Substrate temperature and background pressure effects on nanostructured zinc oxide thin films for thermoelectric applications

Zinc oxide (ZnO) thin films were grown on glass substrate by pulsed laser deposition (PLD) at different substrate temperature ranging from room temperature (RT) to 300ºC and various oxygen background pressures ranging from 14 mTorr to 140 mTorr, respectively. The structural, surface morphology and electrical properties of the ZnO films were investigated for thermoelectric (TE) applications. It was found that all of the fabricated ZnO films are preferentially in c-axis (002) orientation. Results showed that the electrical conductivity increased with higher substrate temperature and higher oxygen pressure. The high conductivity can be attributed to the increased grain size and surface roughness, which consequently reduced the grain boundary scattering.