Annealing temperature dependent structural, optical and electrical properties of thermally deposited CdSe thin films

الملخص EN

CdSe thin films have been deposited on suitably cleaned glass substrates by thermal evaporation method.

The pressure during evaporation was maintained at 10-6 to 10-5 Torr.

The samples are annealed in vacuum for 2h at various temperatures and characterized by structural, optical and electrical properties.

The crystal structure and lattice parameter of these films were determined from X-ray diffractograms.

It was observed that the films have a polycrystalline hexagonal (wurtzite) structure with preferred orientation along (002) plane.

The crystallite size, dislocation density and micro strain were calculated by considering high intense diffraction peaks of the as-deposited and annealed films.

It was found that the average size of the crystallites increases and the average dislocation density decreases with increasing annealing temperature.

Absorption and transmittance spectra of these thin films were studied using UV-visible double beam spectrophotometer in the wavelength range of 300 – 1100 nm.

The energy band gaps have been determined using absorption spectra.

The values of the optical band gap energy, Eg, decreased from 2.37 – 2.08 eV with increasing the annealed temperature.

Dependence of optical band gap on crystallite size has also been studied.

The electrical resistivity and activation energy of CdSe thin films are calculated by two probe resistivity measurements.

The decrease in dc resistivity with increase the grain size was also noted.