EXPERIMENTAL-STUDY OF THE COPPER THIOSULFATE SYSTEM WITH RESPECT TO THIN-FILM DEPOSITION

An experimental study of the copper-thiosulfate system in mild acidic (pH similar to 5) aqueous solutions, with respect to thin-film formati on, was undertaken. Thin films of CuxS (1 less than or equal to x less than or equal to 2) were deposited by a simple electroless technique on glass or transparent polyester films, at 50 degrees C. Thin films w ere deposited from chemical baths in which the ratios of copper to thi osulfate were varied from 1:1 to 1:10. Thin films of different composi tions (Cu2S, Cu1.8S, Cu1.4S and CuS) were prepared and then characteri zed for morphological, optical and electrical properties. The deposite d films chemically close to Cu2S were found to be amorphous, while the CuS films were a mixture of both amorphous and polycrystalline phases . The optical spectra of the Cu2S films exhibited high transmission bo th in the visible region of the spectrum (beyond 600 nm) and throughou t the near-infrared region (800 to 2500 nm), while CuS films were foun d to be highly absorptive throughout the near-infrared region, with pe aked transmission in the visible region at about 560 nm. The sheet res istances of the films, determined by the standard four-probe measureme nts, were between 100 and 650 Ohm/square.