Synthesis and spectroscopic properties of Cr-doped ZnS crystalline thin films

Abstract

It is demonstrated that pulsed laser deposition is a promising “alternative route” for synthesis of middle infrared laser media based on chromium doped ZnS crystalline thin films with a precisely controllable concentration of dopant. The deposition rate and thickness of the thin films synthesized in our experiments varied from 0.017 to 0.109 nm per pulse and 200 nm up to 12 µm, respectively, depending on the laser energy density, number of pulses, and target-substrate distance. Cr concentration in the target mate rial and grown thin film measured by different techniques were very close to each other for a dynamic range of Cr concentration from ~ 10 19 to 3.5 × 10 20 cm -3 . Thin film features luminescence band which is similar to the band in bulk crystal (slightly blue-shifted). The emission lifetime of Cr 2+ : ZnS films with Cr 2+ concentration of ~2 × 10 19 cm -3 was measured to be ~3 µs. The emission lifetime was shortened to 1 µs for 1.8 × 10 20 cm -3 and to 0.67 µs for 3.5 × 10 20 cm -3 concentration of chromium due to the concentration quenching. Spectroscopic study shows that Cr 2+ :ZnS thin films synthesized by pulsed laser deposition are promising