Materials And Optoelectronic Devices Of ZnO Micro-nano Wires And Heterojunctions

?-? group semiconductor zinc oxide(ZnO)is wide direct band semiconductor with a band gap of 3.37 e V,and its exciton binding energy is about 60 meV at room temperature,which acts as a promising candidate material for ultraviolet detectectors.Compared with the film materials,ZnO micro-and nanowires have the larger specific surface area,surface state density and carrier mobility,therefore they have great application prospect in luminescence and ultraviolet detection.However,most photodetectors based ZnO nanowires suffer from low quantum efficiency,slow response,complex device preparation and the integration.In this paper,the author fabricated the ZnO nanowire,the heterostructure and different types photoelectric devices,regulated the performance of device,researched the relevant working mechanism.Finally,we extended the photoelectric detection of ZnO nanowire to the field of photoelectric storage.There are 4 main aspects in this thesis.1.Preparation and photoelectric properties of ZnO nanowiresZnO nanowires were prepared by chemical vapor deposition(CVD).And the ZnO nanostructure can be control by the growth parameters,including the pressure and oxygen flow rate.Then ZnO nanowires were dispersed and transferred onto the target substrate using a wet-transfer technology.The high-quality ZnO nanowire transistors were prepared by optimizing the transfer technology.The results show that the devices exhibit the n-type characteristics,with an ON/VFF ratio>104 and carrier mobility?35 cm2v-1s-1.The photoresponse of the device can reach up to 106A/W for 355 nm,and the response speed can be adjusted using the gate voltage.2.Photoelectric memory based on ZnO nanowire transistorThe electrical hysteresis behavior of ZnO nanowire transistor has been studied systematically.The influence of factors including the gate voltage scanning speed and scanning range on the hysteresis phenomenon of the device under illumination,and the related dynamic mechanism have been investigated.The illumination plays the key role to the hysteresis behavior of device,and the relevant theoretical model is established.Finally,the nonvolatile photoelectric memory based on ZnO nanowire is demonstrated for the first time,which shows the high ON/OFF ratio and reliable programming/erasure repeatability.We have extended the photoelectric detecting to the photoelectric storage using the ZnO nanowire-based devices,which is of significance for developing new devices with both photoelectric detection and storage functions.3.Self-assembled ZnO nanobridge/rubrene heterojunction photodetectorThe randomness of the wet transfer technology and the tedious fabrication process limit its scalability.In response to this challenge,we used Au pattern as catalyst and electrodes to construct a ZnO nanobridge UV detector array using a simple one-step method,that exhibits the excellent photoelectric performance and the integration.A type ? ZnO/rubrene heterojunction device was constructed by coupling p-type rubrene with n-type ZnO nanobridge.The built-in electric field at interface of the heterojunction can significantly increase the separation efficiency of excitons,and accelerate the transfer of photoexcited carrier,improving the responsivity.At the same time,the response spectrum is extended to the visible range using the absorption spectrum of rubrene.This study has a certain reference value for developing the efficient and highly sensitive broadband photodetectors.4.ZnO microwire and ZnO-ZnGa2O4 coaxial heterojunction photodetectorAlthough the ZnO nanowires-based photodetector has made progress.Here,in order to further reduce the dependence on micromachining technology,the ZnO microwires with more macroscopic size and easy fabricated process was preparated by the CVD method.The ZnO microwire have the high crystallization quality that is proved by the XRD,Raman and PL,exhibiting the sensitive photoelectric and piezoelectric characteristics and excellent mechanical flexibility.By the one-step technique,ZnO-ZnGa2O4 coaxial heterostructure were prepared.Under the illumination of 360 nm,the responsivity of ZnO-ZnGa2O4 coaxial heterostructure microwire is about 1900A/W,which is two orders of magnitude higher than that of the pure ZnO microwire.In particular,the responsivity of the device can reach up to 4300A/W for 270 nm.The built-in electric field at the heterojunction interface promote the separation of photogenerated electrons and holes,and it is significant for the highly sensitivity and responsivity.The device shows a great flexible properties,implying that the device can be used in the field of flexible electronics and optoelectronics in future.In summary,the fabrication of ZnO micro or nanowire and heterojunction and photoelectric properties of devices were systematically studied,and the related physical mechanism was also discussed.This study provided an important reference for the design of high-performance photoelectric devices and novel storage devices.