Variations in Optical Properties of ZnS/Cu/ZnS Nanostructures Due to Thickness Change of ZnS Cap Layer

Nanostructures of ZnS/Cu/ZnS were deposited on glass substrate using physical vapor deposition technique. The thickness of the first and last ZnS layers was altered, while the thickness of the embedded Cu layer was fixed at 50 nm. The produced nanostructures were of good quality. Spectrophotometric measurements were carried out on the nanostructures to investigate the optical properties. The transmission and reflectivity spectra were recorded and studied in details. ZnS was selected due to its high refractive index, ease of deposition, and low cost. The copper layer was used because of its low absorption in the visible part of the spectrum and its thermal stability. The ZnS layer was found not only to anti-reflective the Cu layer, but also to stabilize the nanostructure, improve its adherence on glass substrate, and increase the film thermal resistance up to 240 °C. Furthermore, all the samples exhibit good thermal stability up to 240 °C upon annealing for two hours.