A majority of the work published on liquid source misted chemical deposition (LSMCD) has focused on the fabrication of thin ferroelectric films for random access memory (RAM) applications. However, the ability of LSMCD to combine the characteristically good stoichiometry control of a chemical solution deposition process with good film conformality, makes this a desirable technique for other applications, including microactuators and integrated passive components. For these applications, though, LSMCD is limited by its low throughput. This paper describes the feasibility of depositing micron-thick lead zirconate titanate (PZT) films using the LSMCD tool. PZT films of 52/48 composition were deposited on both platinized silicon and platinized alumina substrates. The chamber temperature and the delivery geometry of the LSMCD tool were identified as limiting factors in the rate at which micron-thick samples can be prepared. By switching to a focused nozzle delivery geometry and increasing the chamber temperature from room temperature to 60°C, the total process time for 1 μm thick films can be reduced from 480 min to 90 min. Polarization hysteresis measurements indicated a 75% higher remanent polarization for PZT films deposited on platinized alumina substrates (35 μC/cm2) compared to those deposed on platinized silicon substrates (20 μC/cm2). The polarization loop for the silicon substrate sample was also tilted. These observations are evidence of higher tensile stresses in the PZT films deposited on silicon substrates due to a larger mismatch in the thermal expansion coefficients of the film and the substrate.

Thin films of Ba1-x SrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and low fatigue. Several approaches have been used to improve the properties of thin films such as doping with aliovalent dopants, graded compositions, and layered structures. We have found that interposing layers of an electronic insulator such as ZrO2 in between BST layers results in a significant reduction in the leakage current. In this paper the low temperature electrical properties of these multilayer structures are reported. The structures consist of alternate layers of Ba0.8Sr0.2TiO3 and ZrO2 deposited by a sol-gel process on platinized Si substrates. The thickness and the number of layers are varied while keeping the total thickness of the film constant. Multiple peaks in the dielectric constant vs temperature plots at all frequencies are observed in the multilayered films. The properties of the multilayer films are a complex function of the number of layers and their thicknesses. A structure with several thin layers of ZrO2 interposed between the BST layers produces smoother plots than a single layer of ZrO2 of same total thickness. This is attributed to more uniform distribution, as determined by XPS, of ZrO2 in the multilayer structure due to smaller diffusion distances.

Local piezoelectric signal is measured via Piezoresponse Force Microscopy (PFM) in PbZr0.3Ti0.7O3 films and PbZr1/3Nb2/3O3-0.045PbTiO3 single crystals. It is observed that the amplitude of piezoelectric response is almost independent on frequency for vertical (out of plane) signal and strongly decreases with increasing frequency in the range 10–100 kHz for lateral (in-plane) response. Moreover, the in-plane piezoelectric contrast is reversed when the measurements are done at high enough frequency (phase shift exceeds 90°). As a result, the inplane polarization direction can be misinterpreted if the driving frequency exceeds certain level. For the explanation of observed effect a simple model is proposed that takes into account a possible slip between the conductive PFM tip and moving piezoelectric surface. The implications of the observed frequency-dependent contrast for the domain imaging in ferroelectric materials are discussed.

The memory retention properties of Pt/YMnO3/Y2O3/Si capacitors were investigated for the application of ferroelectric gate transistors. The epitaxially grown Pt/YMnO3/Y2O3/Si capacitors showed ferroelectric type hysteresis loop on the capacitance-voltage properties. Although the retention time of the as-deposited capacitors was ∼103 s, it was prolonged up to 104 s when the leakage current density was reduced from 4×10-8 A/cm2 to 2×10-9 A/cm2 by the annealing under N2 ambience. To reveal the relationship between the retention time and leakage current, the leakage current mechanism was investigated comparing several conduction mechanisms. It was found that the dominant leakage mechanisms at high and low electric fields were Poole-Frenkel emission from the Y2O3 layer and ohmic conduction, respectively. This result indicates that the leakage current was limited by the Y2O3 layer at high electric field and was mainly dominated by the amount of defects in the YMnO3 layer at low electric field. From the pseudo isothermal capacitance transient spectroscopy (ICTS), it was determined that the trap density was in an order of 1015 cm-3. Since the variation of the leakage current by annealing was observed only in the low electric field region, it is suggested that the retention properties of the Pt/YMnO3/Y2O3/Si capacitors was influenced by the amount of defects in the YMnO3 layer.

