Study Of Plasmon-enhanced ZnO Ultravoilet Optoelectronic Properties And Devices

As a kind of wide direct bandgap(3.37 eV)semiconductor materials,ZnO has been considered as a promising candidate for short-wavelength optoelectronic devices.Moreover,due to its high exciton binding energy(60 meV),ZnO presents a very broad application prospects in the field of ultraviolet optoelectronic devices,especially UV lasers.However,the stable and reproducible p-type ZnO is still in challenge,which hinders the design and fabrication of laser diodes,based on the typical multiple quantum well(MQW)structures.Alternatively,an n-ZnO/p-GaN heterojunction has been suggested as an important candidate approach for device fabrication and application,and realize electrically pumped UV laser diodes.Even so,some physical effect or technological approach,such as lattice and bandgap mismatch and self-compensation effect,is still required to improve the IQE and the light extraction outward.Recently,the development of metal surface plasmonics has attracted much attention due to its characteristics of altitudinal spatial localization and intense near-field enhancement.Utilizing of this unique physical effect has been proposed as a promising method to improve the intrinsic luminous efficiency of ZnO and develop SPs-coupled novel optoelectronics devices.In this thesis,the intrinsic near-band emission of ZnO was improved by coupling with the metal suerface plasmons,the enhancement mechanism of ZnO spontaneous and stimulated emission under optical pumping were systematically investigated in these hybrid micro/nanostructures.Furthermore,the plasmon-coupled ZnO-based UV optoelectronic devices and biosensors were fabricated,and the performance was improved obviously.The main contents are listed as following:1.Using vapor transport method and ion sputtering method,the shape-controlled ZnO microstructure and metal nanoparticles were fabricated by controlling the ratio of raw materials,temperature,air condition,sputtering time,etc.,the growth mechanisms and crystal structures were investigated by XRD,TEM,HRTEM,SAED and so on.Using the micro-PL and Raman testing,the optical characteristics were systematically studied in the ZnO microstructures and metal nanoparticles.2.Further using a variety of spectroscopy technology,the spectroscopic behavior of ZnO/metal nanoparticles composite system was analyzed.Combined with the time-resolved PL and temperature-dependent PL,the time and temperature characteristics were measured,and the dynamic processes at the ZnO/metal interface including optical transition,the coupling between the electronic oscillation and optical field were analyzed.Also,the interaction of electrons,excitons and photons in this hybrid ZnO/metal microcavity was analyzed,and investigate the dynamic processes of the plasmon-enhanced spontaneous and stimulated emission.3.The Ag film was fabricated by the magnetron sputtering method,and the ZnO nanorod/Ag film hybrid microcavity was constructed.Utilizing the metal surface plasmon effect,the optical field energy can be confined in nano-scaled spatial range,break through optical diffraction limit and further realize nano-sized plasmonic laser.4.The plasmon-coupled ZnO-based UV optoelectronics devices were designed and fabricated.Using vapor transport method,ZnO nanorod arrays were fabricated on the SiO2 substrate and then Au nanoparticles were decorated on the surface of ZnO nanorods,further construct MSM structured ultraviolet photodetector.The introduction of Al LSPs realized the improvement of the UV detection performance successfully.In addition,a p-GaN/n-ZnO nanorods heterostructured diode was fabricated by vapor transport method.Through Al nanoparticles decoration,the EL performance of devices was improved.5.Combined with ZnO-WGM effect and Ag-LSPs effect,a novel biosensor for Raman signal detection based on ZnO/Ag hybrid microcavity was designed and fabricated.The high quality ZnO microrods were synthesized by vapor transport method and then single ZnO microrod was selected as an optical microcavity.Then,Ag nanoparticles were decorated on the surface of ZnO microrod uniformly,and realized the ultrasensitive SERS signal detection for rhodamine 6G(R6G)and dopamine(DA).