Exploring and controlling intrinsic defect formation in SnO2 thin films†
By investigating the influence of key growth variables on the measured structural and electrical properties of SnO2 prepared by pulsed laser deposition (PLD) we demonstrate fine control of intrinsic n-type defect formation. Variation of growth temperatures shows oxygen vacancies (VO) as the dominant defect which can be compensated for by thermal oxidation at temperatures >500 °C. As a consequence films with carrier concentrations in the range 1016–1019 cm−3 can be prepared by adjusting temperature alone. By altering the background oxygen pressure (PD) we observe a change in the dominant defect – from tin interstitials (Sni) at low PD (<50 mTorr) to VO at higher PD with similar ranges of carrier concentrations observed. Finally, we demonstrate the importance of controlling the composition target surface used for PLD by exposing a target to >100 000 laser pulses. Here carrier concentrations >1 × 1020 cm−3 are observed that are associated with high concentrations of Sni which cannot be completely compensated for by modifying the growth parameters.