Photocurrent Characteristics And Rectifying Properties Of A Single Zno Nanowire Schottky Barirer

ZnO as a direct wide band gap3.37eV (300K) semiconductor with hexagonal wurtzite structure andlarger exciton binding energy60meV has caused a widespread research. One dimensional (1D) ZnOnanowires or nanobelts can be prepared as more excellent ultraviolet detectors, gas sensors, lasertransmitter due to its large surface-to-volume ratio, high surface activity and the quantum size effect. In thispaper, we studied the electrical transport properties of Schottky contacts through I-V-T characteristics, andobserved a persistent photoconductivity effect by means of controlling the Schottky barrier height throughhigh vacuum and UV. In additional, we also studied the rectifying behavior of the schottky contacts inI-V-T characteristics and found the barrier height inhomogeneities in low temperature. Under smallfrequency sine wave and forward bias, a cut-off characteristic was observed.In Chapter2, ZnO nanowires were synthesized by vapour-liquid-solid and hydrothermal method. Themorphology and structure of the products were characterized by SEM、TEM、HRTEM and XRD, then asingle ZnO NW was aligned by AC electric field assemblyIn Chapter3, We first studied the single ZnO nanowire Schottky contacts with the I-V characteristicsin the30-490K. We found schottky contacts trends to ohmic contacts when the test environment waschanged from the atmosphere at room temperature into the vacuum and placed a long time. This shift wasmainly caused by the lower barrier height and tunneling current increases. Under vacuum and UV light, weobserved the photocurrent was first enhancement and then stable, turned off the UV light and placed invacuum for a long time, the photocurrent had a significant increase once again under UV light,which is apersistent photoconductivity effect. This showed that the chemisorbed oxygen was not desorptioncompletely from interface at one time, and chemisorbed oxygen’s desorption was relate to its location. Sowe need chemisorbed oxygen to get in the easy desorption in order to get a high switching ratio under UV.In Chapter4, the new simple of Au/ZnO nanowire/Au exhibited clear rectifying behavior under dark.We also found the rectifying behavior had relation to temperature and voltage in I-V-T testing process. With increasing temperature, rectifying behavior would not only become better but also need much smallbias to reach a saturation current. Loading10-1000Hz and10Vpp sine, square wave in the sample, wewould find sine wave in the forward bias became into cut-off characteristics in a small frequency. Butsquare wave deviated from the original rectangular wave characteristics in high frequency (1000Hz).Under UV, the amplitude of the wave enlarged more than10times compared to the dark state.