激光脉冲外延生长Pb(Zr0.52Ti0.48)O3薄膜及其特性研究

利用激光脉冲法在LaAlO3衬底上沉积制备LaNiO3薄膜作为底电极并外延生长(100) Pb(Zr0.52Ti0.48)O3铁电薄膜,系统研究了生长温度对PZT外延结构和电学特性的影响.研究发现当生长温度高于550℃时即可得到外延(100)PZT薄膜.在对所制备的PZT薄膜的结构和性能测试表明,650℃下生长的PZT薄膜外延性最佳,并且表现出优异的介电和铁电性能,介电常数ε、剩余极化Pr和矫顽场Ec分别为900、26.5 μC/cm2和52.1kV/cm.试验还证实这种外延PZT薄膜具有优良的抗疲劳特性,可用于铁电存储器的制备中去.     

LaAlO_3顶层对Pb(Zr,Ti)O_3薄膜微结构和性能的影响

利用脉冲激光沉积(PLD)法,在LaAlO3(LAO)基片上外延生长了高质量的PbZr0.52Ti0.48O3(PZT)薄膜。通过增加10nm厚的LAO顶层,所制备PZT薄膜的铁电剩余极化(Pr)由28.8μC/cm2增加为55.1μC/cm2。通过对微结构分析,表明薄膜电学性能的增强主要来源于LAO顶层对PZT薄膜表面形貌的优化。另外,与Pr不同,随LAO顶层厚度的增加,PZT薄膜的矫顽场单调增加。     

PZT基NiTi SMA/PZT复合材料的组织结构及其压电性能研究

采用真空直流溅射法在PZT基体上沉积NiTi SMA薄膜,再经过晶化处理而制备出PZT基NiTi SMA/PZT复合材料.使用扫描电子显微镜观察复合材料试样的表面和界面组织结构.使用ZJ-3A型准态仪、Automatic LCR Meter4225测试复合材料的压电常数d33,机电耦合系数KP1,介电损耗tgδ,以考察NiTi SMA薄膜对PZT压电性能的影响.测试结果显示复合材料的压电常数d33,机电耦合系数KP相对于PZT均有提高,而介电损耗tgδ有小幅度降低.NiTiSMA薄膜与PZT基体之间的良好的界面结合结构及界面附近存在的源自膜/基材料间晶格差异的约束应力,有利于电偶极子的定向运动,保障了PZT基体压电性能的发挥.     

PZT基NiTi SMA/PZT复合材料的组织结构及其压电性能研究EI

采用真空直流溅射法在PZT基体上沉积NiTi SMA薄膜,再经过晶化处理而制备出PZT基NiTi SMA/PZT复合材料.使用扫描电子显微镜观察复合材料试样的表面和界面组织结构.使用ZJ-3A型准态仪、Automatic LCR Meter4225测试复合材料的压电常数d33,机电耦合系数KP1,介电损耗tgδ,以考察NiTi SMA薄膜对PZT压电性能的影响.测试结果显示复合材料的压电常数d33,机电耦合系数KP相对于PZT均有提高,而介电损耗tgδ有小幅度降低.NiTiSMA薄膜与PZT基体之间的良好的界面结合结构及界面附近存在的源自膜/基材料间晶格差异的约束应力,有利于电偶极子的定向运动,保障了PZT基体压电性能的发挥.     

以TiO_2为缓冲层在GaN上外延生长PZT铁电薄膜

采用脉冲激光沉积技术在(0001)取向的GaN基片上以TiO2为缓冲层外延生长了PZT(111)单晶薄膜。X射线衍射分析表明PZT(111)衍射峰的摇摆曲线半高宽为0.4°,说明薄膜结晶性能良好。PZT薄膜疲劳特性测试结果表明,在经过107次翻转后PZT薄膜的剩余极化强度开始出现下降。P-E电滞回线和I-V测试表明PZT薄膜矫顽场(2Ec)为350 kV/cm,剩余极化(2Pr)约为96μC/cm2,在1 V电压下薄膜的漏电流密度为1.5×10-7A/cm2。以上性能测试结果表明,在半导体GaN上外延生长的PZT铁电薄膜性能基本满足铁电随机存储器的需要。     

