Effect of substrate temperature on the structural properties of ZnO nanorods

Zinc oxide (ZnO) nanorods (NRs) are very attractive for various applications such as new generation solar cells, photoelectronic devices, laser diodes (LDs) and light emitting diodes (LEDs). ZnO thin films were prepared with various substrate temperatures by the ultrasonic spray pyrolysis (USP) deposition method on glass substrate. The effect of substrate temperature on the structural, morphological, electrical and optical properties of ZnO-NRs was examined by using X-ray diffraction (XRD), field emission electron microscopy (FE-SEM) and ultraviolet-visible range spectrometry (UV-Vis). The XRD patterns revealed that the ZnO samples are polycrystalline in nature having a wurtzite crystal structure with a c-axis preferred grain orientation in the (002) direction. FE-SEM analysis illustrated that the NRs structure of the ZnO samples changes with surface temperature. The average crystal size of the ZnO samples varies from 26 nm to 38 nm with the increase of surface temperature from 350 °C to 500 °C. Variations in the electrical conductivity of the ZnO-NRs with the test temperature in the range of 35-500 °C were also measured by the using four probe dc system. ZnO films are highly transparent in the visible region with an average optical transmittance of over 80%.