Chemically deposited PbS thin film photo-conducting layers for optically addressed spatial light modulators

Abstract

Lead sulfide semiconducting thin films were chemically deposited on indium tin oxide coated glass plates for use as photoreceptor layers in conjugation with optically addressed spatial light modulators (OASLMs). Deposition conditions such as temperature, reagent concentration, pH and deposition time were optimized in order to achieve homogeneous, continuous and adherent films. Mirror-like films with tunable particle size and film thickness were obtained. The microstructure and morphology evolution of the films were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscopy. Electrical and optical properties were studied using four-point probe measurements, FTIR spectroscopy, photoluminescence spectroscopy, photo-current and photo-voltage measurements. Blue shift of the band gap to the short wavelength infra-red (SWIR) range was obtained as a function of particle size, and significant photovoltaic effect was measured. The resistivity of the films, as well as their photo-voltage response, were enhanced after thermal annealing. These results indicate that PbS films can serve as effective photoreceptors in OASLMs for applications including SWIR detection for night vision purposes.