In present paper a new niobate materials Ba5LixTixNb10-xO30 were synthesized by doping Li+ in the system BaO- TiO2- Nb2O5 in millimeter wave field. X-ray diffraction (XRD) quantitative and scanning transition spectroscopy (SEM) analysis were employed to study crystal structure and microstructure of reaction products. It was found that pure products could be obtained at temperature 900°, 8 min which is lower comparing with that by conventional method. The XRD data shown the crystal belongs to tetragonal tungsten bronze structure with space group P4bm. The grain size synthesized in millimeter wave field had smaller size, narrower distribution, better sinter-ability, and without hard agglomeration comparing whit that obtaining from conventional synthesis. At lower temperature Ba5LiTiNb9O30 is a tetragonal ferroelectric phase.

Pb1-x Srx TiO3 (x = 0 to 1.0) films of thickness ∼ 4 μ m have been prepared on sapphire and Pt substrates by metalorganic decomposition (MOD) method. X-ray diffraction results show that the films are polycrystalline with a perovskite tetragonal phase at room temperature for x < 0.5 and a cubic phase for x > 0.5. Room temperature Raman spectra show a systematic variation of lattice vibrational modes with x. The most notable changes in the Raman spectra with x are the decrease in the splitting of A1(3TO) and E(3TO) modes and the disappearance of E(3TO) mode at x ∼ 0.6. Although the x-ray diffraction peaks for films with x > 0.5 show a cubic phase at room temperature, the Raman spectra show the characteristic phonon modes of a tetragonal phase even at x = 0.7. The dielectric permittivity versus temperature measurements for films with x ≤ 0.7 show a broad dielectric anomaly corresponding to a diffuse ferroelectric to paraelectric phase transition. The phase transition temperature (Tc) values are consistently lower than the corresponding bulk ceramic alloys. Furthermore, Tc are also determined by monitoring the temperature dependence of the splitting between E(3TO) and A1(3TO) phonon modes in the Raman spectra of Pb1-x Srx TiO3 films for x ≤ 0.6. There has been good agreement between the two methods.

Ba0.96Ca0.04Ti0.84Zr0.16O3 (BCTZ) films acceptor-doped with 0.8 at. % Sc were deposited on Pt/TiO2/SiO2/Si substrates using rf magnetron sputtering. Substrate temperatures throughout the fabrication process remained at or below 450°C, which allows this process to be compatible with many materials commonly used in IC manufacturing. In addition, this process made no use of oxygen in the sputter gas or in annealing atmospheres and thus it remains compatible with easily oxidized materials. A relative dielectric constant of 166 was achieved along with a loss tangent of 0.006 to 0.17 at 10 kHz. The tunability of the dielectric constant was greater than 50 %. Leakage current densities of 1.6×10-8 A/cm2 were observed at 300K with 300 kV/cm of applied electric field. In comparison, Ba1-xSrxTiO3 (BST) films prepared under similar conditions show much greater leakage.

Two sol-gel processes for producing Pb1-xBaxTiO3 (PBT), a ferroelectric material of interest for sensor and actuator applications, are investigated. Each system incorporates lead nitrate and barium acetate as metal sources and ethylene glycol as a solvent. Diethanolamine is used as a chelating agent for titanium isopropoxide or titanium butoxide. Precursor chemistry was systematically varied and the resulting sols and powders were studied using TGA/DSC, FTIR, and XRD. Thin films were prepared using both precursor sources by spin coating onto single crystal (100) MgO. Spin speed and pyrolysis temperature were optimized to produce oriented thin films with thicknesses of up to approximately 500nm. Sols incorporating titanium isopropoxide and a large excess of diethanolamine were particularly stable against hydrolysis.

We demonstrate submicron ferroelectric domain engineering in liquid phase epitaxy (LPE) LiNbO3 thin films grown on LiNbO3 and LiTaO3 substrates using a direct-write electron beam poling for waveguide applications. LiNbO3 thin films of several-micron thickness were grown using a flux melt of 20 mol% LiNbO3-80 mol% LiVO3. To engineer domain structures in Z- oriented LPE LiNbO3 films, a direct-write electron beam poling was implemented. It is shown that we can engineer the domain structure of LPE LiNbO3 films by using direct e-beam poling, even though the domain orientations of the film and the substrate are opposite. We also compared e-beam poling behavior in a congruent LiNbO3 single crystal and a LPE LiNbO3 film. Using the same e-beam scan parameters, a much enhanced domain structure is obtained in LPE films. Defect structure and composition effects are also discussed.

Electric-field-induced displacements of PZT film capacitor Pt/PZT(5μm)/Pt/SiO2/Si(100) were calculated by finite element method with various parameters of sample geometry: the diameter of top electrode φ TE ranging from 0.2 μ m to 1000 μ m and whether PZT film was continuous or side-etched. If φ TE was larger than 40μ m, surface longitudinal displacement (corresponding to AFM-measured strain) was not equal to net longitudinal displacement of PZT film, including a contribution of the bending motion of substrate. In contrast, if φ TE was smaller than 4μ m and PZT film was continuous, effective d33 evaluated from net longitudinal displacement was smaller than intrinsic d33, because the side PZT film clamped the edge of the capacitor disk and prevented the whole disk from elongating longitudinally. It was also revealed that d33 value calculated from net longitudinal displacement of PZT film depended on the Poisson's ratio of PZT and was not equal to intrinsic d33, excluding the case that φ TE was smaller than 4μ m and PZT film was side-etched. In conclusion, it is suggested that smaller φ TE (< 4μ m, in our case) and side-etch treatment permit a precision measurement of d33; however this condition is difficult to be satisfied experimentally.

