We report on chemically deposited thin films of PbS alloyed with thorium. Material properties, including the optical band gap, are shown to strongly depend on film composition, presenting a clear bowing behavior and enhanced SWIR absorption.

The early stages of growth in chemical solution deposition of lead selenide thin films on GaAs(100) substrates were studied in detail. The deposition was found to depend strongly on substrate pre-treatment with sodium selenosulphate in an aqueous KOH solution. In cases where this stage of the process was neglected, film growth did not occur. The sequence of precursor addition and the pH of the solution were also found to be dominant factors affecting film growth. The film growth rate, grain size and the resulting roughness were all shown to increase with pH. Study of film growth kinetics revealed the selenide limited nature of the system. These factors were shown to be critical for reproducible deposition of high quality PbSe thin films.