Epitaxial thin films of bismuth layer-structured ferroelectrics (BLSF) with different m-numbers, i.e., Bi2VO5.5 (BVO) (m=1), SrBi2Ta2O9 (SBT) (m=2), and Bi4Ti3O12 (BIT) (m=3), were grown by metalorganic chemical vapor deposition (MOCVD). (00l)-oriented films were deposited on (100)SrTiO3. (114)-oriented BVO, (116)-oriented SBT, and (118)-oriented BIT films were deposited on (110)SrTiO3. Moreover, (102)-oriented BVO, (103)-oriented SBT, and (104)-oriented BIT films were deposited on (111)SrTiO3. On (100), (110), and (111)SrTiO3 substrates, c-axis of the deposited films was tilted about 0°, 45°, and 56°, respectively, against perpendicular to the surface of the substrates irrespective of m-number. This suggests the growth of crystallographic equivalent orientation. The distinctive surface morphology originated to the feature of the film orientation was observed. The dielectric constant and the leakage current of c-axis-oriented film was smaller than that of non-c-axis-oriented one, indicating smaller dielectric constant and leakage current along c-axis than a- or b-axes. A larger ferroelectric anisotropy was ascertained for SBT and BIT films. Furthermore, the evaluated spontaneous polarization along a- and c- axes of BIT from the data of the epitaxially grown BIT films well agreed with the reported one for the single crystal. This suggests the ferroelectric property was not strongly affected by the strain in the films.

Piezoresponse measurements using scanning probe microscopy (SPM) were performed for island structures at the initial growth stage of Pb(Zr,Ti)O3 (PZT) (Zr/Ti=0/100, 24/76 and 74/26) thin films prepared by metalorganic chemical vapor deposition(MOCVD). Deposition times were varied from 5s to 7min to control the size of PZT islands. When deposition times were shorter than 3min, (111)-oriented triangular-shaped PZT islands were observed before forming a continuous film. The width and height of PZT islands deposited at 3min were 160 and 70nm for Zr/Ti = 0/100, 100 and 30nm for Zr/Ti = 24/76, and 80 and 20nm for Zr/Ti = 74/26, respectively. The size of islands decreased with increasing the Zr composition. Hysteresis loops due to polarization switching were observed in the phase difference and displacement of piezoresponse measured using scanning probe microscopy (SPM). This result proves that nano-size PZT islands have weak ferroelectricity. The minimum width and height of PZT islands which showed ferroelectricity were 70 and 30nm for Zr/Ti=24/76.

SrBi2Ta2O9 is one of the layered perovskite ferroelectrics with excellent fatigue resistance and thus has gained great interest of semiconductor industries recently in non-volatile ferroelectric random access memory (FERAM) applications. The understanding of the lattice vibrational properties of this material can provide crucial information on its structure and dielectric behavior. In this work, we carried out Raman spectroscopy study of thin film, powder and single crystal SrBi2Ta2O9. At temperatures above the Curie temperature, all 12 Raman modes expected from the tetragonal (I4/mmm) structure have been observed and assigned to the 4 A1g, 6 Eg and 2 B1g modes based the polarized Raman spectra from the single crystal samples. At lower temperature, the Raman spectra have revealed all 22 A1 modes, but only 3 out of the 20 A2 modes and 5 out of the 42 B1/B2 modes were observed in the ferroelectric phase (A21am). The soft mode was found to be of A1 symmetry and appearing only when light polarization lay in the ab-plane.

Barium lanthanum titanate-niobate (Ba1划xLaxNbyTi1划yO3) film deposited on a SiO2/Si substrate by the argon ion-beam sputtering technique has been used to fabricate a thin-film resistor and a metal-insulator-semiconductor (MIS) capacitor by standard integrated-circuit technology. Measurements show that the film resistor has superior sensitivity for visible light and a thermal sensitivity within the range 28∼400 °C, while the MIS capacitor is highly sensitive to relative humidity. The optical absorption spectrum of the film has been measured and the bandgap of the film determined. The effects of test frequency on the impedance of the film resistor at various temperatures and on the humidity-sensitive characteristics of the MIS capacitor have been investigated.

