US films were prepared by chemical bath deposition (CBD) at 60 degreesC without stirring. The crystallographic structure of the films and the size of the crystallites in the films were studied by x-ray diffraction. The energy gap of the films was found to decrease by annealing. The best annealing temperature for CBD grown US films was found to be 350 degreesC from optical properties. The crystallite sizes were found to increase and the x-ray diffraction patterns were seen to sharpen by annealing. The optical properties of the films were seen to be dependent on the film thicknesses. The band edge sharpness of optical absorption was seen to oscillate by thermal annealing. Self-oxidation and sulfur evaporation were found to be responsible for this oscillating behaviour. Annealing over 400 degreesC was seen to degrade the optical properties of the film.