PZT基体沉积条形分布NiTiSMA薄膜复合材料的介电性能

使用模具并采用磁控溅射法在铁电陶瓷PZT基体上沉积具有条形分布结构的Ni Ti SMA薄膜。显微组织结构观察发现,以条形分布结构方式沉积的Ni Ti SMA薄膜晶化处理后具有等轴晶结构。比较所制备PZT/Ni-Ti SMA薄膜复合材料与纯PZT的介电常数及介电损耗发现,两者的介电损耗水平接近;复合材料的介电常数比纯PZT的提高约18%。Ni Ti SMA的沉积使基体中靠近薄膜区域的Zr/Ti物质的量比恰好落在准同型相界区内,致使所制备复合材料的介电性能优于纯PZT。     

溅射PZT薄膜的晶体结构和快速热处理

采用常温射频（RF）溅射法和快速热处理相结合的技术，在Pt／Ti／SiO2／Si衬底上，制备出具有铁电性的PZT薄膜。研究了快速热处理工艺条件对PZT薄膜性能的影响。通过X射线衍射法、SEM和AES等方法，分析了PZT薄膜的晶体结构、微结构、薄膜和电极间的界面效应。     

用Sol—Gel法制备PZT铁电陶瓷及薄膜

用Sol-Gel法制备了Pb(Zr0.5Ti0.5)O3(PZT)铁电陶瓷与薄膜，观察了它们的结晶情况并测定了它们的电学性能。利用Sol-Gel法，可降低PZT陶瓷粉料的预烧温度约200℃，所得陶瓷致密，晶粒均匀；具有较好的介电性能。PZT陶瓷显示弥散相变特征，PZT薄膜的晶化受基底影响很大，基底晶格越完整，与PZT薄膜的晶格失配率越小，PZT薄膜的晶化就越。采用PbTiO3过渡层促进PZT薄膜在镀铂硅片上晶化。PbTiO3过渡层与PZT薄膜的串联电路，其表观电学性能与相应的PZT体材料相近。     

力电多场鼓包法测定PZT铁电薄膜的横向压电系数

为表征Pb(Zr_(0.52)Ti_(0.48))O_3(PZT)薄膜的横向压电性能,以纯力场鼓包测试模型和铁电薄膜材料压电方程为基础,推导了PZT铁电薄膜的力电耦合鼓包本构模型。采用溶胶-凝胶法制备了PZT铁电薄膜,并通过化学腐蚀法获得PZT薄膜鼓包样品。在外加电压为0~14V的条件下进行鼓包测试。结果表明,在纯力场作用下,PZT薄膜的弹性模量和残余应力分别为91.9GPa和36.2MPa;随着电压从2V变化到14V,PZT薄膜的横向压电系数d31从-28.9pm/V变化到-45.8pm/V。本工作所发展的力电耦合鼓包测试技术及力电耦合鼓包本构模型为评价铁电薄膜材料的横向压电性能提供了一种有效的分析方法。     

Al_2O_3衬底上Pb(Zr,Ti)O_3铁电薄膜的外延生长与性能

以SrRuO3(SRO)作为缓冲层,利用脉冲激光沉积的方法,首次在蓝宝石(Al2O3)衬底上制备了PbZr0.52-Ti0.48O3(PZT)外延薄膜。利用X射线衍射分析得到了PZT薄膜与Al2O3衬底的外延关系,即(111)[110]PZT//(0001)[1010]Al2O3。所制备的PZT薄膜具有较强的铁电极化性能,饱和极化值达到138.3μC/cm2。同时,利用对电流-电压性质的测量研究了铁电极化的退反转现象。     

Fabrication and characterization of piezoelectric micromachined ultrasonic transducers with thick composite PZT films

