Fabrication Of Horizontal Well-aligned ZnO Nanowires For UV Sensor Applications

Wide bandgap semiconductor ZnO was used to be the sensor and solar cell due to its special photo and electrics property. Meanwhile,,With the development of information storage and semiconductor fabrication technology, the requirement of the machining dimension for semiconductor memory device become more and more small. Such as, ZnO based nanowire has been combined into the device already, however, the size of nanowire is too small to fabricate the device directly by the traditional micro-nano fabrication technology, which limit the ZnO nanowire to be used in nanoscale device in larger content. In order to solve this problem, the transverse nanowires consisted of ZnO network were grown on the electrode of silicon without catalyst technology by chemical vapor deposition method. The effect factors on ZnO nanowires growth were studied and the UV-vis performance of the ZnO network were measured by ultraviolet in detail, which include the following three parts:The first section mainly focus on the effects of reaction time, reaction pressure, different carbon sources(graphite and nano-diamond) and mass ratio on the growth of ZnO nanowires and network were studied in detail. The result shown that the length of nanowire is increasing with the gowth time increasing; the number of nanowire in content area also increased with the pressure increasing; meanwhile, the nanodiamond as the carbon source intruduce the ZnO into Zn, the growth rate get greatly increasing than the graphite as the carbon source. The mass ratio of ZnO/diamond equal to 4:1 is the best for ZnO nanowire groth.it is reasonable that nanodiamond has large area surface and lower active reaction temperture than graphite.In the second section, the growth mechanism of ZnO nanowire circuit(net-like) on column-like electrode and its UV sensing performance was investigated, respectively. Based on the ZnO controllable growth process, the colum-like Si substrate was firstly fabricated by micro fabrication technology. And then the Si substrate with the face-down was placed on the top of source materials(ZnO and graphite powder). The transverse net- like ZnO nanowires were fabricated secondly by adjusting the gas and inner pressure. The nucleation and growth of ZnO nanowires were analyzed in this section. The reasons transverse grown at the edge of electrodes can be conclude that the edge of electrodes exhibited a higher cohesive energy and vapor concentration of source materials near the edge of electrodes was higher. Finally, the performance test of the ZnO nanowire net shown that the current changed obviously when the ultraviolet shines on the net nanowiresIn the last section, in order to improve performance of the sensor, the electrode was further optimized into strip structure. Nanodiamond were used to manufacture the ZnO nanowire, and these samples would be tested by ultraviolet light. The testing result shown that the dark current of ZnO nanowire bridge circuit under UV irradiation is in 10-9 orders of magnitude, the photocurrent under uv irradiation is in 10-7 orders of magnitude, the optical gain increased greatly with 57 times.