Effect of Al doping on structural, optical and electrical properties of SnO₂ thin films synthesized by pulsed laser deposition

Abstract

Aluminium-doped (Al = 0–5 wt.%) SnO₂ thin films with low-electrical resistivity and high optical transparency have been successfully synthesized by pulsed laser deposition technique at 500 °C. Structural, optical and electrical properties of the as-deposited and post-annealed thin films were investigated. X-ray diffraction patterns suggest that the films transform from crystalline to amorphous state with increasing aluminium content. The root mean square (R_q) surface roughness parameter, determined by atomic force microscopy decreases upon annealing of the as-deposited film. While resistivity of the film is the lowest (9.49 × 10⁻⁴ Ω-cm) at a critical doping level of 1 wt.% Al, optical transparency is the highest (nearly 90%) in the as-deposited condition. Temperature dependence of the electrical resistivity suggests that the Mott’s variable range hopping process is the dominant carrier transport mechanism in the lower temperature range (40–135 K) for all the films whereas, thermally activated band conduction mechanism seems to account for conduction in the higher temperature region (200–300 K).

Keywords:

• thin films
• X-ray diffraction
• atomic force microscopy
• transparent conducting oxides
• amorphous

Acknowledgements

Partial financial supports from the Department of Science and Technology (DST) to I. Manna (J C Bose fellowship) and Council of Scientific and Industrial Research (CSIR), Government of India (Project: GAP 0280 and SRF support to S.K. Sinha) are gratefully acknowledged.