Formation of surface amorphous layers in semiconductors under low-energy light-ion irradiation: Experiment and theory

Abstract

A method to measure the thickness of thin fully disordered layers on the top of crystalline substrates is discussed. Using this method, based on the anisotropy of inelastically backscattered electrons, we study the damage buildup in Si bombarded at room temperature with 10 keV Ne + ions. Results show that the accumulation of disorder can be considered as the growth of an amorphous layer proceeding from the native-SiO 2/Si-crystal interface. No dependence of the amorphous layer growth rate on ion beam flux is observed. Results are explained based on the diffusion of mobile point defects to the surface with a subsequent interface segregation process. The retardation of amorphous layer growth, experimentally observed for low ion doses, is attributed to defect accumulation at saturated sinks which exist in samples before ion irradiation. Calculations based on this model are in good agreement with experimental data.