固溶体KTa1—xNbxO3陶瓷的热释电性质

本文首次报道KTN铁电陶瓷的热释电系数λ与温度的依赖关系。测量了极化强度P。结果表明,x=0.5和0.6的样品在25℃时,P=4.6μc/cm~2和5.0μc/cm~2;λ=2.0×10~(-8)c/cm~2K和1.7×10~(-8)c/cm~2K。并讨论了Nb含量对极化强度的影响。     

PLT15薄膜热释电红外传感器的研制

用射频磁控溅射法在Ｐｔ／Ｔｉ／ＳｉＯ２／Ｓｉ（１００）结构衬底上沉积了高度Ｃ轴取向Ｌａ改性的ＰｂＴｉＯ３（ＰＬＴ１５）薄膜．研究了ＰＬＴ１５薄膜的电晕极化方法,用此方法同时对多个热释电敏感单元进行了极化．利用ＰＬＴ１５薄膜制备了热释电红外传感器,薄膜厚度是２μｍ,真空蒸发的Ｎｉ－Ｃｒ电极面积为１．２ｍｍ×１．０ｍｍ,敏感元下的Ｓｉ（１００）基片用热ＫＯＨ和ＥＰＷ进行刻蚀．用所设计的热释电系数测试系统对ＰＬＴ１５薄膜样品进行了测试,研究了其热释电特性．测试结果表明,ＰＬＴ１５薄膜样品的热释电电流ｉｐ平均为２．１×１０－１１Ａ,而对应的热释电系数ｐ为２．５２×１０－８Ｃ·（ｃｍ２·Ｋ）－１．这类薄膜很适合制备红外传感器     

Pb（In1/2Nb1/2）O3-Pb（Mg1/3Nb2/3）O3-PbTiO3弛豫铁电薄膜厚度尺寸效应研究

新一代弛豫铁电薄膜Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃(PIMNT)因兼具优异的电学性能与高的相变温度,在国内外获得广泛关注.为了探究不同薄膜厚度对PIMNT薄膜的结构及电学性能的影响,通过溶胶凝胶法制备了150 nm～1μm不同厚度的PIMNT薄膜,对其形貌结构以及电学性能进行了对比研究,在此基础上进一步研究了极化对其电学性能的影响.实验结果表明:随着厚度的增加,薄膜介电常数先增加后略有降低,剩余极化强度先增大后减小,矫顽场逐渐增大;在极化电压为18 V、极化温度和时间分别为100℃和5 min时,1μm厚度PIMNT薄膜的介电常数和损耗在100 Hz下分别为1 009和0.022,室温下的热释电系数达6.85×10^-4C·m^-2·K^-1,是目前主流的锆钛酸铅(PZT)薄膜的3倍左右.     

开路和短路电学边界外延铁电薄膜的畴结构及铁电性能

考虑基体对外延铁电薄膜内畴变的约束,采用应力函数方法求解外延铁电薄膜畴变时的本征应力,并结合相场法分析了不同电学边界条件下铁电薄膜的畴结构与极化强度.对短路电学边界下PbTiO_3外延铁电薄膜畴结构的计算表明,由a畴到a/c/a畴转变时的薄膜厚度与采用有限元方法模拟的结果十分接近.通过对开路电学边界下铁电薄膜畴结构的分析发现,由a畴到a/c/a畴转变时的薄膜厚度远大于短路条件下的转变厚度.基体约束引起的应力变化使得薄膜内畴结构出现a畴和a/c/a畴的分层.铁电薄膜的平均自发极化强度随厚度的增加而增加,从a畴向多畴转变后,极化强度有显著的增加.     

锆钛酸铅多晶材料的FR（LT）—FR（HT）相变及其热释电性质

本文研究了用共沉淀技术制备的PZT四种菱方相组分的均匀单相多晶体的介电特性和热释电特性。实验发现。菱方—菱方相变点的极化强度的异常变化是材料组成的函数。从组成PZT90/10和PZT94/6多晶体样品上可观察到介电系数、极化强度和热释电系数随温度发生的异常变化。但对于菱方组分PZT60/40和70/30却只能观察到热释电性质的异常变化。该二组分多晶体的相转变温度范围十分宽。文中引进铁电唯象理论描述了F_(R(LT))—F_(R(HT))相变行为。     

组分梯度铁电薄膜的热释电性质

建立组分梯度铁电薄膜的理论模型,在唯象理论GLD的框架下,引入一个分布函数描述组分梯度的特性,通过改变相关参数、薄膜的厚度及外电场等因素,研究了组分梯度铁电薄膜的热释电性质.结果表明:组分的梯度分布造成了薄膜内极化强度的梯度分布;相关参数和薄膜厚度是影响铁电薄膜性质的2个重要因素;当施加外电场的方向与薄膜内各组分极化方向相反时,薄膜的平均极化强度和温度的关系呈现出类似一级相变的特性,这一现象对薄膜的热释电性质会造成影响.     

