结构优化的异质Ca(Mg1/3Ta2/3)O3/CaTiO3薄膜介电性能

采用Pechini方法,在Pt/Ti/SiO₂/Si(100)基板上沉积了均质Ca(Mg1/3Ta2/3)O3 (CMT),CaTiO₃(CT)和堆叠次序不同以及摩尔比不同的异质Ca(Mg_1/3Ta_2/3)O₃/CaTiO₃(CMT/CT)薄膜。结果表明:以CT为底层的异质CMT/CT薄膜可以形成单一的钙钛矿结构,以CMT为底层的异质薄膜则有杂相产生。对于以CT为底层的不同摩尔比的异质CMT/CT薄膜,随着CMT含量的增加,异质薄膜中CT的衍射峰逐渐减小至消失,而CMT的结晶度变得更强,这说明以CT为缓冲层将有助于上层的CMT形成钙钛矿相。介电性能研究表明:异质CMT/CT薄膜的介电常数高度依赖于CMT的含量,而介电损耗不但与CMT含量有关,还与异质薄膜中界面数有关。当n(CMT):n(CT)=1:1 (摩尔比)时,异质的CMT/CT薄膜的介电常数和损耗分别为56和0.038。     

异质界面个数对PbZr_(0.52)Ti_(0.48)O_3/Ba(Mg_(1/3)Ta_(2/3))O_3薄膜铁电性能的影响

采用溶胶-凝胶法制备PbZr_(0.52)Ti_(0.48)O_3(PZT)薄膜前驱体溶液,采用水溶液凝胶法制备Ba(Mg_1/_3Ta_2/_3)O_3(BMT)薄膜前驱体溶液。研究了异质界面个数对PZT/BMT薄膜微观形貌、铁电性能的影响。在PZT/BMT薄膜中,PZT薄膜没有裂纹、结晶良好,界面个数的增加有利于PZT薄膜结构的致密。界面个数的增加可降低PZT/BMT薄膜剩余极化值和矫顽场。PZT/BMT薄膜在适当偏置电场下存在一个介电峰值,且正负偏置电场下的介电峰值不同,介电偏压特性曲线呈现不对称分布。采用二极管等效界面势垒和对薄膜电滞回线求导可有效解释介电偏压特性曲线不对称和介电峰值的差异。     

基于静电耦合的PZT/BTO多层异质薄膜介电增强研究

采用溶胶凝胶法制备了PbZr_(0.52)Ti_(0.48)O_3/BaTiO_3(PZT/BTO)多层异质薄膜,讨论了保持总厚度相同的情况下,不同周期厚度对多层异质薄膜的铁电和介电性能的影响。研究表明,随着周期厚度的减薄,层数的增加,层间的晶格失配能有效改善薄膜的结晶度,促使薄膜形貌更加平整和均匀,并且有相对较低的损耗和漏电流密度。此外,由于层间极化失配产生的层间静电耦合效应,以及空间电荷极化的存在,PZT/BTO异质薄膜的介电、铁电性能随着周期厚度的减小有着显著的提高。在周期厚度减小到55 nm时,100 k Hz测试频率下,介电常数高达293,品质因数Q为447,并表现出最优的铁电性能。     

退火温度对BaTiO3薄膜的结构和介电性能的影响

采用溶胶-凝胶法制备Si(100)基片上的BaTiO3陶瓷薄膜,并用红外光谱(IR)、x射线衍射(XRD)、扫描探针(SPM)等技术分析了钛酸钡凝胶的热解过程,以及不同退火温度下薄膜的晶粒、晶相、表面形貌、介电性能等指标.实验结果表明:高温有利于钛酸钡由立方相向四方相的转化;温度升高到1023 K时,钛酸钡薄膜的表面形貌平整、均匀并具有良好的介电性能.     

