Preparation Of ZnO, ZnMgO Nanomaterials And Application In UV Photodetectors

In the last decade, one-dimensional or quasi-one-dimensional nanostructures have been widely researched as potential building blocks for photodetectors. It is reported that nanowire (NW) photoconductors can yield higher light sensitivity than their bulk counterparts due to the large surface-to-volume ratio and low dimensions. As aⅡ-Ⅵwide band gap (Eg= 3.4eV) semiconductor, ZnO has a very large family of nanostructures and a great prospect for UV detection. By incorporating Mg, MgxZn1-xO ternary alloy can be fabricated and the bandgap can be tuned continuously from 3.4 eV to 7.8 eV given the different values of x.In this paper, ZnO one-dimensional nanomaterial and ZnMgO ternary alloy nanowires were successfully fabricated using a two-temperature-zone horizontal tube furnace. UV detection prototype device was fabricated taking advantage of ZnO nanonail arrays. The main achievements are as follows:1. Using a thermal evaporation method, a series of ZnO nanostructures were prepared.(1) Controlable growth of ZnO nanorods and nanorod arrays, nanowires and nanowire arrays, nanocombs, and nanowall was achieved.(2) A variety of experimental parameters which influence morphologies of the nanostructures, including temperature and substrate type were studied. We found that when the temperature was raised, the nano-structures would become more dense and the size would also become larger. It is more preferable to prepare long nanowires when the substrate temperature were high(e.g.700 to 900℃); The nanocomb structure tend to grow at about 900-1000℃using a substrate deposited with a layer of Au.2. On the basis of ZnO one-dimensional nanostructures, ZnMgO alloys were successfully fabricated. The main results are as follows:(1) Preparation of hexagonal ZnMgO nanowires. XRD, TEM, and PL results showed that the sample had phase separation, and ZnO and MgO phase coexisted; There were Mg element in the hexagonal nanowires. PL analysis indicated that the Mg content is about 4 at%, which is the solubility limit of Mg in ZnO. (2) Preparation of MgO nanowires and nanorods. In order to prepare cubic phase ZnMgO nanowires, MgO nanowires and nanorods, and other micro-and nano-structures were successfully prepared.(3) For the fist time, cubic Zn0.8Mg0.2O nanowires were synthesized. The nanowires were obtained using the mixture of Zn and Mg powders as the evaporation source. XRD showed that there were also phase separation. TEM analysis showed that the cubic nanowires were poly crystalline. EDX analysis showed that the composition of nanowires was Zn0.8Mg0.2O.3. For the fist time, film-like ZnO nanonail arrays were prepared, A prototype device of UV detector was fabricated using the structure.(1) ZnO nanonail array were prepared. Seen from the top, the top caps of nanonails were interconnected and a layer of quasi-continuous film was formed. The growth mechanism of this structure was also discussed.(2) Using this structure, ZnO UV detector prototype was prepared. Under 364 nm UV irradiation and 5 V voltage, the conductance was amplified 50 times. The decay time of the detector was 28 s.