OPTICAL AND ELECTRICAL PROPERTIES OF ZnSe THIN FILMS: EFFECT OF VACUUM ANNEALING

摘要

Inert gas condensation method has been successfully employed for depositing ZnSe thin films. These films have been deposited at argon gas partial pressure of 2× 10~(-1) mbar and room temperature (298 K). After deposition these films have been annealed (in vacuum at 473 K) for one hour. The optical and electrical properties of these films have been investigated before and after annealing using optical transmission and conductivity measurements. The absorption coefficient (α) and band gap (E_g) are calculated using transmission curves. Optical transmittance measurements indicate the existence of direct allowed optical transition with a corresponding energy gap in the range of 2.80-3.00 eV. The dark conductivity (σ_d) and photoconductivity (σ_(ph)) measurements, in the temperature range 253-358 K, indicate that the conduction in these materials is through an activated process having two activation energies. σ_d and σ_(oh) values increase with the annealing. The values of carrier life time have been calculated and these values increase with the increase in the crystallite size on annealing. Thermal treatment has appreciable effect on above mentioned properties.