Crystallization of Ge Thin Films on Sapphire(0001) by Thermal Annealing

Abstract

We have investigated an impact of thermal annealing in N2 ambience on crystallization of a Ge thin layer with a thickness below 10 nm formed on Sapphire substrate. A SiO2/Ge/Sapphire(0001) structure was prepared by RF sputtering of a Ge thin layer and ALD of a SiO2 capping layer. From the Raman scattering spectroscopy and AFM analyses of the SiO2/Ge/Sapphire(0001) structure before and after the annealing at the temperature in the range from 600°C to 900°C, crystallization of the Ge thin layer and change in the surface morphology has been discussed. And, two-step annealing was found to be effective to grow the Ge crystal layer with keeping surface flatness.