Fluidic self-assembly for MicroLED displays by controlled viscosity.

Displays in which arrays of microscopic 'particles', or chiplets, of inorganic light-emitting diodes (LEDs) constitute the pixels, termed MicroLED displays, have received considerable attention because they can potentially outperform commercially available displays based on organic LEDs in terms of power consumption, colour saturation, brightness and stability and without image burn-in issues. To manufacture these displays, LED chiplets must be epitaxially grown on separate wafers for maximum device performance and then transferred onto the display substrate. Given that the number of LEDs needed for transfer is tremendous-for example, more than 24 million chiplets smaller than 100 μm are required for a 50-inch, ultra-high-definition display-a technique capable of assembling tens of millions of individual LEDs at low cost and high throughput is needed to commercialize MicroLED displays.

Concurrent self-assembly of RGB microLEDs for next-generation displays.

MicroLED displays have been in the spotlight as the next-generation displays owing to their various advantages, including long lifetime and high brightness compared with organic light-emitting diode (OLED) displays. As a result, microLED technology is being commercialized for large-screen displays such as digital signage and active R&D programmes are being carried out for other applications, such as augmented reality, flexible displays and biological imaging. However, substantial obstacles in transfer technology, namely, high throughput, high yield and production scalability up to Generation 10+ (2,940 × 3,370 mm) glass sizes, need to be overcome so that microLEDs can enter mainstream product markets and compete with liquid-crystal displays and OLED displays.

Distinguishing Zigzag and Armchair Edges on Graphene Nanoribbons by X-ray Photoelectron and Raman Spectroscopies.

Graphene nanoribbons (GNRs) have recently emerged as alternative 2D semiconductors owing to their fascinating electronic properties that include tunable band gaps and high charge-carrier mobilities. Identifying the atomic-scale edge structures of GNRs through structural investigations is very important to fully understand the electronic properties of these materials. Herein, we report an atomic-scale analysis of GNRs using simulated X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.

In Situ Spectroscopic and Computational Studies on a MnO-CuO Catalyst for Use in Volatile Organic Compound Decomposition.

In situ near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and density functional theory calculations were conducted to demonstrate the decomposition mechanism of propylene glycol methyl ether acetate (PGMEA) on a MnO-CuO catalyst. The catalytic activity of MnO-CuO was higher than that of MnO at low temperatures, although the pore properties of MnO were similar to those of MnO-CuO. In addition, whereas the chemical state of MnO remained constant following PGMEA dosing at 150 °C, MnO-CuO was reduced under identical conditions, as confirmed by in situ NEXAFS spectroscopy.

Investigation of Thermally Induced Degradation in CHNHPbI Perovskite Solar Cells using In-situ Synchrotron Radiation Analysis.

In this study, we employ a combination of various in-situ surface analysis techniques to investigate the thermally induced degradation processes in MAPbI perovskite solar cells (PeSCs) as a function of temperature under air-free conditions (no moisture and oxygen). Through a comprehensive approach that combines in-situ grazing-incidence wide-angle X-ray diffraction (GIWAXD) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) measurements, we confirm that the surface structure of MAPbI perovskite film changes to an intermediate phase and decomposes to CHI, NH, and PbI after both a short (20 min) exposure to heat stress at 100 °C and a long exposure (>1 hour) at 80 °C. Moreover, we observe clearly the changes in the orientation of CHNH organic cations with respect to the substrate in the intermediate phase, which might be linked directly to the thermal degradation processes in MAPbI perovskites.

Investigation of out-of-plane structural properties of a graphene monolayer with gap-plasmons: mode-selective Raman enhancement and the influence of additional sp(3) type defects.

We report that Raman enhancements of a graphene monolayer sandwiched at the Au nanoparticle-Au thin film junction are different and can be attributed to the influence of a z-polarized incident field. Closer to the center of the junction, radial breathing like-mode (RBLM) shows dramatic Raman enhancement in terms of the coincidence between the z-polarized incident field formed at the junction and the RBLM phonon axis. The appearance of an additional D* peak can be identified and is attributed to the additional out-of-plane sp(3) type defect signal.

Exploring the relative bending of a CVD graphene monolayer with gap-plasmons.

We report a spectroscopic indicator showing the bending of a chemical vapor deposition (CVD) graphene monolayer on Cu foil or an arbitrary substrate after transfer. Using a Au nanoparticle (NP)-graphene monolayer-Au thin film (TF) junction system, the Radial Breathing-Like Mode (RBLM) Raman signal from the sandwiched graphene monolayer is evidently observed by employing a local z-polarized incident field formed at the Au NP-Au TF junction. We also utilized the RBLM intensity as a quantitative tool with a wide dynamic range (∼300%) compared to the 2D peak width (∼35%) for determining the relative degree of bending on the Au TF substrate.

Functional group-selective adsorption using scanning tunneling microscopy.

In this study, we selectively enhanced two types of adsorption of 3-mercaptoisobutyric acid on a Ge(100) surface by using the tunneling electrons from an STM and the catalytic effect of an STM tip. 3-Mercaptoisobutyric acid has two functional groups: a carboxylic acid group at one end of the molecule and a thiol group at the other end. It was found that the adsorption occurring through the carboxylic acid group was selectively enhanced by the application of electrons tunneling between an STM tip and the surface.

Molecular seesaw: a three-way motion and motion-induced surface modification.

We introduce a three-way molecular motion which can be a suitable switching system in future molecule-based nanocircuits. A real-space investigation revealed that vinylferrocene adsorbs site-specifically on the Ge(100) surface and then shows a reversible tilting motion, similar to a seesaw. Unlike conventional molecular motions, it not only has three stable switching states at room temperature but also shows a motion-induced surface-structure modification, allowing surface-mediated signal transmission.

STM tip catalyzed adsorption of thiol molecules at the nanometer scale.

The tungsten oxide covered tungsten (W) tip of a scanning tunneling microscope was found to act as a catalyst to catalyze the S-H dissociative adsorption of phenylthiol and 1-octanethiol molecules onto a Ge(100) surface. By varying the distance between the tip and the surface, the area of the tip-catalyzed adsorption could be controlled. We have found that the thiol headgroup is the critical functional group for this catalysis and the catalytic material is the tungsten oxide layer of the tip.