Study of Ho doped Ag₂S thin films prepared by CBD method

Ho doped Ag₂S thin films were grown on the glass substrate by chemical bath deposition (CBD) method at room temperature. The bath contained aqueous solution of silver nitrate, thiourea, EDTA, ammonia and holmium nitrate. Silver nitrate was used as a silver (Ag⁺) ion source; thiourea as sulfur (S⁻) ion source, EDTA was a complexing agent while ammonia was used to maintain pH, Ho(NO₃)₃ was taken as a source of Ho ions. The optical absorption edge of undoped (pure) and Ho doped silver sulfide films was determined between 324 nm and 298 nm showing blue shift as compared to bulk Ag₂S. Band gaps calculated from Tauc plot also showed an increase in values for doped samples. The increase in band gap indicates reduced particle size in the prepared Ho doped films. The photoluminescence emission peaks were observed at around 578 nm to 601 nm wavelength and excitation peaks were found at 351 nm to 294 nm for undoped and doped films. The SEM micrograph consists of globular ball type and flower type structures observed in the prepared films of Ho doped Ag₂S.