Deng Huiyong

Surface Oxidation Properties in a Topological Insulator Bi2Te3 Film

Bi2Te3 films are grown on (111)-oriented GaAs substrates by using the hot wall epitaxy method and the surface oxidation properties in the films are investigated by x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction. The results show that the films are c-axis oriented. Two pairs of new peaks in the XPS spectra involved with the binding energies from Bi 4f and Te 3d electrons correspond to Bi—O—Te bonds. Besides the A11g, E2g and A21g vibration modes from Bi2Te3 films, two new peaks at 93.5cm−1 and 123cm−1 are observed in Raman spectra, which are assigned to α-Bi2O3 and TeO2, respectively. Our results are helpful for analyzing the degradation mechanism of topological surface states in Bi2Te3.

Ab Initio Study of Structural and Electronic Properties of Sodium Bromide

The structural and electronic properties of sodium bromide (NaBr) are investigated by the density functional theory (DFT) within the generalized gradient approximation (GGA) for the exchange and correlation energy. The equilibrium lattice constant, bulk modulus and its pressure derivative are obtained by fitting the calculated total energy to the third-order Birch–Murnaghan equation of state. The band structure along the higher symmetry axes in the Brillouin zone, the density of states (DOS) and the partial density of states (PDOS) are presented. The results have been discussed and compared with the available experimental and theoretical data.

Electrical Property of Infrared-Sensitive InAs Solar Cells

InAs infrared-sensitive solar cells are fabricated by using the films grown by the liquid phase epitaxy technique. The film microstructures are characterized by x-ray diffraction and scanning electronic microscopy. The current-voltage characteristics of the solar cells in the dark and under AM1.5 illumination at 300 K and 77 K are discussed. The conversion efficiency of p-InAs/n-sub InAs cells decreases when the thickness of the p-type film changes from 1.7 μm to 3.5 μm, which is caused by the reduced effective photons near p-n junction. The p-InAs/n-InAs/n-sub InAs solar cell with the conversion efficiency of 7.43% in 1–2.5 μm under AM1.5 at 77K is obtained. The short circuit current density increases dramatically with decreasing temperature due to the weakened effect of phonon scattering.