Surface reaction mechanisms in the chemical vapor deposition of (Ba,Sr)TiO3 [BST] films were studied by investigating the effects of O2 gas and source supply ratios on the characteristics of atomic incorporation rates. The atomic incorporation rates of Ba, Sr, and Ti increased with increasing incident flux of each source material, and then the values of the atomic incorporation rates became saturated. The saturated values increased monotonously with increasing O2 gas flow rate, in a range where atomic incorporation reactions might be controlled by the kinetics on the film surface (kinetically limited). Accordingly, O2 gas may effect the behavior of film precursors on BST film growth surfaces. From this, we assumed a CVD model, where the precursors are transported onto the film surface and adsorbed on adsorptive sites, and where the O2 gas has an effect on the formation of the adsorptive sites. With this model, atomic incorporation rates and overall sticking coefficients for the CVD of BST films were numerically simulated, and were in good agreement with experimental results for several O2 flow rates and source supply ratios.

In the last few years a wide spectrum of non-contact, intermittent contact and contact scanning probe microscopies have been applied to imaging ferroelectric surfaces. The imaging mechanism in non-contact SPM is ultimately related to the total charge distribution on the ferroelectric surface, including both polarization and screening charges. Contact voltage modulation (piezoresponse) force microscopy (PFM) is sensitive to both local polarization via electromechanical coupling and surface charge via capacitive interactions. In the present research we analyze the electrostatic and electromechanical contrast in PFM using analytical solutions for the electrostatic sphere-dielectric plane problem and for the piezoelectric indentation problem. The contribution of electrostatic forces to the image is estimated. Variable-temperature PRI imaging of domain structures in BaTiO3 is performed and the temperature dependence of the piezoresponse is compared with the Ginzburg - Devonshire theory.

Ferroelectrics used in a memory device such as (Pb,La)(Zr,Ti)O3 (PLZT) are vulnerable to reducing atmosphere and lose remanent polarization easily. In the semiconductor processes, hydrogen gas is generated both from deposition gas of interlayer dielectric and from reaction between metals and moisture in the dielectric. Improving the ferroelectrics resistance to reducing environments is required for the planarization and multi-layer interconnections in future devices. Loss of remanent polarization is related to the imprint properties of the capacitor and can be improved by controlling the deposition condition of sol-gel PLZT and annealing IrOx electrode in oxygen.

We have proposed a new type of simple detector pixel circuit and device structure for application of dielectric bolometer mode (DB) of infrared (IR) image sensor. The DB mode has merits such as uncooled room temperature operation, chopperless, low power dissipation, and high-sensitivity. A stable Ba1划xSrxTiO3 (BST) thin film has been successfully developed as a dielectric bolometer material for IR detector by Metal-Organic-Decomposition (MOD) method. The film was prepared on both Pt/Ti/SiO2/Si-bulk and Pt/Ti/NSG/Si3N4/SiO2 membrane structures, where an IR light is detected at the membrane as a change in dielectric constant (ε). So, the important issue for realizing a reliable IR sensor with high-sensitivity has been achieved to have a good thermal stability in ε against change in the detector temperature. XRD patterns and D-E hysteresis curves were measured and revealed that the BST film has a good perovskite structure and shows an adequate ferroelectric loops, especially for final annealing temperature higher than 700 °C. Temperature Coefficient of Dielectric constant (TCD), which decides the IR sensitivity, of the MOD made BST film is about 1 %/K. The reproducibility in ε, namely IR detector capacitance, was found to be very good in temperature ranging from about 10 to 80 °C within a relative change of 2 %. Finally, the stabilities in both the temperature dependence of ε and the output level have been obtained with a fairly large IR detectivity, where voltage sensitivity(Rv) and specific detectivity(D*) were about 1.2 kV/W and 2.9e8 cmHz 1/2/W, respectively.

Bi-layered ferroelectric compounds are considered most promising for non-volatile memory applications due to their high fatigue endurance. We have prepared SrBi2Ta2O9 powders with Ba (A sites) and Nb (B sites) substitutions using a novel solution based route. The powders were pressed and sintered at 1050°C to obtain high quality targets. Thin films were prepared using these ceramic targets on Pt/TiO2/SiO2/Si substrates using pulsed laser deposition (PLD) technique. The effects of growth conditions on phase formation as well as structural and electrical properties in films are studied. Initial results on films show good hysteretic characteristics. Though phase formation begins at much lower temperature, these films crystallize in a complete layered perovskite phase when prepared at 700°C. Optical phonon modes in these materials exhibit systematic variations with changing compositions. The changes in the Raman spectra are explained in terms of Ba and Nb substitutions at A and B sites, respectively. The temperature dependence of Raman spectra exhibits the substitution induced changes in the transition temperatures of these materials.

