【作者】 尹利君；

【导师】 张联盟；

【作者基本信息】 武汉理工大学 ， 材料加工工程， 2008， 博士

【摘要】 本文研究水热自发结晶的生长条件对ZnO晶体形貌和质量的影响,研制用于生长较大尺寸晶体的防腐高压釜,研究水热有籽晶生长的条件对ZnO晶体质量的影响,比较两者的生长习性和生长机理,结合ZnO晶体-c面和+c面退火前后性能的研究,探索晶体中的缺陷变化对其光电性能的影响。在温度350℃430℃时,自发结晶出现了粒度不同的多种晶体形态。矿化剂KOH浓度至3M,获得质量较好的长度为1.5mm的孪晶;矿化剂NaOH浓度至5M,得到长度接近1mm的双锥晶体。相对于KOH和NaOH,纯LiOH碱性太弱不适于作为矿化剂;增加矿化剂浓度,提高结晶温度,有利于提高晶体质量;碱性矿化剂复合1M KBr后,使ZnO晶体显露O^2-的部位生长速度大大减小。有籽晶生长出的晶体（0002）面X射线衍射摇摆曲线半波宽度FWHM（FullWidth at Half Maximum）达到90弧秒。相对于纯度99%的ZnO粉料,纯度99.99%的ZnO粉料作营养料适宜于生长高质量的晶体;5M KOH矿化剂复合1M LiOH后效果更好;用水热法生长出的ZnO晶体切割作为籽晶比用CVD法的晶体作为籽晶,生长出的晶体结构完整性更好;提高生长温度有助于晶体的排杂,生长出的ZnO晶体质量更高。ZnO晶体中Fe、K、Na离子是影响晶体结构完整性的因素,Fe离子对晶体颜色的影响突出。ZnO晶体（000（?））面的活化能比（0001）面的高,生长温度对（000（?））生长速率的影响比对（0001）面的影响要大,而KOH矿化剂浓度对两极面生长速率的影响是相近的;KOH矿化剂复合LiOH后,晶体两极面的活化能增大,生长速率降低。水热体系ZnO自发结晶成核可以近似采用均匀成核理论来解释,ZnO有籽晶生长成核是不均匀成核。水热有籽晶生长的加温控制和压力检测方式采用人造水晶工业生产中的方式。防腐高压釜采用镶嵌式衬套结构,制造釜体的材料选用镍铬钛耐热合金,防腐内衬选用贵金属银,采用爆炸法使衬套与釜体复合。反应腔尺寸为φ60×770mm,斯特伯格自紧式密封结构适于带贵金属内衬的高压釜,加热状态最高压力达到155MPa。ZnO晶体-c面比+c面吸收大,表明-c面中较松散的价电子更多。+c面退火和未退火室温下的光致发光紫外发光峰和绿光峰强度比值分别为4.5和0.7,表明退火充氧过程减少了由晶体中点缺陷和线缺陷引起的非本征辐射。退火使+c面的电阻率提高5个数量级,载流子迁移率降低了2个数量级,载流子浓度降低了4个数量级,使-c面的电阻率提高72%,载流子迁移率提高了75%,载流子浓度降低了35%,表明两者的载流子迁移方式不同。本论文首次比较了两种ZnO晶体生长方法的不同,研制了生长ZnO晶体镶嵌式衬套结构防腐高压釜,阐述了退火前后晶体中缺陷变化对晶体性能影响的规律。更多还原

【Abstract】 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.更多还原