Ferroelectric thin films based on Pb(Zr0.30Ti0.70)O3 (PZT 30/70) were prepared by Chemical Solution Deposition from lead oxide or lead acetate and transition metal alkoxides in 2-methoxyethanol at 400 °C. The choice of the lead-compound determines the composition of the PZT-sols and as a consequence the course of the thermal decomposition. In the case of PbO the local atmosphere within the bulk of the film during heating is more reducing, i.e. the partial pressure of oxygen is lower, than in the case of Pb(OAc)2 based film. Thus, in the former case a continuous layer of Pt-Pb phase is formed at 400 °C, while in Pb(OAc)2 based film only a low amount of Pt-Pb inclusions could be determined by TEM.

The mixture of PbO-Bi2O3-B2O3 (PBB) were formed on the Ba0.5Sr0.5TiO3 (BST) film and the effects of PBB phase on the dielectric properties of the BST film were investigated. The amorphous PBB layer was deposited on the BST film using rf magnetron sputtering and diffused into the film by heat treatment. The PBB phase in BST film was identified by energy dispersive spectrometer (EDS). Dielectric properties of BST film were significantly improved after the diffusion of PBB. The leakage current density of BST film decreased from 3.24×10-5 A/cm2 to 9.45×10-8 A/cm2 at 1.5 V and the dielectric constant increased from 238 to 533. These results show that the diffusion of insulating metal oxide into the ferroelectric thin film can improve the dielectric properties of the film.

Pb(DPM)2 and Pb(TMOD)2 dissolved in ethylcyclohexane were evaluated as precursors for future atomic layer deposition (ALD) of Pb(Zr,Ti)O3 films. PbO films were deposited by a liquid injection atomic layer deposition on Pt-covered Si substrates at different deposition temperature and precursor volume per cycle. Pb(DPM)2 and Pb(TMOD)2 started thermal decomposition at deposition temperature of around 270°C and 320°C, respectively. Against increasing Pb(DPM)2 injection at 240°C, the deposition rate of PbO films saturated at around 1 Å/cycle, but kept increasing at 300°C, which is above the thermal decomposition temperature. The deposition rate of PbO films at 240°C dropped to a constant value with enough purge time after precursor injection and reactant supply. A saturated deposition rate of PbO films was also observed for Pb(TMOD)2 below the thermal decomposition temperature. However, the saturation behavior observed for Pb(TMOD)2 was slower and the saturated growth rate was higher comparing to Pb(DPM)2. In addition, the film thickness of the PbO films had an apparent gradient over the substrates. These results indicate that Pb(DPM)2 shows more reactive and stable chemisorption comparing to Pb(TMOD)2 for the self-limiting growth rate.

A method providing estimation of the trap density at metal/ferroelectric interfaces of a depleted ferroelectric film located between back-to-back Schottky barriers has been developed. The method is based on the recharge of interface traps induced by external bias pulse applied to the metal/ferroelectric/metal structure. It is shown that the transient current under bias pulse can be controlled by the traps recharge on the reverse-biased interface. Using the method, the trap charge density on interfaces of MOCVD Pt/PZT/Ir(Ti/SiO2/Si) and Ir/PZT/Ir(Ti/SiO2/Si) capacitors were found from transient current measurements.

Epitaxial films of strontium bismuth tantalate (SrBi2Ta2O9, SBT) and strontium bismuth niobate (SrBi2Nb2O9, SBN) were grown using solution deposition techniques on magnesium oxide (MgO) substrates buffered with a 100 nm layer of lanthanum manganate (LaMnO3, LMO). Film structure and texture analyses were carried out using x-ray diffraction. Theta-2theta diffraction patterns were consistent with a c-axis aligned structure for both the buffer layer and the solution deposited films. Theta-2 theta scans revealed (001)SBT, SBN //(001) LMO epitaxial relationships between the solution deposited films and the buffer layer. A pole figure about the SBT, SBN (115) reflection indicated a single in-plane epitaxy. Film quality was assessed using ω and φ scans. Nuclear Magnetic Resonance (13C) was used to characterized the methoxy-ethoxide solutions used for the deposition of the SBN and SBT films.

