Fabrication and characterization of nanocrystalline CdS thin film-based optical sensor grown via microwave-assisted chemical bath deposition

摘要

Highly uniform nanocrystalline cadmium sulfide (CdS) thin films were successfully deposited on Si (111) substrates by microwave-assisted chemical bath deposition technique. Cadmium chloride (CdCl_2) and thiourea [SC(NH_2)_2] precursors with different molar concentrations were used to prepare nanocrystalline CdS thin films. The effect of the molar concentration of reagents on the quality of the deposited thin films was investigated. Structural and morphological studies revealed that the quality of the grown CdS thin films was significantly affected by molar concentrations of reagents. Optimal thin film quality was utilized to fabricate a nanocrystalline CdS-based optical sensor. Current-voltage measurements (Ⅰ-Ⅴ) for the fabricated device showed significant sensing to low-power (0.3 mW/cm~2) 500 nm light. The device exhibited high responsivity of 0.65 AW~(-1) at 3 V applied bias. Time response measurements showed rapid response and baseline recovery under low applied bias voltage, indicating good quality of the deposited thin film. A simple and low-cost method to fabricate a low-power, highly photosensitive optical sensor was introduced.