Band alignment of Cd_((1-x))Zn_xS produced by spray pyrolysis method

摘要

Cd_((1-x))Zn_xS thin films have been grown on glass substrates by the spray pyrolysis method using CdCl_2 (0.05 M), ZnCl_2 (0.05 M) and H_2NCSNH_2 (0.05 M) solutions and a substrate temperature of 260 ℃. The energy band gap, which depends on the mole fraction x in the spray solution used for preparing the Cd_((1-x)) Zn_xS thin films, was determined. The energy band gaps of CdS and ZnS were determined from absorbance measurements in the visible range as 2.445 eV and 3.75 eV, respectively, using Tauc theory. On the other hand, the values calculated using Elliott-Toyozawa theory were 2.486 eV and 3.87 eV, respectively. The exciton binding energies of Cd_(0.8)Zn_(0.2)S and ZnS determined using Elliott-Toyozawa theory were 38 meV and 40 meV, respectively. X-ray diffraction results showed that the Cd_((1-x))Zn_xS thin films formed were polycrystalline with hexagonal grain structure. Atomic force microscopy studies showed that the surface roughness of the Cd_((1-x))Zn_xS thin films was about 50 nm. Grain sizes of the Cd_((1-x))Zn_xS thin films varied between 100 and 760 nm.