Dependence of O2, N2 flow rate and deposition time on the structural, electrical and optical properties of SnO2 thin films deposited by atmospheric pressure chemical vapor deposition (APCVD)

In this research, SnO2 films were prepared by atmospheric pressure chemical vapor deposition technique on a glass substrate. Then, the effects of oxygen and nitrogen flow rates and deposition time on the structural, optical and electrical properties of the thin films were studied. The films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy, atomic force microscopy, electrical resistance measurements using two-point probe technique, Hall Effect, photo-conductivity effect and optical absorption (UV-Vis). The films had uniform polycrystalline structure. The average optical band gap of the films was 3.8 eV. The results of Hall Effect showed that majority carriers were n-type and carrier concentration varies in the range of 5.84 x 10(18)-1.89 x 10(19) cm(-3). Increasing oxygen flow rate led to increasing the specific resistance, photosensitivity and Seebeck coefficient (at 350 K), and also decreasing optical band gap, mean grain size and surface roughness plus higher XRD peaks. Increasing nitrogen flow rate led to decreasing optical band gap, specific resistance, and photosensitivity and Seebeck coefficient (at 350 K). Increasing the deposition time led to an increase-decrease trend in the optical band gap, a decrease-increase trend in specific resistance and an increase in photosensitivity and Seebeck coefficient (at 350 K). The average transmittance and optical band gap of films were 82 % and 3.8 eV, respectively. Hall Effect studies revealed that the films exhibit n-type conductivity.