Ruthenium Oxide (RuO2) thin films were prepared on silicon substrates by solution chemistry technique. X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), micro-Raman, X-ray photoelectron spectroscopy (XPS), and four probe Van-der-paw technique were used for the film characterization. X-ray analysis shows a rutile structure in these films. The films annealed at 700°C showed lowest resistivity of 29 × 10−5 ohm-cm. The presence of Eg, A1g, and B2g modes is consistent with the Raman spectrum of rutile phase. These modes as well as additional unidentified band at about 477 cm−1 were investigated by temperature dependent Raman studies. Based on the result, band at 477 cm−1 that disappears above 370 K is attributed to hydrated RuO2 present in the films. XPS analysis show stoichiometric rutile RuO2 present in the films. Small concentrations of RuCl3, RuO3 and hydrated RuO2 were also detected. Pb0.9La0.15TiO3 (PLT15) thin films were deposited on RuO2/Si substrates and characterized for its ferroelectric properties to demonstrate that solution deposition technique offers an alternative approach for preparing high quality RuO2 bottom electrodes.

Pulsed laser deposition has been used to fabricate thin-film capacitor structures in which the dielectric layer is composed of a superlattice of Ba0.8Sr0.2TiO3 and Ba0.2Sr0.8TiO3. The properties of the capacitors were investigated as a function of superlattice periodicity. The dielectric constant was significantly enhanced, and temperature migration of the peak in dielectric constant as a function of frequency was observed, at stacking periodicities of a few unit cells. However, such ‘relaxor-like’ features were found to be associated with high dielectric loss. Analysis of the imaginary permittivity as a function of frequency showed that fine-scale superlattices conform to Maxwell-Wagner behaviour, indicating that the observed features may be an artefact of increased carrier mobility. Modelling showed that both dielectric enhancement and frequency relaxation could readily be reproduced by Maxwell-Wagner formalism.

The requirements for future ferroelectric non-volatile memories (FRAM) include lower operating voltages, higher densities and tighter design rules. In order to achieve these requirements the key component of the FRAM device, viz., the PbZrxTi1划xO3 (PZT) thin film capacitor must be scaled dimensionally to obtain reduced film thickness and capacitor area. This paper presents the ferroelectric performance of RF magnetron sputtered PLZT thin films with thickness scaled down to 1000Å. The switching performance of the thickness scaled PLZT thin films meets the requirements of 1.8V FRAM device. Though PLZT ceramic thin films, of which the fatigue is often a concern, are utilized as non-volatile component, excellent fatigue performance was observed. The scaled PLZT thin film capacitors are fatigue free up to 1011 fatigue cycles (E=200kV/cm). The scaled 1000Å PLZT thin films also showed good imprint performance. The opposite-state charge after 10 years baking at 150°C was still above the sensing level. The thickness scaled PZT thin films, showing dramatically improved ferroelectric performance, can be applied to the manufacturing of low voltage FRAM products.

Feasibility of SiNx passivation films at low substrate temperatures prepared by catalytic chemical vapor deposition (Cat-CVD) is studied for ferroelectric nonvolatile random access memories (FRAMs). SiNx films were prepared at low substrate temperatures of 100 °C, 175 °C and 200 °C using Cat-CVD. Adjusting on flow rate ratio of SiH4/NH3, the refractive index of SiNx film, deposited at 175 °C and 200 °C, measured by ellipsometry is controlled around 2.0. SiNx films, with the refractive index around 2.0, deposited at only 200 °C show the following properties. 1) No oxidation during air exposure for 3 months was observed for the films. 2) Etching rate of the films in buffered HF is 20 nm/min. The dense SiNx film, which is resistive for oxidation in air exposure and dissolution in buffered HF, is prepared at 200 °C and the film is suitable to the passivation of ferroelectric capacitors.

Due to its resistance to oxidation, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced memory devices. In this study we report on the properties and the resistance to oxidation of TaSiN thin films deposited by reactive magnetron sputtering and processed by rapid thermal annealing (RTA) in 18O2 at 650°C. In order to determine the composition, RBS (Rutherford Backscattering Spectroscopy) and NRA (Nuclear Reaction Analysis) techniques have been used. 18O depth profile concentrations were measured after RTA using the narrow (fwhm=100eV) resonance at 151 keV in the nuclear reaction 18O(p,α)15N.

