Optoelectronic Properties of Zinc Selenide (ZnSe) Thin Films Deposited Using Chemical Bath Deposition (CBD) Technique

Thin films of Zinc Selenide (ZnSe) were deposited on glass substrate at room temperature by Chemical Bath Deposition (CBD) Technique. The sources of Zn and Se were respectively ZnSO4 and Na2SeSO3 while NaOH was employed as complexing agent. The deposited sample slides were annealed in an oven at temperatures of 200°C, 300°C and 400°C. The samples were characterized for optical band gap using Spectrophotometer (Janway 6405 UV-VIS Model) by measuring the optical absorption and transmission and Photo conductivity by using the two point probe method in which silver paint was used for attaching two copper wires (as electrodes) on the sample. The estimated band gaps are 2.89eV, 2.95eV, 3.08eV and 3.05eV for the as-deposited and the annealed thin films at temperatures of 200°C, 300°C and 400°C respectively. Annealing increases band gap energy slightly as substrate temperature increases from room temperature to 400°C which indicate blueshifts from the normal bulk value, while the photo and dark currents of the sample annealed at 300° were observed to increase linearly with the applied electric field, but the former being large and the latter is less, which is an indication of positive photoconductivity.