Thin film BaTiO3 capacitors were deposited by RF magnetron sputtering. The leakage current was suppressed by more than 3 orders of magnitude if a trace of hydrogen was introduced into the sputtering chamber during film deposition. The introduction of hydrogen gas during sputtering makes the dc conductivity as low as 1×10−13 (Ω−cm)−1 for the amorphous films but still gives the dielectric constant a value of around 17. However, this accomplishment could not be achieved for polycrystal BaTiO3 thin film capacitors. As the substrate temperature increased from room temperature to 700°C, the dielectric constant was increased from 16 to 300 by using Ar + O2 gas. But, the dielectric constant was only around 30 at a deposition temperature of 700°C while the leakage current was decreased when using a gas mixture of Ar + H2 + O2 during sputtering.

SrTiO3 and (Ba,Sr)TiO3 thin films have been prepared by ion beam sputtering on Pd coated sapphire substrates. Film compositions were almost the same as target compositions when powder targets were used. Capacitance-voltage characteristics depended on Sr/Ti ratio of the SrTiO3 films. Only small changes of capacitance value were observed in the range from -3V to 3V when the Sr/Ti ratio was 1.0. Compared with rf-magnetron sputtered film, ion beam sputtered SrTiO3 film indicated lower leakage current density in 50nm thickness. In (Bax,Sr1-x)TiO3 thin films, dielectric constant changed with Ba content (x) and showed a maximum at x=0.5. It also changed with the firing temperature of target powder. The highest value was obtained by using the target powder fired at 900°C. A 100nm thick (Ba0.5,Sr0.5)TiO3 thin film indicated a dielectric constant value of 320.

Sol-gel derived barium sodium niobate and bismuth titanate films were successfully prepared from precursor solutions of chelated Ba[Nb(OEt)6]2 and NaNb(OEt)6 and from bismuth 2-ethyl hexanoate and Ti(OEt)4 respectively. Single phase Ba2NaNb5O15 was formed at 750C on platinized Si and at 850C on fused SiO2. Monoclinic (pseudo-orthorhombic) Bi4Ti3O12 was formed at temperatures as low as 500C. Both film compositions showed significant second harmonic generation. The dielectric constant of the bismuth titanate film was comparable to that of sputtered films.

Preparation of BaTiO3 thin films on titanium substrates by hydrothermal-electrochemical methods at temperatures ranging from 80 to 200°C have recently been reported in literature. In the present work, polycrystalline, homogeneous, and electrically insulating films of BaTiO3 have been electrochemically synthesized at temperatures as low as 55°C. Effects of various electrochemical and thermodynamic parameters such as temperature, solution pH, electrolyte composition, current density, and atmosphere on phase stability and film characteristics have been investigated. Formation of BaTiO3 is favored only under highly alkaline conditions. This finding is consistent with the reported phase stability criteria for BaTiO3 in Ba-Ti-CO2-H2O system. Auger spectroscopic analyses with depth profiling indicate a titanium oxide layer, whose thickness depends on current density, acts as a precursor to BaTiO3. Use of highly oxidizing atmospheres promotes the formation of thick, well-crystallized and electrically insulating films of BaTiO3 at low temperatures. Films synthesized at 55'C exhibit a characteristic bilayer structure consisting of a large grained porous top layer above a fine grained and dense bottom layer. In contrast, the films prepared at higher temperatures are uniform, fine grained but porous. Preliminary experiments indicate the feasibility to electrochemically synthesize BaTiO3 at temperatures near 25°C.

The aim of this work was to develop a ceramic material exhibiting a large pyroelectric coefficient p = -dP/dT (P = polarization, T = temperature) and a low dielectric constant ∈ in order to obtain a high figure of merit F = p/∈pCp for applications in infrared temperature sensing (p denotes the sintered density of the ceramic, cp the specific heat). The influence of the dopants is paramount, and it was only possible to investigate a few promising ones. Best results were obtained for PZT 60/40 (Zr:Ti=60:40) doped with 2 mol% MnO2. The effects of various dopants and some aging results for PZT 60/40 with MnO2 are presented.