To achieve quantitative interpretation of Piezoresponse Force Microscopy (PFM), including resolution limits, tip bias- and strain-induced phenomena and spectroscopy, knowledge of elastic and electrostatic field distributions below the tip is required. The exact closed form solution of the coupled electroelastic problem for piezoelectric indentation is derived and used to obtain the tip-induced electric field and strain distribution in the ferroelectric material. This establishes a complete continuum mechanics description of the PFM imaging mechanism. These solutions are reduced to the point charge/force behavior for large separations from contact, and the applicability limits and charge/force magnitude for these models are established. The implications of these results for ferroelectric polarization switching processes are analyzed.

In the present work micro-Raman spectroscopy has been used to understand the lattice dynamics of cation substituted SBT ceramics and thin films. Different concentrations of Ca and V were introduced into SBT lattices. Incorporation of Ca ion at Sr-site was confirmed by decrease in the lattice parameters calculated from x-ray diffraction data. The lowest Raman modes at 27 cm-1 and 58 cm-1 showed upward shift with increasing Ca concentration and was attributed to the lower mass and lower ionic radii of Ca. The temperature dependant Raman studies revealed the increase of the phase transition temperature with increased Ca content, and was attributed to the decrease in tolerance factor. Substitution of smaller cation at Sr site in SBT compound has increased lattice mismatch between SrO and TaO2 planes inside the stable perovskite unit of SrTa2O7 which has pronounced influence on ferroelectric properties of SBT. Substitution of vanadium at Ta-site of SBT did not influence the low frequency Raman modes of SBT. However, it showed a pronounced influence on the O-Ta-O stretching modes by splitting the mode frequency at 810 cm-1. The transition temperature of SBT was reduced with increasing vanadium contents.

a-/b-axis-oriented epitaxial Bi4Ti3O12 and neodymium-substituted Bi4Ti3O12 films with a different a-domain fraction, V(100)/[V(100)+V(010)], were grown by metalorganic chemical vapor deposition above the phase transition temperature. It was demonstrated that the saturation polarization observed for the a-/b-axis-oriented film is proportional to the a-domain fraction estimated by x-ray diffraction. The liner relationship passing through the origin revealed that the 90° domain switching by an external electric field hardly occurred. The extrapolation gave spontaneous polarization of 58 μC/cm2 for a pure a-axis-oriented (Bi3.5Nd0.5)Ti3O12 film. The domain fraction was investigated as a function of thermal strain originated from a difference in thermal expansion coefficient between the film and substrates. The domain fraction of the films changed with the thermal strain along the in-plane [010] in tetragonal a-axis-oriented films as well as epitaxially grown tetragonal Pb(Zr,Ti)O3 films.

Pt/Ti/SiO2/Si substrates seeded by SBT nanoparticles (∼60–80 nm) were used to enhance the phase formation kinetics of Sr0.7Bi2.4Ta2O9 (SBT) thin films. The volume fractions of Aurivillius phase formation obtained through quantitative x-ray diffraction (Q-XRD) analyses showed highly enhanced kinetics in seeded SBT thin films. The Avrami exponents were determined as ∼1.4 and ∼0.9 for unseeded and seeded SBT films, respectively, which reveals different nucleation modes. By using Arrhenius–type plots the activation energy values for the phase transformation of unseeded and seeded SBT thin films were determined to be ∼264 and ∼168 kJ/mol, respectively. This gives a key reason to the enhanced kinetics in seeded films. Microstructural analyses on unseeded SBT thin films showed formation of randomly oriented needle-like crystals, while those on seeded ones showed formation of domains comprised of directionally grown worm-like crystals.

We report sol-gel process of Pb5Ge3O11 (PGO) as well as the microstructure and physical properties of ferroelectric PGO films for memory applications. The PGO sol was prepared from lead acetate hydrate, germanium isopropoxide, and di(ethylene glycol) ethyl ether. The reactions taking place during the sol-gel process were examined in detail. Diethanolamine (DEA) was added to help maintain the desired species ratio and prevent germanium oxide precipitation. The preferred orientation of the PGO thin films was well controlled by the heating and reflux procedures in the sol-gel preparation process. Additionally, to examine the impact of postdeposition processing, selected samples were oxygen annealed at temperatures ranging from 450–650°C. The samples were characterized with X-ray diffraction (XRD), non-contact (planview) atomic force microscopy (NC-AFM). The resulting data indicate that the microstructure and physical properties of PGO films depend strongly on the precursor preparation as well as the post deposition annealing temperature.

