Synthesis and characterization Bi2O2S thin film via chemical bath deposition at low pH.

Bismuth oxysulfide thin film was prepared using Bi(NO3)3 and Na2S as reactive. Since bismuth in the form of bismuth oxide is dissolved into water, bismuth and sulfide concentration of the chemical bath is very important. Bismuth oxysulfide (Bi2O2S) thin films were produced below pH2. Tested bismuth and sulfide concentrations are as follows: 2×10(-1)M, 2×10(-2)M, 2×10(-3)M, 2×10(-4)M bismuth and 1×10(-1)M, 1×10(-2)M, 1×10(-3)M, 1×10(-4)M sulfide. The structure of the films was examined via X-ray diffraction (XRD). Optical properties, such as transmission and absorbance were measured with Ultra violet-visible spectrum, and then refractive index and reflectivity were calculated. The pH of chemical bath was stabilized below pH of 2 using 13.85mL concentrated nitric acid. Deposition time and temperature of the baths were 4h and 30°C. It has been found that bismuth and sulfide concentrations affected the structure and thickness of the film. Also, optical band gap of the films varied with concentration, parallel to the change of the structure and film thickness.