Structural, electrical and optical properties of copper selenide thin films deposited by chemical bath deposition technique

Abstract

A low cost chemical bath deposition (CBD) technique has been used for the preparation of Cu2−xSe thin films on glass substrates. Structural, electrical and optical properties of these films were investigated. X-ray diffraction (XRD) study of the Cu2−xSe films annealed at 523 K suggests a cubic structure with a lattice constant of 5.697 Å. Chemical composition was investigated by X-ray photoelectron spectroscopy (XPS). It reveals that absorbed oxygen in the film decreases remarkably on annealing above 423 K. The Cu/Se ratio was observed to be the same in as-deposited and annealed films. Both as-deposited and annealed films show very low resistivity in the range of (0.04–0.15) × 10−5 Ω-m. Transmittance and Reflectance were found in the range of 5–50% and 2–20% respectively. Optical absorption of the films results from free carrier absorption in the near infrared region with absorption coefficient of ∼108 m−1. The band gap for direct transition, Eg.dir varies in the range of 2.0–2.3 eV and that for indirect transition Eg.indir is in the range of 1.25–1.5 eV.