Effect of thermal annealing on the physical properties of Zn1−x Cu x Se thin films deposited by close spaced sublimation technique

Abstract

Thin films of Zn1−x Cu x Se (x= 0.00, 0.05, 0.10, 0.15, 0.20) were grown on glass substrates by closed space sublimation technique. The deposited films were annealed at 200 °C and 400 °C in air for 1 h. The annealed samples have been investigated through Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), spectroscopic ellipsometer, spectrophotometer and Raman spectroscopy. Through RBS, the composition of the films was calculated and compared with the initial concentration. Structural characterization including crystal structure, crystal orientation, lattice parameter, grain size, strain and dislocation density were carried out using XRD data. From XRD spectra it was revealed that the as-deposited and annealed films were polycrystalline in nature with zinc-blende structure. However, the crystallinity and the grain size were improved with the increase of annealing temperature. According to Raman spectroscopy, it was observed that as deposited and annealed samples have the same characteristic vibrational modes of ZnSe at low and high frequency optical phonon modes while another mode was observed for 400 °C annealed samples at 745 cm−1. Spectroscopic ellipsometer has been used to found annealing effect on the optical properties of ZnSe. The band gap energy has been determined using transmission spectra. It was found that the band gap energy of the film increased with the increase of annealing temperature.