Ferroelectric microelectromechanical systems (MEMS) has been a growing area of research in past decades, in which ferroelectric films are combined with silicon technology for a variety of applications, such as piezo-electric micromachined ultrasonic transducers (pMUTs), which represent a new approach to ultrasound detection and generation. For ultrasound-radiating applications, thicker PZT films are preferred because generative force and response speed of the diaphragm-type transducers increase with increasing film thickness. However, integration of 4- to 20-microm thick PZT films on silicon wafer, either the deposition or the patterning, is still a bottleneck in the micromachining process. This paper reports on a diaphragm-type pMUT. A composite coating technique based on chemical solution deposition and high-energy ball milled powder has been used to fabricate thick PZT films. Micromachining of the pMUTs using such thick films has been investigated. The fabricated pMUT with crack-free PZT films up to 7-microm thick was evaluated as an ultrasonic transmitter. The generated sound pressure level of up to 120 dB indicates that the fabricated pMUT has very good ultrasound-radiating performance and, therefore, can be used to compose pMUT arrays for generating ultrasound beam with high directivity in numerous applications. The pMUT arrays also have been demonstrated.     

Electrolytic PZT films

A novel method of cathodic deposition of complex oxide compounds has been demonstrated on the deposition of ferroelectric PZT films. In the proposed approach, PZT film formation on graphite and carbon fibre mat substrates was achieved via a peroxoprecursor. It was established that the atomic ratio of lead, zirconium and titanium in the deposit closely corresponded to that in the starting solutions. Formation of a perovskite PZT phase was observed at 500°C. By variation of current density and deposition time the amount of the deposited material could be controlled. It was established that films obtained from solutions with hydrogen peroxide as an additive showed less tendency to crack. This revised version was published online in November 2006 with corrections to the Cover Date.     

Study of the integrated growth of dielectric films on GaN semiconductor substrates

Typical perovskite oxides SrTiO? (STO) and PbZr?.??Ti?.??O? (PZT) were fabricated on GaN semiconductor substrates by pulsed laser deposition. STO and PZT films were deposited on bare GaN, TiO?, and MgO-buffered GaN. The effects of TiO? and MgO buffer-layers on the orientations and electric properties of the perovskite films were systematically studied. The crystalline properties were in situ monitored by reflective high energy electron diffraction and ex situ characterized by X-ray diffraction. It was found that the epitaxial temperature of STO and PZT was reduced by inserting a buffer layer. (111)-oriented films were obtained on bare and TiO?-buffered GaN. However, the orientations of the perovskite films were changed to be (110) when deposited on MgO buffer layer. Furthermore, PZT films deposited on MgO- and TiO?-buffered GaN show better electric performance compared with these films directly deposited on GaN. These results show that perovskite oxide could be epitaxially grown on GaN semiconductor substrates by inserting a proper buffer layer.     

Laser reflectometry in situ measurement of lead zirconate titanate film growth

A convenient method is described for optical characterization of thin films during growth. The method has been demonstrated on lead zirconate titanate (PZT) films deposited by pulsed laser ablation for various temperatures. The optical constants of the PZT films as well as the film growth rate were determined in situ by fitting (with three free parameters) the calculated reflectance as a function of film thickness to the experimental reflectance curve as a function of deposition time, as obtained by unpolarized laser reflectometry. The fitted parameters are the uniform complex PZT refractive index and the layer thickness (assumed proportional to time), with the complex refractive index of the platinum substrate being measured previously. These results compare well with the subsequent ellipsometric measurements made to assess the precision of the reflectometry technique.     

PZT/ZnO薄膜制备及其结构特性研究

利用固相反应制备的ZnO-Li_(2.2%)陶瓷靶和RF射频磁控溅射技术在Si(100)基片上制备了高度c轴择优取向的ZnO薄膜,XRD和电性能分析表明掺杂Li离子改善了ZnO靶材的结构和性能,同时研究了不同RF溅射温度对ZnO薄膜结构与取向的影响;然后采用sol-gel前驱单体薄膜制备方法,以ZnO为过渡层淀积PZT薄膜,探讨高度c轴(002)择优取向ZnO薄膜对PZT薄膜结构与性能的影响,实验发现在PZT/ZnO异质结构中,致密、均匀和高度c轴择优取向的ZnO可作为晶核,促进PZT钙钛矿结构转化、晶粒(110)择优取向生长,相应降低PZT薄膜的退火温度.     

