Structural and optical characterization of dip coated PbS nanostructured films prepared at different reaction temperature

PbS thin films were deposited by dip coating technique from lead acetate and thiourea in the reaction temperature range 100-200 degrees C. Nano structured PbS cubic phase was identified by XRD. Crystallite size of 4.8 nm was observed at lower reaction temperature and increased to 5.5 nm as the reaction temperature increases or by annealing at the same reaction temperature, Nano grains in the range 30-70 nm was observed by SEM. EDX analysis shows that the films composition are close to stiochiometric value for all deposited films. Optical absorption and dispersion were deduced from the transmittance curve only for films deposited with different thicknesses. Mathematical treatment was applied to calculate the optical parameters alpha, E(g), n and K. The absorption edge was shifted towards the visible region due to band gap increase due to strong confinement effect in nano structured system.