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 A_1g¹, E_g² andA_1g² vibration modes from Bi₂Te₃ films, two new peaks at 93.5 cm^?1 and 123 cm^?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.