Study On Synthesis Of High Quality Hydrothermal ZnO And Related Optoelectronic Properties

In the present dissertation,the study is on fabricating high quality hydrothermal ZnO crystals,is on influences on crystal's appearances and quality under growing conditions of spontaneous crystallizations,is on manufacturing autoclave with lining for growing large size ZnO crystals,is on crystal's quality under varied growing conditions with seeds.The different growth behaviors and mechanism between spontaneous crystallizations and growing with seeds are compared.By means of test on characters of +c face and --c face of ZnO crystals with or without anneal,effect of varied defects on related crystals photoelectric performances is investigated.There are many forms and granularities of ZnO crystals in spontaneous crystallizations at 350℃and 430℃.1.5mm twin crystal is obtained in 3M KOH. Near 1.0mm crystals with two cones are gotten in 5M NaOH.Compared to KOH and NaOH,LiOH is too weak to be used as mineralizer for ZnO.Increasing growing temperature and mineralizer concentration,more perfect crystals can be obtained.The growing velocity of ZnO crystal faces that have more O^2-is greatly slowed down, when KBr is added into solution further.The FWHW(Full Width at Half Maximum)of X-ray rocking curve for(0002) reflection of ZnO crystals gets to 90 arc seconds.It is more suitable to use 99.99% purity ZnO powder to grow high quality ZnO crystals than 99%,so is 5M KOH and 1M LiOH as mineralizer.The crystalline structure integrality is more perfect to use cutting hydrothermal ZnO crystal as seeds than to use cutting CVD ZnO crystal as seeds.Higher growing temperature is advantage to exclude impurities so that it helps growing high quality crystals.Fe,K,and Na ions in ZnO crystals give influences to crystal integrality.Fe ion gives more prominent influence to ZnO crystal color.Active energy of ZnO(0001)face is higher than(0001)face.Growing temperature gives more influence to growing velocity of(000(?))face of ZnO crystals than(0001)face, but KOH concentrations do that of both face similarly.Aider adding LiOH into KOH solutions,active energy of both face increases,but growing velocity decrease.ZnO nucleation of crystallization without seeds can approximately be explained by uniform nucleation model.ZnO nucleation of crystallization with seeds can be explained by nonuniform nucleation model.The system of heating control and pressure monitor that used in quartz crystal industry can be applied into ZnO crystal growth with seeds.TheΦ60x770mm lining structure autoclave is chosen,which main body material should be chosen as high strength and low deformation local heat-resistant steel alloy,and anticorrosive lining can be chosen as noble metal silver.Both components are constructed by using high-pressure explosive method.Shtemberg self-sealing used in autoclave is suitable for noble metal lining structure autoclave that its highest pressure can get to 155Mpa under heated condition.Absorption of-c face of ZnO crystals is greater than +c face,which shows that there are much more loose electrons in -c face.After annealing in air,the green peak of PL spectrum of +c face of ZnO crystals descends,the ratio of ultraviolet peak of +c face of ZnO to green peak increases from 0.7 to 4.5,which indicates decrease of nonessential emittance caused by point defects and line defects of crystals.Electrical resistivity,carrier mobility and carrier concentration of +c face increase 10⁵ grade, and decrease 10^-2and 10^-4grade respectively,these of-c face increase 72%,75%,and decrease -35%respectively,which indicate that there are different carrier mobile ways between two faces of ZnO crystals.Two ZnO crystals growth methods are compared in this paper firstly.The lining structured autoclave to grow large size ZnO crystals is manufactured.And influence rules that varied defects of ZnO crystals with or without anneal exerted to their properties are presented.