八上英语书Classified Index: TG15
U.D.C.: 621.78
划船的划组词
Disrtation for the Doctoral Degree in Engineering
PREPARATION OF DOPED-PZT THIN FILMS AND ITS MICROSTRUCTURE AND FERROELECTRIC PROPERTIES
狗狗芯片Candidate：Sun Qiu
Supervisor：Prof. Wang Fuping
Academic Degree Applied for：Doctor of Engineering
Speciality：Chemistry Engineering and Technology Affiliation：Department of Applied Chemistry Date of Defence：Oct, 2007
Degree-Conerring-Institution：Harbin Institute of Technology
摘要
阿胶糕的制作方法摘要
生肖鼠今年几岁采用溶胶-凝胶技术结合快速热处理(RTA)及复合热处理工艺在Pt/Ti/SiO2/Si衬底上制备出不同择优取向的Gd、Yb及Gd与Nb复合掺杂Pb(Zr0.52Ti0.48)O3铁电薄膜(简记为PGZT、PYZT、PGNZT，1mol%Gd掺杂的PZT薄膜简记为PGZT1，以此类推)。热分解以及RTA热处理温度对钙钛矿相掺杂PZT薄膜的形成有重要影响。热分解温度高于350℃，RTA热处理温度在600~650℃之间可以得到单一钙钛矿相掺杂PZT薄膜。热分解温度对RTA热处理的薄膜取向性有重要影响，低温热分解，PGZT和PYZT 薄膜为(111)择优取向，高温热分解为(100)择优取向；Gd和Yb的掺入量对薄膜的取向性影响不大；采用RTA热处理工艺，得到的Gd与Nb复合掺杂的PZT薄膜为多晶薄膜。采用复合热处理方式，可制得高度(111)取向的PGZT、PYZT和PGNZT薄膜，热分解温度对复合退火方式制得掺杂PZT 薄膜取向度没有影响。随着预晶化时间的增加，薄膜的(111)取向度增加。
对取向掺杂PZT薄膜的结晶机制进行了分析。溶胶-凝胶法掺杂PZT薄膜的结晶过程是成核控制过程。不同热分解温度下，在PZT/Pt界面生成的界面相化合物不同，生成的界面相化合物与PZT的(111)相匹配，经过RTA 处理后，薄膜以界面相化合物为种子层或模板层，异质成核生长，得到(111)择优取向的薄膜；生成的过渡相化合物与PZT的(100)相匹配，经过RTA处理后，薄膜为(100)择优取向；采用复合退火方式时，平板炉预晶化过程使PZT薄膜先部分晶化，晶粒为(111)取向，经RTA处理，晶粒长大，得到(111)取向的PZT薄膜。XRD的ω 扫描分析表明，450℃热分解，650℃RTA 处理的PGZT和PYZT
薄膜为(100)织构；复合热处理方式得到的PGZT、PYZT和PGNZT薄膜为(111)织构，薄膜的织构比较完善。
SEM和AFM分析表明，Gd、Yb及Gd与Nb复合掺杂使PZT薄膜的结晶特性发生明显变化。当Gd含量不高于1mol%，Yb含量不高于2mol%时，PZT薄膜的晶粒发育完全，晶粒均匀，薄膜致密；随Nb含量的增加，PGNZT薄膜的晶粒尺寸变大。
1mol%Gd掺杂的PGZT1薄膜和1mol%Yb掺杂的PYZT1薄膜的铁电和介电性能较好，薄膜的剩余极化值增大，矫顽场降低，介电常数增大，漏电流减小。2mol%Gd掺杂的PGZT2薄膜与未掺杂的PZT薄膜相比，抗疲劳性能有所改善，但其它铁电性能有所下降，介电性能没有明显改善。对于
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哈尔滨工业大学工学博士学位论文
Gd掺杂PZT薄膜，Gd的掺入量不应大于2mol%；2mol%Yb掺杂的PYZT2薄膜与未掺杂的PZT薄膜相比，铁电性能和介电性能都有明显改善，对于Yb掺杂PZT薄膜，Yb的掺入量不应大于3mol%。适当Gd与Nb掺杂量和相对比例的复合掺杂明显改善PZT薄膜的铁电性能。高度(111)取向的PGNZT薄膜的抗极化疲劳性能优于(100)和(111)取向的PGZT和PYZT薄膜。
掺杂PZT的容限因子计算、缺陷化学及瑞利定律分析表明，Gd和Yb 在PZT中具有施主掺杂和受主掺杂的双重作用，二者作用的相对强弱与掺入量有关。当掺入量低时，施主掺杂作用显著，材料的抗极化疲劳和漏电流特性得到明显改善；随着掺入量的增加，受主掺杂作用逐渐增强，导致材料的铁电性能恶化。Gd与Nb复合掺杂的双重施主作用及对薄膜结晶性能的改善使PGNZT薄膜的铁电性能优于PGZT和PYZT薄膜。
关键词PZT薄膜；掺杂；微观结构；铁电性能；介电性能
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Abstract
Abstract
花蛤的家常做法
Pb(Zr0.52Ti0.48)O3 thin films with Gd, Yb, Gd-Nb dopants (denoted as PGZT、PYZT、PGNZT) and different orientation were prepared on Pt/Ti/SiO2/Si substrates by the sol-gel technique and rapid thermal annealing (RTA) process. Effects of processing parameters including pyrolyzing and post-annealing temperature on the perovskite pha formation and orientation of PZT films were investigated systematically. The results showed that pyrolyzing temperature over 350℃and RTA at 6
00~650℃were the favorable processing for the formation of doped PZT thin films with single perovskite structures. The pyrolyzing temperature has a crucial effect on the orientation of PZT films. (111)-oriented PGZT and PYZT films can be obtained at low pyrolyzing temperature, while (100)-oriented PGZT and PYZT films at a relative high temperature. Gd and Yb dopant contents have little influence on the orientation of the films. Gd and Nb co-doped PZT thin films are polycrystalline prepared by RTA process. Highly (111)-oriented PGZT, PYZT and PGNZT films were obtained by composite thermal annealing. Pyrolyzing temperature has little influence on the orientation of PZT films prepared by composite thermal annealing. With the increa of treating time on hot plate, the (111)-orientation degree of films incread.
