Compound semiconductor nanotube materials grown and fabricated

A new GaAs/InGaAs/InGaP compound semiconductor nanotube material structure was designed and fabricated in this work. A thin, InGaAs-strained material layer was designed in the nanotube structure, which can directionally roll up a strained heterostructure through a normal wet etching process. The compound semiconductor nanotube structure was grown by gas-source molecular beam epitaxy. A good crystalline quality of InGaP, InGaAs, and GaAs materials was obtained through optimizing the growth condition. The fabricated GaAs/InGaAs/InGaP semiconductor nanotubes, with a diameter of 300 to 350 nm and a length of 1.8 to 2.0 μm, were achieved through normal device fabrication

The Micro-Scaled Characterization of Natural Terrestrial Ferromanganese Coatings and Their Semiconducting Properties

Different types of ferromanganese coatings were collected from the Chinese mainland to study their mineralogical characteristics and semiconducting properties. Measurements, including by optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy, micro-Raman spectrometer and transmission electron microscope, were employed to study their morphology, mineral assemblage, element abundance and distribution patterns. Soil Fe coatings are mainly composed of Al-rich hematite and clays. Soil Fe/Mn coatings can be divided into an outer belt rich in birnessite and an inner belt rich in hematite, goethite, ilmenite and magnetite. Goethite is the only component of rock Fe coatings. Rock Fe/Mn coatings mainly consist of birnessite and hematite, and alternating Fe/Mn-rich layers and Fe/Mn-poor layers can be observed. Powders were scraped off from the topmost part of ferromanganese coatings to conduct laboratory photochemical experiments. The photocurrent–time behavior indicates that natural coating electrodes exhibit an immediate increase in photocurrent intensity when exposed to light irradiation. Natural coatings can photo-catalytically degrade 14.3%–58.4% of methyl orange in 10 h. Under light irradiation, the photocurrent enhancement and organic degradation efficiency of the rock Fe/Mn coating, which has a close intergrowth structure of Fe and Mn components, is most significant. This phenomenon is attributed to the formation of semiconductor heterojunctions, which can promote the separation of electrons and holes. Terrestrial ferromanganese coatings are common in natural settings and rich in semiconducting Fe/Mn oxide minerals. Under solar light irradiation, these coatings can catalyze important photochemical processes and will thus have an impact on the surrounding environment

InGaAsPBi grown on InP substrate by gas source molecular beam epitaxy

The effects of growth condition on material quality of quinary alloy InGaAsPBi grown by gas source molecular beam epitaxy (GSMBE) were investigated systematically. It is found that 0.1% of Bi incorporation can play the role of surfactant effects and is beneficial to improve the material quality. The roughness of surface RMS measured by atomic force microscope (AFM) is 0.218 nm. Furthermore, the addition of a small amount of bismuth atoms promotes the binding of phosphorus atoms to group III atmos

Bi-induced highly n-type carbon-doped InGaAsBi films grown by molecular beam epitaxy

Carbon-doped InGaAsBi films on InP/Fe (100) substrates have been grown by molecular beam epitaxy (MBE). It has been found that Bismuth incorporation induces extremely high n-type carbon-doped InGaAsBi films, and its electron concentration increases linearly up to 10(21) cm(-3) (highest reported to date for n-type III-V semiconductor materials) with increased CBr4 supply pressure, implying InGaAsBi to be a prospective ohmic contact material for InP-based terahertz transistors. It also has been proved by secondary ion mass spectroscopy that the alloy composition of carbon-doped InGaAsBi is altered by the preferential etching effect of CBr4, but the etching effect on the Bi content is negligible. ERNATHY CR, 1995, APPLIED PHYSICS LETTERS, V66, P163

Bioremediation Potential of Cr(VI) by <i>Lysinibacillus cavernae</i> CR-2 Isolated from Chromite-Polluted Soil: A Promising Approach for Cr(VI) Detoxification

The present study focuses on an efficient Cr(VI)-reducing bacterial strain (CR-2) isolated from an abandoned chromate plant in Qinghai Province, China. CR-2 was confirmed as Lysinibacillus cavernae using 16S rRNA gene sequencing. CR-2 could survive at 500 mg L−1 Cr(VI) and effectively reduce Cr(VI) at concentrations of −1, a pH of 5–9, a temperature of 20–40 °C, and a salinity of 5–15 g L−1. According to the Box–Behnken experimental design, the maximum Cr(VI) removal efficiency by L. cavernae CR-2 was 76.21% under optimum conditions, which comprised a pH of 6.68, a temperature of 28.90 °C, and a salinity of 9.85 g L−1. With regard to Cr(VI) reduction mediated by L. cavernae CR-2, enhancement in efficiency was observed in the presence of Cu2+ and Ca2+, while significant inhibition in the reduction capacity occurred upon exposure to Mg2+, Ba2+, Ni2+, Pb2+, or Cd2+. Moreover, L. cavernae CR-2 tends to use glucose as an electron donor for the reduction of Cr(VI). Results of cell fraction separation and degeneration indicated that the Cr(VI) removal was primarily due to the reduction of Cr(VI) via chromium reductase in the cytoplasm. In addition, bioanalysis of L. cavernae CR-2 by SEM-EDS and TEM-EDS suggested that Cr was distributed both on the surface and in the cell cytoplasm. FT-IR analyses established that multiple functional groups (hydroxyl, carbonyl, amide, amino, and aldehyde groups) participated in the Cr(VI) biosorption on the cell surface. XPS and HPLC also showed that the Cr(III) end-products could be present as Cr(III) hydroxides or as organic–Cr(III) complexes. This study yields insights into the Cr(VI) bioreduction mechanism of L. cavernae CR-2.</p

Accumulation Mechanism and Risk Assessment of Artemisia selengensis Seedling In Vitro with the Hydroponic Culture under Cadmium Pressure

Artemisia selengensis is a perennial herb of the Compositae with therapeutic and economic value in China. The cadmium (Cd) accumulation mechanism and healthy risk evaluation of A. selengensis were investigated in this study. Tissue culture seedlings were obtained by plant tissue culture in vitro, and the effect of Cd stress (Cd concentration of 0.5, 1, 5, 10, 25, 50 and 100 &mu;M) on A. selengensis was studied under hydroponic conditions. The results showed that low-Cd (0.5&ndash;1 &mu;M) stress caused a rare effect on the growth of A. selengensis seedlings, which regularly grew below the 10 &mu;M Cd treatment concentration. The biomass growth rate of the 0.5, 1, and 5 &mu;M treatment groups reached 105.8%, 96.6%, and 84.8% after 40 days of cultivation, respectively. In addition, when the concentration of Cd was greater than 10 &mu;M, the plant growth was obviously inhibited, i.e., chlorosis of leaves, blackening roots, destroyed cell ultrastructure, and increased malondialdehyde (MDA) content. The root could be the main location of metal uptake, 57.8&ndash;70.8% of the Cd was concentrated in the root after 40 days of cultivation. Furthermore, the root cell wall was involved in the fixation of 49&ndash;71% Cd by subcellular extraction, and the involvement of the participating functional groups of the cell wall, such as -COOH, -OH, and -NH2, in metal uptake was assessed by FTIR analysis. Target hazard quotient (THQ) was used to assess the health risk of A. selengensis, and it was found that the edible part had no health risk only under low-Cd stress (0.5 to 1 &mu;M) and short-term treatment (less than 20 days)