Fabrication And Field Emission Properties Of The One-dimensional ZnO Semiconductor Nanowires

Low dimension ZnO nanowires have many unique properties. As a result, they are widely used in the field emission of cold cathode. The studying fields arouse the researchers' interest and attention.ZnO is a kind of large energy gap semiconductor material. It is suitable for the preparation of field emission devices, because of its favorable physic and chemical features, such as high surface-to-volume ratio and the aspect ratios. Therefore, the study of its characteristics of is very necessary and has important practical significance. In this article, well-aligned one-dimensional ZnO nanowires were synthesized via a simple solution-phase approach and their field emission properties were studied, mainly the following:1. Using the solution-phase approach, well-aligned one dimension ZnO NW arrays were directly prepared on zinc foil substrates reacting in aqueous ammonia at a constant temperature of 95℃. During the experimental processes, some zinc foils were vertically immersed into 20 ml aqueous ammonia solution of 4,7,10, and 15%(V/V) for 24 h, respectively. And some treated zinc foils were reacted in 15% aqueous ammonia for 6,12 and 24 h. The morphology and microstructure of the synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).2. The field emission characteristics of the ZnO samples were obtained with a field emission measurment instrument using a diode structure. In the test process, the cathode is one-dimensional ZnO nanowires, and the anode is a polishing copper. The turn-on field and threshold field and field enhancement factor (β) were measured as well. In addition, the JE and the FN curve were described with the measured data of field emission. The results showed that the ZnO samples have good field emission characteristics:the open field of samples synthesized with different concentrations of the reactants is about 10～17V/μm, the threshold electric field is about 17～26V/μm; the open field of ZnO sample with different growth time is about 10～14V/μm, the threshold electric field is about 17～22 V/μm. And field emission characteristics of the different ZnO samples showed very good stability. We found that the field emission characteristics of the 1D ZnO NW arrays can be adjusted by their geometrical structure, such as mean diameter, growth length as well as its surface-to-volume ratio. 3. The influence factors of field emission characteristics to the synthesized one-dimensional ZnO nanowire is studied. And the field emission characteristics is mainly affected by the field screening effect and the emitter geometric morphology of the ZnO nanowires. By the theoretical formulaβ0=1/kr, we can work out that the smaller the sample's radius is, the greater the field enhancement factor is, which is consistent with experimental findings.