Effects of annealing on the structural and optical properties of amorphous thin films of Ga-55 mol% S

Abstract

Thin amorphous films of Ga-55 mol% S were prepared by ion-beam sputtering on glass substrates at room temperature. The structural changes, optical absorption and dark conductivities were examined on annealing the amorphous films. The crystallization of the films occurred after annealing at temperatures higher than about 773 K for 0.5 h, resulting in the formation of a disordered cubic-phase of GaS. The optical absorption coefficient, α, appeared to follow the relation, α h ̵ ω∝ ( h ̵ ω−E g opt) 2 , in the photon energy range 2–3 eV. The optical gap, E g opt , and dark conductivity activation energy for the as-deposited films were estimated to be 2.1 and 0.78 eV, respectively, which showed an increasing tendency after annealing at a temperature > 573 K. The results are discussed based on the structural evolution in the amorphous films by thermal annealing.