We overall evaluated the enthalpies of formation and the formation energies of neutral vacancies in ANbO3 (A = Li, Na, K) using a plane-wave pseudopotential method within a density functional formalism. The LiNbO3 phase with the LiNbO3-type structure was confirmed to have lower enthalpy of formation than that with perovskite- or ilmenite-type structure. The NaNbO3 (R3c) and KNbO3 (Bmm2 and R3m) phases with the lowest symmetry were found to have the lowest enthalpy of formation. The formation energy of a A vacancy was found to be the lowest under an oxidizing atmosphere and that of an O vacancy was found to be the lowest under a reducing atmosphere. The formation energy of a Nb vacancy was the highest under both oxygen-rich and -poor conditions. These results are in agreement with the empirical rule that B site defects in perovskite-type oxide do not exist.

When an electric field is applied to a ferroelectric the crystal lattice spacing changes as a result of the converse piezoelectric effect. Although the piezoelectric effect and polarization switching have been investigated for decades there has been no direct nanosecond-scale visualization of these phenomena in solid crystalline ferroelectrics. Synchrotron x-rays allow the polarization switching and the crystal lattice distortion to be visualized in space and time on scales of hundreds of nanometers and hundreds of picoseconds using ultrafast x-ray microdiffraction. Here we report the polarization switching visualization and polarization domain wall velocities for Pb(Zr0.45Ti0.55)O3 thin film ferroelectric capacitors studied by time-resolved x-ray microdiffraction.

The Pb(Zr,Ti)O3 ferroelectric gate was successfully integrated into the GaN/AlGaN heterostructure with 2D electron gas. The processing conditions were optimized in a way to obtain high quality textured Pb(Zr,Ti)O3 films without destroying the 2D gas situated as close to the interface as 20nm. Study of transport properties in this system demonstrates a possibility to control the 2D gas by switching the spontaneous polarization in the gate. Concentration and mobility of electrons in the 2D gas were monitored using Hall effect and resistivity measurements in a wide temperature range from 4.2K to 300K. The polarization oriented in the direction “from bottom to top” provokes a partial depletion effect in the channel resulting in a conductivity decrease. A correlation between the depletion effect in 2D gas and the change of the spontaneous polarization with temperature has been observed. The depletion effect is found to be reversible so that the initial conductivity in 2D gas can be restored by inversing the spontaneous polarization in the gate. These results suggest that ferroelectric gates integrated into systems with 2D electron gas may be potentially interesting for a number of experiments and applications as a flexible and nondestructive way of making rewritable nanopatterns on semiconductor heterostructures.

The synthesis of SrBi2Ta2O9 (SBT) thin films has been investigated using a superlattice approach. Thin films were deposited on silicon by independent injection of each source to produce Bi2O3/SrTa2O6 superlattices. The effects of post-deposition annealing have been investigated using high-resolution TEM and medium energy ion scattering (MEIS) to depth profile the superlattices. X-ray diffraction has also been used to characterize the conversion of the superlattices from distinct layers of Bi2O3 and SrTa2O6 into a polycrystalline layer of strontium bismuth tantalate.

Lead Zirconate Titanate (PZT) powders have been synthesized by a hydrothermal method at the processing temperatures of 120-220 °C for 1.5-50 hours, based on the reaction of Pb(CH3COOH)2·3H2O, ZrOCl2·8H2O, Ti(C4H9O)4 and KOH. Hydrothermally treated PZT powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transformation infrared (FTIR) techniques respectively. The influences of hydrothermal synthesize conditions on the crystalline structure and the morphology of PZT particles were investigated. Crystallized PZT powders could be synthesized at the KOH concentration of >2.5 mol/l.

