Surface oxidation properties in a topological insulator Bi ₂Te₃ 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 Bi₂Te ₃.