Temperature and voltage dependence of fatigue parameters were studied for PZT thin film capacitors on the basis of our fatigue model. It was found that the coefficient of dielectric viscosity of PZT and initial internal field difference of PZT capacitors play a key role in determining fatigue rate. Jump distance was calculated from voltage dependence of decay constant, and it turned out to be essentially the same as the lattice parameter. This result indicates that vacancies (oxygen vacancies, mainly) move parallel to the polarization direction during fatigue. Activation energy was calculated from the temperature dependence of the decay constant. It was confirmed that activation energy for domain wall movement determines fatigue rate at various temperatures. This fatigue model can be used to predict the fatigue behavior and can be extended to develop an accelerated test for fatigue.

It is proposed that the polarization reversal mechanism in ferroelectric ceramics such as titanates is controlled by nucleation, growth, merging and shrinkage of ferroelectric domains. These domain phenomena are in turn determined by the nature of Barkhausen jumps, internal electric field, and dielectric relaxation times of the dipoles. Based on the proposed polarization reversal mechanism, a quantitative model was developed for simulating the hysteresis properties of lead zirconate titanate (PZT) thin films. The simulated hysteresis loops are in good agreement with the experimental results.

It was observed that dielectric viscosity, which is very useful in understanding fatigue and aging behavior of PZT thin films, is one of the key parameters that controls the hysteresis properties.

For i roving the metalorganic decomposition (MOD) process, such that perovskite Pb(ZrxTi1-x)O3 thin films can be fabricated at low temperatures, understanding of structure development is required. Here we report a nondestructive optical method for investigating the structure development in MOD PZT films. Using this method we have identified the temperatures at which the formation of both pyrochlore and perovskite was completed as a function of Zr/Ti ratio. Also for PZT solid solutions, we have identified the temperatures at which the initial presence of both pyrochlore and perovskite was observed. These temperatures compare very well with those obtained from the X-ray diffraction studies. In contrast to X-ray methods, the proposed technique can also be effectively utilized for studying the pyrochlore formation from the amorphous phase. Furthermore, it was also shown that the optical method can be used for characterizing the phase transformation kinetics in PZT films.

The residual stress in solution derived Pb(Zr.53Ti.47)o3, PZT 53:47, films was determined by measuring the bending of the substrate due to the stress. The substrate consisted of an oxidized (100) silicon wafer with 300 nm coating of platinum. In all cases the stress was tensile. Films fired at a temperature in the range where pyrochlore formation occurs (500° to 575°C) had the highest residual stresses, 200 to 350 MPa, whereas those fired at higher temperatures, 600° to 650°C, where the perovskite phase forms had stresses of 100 to 200 MPa. Stress measurements made during film firing indicate that the pyrochlore containing films had higher residual stress because their coefficient of thermal expansion was much larger than that of predominantly perovskite films. The effect of the amount of stress on ferroelectric properties was studied by making measurements on a film with and without the application of an external stress. The external stress was applied by bending a circular section of the substrate, which effectively lowered the amount of tensile stress in the film by ∼30%. Decreasing the stress in this manner was found to increase the remanent polarization by ∼11% and the dielectric constant by ∼2%.

Hysteresis loops obtained from sub-micron films of ferroelectric polymers show a maximum polarization which depends on the frequency of the driving field, the thickness of the film and the number of loops previously traversed (fatigue). We speculate that these effects result from changes in domain wall mobility. For films with thickness above 200nm, the hysteresis loops show no significant thickness dependence. This implies that the dimension of regions of field non-uniformity near the electrodes is less than 200 nm.

In ferroelectric polymers subject to a uniformly increasing field, the variation of breakdown strength with the field ramp-rate indicates that sample heating has a significant effect on the dielectric strength. At low ramp rates (below 100 MVm−1s−1) the heating in the sample is mainly due to Joule heating and the dielectric strength increases with increased ramp rate. At higher ramp rates the predominant heating mechanism is dipolar dielectric loss and the dielectric strength decreases with increased ramp rate. The two mechanisms combine to produce a maximum in the dielectric strength vs ramp-rate plot.

