Effect of Energy and Number of Laser Pulses on the Optical Properties of ZnS Thin Films Prepared By Pulse Laser Deposition Technique

Abstract

The field of this research was thin films fabrication using pulse laser deposition technique. The aim of this work is to study the effect of the laser parameters (number of pulses and laser pulse energy) on the optical properties of the ZnS thin films fabricated by pulsed laser deposition technique. Eight Samples of ZnS thin films were fabricated by using Q-Switched Nd: YAG laser with the fundamental wavelength of 1064 nm, four of the samples were fabricated using different number of pulses (10, 15, 20, and 25) with 100 mj pulse energy and 2 Hz pulse repetition rate, the other four samples were fabricated using laser pulse energies of (125, 150, 175, and 200) mj with fixed number of pulses of 20, and pulse repetition rate of 5 Hz. The target to the substrate distance and angle were kept fixed, 2 cm, and 45o respectively. The film thicknesses were measured using FESEM measurement tool. The results showed that for the case of changing the number of laser pulses, the transmission spectra in the region (532 to 915) nm were found to be in the range from 0.40 to 0.62% depending on the ZnS thin film thickness and for each ZnS thin film the transmission spectrum is unique., and the absorption coefficients were found to be varied from (28.287 to 7.300) *103 cm-1 depending on the film thickness and wavelength. And for the case of fabricating the thin films using varied pulse energy, the thickness of the deposited ZnS thin films was found to be increased when pulse energy is increased. The transmission spectra in the tested region (532 to 915) nm were found to be in the range from 0.41 to 0.59 % depending on the ZnS thin film thickness, and for each ZnS thin film the transmission spectrum is unique. The refractive indices of all samples were found to be (2.51 lower and 3.38 higher) and change with the thin film thickness and with the wavelengths. Transmission spectra, absorption coefficients and the refractive indices of all samples they were in good agreement with the literature.