Characterization of Pb(Zr,Ti)O3 thin films obtained by MOD

Pb(Zr, Ti)O₃ thin films were deposited by dip-coating on polycrystalline alumina substrates by using an MOD method. The thickness and homogeneity of the films were measured as a function of dip rates and solution concentration. Heating and cooling schedules determined the main structure of the crystallized films. Rheology measurements and Fourier transform-infrared spectra were carried out to obtain a better knowledge of the solution features. A microstructural development study and some ferroelectric measurements were also carried out.     

LaNiO3缓冲层对Pb(Zr,Ti)O3铁电薄膜的影响

采用化学溶液法在Pt／Ti／SiO2／Si衬底上制备了PbZr0．4Ti0.6O3／LaNiO3(PZT／LNO)多层薄膜。X射线衍射测量表明LNO缓冲层的引入使PZT薄膜(111)择优取向度减小,(100)取向增加。原子力显微镜测量表明引入LNO缓冲层使得PZT薄膜表面更加平整、致密。在LNO缓冲层上制备的PZT薄膜具有优良的铁电特性和介电特性：LNO缓冲层厚度为40nm时,500kV／cm的外加电．场下。剩余极化(Pr)为37．6μC／cm^2,矫顽电场(Ec)为65kV／cm;100kHz时,介电常数达到822,并且发现LNO缓冲层的厚度为40nm,PZT的铁电、介电特性改进最为显著。     

Measurement and modeling of dielectric properties of Pb(Zr,Ti)O3 ferroelectric thin films

In this study, the real and imaginary parts of the complex permittivity of lead zirconate titanate ferroelectric thin films are studied in the frequency range of 100 Hz to 100 MHz. The permittivity is well fitted by the Cole-Cole model. The variation of the relaxation time with the temperature is described by the Arrhenius law and an activation energy of 0.38 eV is found. Because of its nonlinear character, the dielectric response of the ferroelectric sample depends on the amplitude of the applied ac electric field. The permittivity is composed of three different contributions: the first is due to intrinsic lattice, the second is due to domain wall vibrations, and the third is due to domain wall jumps between pinning centers. This last contribution depends on the electric field, so it is important to control the field amplitude to obtain the desired values of permittivity and tunability.     

Preparation of (001)-oriented Pb(Zr,Ti)O3 thin films and their piezoelectric applications

Preparation of (001)-oriented Pb(Zr,Ti)O(3) (PZT) thin films and their applications to a sensor and actuators were investigated. These thin films, which have a composition close to the morphotropic phase boundary, were epitaxially grown on (100)MgO single-crystal substrates by RF magnetron sputtering. These (001)-oriented PZT thin films could be obtained on various kinds of substrates, such as glass and Si, by introducing (100)-oriented MgO buffer layers. In addition, the (001) oriented PZT thin films could be obtained on Si substrates without buffer layers by optimizing the sputtering conditions. All of these thin films showed excellent piezoelectric properties without the need for poling treatment. The PZT thin films on the MgO substrates had a high piezoelectric coefficient, d(31), of -100 pm/V, and an extremely low relative dielectric constant, epsilon(r), of 240. The PZT thin films on Si substrate had a very high d(31) of -150 pm/V and an epsilon(r) = 700. These PZT thin films were applied to an angular rate sensor with a tuning fork in a car navigation system, to a dual-stage actuator for positioning the magnetic head of a high-density hard disk drive, and to an actuator for an inkjet printer head for industrial on-demand printers.     

Conduction at domain walls in insulating Pb(Zr0.2 Ti0.8)O3 thin films

Domain wall conduction in insulating Pb(Zr(0.2) Ti(0.8))O(3) thin films is demonstrated. The observed electrical conduction currents can be clearly differentiated from displacement currents associated with ferroelectric polarization switching. The domain wall conduction, nonlinear and highly asymmetric due to the specific local probe measurement geometry, shows thermal activation at high temperatures, and high stability over time.     

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.     

