Abstract
In this study, a series of electrical property measurements and discussions about metal oxide nanowires were carried out, including tungsten oxide (WO3) and iron oxide (α-Fe2O3 and Fe3O4) nanowires. There was a large discrepancy in the two-probe measured resistance from various two-probe devices. In general, a total measured resistance containing both of the contact resistance and the wire resistance were obtained by the two-probe measurement technique. In order to avoid the influence of contact resistance, the four-probe measurement technique was utilized to get the real resistance of α-Fe2O3 nanowire. In addition, due to the solution dispersing method utilized for transferring nanowires onto the chips, there were residual solvent contaminants on the chips to induce leakage current even the devices not work. Due to the semiconducting behavior of tungsten oxide and iron oxide nanowires, their field effect characteristics are interesting. In the measurement of tungsten oxide nanowires, there was no field effect when applying high gate voltage from +20 volt to -20 volt. In addition, by measuring at lower temperature (T~4K), the activation energy can be calculated as 0.02 eV caused by the high bandgap and more intrinsic transport property of the WO3 nanowires. In the case of α-Fe2O3 nanowires, the four-probe measurement technique was utilized to get the real resistance in nature. In addition, the p-type behavior for semiconductor was first measured, and then the n-type character for semiconductor was measured. The appearance of different atmosphere and the existence of oxygen vacancy are explained. In the study of Fe3O4 nanowires, the field-effect can’t be found from the Fe3O4 nanowires even through the gate voltage is increased to ±20 volt and the source-drain bias is also increased to ±2 V, the I-V characteristic almost remains unchanged. Moreover, by measuring at lower temperature (T~4K), the activation energy can be calculated as 0.214 eV higher than the value of Fe3O4 core-shell structure (0.1eV). This could be explained by the different work functions between metal electrodes we chose and nanowires. From the curve of resistance versus temperature, the Verwey temperature about 122 K can be found.