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Photoelectric Response Of ZnO Nanorod Arrays Based Heterojunctions With AZO Seed Layers

Posted on:2018-08-01Degree:MasterType:Thesis
Country:ChinaCandidate:Y Z ZhangFull Text:PDF
GTID:2348330536457273Subject:Condensed matter physics
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ZnO is a typical n-type wide band-gap semiconductor and has excellent optical and electrical properties.One-dimensional ZnO nanorod arrays?ZnO NRs?have the advantages of large specific surface area,electron directional transmission and so on,which can be widely used in the field of ultraviolet photodetectors.However,more defects on the surface and in bulk of ZnO NRs can act as carrier trapping centers and hinder the carrier transport.The performance of UV photodetectors based on ZnO NRs heterojunctions,such as photosensitivity,response speed and responsivity,need to be further improved.Effectively reducing the surface states and defect states of ZnO NRs and improving the carrier transport is an important mean to enhance the performance of the photodetectors based on ZnO NRs.In this paper,ZnO NRs were prepared by simple chemical bath deposition method.The morphology,crystal quality and photoelectric properties of ZnO NRs were modified by Al-doped ZnO?AZO?seed layers.ZnO NRs based Schottky junctions were prepared using Au electrode and ZnO NRs,whereas ZnO NRs based heterojunctions were constructed using CuSCN or MoS2 nanosheets and ZnO NRs,respectively.The photogenerated carriers can be effectively separated by the built-in electric field.The specific research contents and results are as follows:?1?ZnO NRs were prepared on AZO seed layer films with different Al doping concentrations.The effects of AZO seed layer on the morphology,crystal quality and photoelectric properties of ZnO NRs and then the photoelectric response characteristics of Au/ZnO NRs/AZO schottky junctions were studied.The results show that small surface roughness,high light transmittance and large carrier concentration for AZO?0.5 %?seed layer.ZnO NRs grown on AZO?0.5 %?seed layer have higher density,better crystal quality,low concentration of defects,high light transmittance in UV region,larger carrier concentration and narrower surface depletion.The direct and close contact between ZnO NRs and Au electrodes reduces the leakage current.Au/ZnO NRs/AZO schottky junctions exhibit the photoresponse under illumination of 360 nm with the intensity of 3.2 m W/cm2 at +2 V bias.The photocurrent and responsivity of the schottky junctions based on ZnO NRs grown on AZO?0.5 %?seed layers are the largest.?2?The p-CuSCN/n-ZnO NRs heterojunctions were fabricated using by CuSCN films electrochemical deposited on the surface of ZnO NRs and the photoelectric response characteristics of the heterojunctions were investigated.CuSCN grain with pyramid shape can completely cover ZnO NRs surface and fill most of the large voids close to the top of ZnO NRs.CuSCN film avoids direct contact between Au electrode and ZnO NRs and reduces the leakage current of heterojunctions.The results of opticalelectrical tests show that the CuSCN/ZnO NRs heterojunctions has the characteristics of rectification and show the photovoltaic effect under light condition,indicating the presence of self-powered performance without external electric field for the heterojunctions under light condition.CuSCN/ZnO NRsheterojunctions show a good spectral selectivity without external field driving.A large photocurrent value and responsivity of 22.5 mA/W are achieved at a zero-bias voltage for CuSCN/ZnO NRs heterojunctions with AZO?0.5%?seed layer,which can be attributed to the enhanced light absorption and good carrier transport properties of ZnO NRs.?3?MoS2/ZnO NRs heterojunctions were fabricated by spin-coating MoS2 nanosheets stripped with liquid phase on ZnO NRs grown on AZO?0.5 %?seed layers.The photoelectric response properties of the heterojunctions were investigated.The results revealed that the MoS2 nanosheets were standing on the surface of ZnO NRs and the heterojunctions exhibit photoelectric response in both ultraviolet and red light region.Compared with MoS2/ZnO NRs heterojunctions based on multilayer MoS2,the heterojunctions with few-layer MoS2 show a large photocurrent and responsivity in both light region,which can be attributed to more electron transport channels of the carriers and small contact resistance between MoS2 nanosheets and ZnO NRs.
Keywords/Search Tags:AZO seed layer, ZnO NRs, MoS2 nanosheets, schottky junction, heterojunction, photoelectric response characteristic
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