INVESTIGATING THE EFFECT OF THICKNESS ON OPTICAL PROPERTIES OF CHEMICAL BATH DEPOSITED ZINC SELENIDE THIN FILM FOR OPTOELECTRONIC DEVICES

Abstract

The ZnSe thin films have been deposited onto glass substrates by the simple chemical bath
deposition method using Sodium selenosolphite solution, zinc acetate, hydrazine hydrate, liquor
ammonia and sodium hydroxide in which hydrazine hydrate was employed as complexing agent.
Extrapolation of the absorption curves to the photon energy axis of ZnSe films with thicknesses
350 nm, 500 nm and 700 nm gives a wavelength of ~490 nm, ~ 520 nm and ~540 nm
respectively. The as deposited ZnSe thin films are red in colour. ZnSe thin film of three different
thickness which are 350 nm, 500 nm, and 700 nm were obtained and the optical properties of the
different thickness were investigated using ultraviolet - visible spectrophotometer. The estimated
energy bandgap values for ZnSe layers with thickness of 350 nm, 500 nm and 700 nm were
estimated to be 2.80 eV, 2.70 eV and 2.64 eV respectively. The reflectance effect started
originating in the visible region when the wavelength is~510 nm, ~560 nm and ~580 nm for
thicknesses 350nm, 500nm, and 700nm respectively. Average Absorption Coefficient, a , Average
Extinction Coefficient k and Average Refractive Index,n at their various thickness were
determined.