Effect of substrate on thermoelectric properties of Al-doped ZnO thin films

Abstract

We have prepared 2% Al doped ZnO (AZO) thin films on SrTiO3 (STO) and Al2O3 substrates by Pulsed Laser Deposition technique at various deposition temperatures (Tdep = 300 °C–600 °C). Transport and thermoelectric properties of AZO thin films were studied in low temperature range (300 K–600 K). AZO/STO films present superior performance respect to AZO/Al2O3 films deposited at the same temperature, except for films deposited at 400 °C. Best film is the fully c-axis oriented AZO/STO deposited at 300 °C, which epitaxial strain and dislocation density are the lowest: electrical conductivity 310 S/cm, Seebeck coefficient −65 μV/K, and power factor 0.13 × 10−3 W m−1 K−2 at 300 K. Its performance increases with temperature. For instance, power factor is enhanced up to 0.55 × 10−3 W m−1 K−2 at 600 K, surpassing the best AZO film previously reported in literature.