A suitable choice of an electrode material is important for an acceptable electrical contact to a high-permittivity dielectric, such as PLZT. A material which does not form a low-permittivity oxide is necessary, since these dielectrics generally require high temperature deposition or annealing in an oxidizing environment. Platinum, which is one of the few metals that satisfy this requirement, has been widely employed for contacting PLZT. However, for integrated circuit applications, an adhesion layer must be superposed between Pt and the substrate, and Ti is used frequently. Therefore, we have investigated the Pt/Ti combination to determine its suitability as an electrode for contacting PLZT. Using x-ray diffraction, Rutherford backscattering spectrometry, Auger electron microscopy, and scanning electron microscope techniques, interdiffusion of Pt/Ti bilayers has been investigated. Pt/Ti films with or without PLZT overlay were annealed in either O2 or N2 ambients or in N2 followed by O2. Annealing temperatures varied from 500 to 800 °C. It was observed that the anneal ambient has a marked effect on the interdiffusion processes, the reaction products, the morphology of the structures, and the crystallization of PLZT.

Ferroelectric thin films of PZT and PMN-PT were fabricated by the solgel spin-on technique. The films show high dielectric constants, polarization and breakdown strength values. Using a laser interferometer (ultradilatometer), the piezoelectric and electrostrictive coefficients of the films were measured. The results indicate that the sol-gel derived ferroelectric thin films have good electromechanical properties and can be used in rnicroactuator applications.

The Pt-Lead Zirconate Titanate (PZT) thin film interface plays a key role in determining the electrical properties and phase transformation kinetics of Pt-PZT-Pt thin film capacitor structures. The results of the electrical and material properties of PZT (65/35) films that vary in thickness between 500 Å to 4000 Å deposited by DC-magnetron sputtering under identical deposition conditions, and subjected to the same post-deposition thermal processing conditions shows that the Pt-PZT interface dominates thin film properties at low thicknesses (≦ 2000 Å). The charge storage density (Qc') and maximum polarization (Pmax) shows an anomalous variation with thickness, showing an initial increase followed by a drastic decrease as the film thickness is scaled down to 500Å. Significant interdiffusion at the PZT film-Pt electrode retards the pyrochlore-to-perovskite phase transformation nucleation and growth rate in PZT films of thickness 2000Å and lower. Gate polarity dependence of the time-tobreakdown and the degradation field is observed for all PZT film thicknesses (including 4000Å). This indicates that the ferroelectric film-electrode interface has an important role to play in determining the electrical reliability properties even in the 4000Å thick PZT film, although Qc' and Pmax are not adversely affected at these thicknesses.

The effects of excess Pb and Zr/Ti ratio on crystallization behavior and ferroelectric properties of sol-gel derived films were studied. Excess Pb was found to reduce the crystallization temperature. Films with good ferroelectric properties (remanent polarization greater than 8 μC/cm2 ) were achieved after 550 °C, 5 minute crystallization. The difference in the magnitude of the charge in response to switching and non-switching pulses was greater than 1 μC/cm2 after 1011 fatigue cycles for many of the films. The arnount of charge remaining after fatigue was found to be dependent on the initial charge. Reducing the partial pressure of oxygen during crystallization affected both the remanent polarization and fatigue behavior. The fatigue rate was relatively independent of composition and crystallization temperature.