A two-step growth technique was used to achieve effective strain relaxation and dislocation confinement of epitaxial SrTiO3(STO) films and through this to improve their microwave dielectric properties. The crystallization of a very thin quasi-amorphous STO layer deposited at a low temperature in the initial growth step enhanced the strain relaxation from the lattice mismatch at the expense of the formation of high density of misfit dislocations. By varying the thickness of the first layer, different strain states of the films were systematically achieved while keeping the total film thickness unchanged. This allowed the study of the effect of strain on permittivity, and showed good agreement with theoretical predictions. Further more, the two-step growth technique suppressed significantly the threading dislocation density in the film, the dislocations being confined to the first layer. This in turn caused reduction in the extrinsic dielectric loss at microwave frequency. The loss reduction was analyzed and explained based on a dielectric composite model.

Electric-field-induced displacements of PZT film capacitor Pt/PZT/Pt/SiO2/Si(100) were calculated by finite element method (FEM) with changing all piezoelectric and elastic constants of PZT so as to discuss how to evaluate intrinsic d33 of piezoelectric thin films. Two kinds of conditions, namely, “ideal conditions” and “second-best conditions” are discussed. The ideal conditions indicate that the diameter of top electrode φTE is equal to or less than PZT film thickness tPZT and continuous PZT is etched to isolate the capacitor from the continuous piezoelectric film layer. Under the ideal conditions, d33 measured by atomic force microscopy (AFM) and double beam interferometry (DBI) were the same value that was equal to intrinsic d33 of PZT and was independent of other material constants. Under the second-best conditions, i.e. 20×tPZT < φTE for DBI and 20×tPZT < φTE < 0.5×(tsub: substrate thickness) for AFM, measured d33 depended on only d31, s11, s12 and s13, and obeyed the Lefki's equation qualitatively. However, quantitative differences between FEM analysis and the Lefki's equation were not negligible.

Lanthanum-modified lead zirconate titanate and lead zirconate titanate epitaxial films with (100) and (111) orientations are grown respectively on (100) and (111) niobium, lending conductivity to strontium titanate through chemical solution deposition. This study investigates changes in the ordinary and extraordinary refractive index no and ne induced by the electric field in these films using the prism-coupling method. Anisotropic electrooptic effects arise from Pockels effect and switching among polar clusters. Isotropic electrooptic effect is realized on PLZT 8/65/35 and PZT 70/30 of (100) epitaxial films.

The nonlinear thermodynamic theory of epitaxial ferroelectric films has predicted several important strain-induced phenomena, which have been already observed experimentally. This justifies further development of this theory aiming at the better understanding of the structure/property relationships in thin-film ferroelectrics. To that end, a number of new theoretical studies have been performed recently. First, the thermodynamic formalism has been extended to epitaxial films grown on dissimilar substrates inducing anisotropic strains and a shear deformation in the film plane. Second, the polarization states and dielectric properties were calculated for polydomain Pb(Zr1-xTix)O3 films deposited on cubic substrates. Third, the effect of depolarizing field on the physical properties of strained single-domain films sandwiched between continuous electrodes was described. The results of these studies will be discussed in this paper.

Piezoresponse force microscopy (PFM) is the method of choice to investigate piezoactivity on a nanometer scale. A careful distinction between intrinsic and extrinsic effects are mandatory, especially when measuring ferroelectric nanostructures. We focus on two omnipresent extrinsic contributions with a substantial impact: firstly adsorbates on the surface of perovsike materials and secondly the dependence of the lateral piezoresponse on the topography. A thorough understanding of these extrinsic contributions is essential in order to avoid ambiguities in the analysis of PFM measurements.

We performed x-ray diffraction measurements by using highly brilliant synchrotron radiation on epitaxial Pb(Zr0.35Ti0.65)O3 film capacitor structures. Small regions of 300-nm-thick epitaxial Pb(Zr,Ti)O3 thin films with Pt and SrRuO3 top electrodes were measured after applying various numbers of switching cycles of the electric field. Epitaxial Pb(Zr,Ti)O3 thin films were prepared on epitaxial (100)cSrRuO3/(100)SrTiO3 substrates by pulsed-metalorganic chemical vapor deposition. The volume faction of c-domain and remanent polarization was plotted against the number of switching cycles. In the both capacitors, the Vc increased as the switching cycle increased independent of fatigue behavior.