锆钛酸钡钙铁电薄膜的制备及性能研究

利用溶胶-凝胶(sol-gel)法,在Pt/TiO_2/SiO_2/Si衬底上制备出无铅钙钛矿结构薄膜Ba_(0.8)Ca_(0.2)-Zr_(0.05)Ti_(0.95)O_3。溶胶液旋涂后进行前烘时,温度由室温缓慢上升至200℃有利于得到表面较为平整的薄膜。通过XRD、铁电测试仪和AFM对薄膜微观结构及电学性能进行表征,研究退火温度、退火时间等退火工艺对薄膜晶体结构与电学性能的影响。实验结果表明在退火温度和退火时间分别为700℃、11 min时,得到具有饱和极化值、剩余极化值分别为19.6μC/cm~2和5.6μC/cm~2的BCZT钙钛矿结构铁电薄膜。     

钛酸锶钡薄膜的制备及其铁电性能研究

本文采用溶胶-凝胶法(Sol-gel)制备Ba_(0.5)Sr_(0.5)TiO_3(BST)铁电薄膜,研究了在退火时间为450 s条件下,溶胶浓度、退火温度以及涂膜层数对薄膜的结晶结构和铁电性能的影响。利用X射线衍射分析仪(XRD)、铁电测试仪对BST薄膜的微观结构和电学性能进行了表征分析。结果表明:当溶胶浓度为0.4 mol/L,涂膜层数为4层,退火温度为650℃时,BST薄膜的矫顽场(EC)约为230 kV/cm,饱和极化值(PS)约为18μC/cm~2,剩余极化值(Pr)约为7.5μC/cm~2,表明薄膜具有良好的铁电性能。当电场强度为175 kV/cm时,BST薄膜达到饱和状态时而未被击穿,此时薄膜的电流密度J约为0.29μA/cm~2,表明所制备的薄膜质量较好。     

PbTiO_3铁电薄膜的制备及性能研究

本文讨论PbTiO_3铁电薄膜的溶胶-凝胶制备技术、机理及PbTiO_3薄膜的结构和电性能.研究结果表明,在MgO和SrTiO_3单晶基片上制备的PbTiO_3薄膜为钙钛矿型结构的高度取向薄膜;在Si单晶基片上制备的PbTiO_3薄膜为钙钛矿型结构的陶瓷薄膜.PbTiO_3薄膜具有良好的铁电性能和热释电性能,这些膜薄适合于制备铁电存储器和热释电红外探测器.     

PLT15薄膜热释电红外传感器的研制

用射频磁控溅射法在Ｐｔ／Ｔｉ／ＳｉＯ２／Ｓｉ（１００）结构衬底上沉积了高度Ｃ轴取向Ｌａ改性的ＰｂＴｉＯ３（ＰＬＴ１５）的薄膜,研究了ＰＬＴ１５薄膜的电晕极化方法,用此方法同时对多个热释电敏感单元进行了极化,利用ＰＬＴ１５薄膜制备了热释电红外感器,薄膜厚度是２μｍ,真空蒸发的Ｎｉ－Ｃｒ电极面积为１．２ｍｍ×１．０ｍｍ,敏感元一的Ｓｉ（１００）基片用热ＫＯＨ和ＥＰＷ进行刻蚀,用所设计的热释电系统测试系     

Magnetic properties and giant magnetoresistance effect of nanometer Fe-In2O3 granular films

Nanometer ferromagnetic metal-semiconductor matrix Fe-In2O3 granular films are fabricated by the radio frequency sputtering. Magnetic properties and the giant magnetoresistance (GMR) effect of Fex(In2O3)1x granular film samples are studied. The result shows that the magne-toresistance (MR) ratio/0 value of the granular film samples with Fe volume fraction x = 35% is 4.5% at room temperature. The temperature dependence (T = 1.5-300 K) of the MR ratio /0 value of Fe0.35(In2O3)0.65 granular films shows that /0 value below 10 K increases rapidly with the decrease of the temperature, and when T = 2 K,/0 value is 85%. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that, when the temperature decreases to a critical point TP = 10 K, the change of the structure in Fe0.35(In2O3)0.65 granular films results in the transformation of state from ferromagnetic to spin-glass-like. The remarkable increase of the MR ratio ???/??0 value of Fe0.35(In2O3)0.65 granular films below 10 K seems to arise from the peculiar conducting mechanism of the granular film samples in the spin-glass-like state.     

