Kinetic study of GeOx amorphous film disproportionation into a-Ge nanoclusters / GeO2 system using Raman and infrared spectroscopy

Abstract

In this paper, based on the analysis of Raman spectroscopy data, the kinetics of the disproportionation reaction process (GeOx → (1−x/2)Ge + (x/2)GeO2) of an amorphous GeOx film during furnace annealing were studied. An approximation of the experimental kinetics of the disproportionation reaction to the theoretical Kolmogorov–Johnson–Mel–Avrami dependence has been carried out. By analyzing the temperature dependence of the formation time of amorphous germanium clusters, the activation energy of the formation process was obtained, which amounted to 0.9 ± 0.1 eV. In addition, it was found that the position of the Raman peak from amorphous germanium nanoclusters depends on their size. Thus, the phonon localization model can be applied not only to germanium nanocrystals but also to amorphous germanium clusters in the case of their ultra-small sizes (less than 1.5 nm), which is less than the phonon correlation length in amorphous germanium.