磁控溅射工艺参数对Pb(Zr,Ti)O3薄膜织构的影响

利用RF磁控溅射法制备了Pb(Zr,Ti)O3(PZT)铁电薄膜,利用X射线衍射(XRD)法研究了薄膜的相组成及溅射工艺参数对薄膜织构的影响.结果表明,在小靶基距时,过高溅射功率不利于获得纯钙钛矿相的PZT铁电薄膜.溅射功率及溅射气压影响PZT薄膜的织构及其织构散漫度,提高溅射气压及溅射功率,(111)织构漫散度随之提高.在靶基距为80mm时,选择150w、0.7Pa的溅射工艺可获得具有最佳(100)织构的PZT薄膜.     

Preparation of (001)-oriented Pb(Zr,Ti)O/sub 3/ thin films and their piezoelectric applications

Preparation of (001)-oriented Pb(Zr,Ti)O₃ (PZT) thin films and their applications to a sensor and actuators were investigated. These thin films, which have a composition close to the morphotropic phase boundary, were epitaxially grown on (100)MgO single-crystal substrates by RF magnetron sputtering. These (001)-oriented PZT thin films could be obtained on various kinds of substrates, such as glass and Si, by introducing (100)-oriented MgO buffer layers. In addition, the (001)-oriented PZT thin films could be obtained on Si substrates without buffer layers by optimizing the sputtering conditions. All of these thin films showed excellent piezoelectric properties without the need for poling treatment. The PZT thin films on the MgO substrates had a high piezoelectric coefficient, d₃₁, of -100 pm/V, and an extremely low relative dielectric constant, epsiv_r, of 240. The PZT thin films on Si substrate had a very high d₃₁ of -150 pm/V and an epsiv_r = 700. These PZT thin films were applied to an angular rate sensor with a tuning fork in a car navigation system, to a dual-stage actuator for positioning the magnetic head of a high-density hard disk drive, and to an actuator for an inkjet printer head for industrial on-demand printers.     

A study of vacancy-related defects in (Pb,La)(Zr,Ti)O(3) thin films using positron annihilation

The formation of vacancy-type defects in La-doped lead zirconate titanate (PLZT) thin films (Zr/Ti=20/80) was studied as a function of lanthanum doping and after cooling in an oxygen-reduced ambient. The changes in the Doppler-broadening S parameter are consistent with the progressive introduction of Pb-vacancies upon La-doping. Cooling of PLZT thin films with 0 and 10% La doping in 10(-5) Torr oxygen partial pressure after growth exhibits an increase in the density of vacancy-type defects compared to films cooled in 760 Torr. It is proposed that the defects formed are likely cation-oxygen vacancy complexes.     

TiOx interlayer characterization for sol–gel derived Pb(Zr, Ti)O3 thin films on titanium foil

Pb(Zr, Ti)O₃ films were prepared on titanium foil using sol–gel processing. The films were of large area, crack-free, uniform, with perovskite structure and exhibiting strong adhesion to the titanium foil substrate. Films and the interface region between the film and the substrate were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and dielectric property measurements. The measurements revealed the formation of a TiO_x layer at the interface between the film and the foil. The thickness of the TiO_x interlayer increases with increasing annealing temperature, and was amorphous when annealed below 600 °C. The dielectric properties of films depend on the thickness of the TiO_x interlayer. Films on Ti foil with dielectric constant of 200–400, dielectric loss <5%, leakage current of <1×10^–7 A cm^–2 at 100 kV cm^–1 and breakdown field strength of 0.6–1.13 MV cm^–1 were demonstrated. The TiO_x interlayer resulted in asymmetric C–V hysterisis behavior attributed to trapped charge in the vicinity of the TiO_x interlayer and to elastic mismatch strain.     

Asymmetric switching behavior of Ni/Pb1.1(Zr0.3Ti0.7)O3/Pt thin films

An asymmetric behavior of P–E response was observed in Ni/Pb_1.1(Zr_0.3Ti_0.7)O₃/Pt multilayer thin films where Ni was used as top electrode. This interesting phenomenon was investigated by comparative analysis of the hysteresis loops and dynamic pyroelectric responses. The PZT thin films were prepared under the same conditions but different Ni and Pt top electrodes were used in the hysteresis loop measurement, and the Pt was used as the common bottom electrode. It is believed that this asymmetric behavior in hysteresis loop is originated from the strong domain pinning near the top Ni electrode. Dynamic pyroelectric response to 633 nm radiation of the Ni/Pb_1.1(Zr_0.3Ti_0.7)O₃/Pt thin films with polarization up and down was carried out. Higher dynamic pyroelectric response was observed in the positively poled film, in which the direction of the polarization was from the top to bottom electrode. It provides further evidence that the domain pinning near the top electrode dominates the asymmetric switching behavior.     

