Raman spectra and valence force field of single-crystalline β Ga2O3

Single-crystalline β Ga2O3 was studied by Raman spectroscopy between 10 and 1000K. A complete valence force field was obtained. The agreement between observed and calculated Raman active frequencies is 0.8% for the whole spectrum. The potential energy distribution shows that stretching and bending modes are not independent. A complete description of the modes is given in terms of cartesian displacements. The temperature dependence of the Raman band half-widths was studied and is discussed in terms of anharmonicity at high temperature; the broadening which appears above 100K seems to be related to the appearance of defects. Our spectra are better understood in terms of the C2m space group proposed by Geller rather than P1 as recently proposed by G. M. Wolten and A. B. Chase (J. Solid State Chem. 16, 377, 1976).