Focused ion beam milling was used to fabricate ferroelectric islands in Pb-Zr-Ti-O thin films. The islands ranged in size from 200μm×200μm to 0.3μm×0.3μm. The inverse piezoelectric effect was studied in these islands as a function of their size by tracking the surface displacement of the top electrode of the island (under an applied electric field) using an atomic force microscope (AFM). It was found that there was a substantial increase in the piezoresponse as the size of the island decreased below 100μm×100μm. This increase was attributed to the elastic deformation of the substrate.

The epitaxial (100)ZrN film on the (100)Si substrate is oxidized during Ir film sputtering deposition on (100)ZrN/(100)Si structure. Although the oxidation could be suppressed somewhat by increasing the deposition rate of the Ir film, it was not enough. In order to suppress the oxidation completely, 10 pieces of 10 × 10 mm2 Zr metallic plates were circularly placed on the non-erosion area of the Ir disc target. Using this target, the oxidation of the ZrN film was suppressed perfectly. Also, by adjusting of the diameter of the placed Zr circle, the contamination caused by Zr to the Ir film is avoided.

CaBi2Ta2O9 (CBT) thin films were successfully prepared on Pt-passivated quartz glass substrates using a triple-alkoxide solution. The thin film crystallized to a single phase of perovskite at 750°C via a mixture of fluorite and perovskite phases. The 750°C-annealed thin film showed random orientation and consisted of fine grains with a diameter of about 80 nm. The dielectric constant and loss factor were 124 and 0.04, respectively, and were constant in the frequency range of 10 kHz to 1 MHz. The thin film exhibited P-E hysteresis loops at relatively high voltages. The remanent polarization and coercive electric field were 6.9 μC/cm2 and 170 kV/cm at 13 V, respectivey. The fatigue behaviors against various electric pulse sequences were examined. The polarization did not change when the pulse width was short such as 10-6 s, however, it increased gradually with number of switching cycles when the pulse width was relatively long such as 10-3 s.

Single crystalline, ferroelectric BaTiO3 as material with the highest piezoelectric constants among the perovskites with ordered sublattices was implanted with 111In(111Cd). The electric field gradient at the Ti position was measured with perturbed γγ-angular correlation spectroscopy (PAC) while the crystal was exposed to an external electric field. A quadratic dependence could be observed: νQ(E) = (34.8(1) + 0.16(4) E/kV/mm + 0.080(2) E2/kV2/mm2) MHz. Point charge model calculations reproduce the linear change of Vzz, but not the quadratic term. The polarizability of the host ions of BaTiO3 is known to be nonlinear with respect to an electric field. The resulting quadratic shift of the electron density is reflected in the strength of the EFG.

Ferroelectric Pb(Zr1划xTix)O3 (PZT) films have been extensively studied for active components in microelectromechanical systems. The properties of PZT films depend on many parameters, including composition, orientation, film thickness and microstructure. In this study, the effects of crystallographic orientation on the dielectric and transverse piezoelectric properties of Pb(Zr0.52Ti0.48)O3 (PZT 52/48) films are reported. Crack free random and highly (100) oriented PZT(52/48) films up to ∼ 7 μm thick were deposited using a sol-gel process on Pt (111)/Ti/SiO2/Si and Pt(100)/SiO2/Si substrates, respectively. The dielectric permittivity (at 1kHz) for the (100) oriented films was 980-1000, and for the random films ∼ 930-950. In both cases, tanä was less than 0.03. The remanent polarization (∼ 30 μC/cm2) of random PZT films was larger than that of (100) oriented PZT films. The transverse piezoelectric coefficient (d31(eff)) of PZT films was measured by the wafer flexure method. The d31(eff) coefficient of random PZT thick films (-80pC/N) was larger than that of (100) oriented films (-60pC/N) when poled at 80 kV/cm for 15 min.

The Thermally Stimulated Depolarization Current (TSDC) and pyroelectric properties of the modified SBN ferroelectric ceramic system were studied for different lanthanum and titanium doping concentrations. The TSDC measurements show the pyroelectric peak for all compositions while a second smaller peak at higher temperature, possibly associated to induced vacancy-impurity dipoles, is also observed in all cases. The second peak contribution was experimentally and mathematically eliminated to determine the remanent polarization and pyroelectric coefficient, both associated only to permanent ferroelectric dipoles. The figures of merit for sensor devices are determined for all compositions and compared with those of other pyroelectric systems. The La0.03Sr0.255Ba0.7 Nb1.95Ti0.05O5.975 sample, in particular, has excellent pyroelectric response, making this material very suitable for pyroelectricity-derived applications.