Optical and photoconductive properties of Pb 0.9Sn 0.1Se nano-structured thin films deposited by thermal vacuum evaporation and pulsed laser deposition

Abstract

In this work, thin films of Pb 0.9Sn 0.1Se were deposited by thermal vacuum evaporation and pulsed laser deposition techniques. XRD measurements reveal a cubic crystalline structure for the prepared powder and deposited films. SEM micrographs show that the films consist of fine grains of size in the nanoscale. EDX analysis confirms the compositional analysis of both powder and films. Both the optical and photoconductive properties of those films were studied for comparison. Free carrier absorption was observed in the thermally evaporated films which were reduced by vacuum annealing at 773 K for 1 h under as a result of removing defects. The optical band gap of the thermally evaporated films was also reduced by annealing which was explained by removal of a Burstein–Moss shift. A strong increase of band gap of films deposited by pulsed laser technique was also abserved while it was explained by enegy gap confinment effect associated with nanostructures of semiconducting materials. Photoconductivity measurment shows that the photosensitivity of the pulsed laser deposited films is higher than those of the thermally deposited films by five order of magnitude. While the photoconduction process of thermally evaporated films is slower than that in pulsed laser deposited films.