Lead bis-heptafluorodimethyloctadione, or Pb(fod)2 and lead bis-tetramethylbeptadione, or Pb(thd)2 are useful precursors for MOCVD of PbO, a component of PZT ferroelectrics. The two compounds differ only by substituents on their respective ligands, and properties such as volatility and thermal stability differ as a function of the substituents. The volatilities and thermal stabilities of Pb(fod)2 and Pb(thd)2 were examined and compared, in order to further determine usefulness as precursors for MOCVD. Pb(fod)2 and Pb(thd)2 were synthesized and purified via a procedure developed in our laboratory, and purity was confirmed by several techniques. Isothermal and dynamic thermogravimetric analysis experiments were carried out. Regions of thermal stability and thermal instability were identified as a function of heating time and temperature. The region of instability was further examined by heating experiments and chemical ionization mass spectrometry. It was proposed that vaporization of the monomeric form of Pb(fod)2 and Pb(thd)2 controls the rate of weight loss observed in the region of thermal stability, and oligomerization controls the observed rate of weight loss in the region of thermal instability. Heat of vaporization was calculated to be 75 KJ/mol for Pb(fod)2 and 86 KJ/mol for Pb(thd)2.

PbTiO3 and PbZrO3 thin films were successfully fabricated from oxide multilayers by employing ion-assisted deposition process (IAD). Excellent control of the film thickness and composition were achieved by using the multilayer deposition technique. A (001)-oriented phase was found in the PbTiO3 films at 550°C with 300 and 600eV Ar+ ion bombardment. Very fine equiaxial grain size of 0.2μm was seen in the IAD deposited PbTiO3 films, which is independent of the Ar+ ion beam energy. The optical properties of the PbTiO3 films were studied for different energies of Ar+ ion beam and for various post-deposition annealing temperatures. PbTiO3 films with packing density of near unity (≅0.99) were obtained at temperatures as low as 600°C.

The properties of ferroelectric thin films can be significantly influenced by the presence of point defects. The concentration of vacancies presented in these thin films is known to be one of the key parameters causing the degradation of these films when these films are subjected to polarization reversals.

To study the effects of the vacancy concentration on the ferroelectric properties, sol gel PZT films and powders were annealed in different oxygen partial pressures. For the PZT films, the reduction of oxides to pure metals was not observed even with films annealed at 2×10−5 atmosphere of oxygen partial pressure. Samples annealed at low oxygen partial pressure (for instance, 10−3 and 2×10−5 atmosphere), which has more Pb and O2 depletions and consequently has more Pb and O2 vacancies, cannot be switched easily. The ratios of coercive field after and before fatigue increase as the defect concentrations of the annealed samples increase.

Epitaxial PrBa2Cu3O7 superconductor/ferroelectric bismuth titanate heterostructures grown on [001] oriented LaAlO3 by pulsed laser deposition are being studied. X-ray diffraction studies of the heterostructures have shown that all the layers grow in the c-axis orientation. In this investigation, the early stages of ferroelectric film growth have been studied using transmission electron microscopy (TEM) of crosssectioned samples. High resolution lattice imaging has been carried out to study the atomic structure of the ferroelectric/superconductor growth interface and the defect structure of the ferroelectric film.

We have investigated laser ablation of molecular ions from the ferroelectric LiNbO3 at 532, 355 and 266 nm, comparing the effects of changing wavelength and intensity. The time-of-flight spectra show great sensitivity to the onset of plasma formation. Just below the plasma formation threshold, production of the monomer, dimer and trimer negative molecular ions were observed. Possible implications for thin-film deposition processing are discussed.

Bi12SiO20 thin films have been prepared on glass and (0001) sapphire substrates by ECR plasma sputtering with a Bi and Si multitarget system. Polycrystalline thin films of δ-phase Bi12SiO20 have been obtained without any substrate heating. These films can be transformed into γ-phase Bi12SiO20 by heat treatment above 400°C in air and show a large photoconductivity in the range of 380–460 nm. Epitaxial thin films of γ-phase Bi12SiO20 have been obtained on (0001) sapphire substrates at the substrate temperature of 600δ during the sputtering process. Excellent quadratic electrooptic effects for these epitaxial thin films are successfully observed for the first time, and a spatial light modulator using this γ-phase Bi12SiO20 thin film has also been demonstrated. The details of the preparation, structure and some electrical and electrooptic properties of the Bi12SiO20 thin films are described.