Exploring and controlling intrinsic defect formation in SnO2 thin films

Abstract

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 (V_O) 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 (P_D) we observe a change in the dominant defect – from tin interstitials (Sn_i) at low P_D (<50 mTorr) to V_O at higher P_D 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 Sn_i which cannot be completely compensated for by modifying the growth parameters.