We grew the epitaxial Pb(Zr1-xTix)O3 [PZT] and (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 [PMN-PT] films, above 2 μm in thickness, on (100)cSrRuO3//(100)SrTiO3 substrates by metalorganic chemical vapor deposition (MOCVD). PbTiO3 content (x) dependencies of the crystal structure, dielectric and piezoelectric properties were systematically investigated for these films. The constituent phase changed from a rhombohedral (pseudocubic) single phase, a mixture phase of rhombohedral (pseudocubic) and tetragonal phases, and a tetragonal single phase with increasing x for both of PZT and PMN-PT films. The mixture phase region was observed when x=0.40−0.60 for PZT films and x=0.40−0.55 for PMN-PT films, which became wider than that reported ones for PZT sintered bodies and PMN-PT single crystals. In addition, x value moves to the higher one than that reported for the single crystal and/or the sintered body in case of PMN-PT films, while was almost the same in case of PZT films. The dependence of relative dielectric constant εr was maximum at the mixed phase region for both films, which were similar to the case of their bulk materials. The higher value of εr was ascertained for the PMN-PT films compared with PZT films, however, the magnitude was lower than the reported one for bulk materials. The longitudinal electric-field-induced strain Δx33 and transverse piezoelectric coefficient e31,f for PZT films were also maximum at the mixed phase region, on the other hand, that for PMN-PT films were maximum at larger x edge of rhombohedral (pseudocubic) region. Almost the same order of Δx33 was observed under applied electric fields up to 100 kV/cm, while larger e31,f was observed in PMN-PT films compared with the case of PZT films. e31,f coefficients of ∼−8.9 C/m2 and ∼−11.0 C/m2 were calculated for the PZT film with x=0.46 and for the PMN-PT film with x=0.39, respectively.

PZT (52/48) and PLZT (7/65/35) thin films were prepared by chemical solution deposition (CSD) on Pt/SiO2/Si and Cu foil substrate, respectively. For PZT thin films on Pt/SiO2/Si substrates, pO2 control during thermal treatment affected both perovskite phase formation and orientation, but did not show significant impact on the ferroelectric and dielectric properties. When PLZT thin films (7/65/35) were prepared on Cu foil to tailor ferroelectric/dielectric properties, it was observed that ferroelectric and dielectric properties were significantly affected by the strains, possibly from the coefficient of thermal expansion (CTE) mismatch between PLZT and Cu foil during cooling after high temperature crystallization. It was also experimentally observed that, depending on the direction of applied strain, the PLZT films could be cycled between ferroelectric and paraelectric phases. It was suggested that PZT based thin films on base metal substrate requires very careful processing for optimized electrical performance.

The effects of P-E properties of epitaxially grown rhombohedral Pb(Zr,Ti)O3 film on the film thickness and temperature were systematically investigated. (100)-oriented rhombohedral Pb(Zr0.65Ti0.35)O3 films with 50 - 3200 nm in thickness were grown on (100)cSrRuO3//(100)SrTiO3 substrates by metalorganic chemical vapor deposition (MOCVD). The ratio of the remanent polarization (Pr) to saturation polarization (Psat), the Pr/Psat ratio, at room temperature decreased with decreasing the film thickness. Moreover, the Pr/Psat ratio at 10 K of 180-nm-thick films was smaller than that of 3200-nm-thick film and dropped at lower temperature with increasing the film thickness. These results suggest that the small Pr/Psat ratio of thin film at room temperature is originated to both of small Pr/Psat ratio even at 10K and their drop starting at lower temperature when the temperature increased.

The surface potential distribution following polarization reversal by scanning probe microscopy is examined in order to determine the mechanism of anti-parallel polarization reversal and ring-shaped domain formation in single-crystal lithium tantalate. Lithium vacancy lattice defects are identified as charge-trapping sites, with the resultant surface potential distribution governing the formation of ring-shaped nano-domains. The behavior of this charge injection is shown to be dependent on atmospheric humidity.