Characterization of ultrathin SiO 2/Si interface grown by low temperature plasma oxidation

Ultrathin SiO 2 layers on Si (100) wafers were prepared by plasma oxidation at a low temperature (250℃). The analyses of X-ray photoelectron spectroscopy (XPS) and TEM reveal that the chemical composition of the oxide layer is stoichiometric SiO 2 and the SiO 2/Si interface is abrupt. The thickness of the ultrathin oxide layer obtained from XPS, capacitance-voltage (C-V) and ellipsometry measurements indicate a nonlinear time dependence. The high frequency C-V characterization of MOS structure shows that the fixed charge density in SiO 2 film is about 10 11 cm -2 . It is also shown that the strength of breakdown electrical field of SiO 2 film with 6 nm thickness is of the order of 10 6 Vcm -1 . These properties of the ultrathin SiO 2 layer ensure its application in silicon quantum devices.     

应力对La_(0.8)Ca_(0.2)MnO_3薄膜电输运性能的调控研究

采用脉冲激光沉积技术,在LaAlO3和0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3两种单晶基片上外延生长了La0.8Ca0.2MnO3薄膜.X射线衍射分析表明两种薄膜皆为单取向生长,且面内分别受到压应力和张应力作用.晶格失配造成的应力对薄膜的电阻和金属-绝缘相转变温度Tp影响很大.对LCMO/PMN-PT施加外电场,从而调节薄膜所受应力也可以调制其电阻和Tp.     

Differenc es between amorphous indium oxide thin films

A series of 60~nm thick indium oxide thin-films,all amorphous as determined by x-ray diffraction,were found to have physical and electrical properties that depended on the temperature of deposition.The carrier mobility and flm conductivity decreased with decreasing deposition temperature;the best electrical properties of high mobility and conductivity were observed at a deposition temperature just below the temperature at which crystalline films formed.The density of the flm also decreased with deposition temperature from 7.2g/cm3 at+50℃ to 5.3g/cm3 at 100℃.     

溶胶-凝胶法制备BiFeO3多铁性薄膜及其电磁性能研究

采用溶胶-凝胶法在SiO2/Si基底上制备纯相BiFeO3多铁性薄膜.利用X射线衍射仪对不同退火温度的薄膜样品进行晶体结构的测定和分析,结果表明：样品为钙钛矿结构,并呈随机取向.在室温下测量500℃退火样品的电滞回线及其不同频率下的介电常数和介电损耗;当外加电场达到14×107 V/m时,剩余极化强度（Pr）和饱和极化强度（Ps）分别为10.12μC/cm2和14.62μC/cm2;当频率范围在1kHz～1MHz时,样品的介电常数和介电损耗基本稳定,且损耗较小.此外,在室温下测量薄膜的磁性能,M-H曲线表明样品具有铁磁性.     

BiFeO_3薄膜的so-lgel制备及其铁电性能研究

采用sol-gel方法在Pt(111)/Ti/SiO2/Si(100)衬底上制备出了(100)择优取向的BiFeO3薄膜.XRD研究表明,600～650℃退火的薄膜结晶较好.AFM形貌显示,650℃退火的薄膜中等轴状晶粒大小均匀(直径100～150nm),薄膜较为致密.电学性能测量结果表明,650℃退火、厚度为840nm的薄膜的2Pr值为2.8mC/cm2;在50kV/cm外加电场下,漏电流为2.7×10-5 A/cm2.电流-电压特性显示,在欧姆区之上,薄膜的主要导电机制为波尔-弗兰克尔发射导电.     

两种TGS晶体在低温下的热电和介电性

测量了TGS、ATGSP两种晶体在室温至20K温度范围内的介电常数K_(22)和热电系数p_2。这两种参数都随温度降低而单调下降,不显示相变的迹象。在此范围内的任一温度,ATGSP的热电系数p_2和优值p_2/K_(22)均较TGS的大。优值p_2/K_(22)随温度下降而减小,与自发极化的温度特性不相一致。     

Great diversity in stability of perovskite-type oxides studied by electrochemical hydrogen charging

Single crystals of 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3,SrTiO3 and BaTiO3,and ceramic pellets of CaCu3Ti4O12 and BiFeO3 have been studied and compared through electrochemical hydrogen charging,in which the oxides were coated with silver electrodes to electrolyze water as the cathode.Great diversity has been observed in the stability of the oxides:0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 was quickly decomposed;hydrogen could enter the lattice of the other four oxides,but their properties were influenced at extremely different speeds.Such a great diversity in stability against hydrogen among perovskite-type oxides highlights the importance of reliability study over functional oxides materials.     

热释电薄膜在红外探测器中的应用与研究进展

探讨了热释电效应及热释电薄膜红外探测器的工作模式,特别是探测器单元对热释电薄膜的材料与低温生长要求.为了克服薄膜生长过程中较高的基片温度对ROIC的破坏性影响,一方面发展了离子束辅助沉积、外延缓冲层等多种低温生长技术;另一方面发展了复合探测器结构设计,已研制出了性能良好的铁电薄膜非制冷红外焦平面阵列,其NEDT可达20 mK.