Fabrication Of Wide-band Semiconductor Nanostructures And Study Of Its Field Emission Application

Wide-band semiconductor nanostructures materials have received great interests due to their relatively wide energy gap and special physical and chemical properties. So they have great potential application in Photonics, Electronics, Magnetics, and Bichemistry. In this Master degree thesis, fabrication of ZnO nanostructures and GaN nanostructures has been studied, and their application in field emission has also been studied. Main concludes and results are listed as follow:1. Different growth methods are employed in fabricating ZnO nanostructures, and we have successfully synthesized different morphology ZnO nanostructures such as nanobelts, nanowires, nanorods. Via changing the growth conditions, quasi-cubic ZnO nanorods, for the first time, are synthesized. XRD, SEM, TEM and HRTEM are used to study the morphology and structure characteristics of the ZnO nanostructures. In conclusion, growth of ZnO nanostructs is closely relative to substrate and growth condition.2. Fabrication of patterned ZnO nanostructures is studied. We have successfully synthesized patterned ZnO nanowires on patterned substrate, and we also have gotten ZnO nanowires with different patterned pattern according to the growth mechanism of VLS. Additionally, nanocircuit made of ZnO nanowires has been fabricated, which pave the way of its application in field emission devices and nano-electronic circuit.3. The field emission properties of ZnO nanostructures acted as cold cathode have been studied. The effect of two parameters of size of ZnO nanostructures and substrate on field emission is studied. The results of field emission reveal that turn-on field and threshold field are lower when the sizes become smaller. Additionally, the field emission properties become better when the resistivity of substrate is lower. The field emission property of ZnO nanorods with cubic morpholy is best among the products with turn-on field of 2.5V/ μm and threshold field of 7.2V/ μm. Its field emission density is about 10~4cm~-2Meanwhile, stability of cubic ZnO nanorods has been tested, and the field emission current is kept 500MA/cm~2 during 10 h with current fluctuation within ±3%.4. Via changing the growth condition, GaN nanoparticles and nanobelts havebeen synthesized. The XRD, SEM, TEM, and HRTEM are employed to analyze the morphology and structures of GaN nanostructures. It is worthy to mention that GaN nanobelts with herringbone morphology is clearly observed by TEM. This kind morphology can benefit the field emission of GaN nanobelts. We have measured GaN nanobelts field emission. Its turn-on field is low as 6.1V/μm, what's more, its emission stability is very good with fluctuation within ±6%. So this kind of GaN nanostructures has wide applications in plan field emission display.