The Oxford-Diamond In Situ Cell for studying chemical reactions using time-resolved X-ray diffraction Rev. Sci. Instrum. 83, 084101 (2012) Synchrotron-based ultrafast x-ray diffraction at high repetition rates Rev. Sci. Instrum. 83, 063303 (2012) Shortening x-ray pulses for pump-probe experiments at synchrotrons J. Appl. Phys. 109, 126104 (2011) High-pressure and high-temperature x-ray diffraction cell for combined pressure, composition, and temperature measurements of hydrides Rev. Sci. Instrum. 82, 065108 (2011) High resolution short focal distance Bent Crystal Laue Analyzer for copper K edge x-ray absorption spectroscopy Rev. Sci. Instrum. 82, 063106 (2011) Additional information on Appl. Phys. Lett.

The structure, morphology, and optical properties of homoepitaxial GaN layers grown by molecular beam epitaxy on metalorganic chemical vapor deposition (MOCVD)-grown GaN “template” layers were investigated as a function of the group III/group V flux ratio during growth. GaN layers grown with a low III/V ratio (N-stable growth) displayed a faceted surface morphology and a tilted columnar structure with a high density of stacking faults. In contrast, films grown with a high III/V ratio (Ga-stable growth) displayed comparable structure to the underlying MOCVD-grown template. The transition from N-stable to Ga-stable growth modes was found to occur over a narrow range of Ga fluxes at a growth temperature of 650 °C. Evidence of Ga accumulation and step-flow growth was observed for films grown under Ga-stable conditions, leading to the formation of spiral growth features at the surface termination of mixed edge/screw dislocations. Photoluminescence measurements indicate that the deep-level (∼550 nm) emission is increased relative to the near-band edge emission for films grown under N-stable conditions.

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Converting renewable biomass and their derivatives into chemicals and fuels has received much attention to reduce the dependence on fossil resources. Photocatalytic ethanol dehydrogenation–acetalization to prepare value‐added 1,1‐diethoxyethane and H2 was achieved over non‐precious metal CdS/Ni‐MoS2 catalyst under visible light. The system displays an excellent production rate and high selectivity of 1,1‐diethoxyethane, 52.1 mmol g−1 h−1 and 99.2 %, respectively. In‐situ electron spin resonance, photoluminescence spectroscopy and transient photocurrent responses were conducted to investigate the mechanism. This study provides a promising strategy for a green application of bioethanol.