Mechanisms of the Phase Separation of Nonstoichiometric Si Oxide Films: What Can One Learn From Thermodynamics?

Abstract

This paper describes thermodynamic approach to the study of the mechanisms of phase separation in nonstoichiometric silicon oxide (SiOx, x < 2) films during high temperature annealing, which produces the nanometer sized Si inclusions embedded in the Si oxide matrix. The expression for the Gibbs free energy of Si/Si oxide systems is derived based on the analysis of the processes taking place during the phase separation. The progress of phase separation is characterized by the evolution of the stoichiometry index of Si oxide matrix x. The mechanisms assisting and counteracting the phase separation of SiOx films are determined based on that whether their contributions to the Gibbs free energy decrease or increase with the progress of Si and Si oxide separation (increase of x). The mechanisms responsible for the formation of equilibrium states in the Si/Si oxide systems (equilibrium values of x) are determined.