Ultrasonic spray pyrolysis of Cd-doped SnO2 thin films for transparent conducting electrode applications

Abstract

SnO2-based transparent conducting oxides are often limited by low intrinsic carrier concentration despite their wide bandgap and high transparency. In this study, Cd-doped SnO2 thin films with composition CdxSn1−xO2 (CTO) for x = 0.00, 0.02, 0.03, 0.04 and 0.05 were synthesized on glass substrates by ultrasonic spray pyrolysis at 350 °C. The structure of the studied CTO was evaluated by the X-ray diffraction study which confirms the formation of polycrystalline tetragonal rutile structure (P42/mnm space group) without the presence of secondary phase. In addition, the microstructure of the deposited materials was obtained by the field emission scanning electron microscopic (FESEM) measurement that reveals grain sizes in the range of ~ 32–47 nm, with an optimal grain size of ~ 46.1 nm and reduced surface porosity, at x = 0.03. Optical studies show a systematic reduction in bandgap from 3.54 eV to 2.90 eV with increasing Cd content . Hall measurements indicate enhanced carrier concentration from ~ 0.35 × 1020 cm−3 to ~ 2.98 × 1020 cm− 3 and conductivity from ~ 4.79 S.cm−1 to ~ 7.13 S.cm− 1, while hall mobility decreases from ~ 8.56 to ~ 3.18 cm2/V·s due to increased impurity scattering. Finally, the composition x = 0.03 with exhibits an optimal balance of microstructural, optical, and electrical properties, making it a promising candidate for transparent electrode applications in optoelectronic devices.