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Silicon carbide (SiC) is used in a variety of applications including photovoltaic due to its high stability. The wide bandgap of SiC limits these applications and necessitates bandgap tuning toward lower energy for efficient solar absorption. In this regard, the electronic properties of highly stable SiC polytype 6H‐SiC are studied by first‐principles calculations. By varying the Si composition of 6H‐SiC the electronic properties are tailored. The calculated results show that increasing the Si composition of 6H‐SiC from 50% to 66.66% reduces the bandgap from 2.98 to 1.54 eV. It is observed that this reduction in bandgap occurs due to the addition of extra Si s/p orbitals which close the conduction band and valance band. From the electronic conductivity calculations, it is found that with increasing Si composition of 6H‐SiC the conductivity is improved due to higher hole density which can be verified by the spectrum peaks shifted toward near‐infrared and visible region. [ABSTRACT FROM AUTHOR]

Abstract: High-density Ge quantum dots (QDs) have been grown on Si(111) surface covered by a ultra-thin SiO2 film whose thickness, determined by synchrotron radiation photoelectron spectroscopy (SRPES), is about one monolayer (ML). The influences of substrate temperature and Ge thickness have been demonstrated by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force spectroscopy (AFM). The experimental results show that at 500°C, Ge adatoms can create nucleus by reacting with the oxide film and then produce uniform and dense Ge QDs. The QDs in form of “frustum of tetrahedron” can be formed at 650°C, which case is similar with the growth on Si(111) surface. According to the growth results under different Ge thicknesses, 0.5-nm-thick (1.60ML) Ge is necessary for the production of QDs, which indicates quantitatively that Ge QDs’ growth on ultra-thin SiO2 surface does not follow the Stranski–Krastanov (S–K) mode. After depositing 1.1-nm-thick Ge, Ostwald ripening process occurs. [Copyright &y& Elsevier]

The article provides information on simple designs to avoid high-voltage (HV) discharge in a silicon electron beam-heating cell. It is noted in the article that although compact electron beam evaporators (EBE) used for silicon evaporation are already commercially available, they are normally expensive and complex to maintain. To prevent HV discharge, much attention had been focused on the alumina support ring.

A combination of a semiconductor-based photosensitizer with molecular catalysts via covalent bonds is an effective way to utilize solar energy to reduce CO 2 into value-added chemicals with high efficiency and selectivity. In this study, 2,2'-bpy-5,5'-dialdehyde functioned as organic ligands and were embedded into the skeleton of g-CN through imine bonds via thermal copolymerization. The introduction of 2,2'-bpy can not only chelate with earth-abundant Co as single-site catalytic centers but also can optimize the properties of original g-CN such as the enlarged specific surface area and extended visible light absorption range. The CO evolution rate of g-CN-bpy-Co can reach up to 106.3 μmol g -1 h -1 with a selectivity of 97% over proton reduction, which was 82-fold than that of g-CN-Co. The different coordination environments and valence states of cobalt were also studied simultaneously and the results showed that Co(II) exhibited superior catalytic activity towards Co(III). Control experiments demonstrated that the covalent linkage between g-CN and Co-2,2'-bpy plays a vital role in photocatalytic activity and selectivity. Besides, the CO generation rate demonstrated linear growth upon visible light irradiation up to 72 h and preferable recyclability. This research provides a new facile way to fabricate low-priced photocatalysts with high activity and selectivity and bridge homogeneous and heterogeneous catalysis.