CaZrO_3薄膜的微观结构与介电性能研究

采用射频磁控溅射技术在Pt/Ti/SiO_2/Si衬底上制备了单一钙钛矿结构的CaZrO_3薄膜。研究了CaZrO_3薄膜的介电性能和微观形貌,利用X射线衍射技术和扫描电子显微镜技术对所制备薄膜的微观结构进行了表征,并对所制备薄膜的介电性能进行了系统测试,侧重讨论了制备工艺参数O_2:Ar比对所制备薄膜的物相及电学性能的影响。研究结果表明,O_2:Ar比对所制备薄膜的相纯度有显著影响,在O_2:Ar比为10:40和20:40时获得单一钙钛矿相的CaZrO_3薄膜,O_2:Ar比为30:40和40:40时,薄膜中可观察到第二相Ca_(0.2)Zr_(0.8)O_(1.8)(CSZ)杂相。O_2:Ar比为10:40条件下所制备的单一钙钛矿相CaZrO_3薄膜在1MHz介电常数约为30,介电损耗为0.006,并且该薄膜在40 V直流电压下,漏电流密度为5×10_~7 A/cm~2。单一钙钛矿相的CaZrO_3薄膜在薄膜型电容器和微波器件方面具有潜在应用。     

SiO2表面包覆改性钛酸钡/聚酰亚胺复合薄膜的制备

通过溶胶凝胶法在BaTiO3纳米粉体表面包覆了一层SiO2壳层,在此基础上利用原位聚合法成功制备了SiO2包覆的钛酸钡(BT)/聚酰亚胺(PI)复合薄膜.SiO2通过范德华力等物理作用在BaTiO3表面形成了4 nm左右的SiO2壳层.SEM测试和介电性能测试表明,10％ SiO2@BT/PI具有较好的界面相容性和介电性能.在1 kHz下,复合薄膜介电常数为4.50,介电损耗达到0.148.热学性能测试表明,复合薄膜在500℃下具有良好的热稳定性.     

退火时间对Bi/Te多层薄膜结构和热电性能的影响

采用磁控溅射法在玻璃衬底上室温沉积厚度不同的Bi/Te多层薄膜,在氩气保护下对薄膜在150℃进行不同时间退火处理,研究了退火时间对Bi/Te多层薄膜物相组成、微观形貌、表面粗糙度和热电性能的影响。结果表明:退火过程使Bi、Te原子在相邻单质层界面上产生了强烈的扩散反应,生成以Bi_2Te_3为主相的Bi-Te化合物;随退火时间的延长,薄膜的界面空洞增多,表面粗糙度变大。短时间退火可提高薄膜的热电性能;而随退火时间的延长,量子尺寸效应逐渐显现,薄膜的载流子浓度、迁移率、电导率和Seebeck系数均出现明显的振荡现象,沉积的单质层越厚,振荡周期越大。     

PVP添加剂改善溶胶-凝胶法制备BST薄膜表面结构及介电性能

以聚乙烯吡咯烷酮(polyvinyl pyrrolidone, PVP)为添加剂采用改善的溶胶凝胶法制备了Ba0.6Sr0.4TiO3(BST)薄膜,并采用扫描电镜(SEM)及原子力显微镜(AFM)研究了薄膜的表面结构与介电性能.结果表明:PVP显著改善了BST薄膜的表面形貌,当PVP∶ Ti的物质的量比为0.7%时,BST薄膜表面形貌最佳,光滑致密无裂纹无缩孔.X射线光电子能谱(XPS)表明,PVP有助于减少BST薄膜表面非钙钛矿结构.介电性能测试表明,在40 V外加电压下BST薄膜的介电调谐率达45%,零偏压下的介电损耗低于0.02.另外,对PVP的作用机理进行了讨论.     

厚度对钇掺杂氧化铪薄膜性质的影响

通过中频磁控溅射在p型(100)硅基片上沉积了不同厚度的Y掺杂Hf O_2(Y∶HfO2)薄膜。利用X射线光电子能谱(XPS)分析薄膜的Y掺杂浓度及元素结合状态。掠入射X射线衍射(GIXRD)分析表明,3.25 mol.%的Y掺杂HfO_2薄膜相结构为立方相。利用X射线反射率(XRR)测量得到了不同溅射时间的薄膜厚度、密度和粗糙度。电性能测试表明,Y掺杂HfO_2薄膜基电容器介电常数随膜厚的增大而增大。基于界面层分压原理,详细讨论了SiO_2界面层对薄膜介电特性的影响。     

