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Construction And Performance Modulation Of Graphene/ZnO Heterojunction Photodetector

Posted on:2018-08-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:S LiuFull Text:PDF
GTID:1318330515966048Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
Due to its outstanding carrier transport ability and remarkable transparence,flexibility and strength,graphene has been considered as a promising material for next generation electronics and optoelectronics.In this regards,combing graphene with other semiconductors who possess prominent photoelectric conversion ability has been a valid way to obtain high-performance photodetector.In this article,high-quality graphene and ZnO nanowire were synthesized,graphene was transferred by a trbioelectricity-aasited method to other substrate and hybrids structures based on graphene and single ZnO nanowires as well as ZnO nanowires array were constructed.Piezoelectronic effect influence on the device performance was systematically investigated.Graphene was synthesized by the CVD method.The influence of growth parameters was investigated by SEM and Raman spectrum.By tuning the growth parameters,single-layer,bi-layer and multi-layer graphene were obtained.Single ZnO nanaowire and ZnO nanowires array were synthesized through CVD and shuire respectively.Characterizations results show that ZnO nanowire obtained by these two methods grow along[0001]direction.Compared with the CVD growth sample,ZnO nanowire synthesized by the hydrothermal growth method posesse more defects but higher uniformity of the growth direction.Using the trbioelectricity-aasited method,graphene was successfully transferred from copper foil to other substrates including PET,PI,PTFE,by the attraction force from the friction induced accumulated charge.Through the SKPM model of AFM,the charge density on the substrate was investigated.It is found the accumulated chage can stay on the substrate for more than 2 h,which is enough for the graphene transfer,due to the typical copper etching process is only 15 min.Characterization results show the structure integrity of transferred graphene is preserved and no residue is observed.To verify the electrical properties of graphene,a hybrid photodectector was constructed by decorating ZnO nanoparticles on graphene.The devie shows good detection ability to UV light and no performance degradation was observed even under bending,confirming the stability of the transferred graphene by the trbioelectricity-aasited method.Graphene/ZnO nanowire hybrid photodectector was successfully constructed.By connecting the different part of the device into test circuit,two detection models were realized,named photovoltage model and photo-gating model.Owing to the outstanding carriers transport ability of graphene and photo absorption ability of ZnO,the device shows good performance in both two models.The modulation of the device performance by piezoelectronic effect was then investigated.It is found the responsivity was improved by 2.54 times under-0.44%compressive strain for the photovoltage model and 26%under 0.44%tensile strain for the photo-gating model.Another Graphene/ZnO hybrid photodectector was constructed by transfer graphene on the ZnO nanowires array for UV detection.Surface passivation by H2O2 was first carried out to improve the contact properties between graphene and ZnO.As a result,the on-off ration was enhanced and the leakage current was decreased.Piezoelectronic effect was then used to improve the device perforamance further.The responsivity was enhanced by 17%under-0.349%compressive strain due to the dramatical modulation of the band structure in the device interface by the ZnO piezopotential.
Keywords/Search Tags:Graphene, ZnO, Photodectector, Piezoelectronic effect
PDF Full Text Request
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