The Preparation Of Oxide/ZnO Double Membrane With Different Interfaces And The Study Of Its Defects And Electrical Properties

ZnO varistors have schottky barrier on its grain boundary,so they have special I-V characteristics.ZnO materials are widely used as a high-tech electronic equipment,civilian orbit transportation,ultra-high voltage power grids in areas such as overcurrent protection components,to suppress the voltage stability and transient surge.With the development of very large scale integrated circuit,ZnO varistors gradually become more and more miniature,multi-functional and complanate.Recently,our research grop and the Joseph stephens institute in Slovenia cooperated and have found that the new ZnO-Ca O-Cr2O3 system shows great nonlinear characteristics,and this system without Bi can improve the weakness of traditional ZnO-Bi2O3 system which is strong volatility and high sintering temperature,but the mechanism of this system is not yet clear,so that we lack of theoretical guidance for the performance improvement.Therefore,this paper uses the method of rf magnetron sputtering to preparate ZnO thin film with high quality on the Si substrate.And different components of the oxide film is prepared on the formation of double layer film which has a clear interface to study in the absence of Bi2O3,the causes of the grain boundary nonlinear.Then further study is carried on how heat treatment influences the defects and electrical properties.The main research content on this paper is as follows:(1)Get ZnO thin films prepared by rf magnetron sputtering method,through the optimization of sputtering conditions,such as sputtering power,deposition pressure,substrate temperature,etc.It is demonstrated that the best parameters is 1.2 Pa for deposition pressure,100 W for sputtering power,200? for substrate temperature,20 cubic cm/min for Ar flow,Under the condition of the preparation,ZnO thin films can get the good structure,smooth surface,uniform grain size,all films have excellent(002)orientation with the six-party wurtzite structure.(2)Using commercial ZnO varistor as target material,and preparated by rf magnetron sputtering method,we can get varistor film with the ZnO,Bi2O3 and spinel phase composition,and the film grow along c axis orientation,it's nonlinear coefficient can be as high as 152.6,pressure-sensitive voltage is 8.55 V,the leakage current is 0.2 m A.(3)Through the preparation of thickness controllable ZnO and additive films to obtain different interface.To study the I-V characteristic curve of double film(ZnO/Ca O,ZnO/Co3O4,ZnO/Cr2O3,ZnO/La2O3).After the measure of I-V characteristic curve,the nonlinear source of this system can be found in this free of Bi2O3 system.The nonlinear coefficient of ZnO/Cr2O3 films can reach 4.93,pressure-sensitive voltage of 12.79 V,leakage current of 0.57 m A,this kind of material has wide development prospects in the field of extremely large scale integrated circuit.The mechanism is,in ZnO/Cr2O3 films,Cr3+ moves into the crystal lattice,replaces the Zn2+,Cr element segregates in ZnO grain boundary place,will adsorb oxygen to enlarge the schottky barrier at grain boundaries,thus forms a good nonlinear characteristics.(4)After annealing,the surface atoms of ZnO and ZnO/Cr2O3 films gain energy and move again,causing the grain growth,so as to make the film become more dense,grain shape becomes more smooth,intergranular stress increases and lattice parameters is reduced,the(002)peak shows a little shift to the right.At the same time crystallization peak becomes more sharply,which means the quality of the films are improved.ZnO thin film after annealing in CO+N2 atmosphere gets weaker deep-level emission peak and fewer defects.ZnO/Cr2O3 films heated under N2 atmosphere can obtain the best surface topography,after annealing in O2 atmosphere,best crystallization quality of the film can be obtained,the uv light emission intensity can be as high as 100.This is due to the oxygen in the air can be spread to the lattice,thus makes the oxygen vacancy in crystal get compensation and disappear,so that the defect concentration decreases.And under the condition of O2 heat treatment of ZnO/Cr2O3 membrane has the best nonlinear,it has excellent application value.