Effects of a PbTiO3 insertion layer on the morphological and electromechanical characteristics of sol-gel-driven 0.2PZN-0.8PZT piezoelectric films for energy harvesters

This study investigated the morphological and electromechanical characteristics of 0.2PZN-0.8PZT films fabricated using a PbTiO3 layer. Crack-free 1-microm-thick films with a pure perovskite phase were obtained on Pt/Ti/SiO2/Si substrates using a modified sol-gel deposition method. A highly dense and smooth morphology and a high piezoelectric coefficient (d33) of 230 pC/N were observed in a 0.2PZN-0.8PZT film with a PbTiO3 insertion layer after annealing at 750 degrees C. The as-produced sol-gel-driven 0.2PZN-0.8PZT thin films are attractive for application to piezoelectrically operated microelectronic actuators, sensors, or energy harvesters due to their low facility cost, smooth surface, and excellent electromechanical characteristics.     

Orientation control and electrical properties of sputtered Pb(Zr,Ti)O3 films

Relationship between the crystallographic orientation and the electrical properties of the Pb(Zr,Ti)O₃, (PZT) thin films prepared by rf magnetron sputtering was investigated. The PZT films were deposited at 150, 250 or 340°C and, followed by rapid thermal annealing (RTA). It was found that the crystallographic orientation of the PZT films could be controlled only by the deposition temperature and the ferroelectric properties were dependent upon the orientation of the films. It was suggested that the difference in the atomic mobility at the substrate surface during deposition was closely related to the film orientation. The films with (111) orientation showed relatively high capacitance and the remanant polarization values.     

Online in-situ control of lead zirconate titanate film growth in gas discharge chamber

Online in situ monitoring of the gas-discharge deposition of lead zirconate titanate Pb(Zr _x Ti_{1 − x} )O₃ (PZT) films onto a stainless steel substrate revealed oscillatory decay in the intensity of light with a wavelength of 0.640 μm specular reflected from the growing film. It is established that the parameters of the reflectance curves depend on the electric power deposited in discharge and correlate with the type of growing films (possessing pyrochlore or perovskite structures). Using the proposed method, it is possible to control technological parameters of the deposition process, which determine the physical characteristics of the obtained PZT films.     

Optical properties of pb(Zr,Ti)O(3) films prepared by aerosol deposition

The optical properties and related band structure of ferroelectric lead zirconate titanate [PZT, Pb(Zr0(0.6)Ti0(0.4))O(3)] films prepared on glass substrates at room temperature by aerosol deposition were investigated. The reflectance and transmittance of the PZT films were measured in the wavelength range from UV to nearinfrared. The measured optical spectra were analyzed using dielectric function models that describe optical transitions in the band gap region. Optical absorption of the as-deposited PZT films was found to be larger than that of the annealed PZT films in the near-infrared wavelength range. The analyzed results indicated that post-deposition annealing increased the band gap energy of the PZT films, corresponding to a decrease in optical absorption.     

Optical Properties of Pb(Zr,Ti)O/sub 3/Films Prepared by Aerosol Deposition

The optical properties and related band structure of ferroelectric lead zirconate titanate [PZT, Pb(Zr_0.6Ti_0.4)O₃] films prepared on glass substrates at room temperature by aerosol deposition were investigated. The reflectance and transmittance of the PZT films were measured in the wavelength range from UV to near-infrared. The measured optical spectra were analyzed using dielectric function models that describe optical transitions in the band gap region. Optical absorption of the as-deposited PZT films was found to be larger than that of the annealed PZT films in the near-infrared wavelength range. The analyzed results indicated that post-deposition annealing increased the band gap energy of the PZT films, corresponding to a decrease in optical absorption.