Electrodeposition of tin oxide thin film from nitric acid solution: the role of pH

Abstract

Tin oxide (SnO2) thin films were synthesized by electrodeposition method from nitric acid medium with SnCl2 precursor and NaNO3 supporting electrolyte at 70 °C. The effect of pH electrolyte in the properties of SnO2 thin films was investigated. Cyclic voltammetry (CV) was utilized for the determination of the selective potential for electrodeposition of pure SnO2. Mott–Schottky (M–S) plots and electrochemical impedance spectroscopy (EIS) techniques were carried out to estimate the electrical characteristics of the SnO2 thin films deposited at different pH electrolytes. These latter techniques show n-type conductivity for all the samples with optimal carrier density of 8.41 × 1020/cm3 and high value of conductivity for the films electrodeposited at pH ~ 1.10. Atomic force microscopy (AFM) observations showed that the SnO2 thin films obtained at different pH are more homogenous in appearance and present lower surface roughnesses at lower pH value. Structural analysis of the SnO2 thin films was performed by X-ray diffraction (XRD) which exhibit a polycrystalline structure for pH ~ 1.25 and amorphous one for another pH values. From the optical study, the transmittance and the gap energy were founded to be depending to the pH of electrolyte.