Trilayer Raman scattering of variably ordered amorphous Ge

Abstract

Interference-enhanced Raman scattering measurements are reported on rf diode sputtered a-Ge as a function of annealing temperature. The results on films ∼50 Å thick indicate a monotonic decrease of the half-width of the TO-like phonon band for the depolarized Raman component as a function of annealing temperature. In addition, the ratio of the TA to TO peak intensities is also found to monotonically decrease with temperature. These results indicate changes in the vibrational spectrum of a-Ge that arise from increasing short range order and parallel studies on thicker a-Ge and a-Si films with deposition conditions. During crystallization the Raman spectra also indicate that the amorphous phase continues to increase its structural order. A comparison with the Raman spectra of thicker films allows an estimate of the optical gap to be obtained in the very thin a-Ge films.