In-situ formation of SiGe alloy by electron beam evaporation and the effect of post deposition annealing on the energy band gap

TL;DR

This study demonstrates the in-situ formation of polycrystalline SiGe alloy thin films via electron beam evaporation and explores how post-deposition annealing influences their energy band gap, revealing dual band gaps and phase evolution.

Contribution

It introduces a low-temperature synthesis method for SiGe alloys using electron beam evaporation and analyzes the effects of annealing on phase composition and optical properties.

Findings

Amorphous Si subsumes into SiGe phase after annealing.

Dual energy band gaps observed in annealed films.

Phase evolution influenced by diffusion of Si during annealing.

Abstract

We report the synthesis of polycrystalline (poly)-SiGe alloy thin films through solid state reaction of Si/Ge multilayer thin films on Si and glass substrates at low temperature of 500 {\deg}C. The pristine thin film was deposited using electron beam evaporation with optimized in-situ substrate heating. Our results show the co-existence of amorphous Si (a-Si) phase along with the poly-SiGe phase in the pristine thin film. The a-Si phase was found to subsume into the SiGe phase upon post deposition annealing in the temperature range from 600 to 800 {\deg}C. Additionally, dual energy band gaps could be observed in the optical properties of the annealed poly-SiGe thin films. The stoichiometric evolution of the pristine thin film and its subsequent effect on the band gap upon annealing are discussed on the basis of diffusion characteristics of Si in poly-SiGe.