The Controlled Synthesis And UV Detection Properties Of â…¡-â…¥ Nanostructures

Ultraviolet detection device have broad application prospects in missile early warning, ultraviolet communication, environmental monitoring, medical and other fields. As an ideal material for building UV detector, wide band gap semiconductor ZnO is attracting ever-increasing attention. The thesis firstly introduced the research progress of UV detector constructed by ZnO nanostructures in recent years and listed the problems in the frabrication of UV detectors.In chapter2, a chemical vapor deposition method was used to synthsize the tetrapod ZnO nanostructures. The product was examined by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM). The corresponding mechanism was slao discussed. Then, several ZnO nanostructures including flower structures, tetrapod sheets, and other complex structures were also fabricated and characterized.In chapter3, a highly sensitive ultraviolet (UV) photodetector based on spatial network of tetrapod ZnO nanostructures was fabricated by a new simple and cost-effective method. The device showed drastic and fast response to UV illumination in atmosphere at room temperature, but no response to visible light. The photocurrent and dark current contrast ratio is up to approximately6orders of magnitude at an applied bias of â…£. The photoresponse mechanism is also analyzed and discussed. Then, another new simple technique was used to fabricate the ultraviolet photodetector with ITO/ZnO/ITO structure. The ultraviolet detecting properties were examined and the corresponding mechanism was discussed. The results show that the device based on the tetrapod ZnO nanostructures responds very well to ultraviolet (365nm). The corresponding responsivity is about0.8A/W. The photocurrent and dark current ratio is4to5orders of magnitude at a bias of1V. The photoresponsivity of the detector has a maximum value near by372nm. Our approach provides two facile and effective ways to fabricate high-performance photodetector or other nanodevices.In chapter4, ZnS nanobelts were firstly synthesized by CVD method. The product was characterized by XRD, SEM and TEM. Then, the above simple technique was also used to fabricate the ultraviolet photodetector with Au/ZnS/Au structure. The I-V and ultraviolet detecting properties were examined and the corresponding mechanism was discussed. The results show that the device based on the ZnS nanobelts responds very well to ultraviolet (300nm).