Conversion of SILAR deposited Cu3Se2 thin films to Cu2-xSe by annealing

Thin films of copper selenide were deposited onto glass substrates using SILAR method at room temperature and annealed at 573 K for an hour in nitrogen atmosphere. As-deposited and annealed films were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, Raman spectroscopy, and optical absorption measurements. X-ray diffraction studies revealed that annealing the films in nitrogen atmosphere led to conversion of the tetragonal Cu3Se2 phase to cubic Cu2-xSe phase. Scanning electron microscopy images showed a considerable change in the morphology of the films and energy dispersive X-ray analysis demonstrated a reduction in selenium content with annealing. Typical Raman spectra of copper selenide thin films were obtained from the as-deposited and annealed films. Using optical absorption measurements, direct band gap energies of Cu3Se2 and Cu2-xSe phases were found to be 2.72 eV and 2.15 eV, respectively. (C) 2015 Elsevier B.V. All rights reserved.