Mechanism for the growth of oriented doped PZT thin films was discusd. The growth of sol-gel derived PZT thin films is controlled by the nucleation and the nuclei growth. The Pb-rich intermetallic pha formatted in pyrolyzing procedure may affect the lection of texture in PZT films. Pb-rich intermetallic pha (transient compound) in PZT/Pt boundary is veried at different pyrolyzing temperature. When the transient compound in PZT/Pt boundary is well epitaxial with Pt(111), the (111)-oriented PZT films can be obtained by RTA process, in which PZT films grow on the transient compound as a eding layer. The intermediate pha in PZT/Pt boundary provides a good lattice-m
atching with PZT (100)，the (100)-oriented PZT films can be obtained. During composite thermal annealing, PZT thin films are partially crystallized with (111)-orientation by annealing on the hot plate, and grains grow on the condition of RTA. ω-scan
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哈尔滨工业大学工学博士学位论文
水果发电XRD technique was utilized to analyze the texture of PZT films. It showed that (100)-textured PGZT and PYZT films can be formed by pyrolyzing at 450℃ and RTA at 650℃. (111)-textured PGZT, PYZT and PGNZT films can be prepared by composite thermal annealing process.
歌曲今夜无眠原唱Bad on the analysis of SEM and AFM, an obvious difference of crystallization properties of PZT thin films with Gd, Yb, Gd-Nb dopants are obrved. Compared with undoped PZT thin films, grains with large size and uniform distribution are shown in PZT with 1mol% Gd and 1~2mol% Yb dopants, while small sized grains exist in PZT films with more than 1 mol% Gd and 2mol% Yb dopants. Large sized grains could be obrved in PGNZT films with the increa of Nb content.
Improved electric properties such as incread dielectric constant and remanent polarization, lowere
d leakage current and coercive field, improved antifatigue properties of PZGT1 and PYZT1 films were obtained. Compared with undoped PZT films, the antifatigue performance of PGZT2 film was improved, the other ferroelectric properties decrea, and there was no obvious improvement of its dielectric properties.The doping content of Gd should be no more than 2mol%. Ferroelectric and dielectric properties of PYZT2 films were improved obviously. The Yb doping level should be no more than 3mol%. Porper composite doping level and ratio of Gd and Nb may promote ferroelectric properties of PZT thin films. Highly (111)-oriented PGNZT films posss improved antifatigue performance in contrast with (100) and (111)-oriented PGZT and PYZT films.
Theoretical calculation of tolerance factor, analysis of defect chemistry and Rayleigh law show that Gd and Yb act as donor dopants in low content level and donor effect is dominant. Therefore improved leakage current and polarization fatigue of the films are obtained. With the doping level incread, the acceptor effect could be dominant. Bad on this result, electric properties deteriorate. Ferroelectric properties of PGNZT films are better than that of PGZT and PYZT films，which could be attribute to dual-donor effect of Gd-Nb co-doping.
Keywords PZT thin films, Doping, Microstructure, Ferroelectric properties, Dielectric Properties
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