Photoluminescence and structural properties of tin-doped ZnO thin films deposited by sol-gel dip coating

Tin-doped ZnO (TZO) thin films with various tin concentrations (0, 1, 2, 3, 4, and 5 atomic percent [at. %]) are prepared by the sol–gel dip-coating method. The doping effects of tin on the structural and optical properties of the TZO thin films are investigated. All the samples have a granular structure consisting of small particles and exhibited a preferred c-axis orientation. The transmittance and optical band gap of the TZO thin films increase at relatively low tin concentrations of 1–2 at. %, whereas they decrease at higher concentrations of 3–5 at. %. The ratio of near-band-edge emission intensity to deep-level emission intensity significantly increases with increasing tin concentrations from 0 to 4 at. %. In addition, low-temperature photoluminescence for undoped and 4 at. % TZO thin films are measured at 12 K to thoroughly analyze the effects of tin doping