Ba(Zr0.3Ti0.7)O3薄膜的结构及性能

用溶胶-凝胶法分别在Pt/Ti/SiO2/Si和LaNiO3/Pt/Ti/SiO2/Si衬底上制备了锆钛酸钡[Ba(Zr0.3Ti0.7)O3,BZT]薄膜.相结构及介电性能研究表明:衬底和薄膜厚度对BZT薄膜性能具有显著影响.制备在LaNiO3/Pt/Ti/SiO2/Si衬底上的BZT薄膜具有(100)面的择优取向,其介电常数及介电损耗则随着薄膜厚度的增加而降低.对制备在Pt/Ti/SiO2/Si衬底上的BZT薄膜,在薄膜厚度低于500nm时,其介电常数随薄膜厚度增加而增加,大于500nm时又有所减小.     

Effects of Stacking Scheme on Microwave Dielectric Characteristics of Ca(Mg1/3Nb2/3)O3–Ba(Zn1/3Nb2/3)O3 Layered Dielectric Resonators

Ca(Mg_1/3Nb_2/3)O₃ (CMN) and Ba(Zn_1/3Nb_2/3)O₃ (BZN) ceramic disks were stacked with three stacking schemes, designated as CMN/BZN, CMN/BZN/CMN, and BZN/CMN/BZN, to yield layered dielectric resonators, and the microwave dielectric characteristics were evaluated with the TE_01δ mode. Both experiments and finite element analysis showed that the microwave dielectric characteristics of the layered resonator were determined not only by the volume fraction of BZN but also by the stacking scheme. For each stacking scheme, a good combination of microwave dielectric characteristics with an effective dielectric constant of 34.33–34.52, a Q × f value of 58 800–62 080 GHz, and a near-zero temperature coefficient of resonant frequency could be achieved by adjusting the volume fraction of BZN. The effects of the stacking scheme on the microwave dielectric characteristics of the temperature-stable layered resonator were discussed by combining finite element analysis and dielectric composite models.     

喷雾热解法制备的γ-Gd2S3薄膜的物性研究

用喷雾热解法,在玻璃衬底上沉积得到了γ-Gd2S3纳米多晶薄膜。通过LCR仪和紫外可见光分光计对样品的物性进行了测试,结果表明:γ-Gd2S3纳米多晶薄膜的介电常数与常规材料有较大差异,特别是在低频范围内,等价于双层电介质模型,其响应行为类似于德拜驰豫;本征吸收区处在可见光范围内,与常规γ-Gd2S3吸收谱相比发生了红移。     

Low dielectric loss and enhanced tunability of Ba(Zr0.3Ti0.7)O3-based thin film by sol–gel method

In this work, dopants and buffer layers were employed to simultaneously lower the dielectric loss and enhance the dielectric tunability of Ba(Zr_0.3Ti_0.7)O₃ (BZT) thin films. The BZT, 1 mol% La doping BZT (BZTL) with and without La_0.5Sr_0.5CoO₃ (LSCO) buffer layers were prepared by sol–gel technique. The dielectric properties of the thin films were investigated as a function of frequency and current bias field. As a result, the BZTL thin film with LSCO buffer layer showed lower dielectric loss and higher tunability simultaneously, which can be a promising candidate for tunable microwave device applications.     

Effects of Heating Profiles on the Orientation and Dielectric Properties of 0.5Pb(Mg1/3Nb2/3)O3-0.5PbTiO3 Thin Films by Chemical Solution Deposition

0.5Pb(Mg_1/3Nb_2/3)O₃-0.5PbTiO₃ thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by varying the film formation procedures and heating processes. Depending on the multilayer film formation and appropriate heating process, the films were grown with a preferential orientation. The films showed a (100)-preferred orientation and large grain-size distribution when they were directly heat-treated after deposition of amorphous layers. The films showed a (111)-preferred orientation and small grain-size distribution when formed layer-by-layer or directly heating amorphous thin films with a perovskite seed layer. These results were explained by the effect of a seed layer. Saturation polarization of the (111)-preferred films was ∼35 µC/cm², which was somewhat higher than that of the (100)-preferred film. In contrast, the dielectric constant of the (100)-preferred film was ∼1600, which was larger than that of the (111)-preferred film.     

