Structure and optical properties of chemically deposited Sb2S3 thin films

Chemical bath deposition was used to prepare antimony trisulfide (Sb2S3) thin films, of different particle size and with noticeably different band gaps, onto glass substrates. The structural investigations revealed that the as-deposited films are amorphous in nature. The particle size determined from the intercept method using SEM micrographs increases from 20 nm to 100 nm as the duration of the deposition increases. The optical absorption edge shifted from the bulk energy gap of 2.2 to 3.8 eV on decreasing the particle size. This phenomenon is interpreted in terms of the quantum size effect of electrons and holes in Sb2S3 nanoparticles. The optical constants of the Sb2S3 thick films (589 nm) were determined from the interference maxima and minima in the wavelength range 400-2500 nm using the Swanepole method. The Wemple-DiDmenico single-oscillator model parametrizes the refractive index.