Influence of substrate temperature on the properties of spray deposited nanofibrous zinc oxide thin films

Zinc oxide (ZnO) thin films were deposited onto glass substrates by a spray pyrolysis technique at the substrate temperatures (T-s) between 250 and 500 degrees C. T-s was observed to be one of the key parameters to influence the structural, surface morphological, optical and transport properties of ZnO thin films. X-ray diffraction patterns of the ZnO thin films showed polycrystalline hexagonal wurtzite structure and the preferred orientation was along (002) plane which got more prominent with the increase of T-s. Field emission scanning electron microscopy of ZnO thin films showed the existence of nanofibers in the films with the average thickness ranging from 308 to 540 nm. Atomic force microscopy revealed that roughness of the ZnO thin film increased at higher T-s. ZnO thin films were highly transparent in the visible to near infrared region with the maximum transmittance of 89% and the optical band gap was found from 3.23 to 3.31 eV. ZnO thin films showed n-type conductivity with the carrier concentrations ranging between 10(19) and 10(20) cm(-3). ZnO thin film deposited at the T-s of 400 degrees C showed the highest mobility, highest carrier concentration and less resistivity.