TEMPERATURE EFFECT ON STRUCTURAL AND ELECTRONIC PROPERTIES OF ZINC OXIDE NANOWIRES SYNTHESIZED BY CARBOTHERMAL EVAPORATION METHOD

Zinc Oxide (ZnO) nanowires were synthesized on the Si substrates by carbothermal evaporation of ZnO + C at elevated temperatures. The syntheses were carried out at different temperatures from 750 degrees C to 950 degrees C. Characterizations of layers were performed to study the effect of synthesis temperature on morphology, crystal structure and electrical behavior of fabricated nanowires. The physical characterization was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDAX) methods. SEM micrograph of layers revealed that the samples grown at the lower temperatures have better quality. However, below 800 degrees C the growth of nanowires was stopped. So the 800 degrees C was concluded to be the optimum temperature for growth of high quality nanowires by proposed system. By recording the conductivity variations as a function of inverse temperature, 1/T, the semiconductor property of the samples was verified. It is demonstrated that two distinct factors affect the electrical conductivity of layers, which are due to the bulk and grain boundary. We experimentally proved that the activation energy corresponding to grain boundary is higher than that of the bulk. As another result we have established for the first time that by increasing synthesis temperatures, both activation energies shift to higher values.