Raman Study of Epitaxial Ga₂Se₃ Films Grown by Molecular Beam Epitaxy

Epitaxial Ga 2 Se 3 films grown by molecular-beam epitaxy were characterized by Raman spectroscopy. Raman spectra of the obtained Ga 2 Se 3 films showed two broad peaks at 250 cm -1 and 300 cm -1 , and one sharp peak at 155 cm -1 . The intensity of the sharp peak strongly depended on the VI/III ratio (Se beam flux/Ga beam flux), and maximum intensity was obtained for the film grown with a VI/III ratio of 150. The experimental spectra were analyzed in terms of an axially symmetric lattice-dynamical model for the first time. It is determined from both calculation and experiment that the sharp peak at 155 cm -1 shows A 1 symmetry, which originates in the vacancy-ordering of Ga 2 Se 3 .