Annealing Effect of Amorphous Gallium Selenide Thin Films
Annealing effects of GaSe thin films prepared by flash evaporation were investigated using optical transmission measurement, photoacoustic (PA) spectroscopy, microscopy, and X-ray diffraction technique. As-deposited films have amorphous structure and their PA signals showed strong absorption in the range from 300 to 800 nm. With the increase of annealing temperature the optical transmission increased abruptly due to the nucleation and growth of spherulites. After further annealing the PA spectra of the crystallized films were resembling the PA spectrum of a single crystal more and more and showed the clear absorption edge near 2.0 eV. Thus, by the annealing of the as-deposited films a number of the localized levels in the band gap have been removed.