Effects of excess Pb on structural and electrical properties of Pb(Zr0.48Ti0.52)O3 thin films using MOD process

Pb(Zr_0.48Ti_0.52)O₃ thin films at 20% excess Pb were synthesized on Pt/Ti/SiO₂/Si(100) substrates at different annealing temperatures by a metal-organic decomposition process. The microstructure of the PZT films was investigated by x-ray diffraction and atomic force microscopy. The composition of the films was characterized by Rutherford Backscattering Spectroscopy (RBS). These results showed that The PZT films have perovskite phase coexisted with PbO₂ phase. The PbO₂ phase mainly was formed by excess Pb which congregate at boundaries of crystalline grains during the annealing process and may be absorbed part of oxygen ion at normal sites, thus leading to an increase of oxygen vacancies in the PZT film. PbO₂ phase and oxygen vacancies act as pinning centres, which has an effect on the ferroelectric domain switching. This eventually resulted in an increase of fatigue rate in PZT films.     

A new and rapid process for production of solution-derived (Pb, La)(Zr, Ti)O3 thin films and powders

A simple and rapid process for synthesizing (Pb,La)(Zr,Ti)O₃ (PZT, PLZT, and PLT) precursor solutions has been developed. This process, termed the “basic route to PLZT” (or BRP) process, offers several advantages over standard methods, including rapid solution synthesis (<10 min), use of commercially available materials, film production under ambient conditions, ease of lanthanum dissolution at high concentrations (<1 min), and no heating requirements during solution synthesis. The PLZT precursor solution synthesis involves dissolution of lead acetate (or acetyl acetate) in pyridine followed by addition of a pre-dissolved mixture of titanium and zirconium iso-propoxide in toluene. The lanthanum source can then be added and, depending on the precursor, total synthesis time was <10 min. The preferred lanthanum starting material is a highly soluble bis(iso-propyl)aryloxide complex; however, this compound is extremely air and water sensitive. The compositions investigated in this study include PZT 40/60, PLZT 3/30/70, 5/30/70, and 10/40/60, and PLT films with 10–20 mol % La. All films were crystallized at 650 19°C and exhibit ferroelectric properties comparable to films produced by other techniques which require higher crystallization temperatures. This revised version was published online in November 2006 with corrections to the Cover Date.     

Pb(Zr0.5, Ti0.5)O3 nanofibres by electrospinning

Lead zirconate titanate Pb(Zr_0.5, Ti_0.5)O₃ nanofibres with diameters ranging from 200–300 nm have been synthesized by calcination of the electrospun lead zirconate titanate/polyvinyl acetate composite fibres. The morphology and crystalline phase features of these lead zirconate titanate (PZT) nanofibres have been studied by various physico-chemical methods such as SEM, AFM, XRD and FT–IR. The formation of perovskite PZT phase was observed at temperatures as low as 550 °C.     

Compositionally graded Pb(Zr,Ti)O3 thin films with different crystallographic orientations

Compositionally graded ferroelectric PbZr_xTi_1−xO₃ (PZT) films were deposited using a sputtering method and crystallized in situ at 500 °C. The films showed purely (100) or (111) crystallographic orientation when grown on Si/SiO₂/TiO₂/Pt substrates, while they exhibited c-axis epitaxial microstructure when prepared on MgO/Pt substrates. Their crystallographic orientation was controlled owing to a thin TiO_x layer sputtered on substrates prior to PZT deposition. Analysis performed by Auger depth profile clearly confirmed the variation of composition in the films. Coercive fields from 80 kV/cm to 200 kV/cm and remnant polarization as large as 45 μC/cm² were obtained. However, no typical offset was observed on hysteresis loops, unlike previous works related to graded PZT films.