Effects of thermally-induced changes of Cu grains on domain structure and electrical performance of CVD-grown graphene

During the chemical vapor deposition (CVD) growth of graphene on Cu foils, evaporation of Cu and changes in the dimensions of Cu grains in directions both parallel and perpendicular to the foils are induced by thermal effects. Such changes in the Cu foil could subsequently change the shape and distribution of individual graphene domains grown on the foil surface, and thus influence the domain structure and electrical properties of the resulting graphene films. Here, a slower cooling rate is used after the CVD process, and the graphene films are found to have an improved electrical performance, which is considered to be associated with the Cu surface evaporation and grain structure changes in the Cu substrate.open

Deep-ultraviolet photonics for the disinfection of SARS-CoV-2 and its variants (Delta and Omicron) in the cryogenic environment

Deep-ultraviolet (DUV) disinfection technology provides an expeditious and efficient way to suppress the transmission of coronavirus disease 2019 (COVID-19). However, the influences of viral variants (Delta and Omicron) and low temperatures on the DUV virucidal efficacy are still unknown. Here, we developed a reliable and uniform planar light source comprised of 275-nm light-emitting diodes (LEDs) to investigate the effects of these two unknown factors and delineated the principle behind different disinfection performances. We found the lethal effect of DUV at the same radiation dose was reduced by the cryogenic environment, and a negative-U large-relaxation model was used to explain the difference in view of the photoelectronic nature. The chances were higher in the cryogenic environment for the capture of excited electrons within active genetic molecules back to the initial photo-ionised positions. Additionally, the variant of Omicron required a significantly higher DUV dose to achieve the same virucidal efficacy, and this was thanks to the genetic and proteinic characteristics of the Omicron. The findings in this study are important for human society using DUV disinfection in cold conditions (e.g., the food cold chain logistics and the open air in winter), and the relevant DUV disinfection suggestion against COVID-19 is provided

Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells

National Research Program of China [2012CB619301, 2011CB301905, 2011CB925600]; National Natural Science Foundation of China [61108064, 61227009, 90921002]; Fundamental Research Funds for the Central Universities [2011120143]We report the development of complete structural AlGaN-based deep-ultraviolet light-emitting diodes with an aluminum thin layer for increasing light extraction efficiency. A 217% enhancement in peak photoluminescence intensity at 294 nmis observed. Cathodoluminescence measurement demonstrates that the internal quantum efficiency of the deep-UV LEDs coated with Al layer is not enhanced. The emission enhancement of deep-UV LEDs is attributed to the higher LEE by the surface plasmon-transverse magnetic wave coupling. When the proportion of the TM wave to the Al layer increases with the Al content in the AlxGa1-xN multiple quantum wells, i.e., the band edge emission energy, the enhancement ratio of the Al-coated deep-UV LEDs increases

Resistance Switching Behavior in Rectangle-Nano-Pattern SrTiO3 Induced by Simple Annealing.

The tunability of semi-conductivity in SrTiO3 single crystal substrates has been realized by a simple encapsulated annealing method under argon atmosphere. This high temperature annealing-induced property changes are characterized by the transmission spectra, scanning electron microscopy (SEM) and synchrotron-based X-ray absorption (XAS). We find the optical property is strongly influenced by the annealing time (with significant decrease of transmittance). A sub gap absorption at ~427 nm is detected which is attributed to the introduction of oxygen vacancy. Interestingly, in the SEM images, annealing-induced regularly rectangle nano-patterns are directly observed which is contributed to the conducting filaments. The XAS of O K-edge spectra shows the changes of electronic structure by annealing. Very importantly, resistance switching response is displayed in the annealed SrTiO3 single crystal. This suggests a possible simplified route to tune the conductivity of SrTiO3 and further develop novel resistance switching materials

Multi-hot spot configuration on urchin-like Ag nanoparticle/ZnO hollow nanosphere arrays for highly sensitive SERS

MOST of China under the 973 programs [2009CB930704]; National Natural Science Foundation of China [61106118]; Science and Technology Project of Fujian Province of China [2013H0046]; Natural Science Foundation of Fujian Province of China [2011J01362]; Fundamental Research Funds for the Central Universities [2011121026]Urchin-like Ag nanoparticle (NP)/ZnO hollow nanosphere (HNS) arrays were fabricated employing a simple, low cost and wafer scale method consisting of nanosphere lithography (NSL) and solution processes. This three-dimensional (3D) multi-hot spot decorated nanocomposite presents an as high as 108 Raman enhancement using Rhodamine 6G (R6G) as the probe with the concentration down to 10(-10) M. The high density hot spots in a unit area and strong field intensity around each individual hot spot in 3D layout are believed to be the major reasons for this high sensitivity Raman phenomenon, which is further proved by the theoretical simulation results. Given its high Raman sensitivity and good reproducibility in a large area, this urchin-like Ag NP/ZnO HNS hybrid nanoarray can be reasonably proposed to be used as a SERS substrate in practical applications, including bio-sensing, materials characterization, environmental science and so on

Fabrication of 3D hexagonal bottle-like Si-SnO2 core-shell nanorod arrays as anode material in on chip micro-lithium-ion-batteries

National Basic Research Program of China [2009CB930704]; National Natural Science Foundation of China [61106118]; Natural Science Foundation of Fujian Province of China [2011J01362]; Fundamental Research Funds for the Central Universities [2011121026]Three-dimensional (3D) Si-SnO2 composite core-shell nanorod arrays were fabricated as the anode material in lithium ion micro-batteries by nanosphere lithography (NSL) combined with inductive coupled plasma (ICP) dry etching technology. The hexagonal bottle-like Si NR arrays in wafer scale with homogeneous morphology and good mechanical structure provide enough space to accommodate the volume expansion during Li ion insertion/de-insertion processes, while the additionally deposited SnO2 thin film was prepared to successfully improve the capacities and cycle performance by configuring the 3D Si-SnO2 NR composite electrode arrays. This fabrication method has the advantages of simplicity, large scale production, easy size and shape manipulations, low cost and Si-process compatibility. This work will facilitate the configuration of solid state micro-batteries for power supply in micro-electronic devices, such as MEMS devices or smart IC chips