Control of Microstructure and Orientation in Solution-Deposited BaTiO3 and SrTiO3 Thin Films

Columnar and highly oriented (100) BaTiO₃ and SrTiO₃ thin films were prepared by a chelate-type chemical solution deposition (CSD) process by manipulation of film deposition conditions and seeded growth techniques. Randomly oriented columnar films were prepared on platinum-coated Si substrates by a multilayering process in which nucleation of the perovskite phase was restricted to the substrate or underlying layers by control of layer thickness. The columnar films displayed improvements in dielectric constant and dielectric loss compared to the fine-grain equiaxed films that typically result from CSD methods. Highly oriented BaTiO₃ and SrTiO₃ thin films were fabricated on LaAlO₃ by a seeded growth process that appeared to follow a standard "two-step" growth mechanism that has been previously reported. The film transformation process involved the bulk nucleation of BaTiO₃ throughout the film, followed by the consumption of this matrix by an epitaxial overgrowth process originating at the seed layer. Both BaTiO₃ and PbTiO₃ seed layers were effective in promoting the growth of highly oriented (100) BaTiO₃ films. Based on the various processing factors that can influence thin film microstructure, the decomposition pathway involving the formation of BaCO₃ and TiO₂ appeared to dictate thin film microstructural evolution.     

Preparation of 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 Thin Films Via a Polyvinylpyrrolidone-Assisted Aqueous Sol–Gel Process and Dielectric Properties

Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PMN–PT) thin films were prepared by spin coating using aqueous solutions of metal salts containing polyvinylpyrrolidone, where niobium oxide layers and lead—magnesium–titanium oxide layers were laminated on Pt(111)/TiO _x /SiO₂/Si(100) substrates and fired at 750° or 800°C. 250 ± 20 nm thick 0.7PMN–0.3PT thin films of a single-phase perovskite could be prepared, and the film fired at 750°C had dielectric constants and dielectric loss of 1900 ± 350 and 0.13 ± 0.03, respectively, exhibiting polarization-electric field hysteresis with a remanent polarization of 5.1 μC/cm² and a coercive field of 21 kV/cm.     

Effect of Stacking Layers on the Microwave Dielectric Properties of MgTiO3/CaTiO3 Multilayered Thin Films

Effect of stacking layers on the microwave dielectric properties of the MgTiO₃/CaTiO₃ (MTO/CTO) multilayered thin films prepared by the metalorganic solution deposition technique (MOSD) was investigated. As the thickness of CTO film in the MTO/CTO multilayered films increased, the dielectric constant ( K ) increased and temperature coefficient of dielectric constant ( TCK ) changed from positive to negative values by dielectric series mixing rule. Especially, MTO(100 nm)/CTO(200 nm) multilayered films exhibited a TCK of +10 ppm/°C, indicating temperature stability. The dielectric losses (tan δ) of MTO/CTO multilayered films increased with an increase of CTO layers. This result was attributed to the fact that the stresses induced by the higher thermal-expansion coefficient of CTO than that of MTO. Also, as compared with MTO(100 nm)/CTO(200 nm) film, the K and TCK of MTO(50 nm)/CTO(200 nm)/MTO(50 nm) film were not changed, but the dielectric losses increased. This result indicated that the dielectric loss was affected by the number of interfaces between CTO and MTO layers.     

生长温度对单晶衬底上生长Ba(Zr_(0.2)Ti_(0.8))O_3薄膜微结构和介电性能的影响(英文)

采用脉冲激光沉积方法,在制备有LaNiO3(LNO)底电极的LaAlO3(LAO)衬底上,分别在500,600℃和700℃的沉积温度下制备了锆钛酸钡Ba(Zr0.2Ti0.8)O3(BZT)薄膜.通过X射线衍射表征薄膜的结构特性,原子力显微镜和扫描电子显微镜分别用来表征样品的表面和断面形貌.结果表明:BZT薄膜与LNO具有c轴取向,并以cube-on-cube方式排列生长.BZT薄膜表面致密无裂缝,具有柱状生长的晶粒.薄膜的介电性能测试显示:600℃下沉积的BZT薄膜具有较高的介电可调性(49.1%)和较低的介电损耗(2.5%).在600℃下沉积的BZT薄膜的优值因子(figure of merit,FOM)达到19.8.