导　　师： 王耘波

学科专业： H0903

授予学位： 硕士

作　　者： ;

机构地区： 华中科技大学

摘　　要： 近年来，钛酸铋（BI4TI3O12，BIT）铁电薄膜材料及薄膜器件成为国内外科学工作者研究的热点。BI4TI3O12薄膜材料与SI单晶的晶格失配度小，易与硅半导体集成电路兼容，对于铁电存储器有着广阔的应用前景。因此对于铁电薄膜的制备、结构及性能的研究具有重要的意义。本文对SI衬底和PT/TI/SIO2/SI衬底BI4TI3O12薄膜的SOL－GEL法制备工艺及铁电性能进行了实验研究。在总结和分析BI4TI3O12铁电薄膜研究现状的基础上，通过实验探索BI4TI3O12薄膜的工艺参数和工艺流程的优化，分别在SI衬底和PT/TI/SIO2/SI衬底上制备了BI4TI3O12薄膜；通过XRD微观分析手段对钛酸铋薄膜的晶格结构进行了分析，直接淀积在SI衬底上的BI4TI3O12薄膜在600－800℃退火温度下均未出现焦绿石等杂相，而且随退火温度升高其沿C轴取向生长的比重增加。而淀积在PT/TI/SIO2/SI衬底上时，退火温度超过800℃后，薄膜中会出现焦绿石相，其生长取向随退火温度无明显变化；通过SEM微观分析手段对钛酸铋薄膜的表面形貌进行了分析，650℃对应的薄膜表面形貌最好，观察到很少的针孔。晶粒尺寸大约在数十个纳米左右。晶粒均匀而且致密，呈不规则球柱状，晶粒清晰可辨，说明制备的BI4TI3O12薄膜结晶情况良好。用慢正电子束测量了不同退火温度处理的SI衬底BI4TI3O12薄膜的S参数与入射正电子能量E的关系，研究退火温度对BI4TI3O12薄膜及表面、界面缺陷的影响。在测试的基础上讨论了PT/TI/SIO2/SI衬底BI4TI3O12铁电薄膜的J-V特性。讨论了金属－铁电薄膜形成的整流接触对正反向电流不对称的影响，以及不同电压范围的导电机制。在研究了不同退火温度处理下钛酸铋薄膜的电滞回线的基础上，探讨了工艺条件及衬底选取对薄膜铁电性能的影响。铁电性随退火温度的变化是尺寸效应和BI4TI3O12中载流子两种因素共同作用的结果。在650℃退火温度处理的SI衬底BI4TI3O12薄膜剩余极化为11.25μC/CM2，矫顽场为47.2KV/CM。与薄膜接触处的SI衬底空间电荷层的形成造成SI衬底上生长的BI4TI3O12薄膜电滞回线不对称，剩余极化降低，矫顽电场增大。 Recently, there has been an increased interest in ferroelectric Bismuth Titanate /(Bi/_4Ti/_3O/_12,BIT/) thin films for ferroelectric devices, which are compatible for silicon semiconductor integrated circuits. It is important to study the preparations, microstructure and properties of ferroelectric thin films. This disseration present a theoretical and experimental investigation of preparation and properties of Bi/_4Ti/_3O/_12 ferroelectric thin films deposited on silicon substrate and Pt//Ti//SiO/_2//Si substrate. The optimum fabrication conditions of Sol-Gel technique were investigated on the basis of the analysis of the progresses of Bi/_4Ti/_3O/_12 ferroelectric thin film materials. The patterns of XRD exhibited that there were not any pyrochlore phase or other second phase in Bi/_4Ti/_3O/_12 thin films deposited on Si substrate being annealed between 600 and 800℃ , it was otherwise in Bi/_4Ti/_3O/_12 thin films deposited on Pt//Ti//SiO/_2//Si substrate when annealing temperature up to 800 ℃. The surface morphology of the thin films examined by SEM showed that Bi/_4Ti/_3O/_12 ferroelectric thin films with crack-free and compact structure had been successfully fabricated annealed at 650 ℃. It was the first time that the defects in Bi/_4Ti/_3O/_12 ferroelectric thin films were studied using a slow positron beam technique. The effect of annealing temperature on the defects in ferroelectric thin films was studied. The J-V characteristics of Bi/_4Ti/_3O/_12 ferroelectric thin films deposited on Pt//Ti//SiO/_2//Si substrate was measured through metal-ferroelectric film-metal/(MFM/) structure. And the rectifying junction characteristics of metal-ferroelectric film and different conductive mechanism in different voltage range were discussed. The annealing temperature and substrate type dependence of ferroelectric properties is displayed through the corresponding hysteresis loops. The annealing temperature affected the size of grain and consistence of charge carrier. The ferroelectric properties of Bi/_4Ti/_3O/_12 thin films varied with the annealing temperature, which was affected by these facts jointly. The characterization of Bi/_4Ti/_3O/_12 thin films deposited on Si substrate annealed at 650℃ showed remanent polarization of 11.25μC//cm2,and coercive field of 47.2kV//cm. The asymmetry in hysteresis, lower remanent polarization and higher coercive field were due to the existence of space charge layers.

关 键 词： 法 铁电薄膜 铁电存储器 慢正电子束 特性 电滞回线

分 类 号： [TM221]

领　　域： [电气工程] [一般工业技术]