved in gelatin is presented. Its simple fabrication method ensures the uniform distribution of Ag dots. Memory devices based on AgG exhibit good device performance, such as the ON/OFF ratio in excess of 10⁵ and the coefficient of variation in less of 50%. To further investigate the position of filament formation and the role of each element, current sensing atomic force microscopy (CSAFM) analysis as well as elemental line profiles across the two different conditions in the LRS and HRS are analyzed. The conductive and nonconductive regions in the current map of the CSAFM image show that the conductive filaments occur in the AgG layer around Ag dots. The migration of oxygen ions and the redox reaction of carbon are demonstrated to be the driving mechanism for the resistive switching of AgG memory devices. The results show that dissolving metal salts in gelatin is an effective way to achieve high‐performance organic–electronic applications.