Study On Modification And Broadband Photosensitivity Properties Of ZnO Nanowires

Photodetection technology has been widely used in various civilian fields.In order to meet the needs of different applications,the preparation of broadband optical devices with broad spectrum detection capabilities,high responsibility,small size and easy to integrate with other devices is one of the key development directions of future photodetection technologies.Zinc Oxide(ZnO),a direct band gap semiconductor,has many advantages,such as a large exciton binding energy(about 60 meV),easy to prepare,compatible with Si processing technology,stable physical and chemical properties,safe and environmentally friendly.Compared with its bulk materials,represented by ZnO nanowires(NWs),ZnO nanomaterials have a larger specific surface area,a higher surface atom ratio,and more surface dangling bonds and adsorption sites,which not only contribute to their excellent photoelectric properties,but also provide the possibility of material modification and performance optimization.In this paper,the methods of ZnO NWs modification with organic dyes Rhodamine B(RhB)and Au nanoparticles(NPs)were proposed.ZnO NWs-RhB nano-composite film and ZnO NWs-Au NPs composite film were designed and prepared successfully.A broadband photodetector and an ultraviolet photodetector with high responsivity were realized.In the second chapter of this paper,the modification of ZnO NWs and the photosensitivity mechanism were analyzed theoretically.The response spectrum was broaded by the modification of ZnO NWs with RhB.Then,the finite-different time-domain(FDTD)was used to simulate the effection of Au NPs induces local surface plasmon resonance(LSPR)at the metal-semiconductor contact interface for the improvement of material absorptive properties and the device responsivity.In the third chapter of this paper,the fabrication process of device was dicussed.The photodetector based on ZnO NWs was fabricated by spray-up method.A broadband photodetector based on ZnO NWs-RhB nano-composite film and a photodetector with high responsivity based on ZnO NWs-Au NPs composite film were successfully prepared by solution-casting and spin coating processes.And the above composite films were characterized and analyzed.In the forth chapter of this paper,the two photodetectors above were tested and discussed.The broadband photodetector based on ZnO NWs-RhB nano-composite film was realized.The as-prepared device demonstrates photoresponsivity ranging from 300 nm to 700 nm with a bandwidth larger than 350 nm.The device exhibits a prominent responsivity in the interested band with maximum responsivity of 5.5 A/W for ultraviolet light and 3 A/W for visible light,respectively.The external quantum efficiency(EQE)leaping up to 771% and the UV(Visble)response time is approximate 3 s(4 s).And the performance of the device is relatively stable in a period of time.The photodetector based on ZnO NWs-Au NPs composite film shows a peak responsivity of 9.4 A/W,which is two times compared with the device without modification.And the dark current is significantly restrained.This paper demonstrates that the response spectrum of the photodetector can be broaded sucessfully by the modification of ZnO NWs with RhB.The responsivity of the photodetector can be improved effectively by the modification of ZnO NWs with Au NPs.Both methods have promising application prospects.