Post annealing effects on the structural, compositional, optical and dielectric properties of Cd doped GaSe thin films

In this work, the heat treatment effects at temperatures (T-a) of 200, 300 and 400 degrees C on the compositional, structural, optical and dielectric properties of Cd doped GaSe are explored by means of energy dispersive X-ray spectroscopy, X-ray diffraction and UV-VIS spectrophotometry. The annealing process of the Cd doped GaSe thin films revealed a highly oriented orthorhombic structure type that exhibit a systematic increase in the grain size. While the strain, degree of orientation and dislocation density of the annealed films are weakly affected by the annealing process. The optical energy band gap of the doped films decreased from 1.23 to 0.90 eV and the exponential energy band tails rose from 0.16 to 0.23 eV when the annealing temperature is raised from 300 to 400 degrees C. In addition, the analysis of the dielectric spectral curves which were studied in the frequency range of 270-1500 THz, allowed to investigate the oscillator and dispersion energies and the static (epsilon(s)) and lattice (epsilon(l)) dielectric constants. The annealing process on the doped samples decreased the dispersion and oscillator energies as well as es. Oppositely, el values increased from 12.52 to 24.45 as a result of larger grain size and less defect density associated with annealing process when T-a is raised from 200 to 400 degrees C, respectively. (C) 2015 Elsevier B.V. All rights reserved.