We have examined the growth of a number of important ferroelectric oxides by MOCVD using a rotating disk reactor. Highly uniform and reproducible films over 6” wafers have been routinely achieved. Materials include Lead Zirconate Titanate (PZT, PbZrxTi1-xO3), Lead Lanthanum Zirconate Titanate (PLZT), Strontium Bismuth Tantalate (SBT), CeMnO3 (CMO), and others. Emphasis has been on achieving highly crystalline and oriented films at the lowest deposition temperatures possible, for compatibility with other integrated device materials and processing; and the achievement of optimum ferroelectric and pyroelectric performance. The effects of varying growth parameters, barrier and/or template layers, and post-growth annealing have been studied. The growth process, physical characterization, and ferroelectric film properties will be discussed.

Thin films of BaZrO3 (BZ) were grown using a pulsed laser deposition technique on platinum coated silicon substrates. Films showed a polycrystalline perovskite structure upon different annealing procedures of in-situ and ex-situ crystallization. The composition analyses were done using Energy dispersive X-ray analysis (EDAX) and Secondary ion mass spectrometry (SIMS). The SIMS analysis revealed that the ZrO2 formation at the right interface of substrate and the film leads the degradation of the device on the electrical properties in the case of ex-situ crystallized films. But the in-situ films exhibited no interfacial formation. The dielectric properties have been studied for the different temperatures in the frequency regime of 40 Hz to 100kHz. The response of the film to external ac stimuli was studied at different temperatures, and it showed that ac conductivity values in the limiting case are correspond to oxygen vacancy motion. The electrical modulus is fitted to a stretched exponential function and the results clearly indicate the presence of the non-Debye type of dielectric relaxation in these materials.

Excimer laser annealing studies were conducted of SrBi2Ta2O9, Pb(ZrxTi1-x)O3 and CeMnO3 thin films. The main incentive was to develop a low temperature process for SrBi2Ta2O9 thin films, which typically require a 750 C anneal to crystallize and achieve optimum ferroelectric properties. The results show that room temperature laser annealing can crystallize SrBi2Ta2O9, with a strong (200) preferred orientation. The Pb(ZrxTi1-x)O3 and CeMnO3 thin films investigated in this study were crystalline as deposited. Laser annealing of the Pb(ZrxTi1-x)O3 and CeMnO3 films did not result in a significant increase in crystallinity, as evidenced by the intensities of the x-ray diffraction peaks. Electrical characterization of laser annealed SrBi2Ta2O9 thin films showed good dielectric properties and the onset of ferroelectric behavior. Low temperature laser annealing is shown to be a viable approach to enable integration of ferroelectric SrBi2Ta2O9 films with silicon based micro-electronics, for ferroelectric memory applications.

The low temperature synthetic method, which combines chemical solution deposition and nm-seeding technique, was applied to the fabrication of lead zirconate titanate (PZT) thin films. Nano-crystallines of barium strontium titanate (BST) particles were prepared by the hydrolysis reaction of the complex alkoxides. PZT precursor solutions containing the BST particles were spin-coated on Pt/Ti/SiO2/Si substrates to film thickness of 500 − 800 nm at particle concentrations of 0–25.1 mol%, and annealed at various temperatures. Seeding of BST particles prevented the formation of pyrochlore phases, which appeared at temperatures above 400 °C in unseeded PZT films, and crystallized PZT into perovskite structures at 420 °C, which was more than 100 °C below the crystallization temperature of the unseeded PZT films. Measurement of dielectric properties at 1 kHz showed that the 25.1 mol% BST-seeded PZT films annealed at 450 °C had a dielectric constant as high as 300 with a dissipation factor of 0.05. Leakage current density of the film was less than 1×10-6 A/cm2 at applied electric field from 0 to 64 kV/cm.

A novel liquid iridium precursor (1,3-cyclohexadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(CHD), was synthesized and its physical properties were examined. Ir(EtCp)(CHD) exhibited enough vapor pressure (0.1 Torr/75°C), excellent volatility and adequate decomposition temperature. Characteristics of the Ir films deposited using Ir(EtCp)(CHD) and the conventional Ir precursor (1,5-cyclooctadiene)(ethylcyclopentadienyl)iridium, Ir(EtCp)(COD), by metal-organic chemical vapor deposition (MOCVD) method were compared. Ir films grown using Ir(EtCp)(CHD) showed shorter incubation time and higher nucleation density than those of films using Ir(EtCp)(COD).