Influence of rapid-thermal-annealing temperature on properties of rf-sputtered SnOx thin films

We investigated rf-sputtered SnOx thin films that were processed by the infrared rapid thermal annealing (RTA) technique. The films were RTA-processed at 225, 245, and 265 °C for 2.5 min in ambient air. X-ray diffraction analyses indicate the existence of metallic Sn and SnO phases in the films. After RTA processing, metallic Sn decreases and the total amount of SnO increases. The oxidation of metallic Sn in the films becomes more significant as the temperature increases from 225 °C to 265 °C. X-ray photoelectron spectroscopy reveals that the SnO phase is the dominant phases after RTA processing. The transmittance in the visible light wavelength region improves after RTA processing and increases with the annealing temperature. The Tauc bandgap is calculated as 1.8 eV for as-deposited and increases to ∼2.8 eV after RTA processing. p-Type conductivity is confirmed for all measurable RTA-processed films by Hall measurement and Seebeck coefficient measurement. The best hole mobility achieved is 0.78 cm2 V−1 s−1 for films annealed at 265 °C and the corresponding hole carrier concentration is 4.28 × 1017 cm−3.