Lead magnesium niobate thin films have been grown on {100} MgO substrates using pulsed laser deposition (PLD). Several series of films were made using targets of varying perovskite and PbO content. The conditions necessary to produce almost 100% perovskite Pb(Mg1/3Nb2/3)O3 (PMN) films were most sensitive to the growth temperature rather than the starting target crystallography. The electrical properties were determined by fabricating planar thin film capacitor structures and monitoring capacitance and dielectric loss as a function of temperature. Our best capacitors yielded a loss of 0.1 at 1 kHz over a wide temperature range.

Single phase BaxSr1−xTiO3 (BST) films (∼0.5-7 μm thick) have been deposited onto single crystal substrates (MgO, LaAlO3, SrTiO3) by pulsed laser deposition. Silver interdigitated electrodes were deposited on top of the ferroelectric film. The room temperature capacitance and dielectric Q (1/tanδ) of the film have been measured as a function of electric field (≤80 kV/cm) at 1 - 20 GHz. The dielectric properties of the film are observed to strongly depend on substrate type and post-deposition processing. After annealing (≤1000° C), it was observed that the dielectric constant and % tuning decreased and the dielectric Q increased for films deposited onto MgO, and the opposite effect was observed for films deposited onto LaA1O3. Presumably, this change in dielectric properties is due to the changes in film stress. Very thin (∼50 Å) amorphous BST films were successfully used as a stress-relief layer for the subsequently deposited crystalline BST (∼5000 Å) films to maximize % tuning and dielectric Q. Films have been deposited from stoichiometric targets and targets that have excess Ba and Sr. The additional Ba and Sr has been added to the target to compensate for deficiencies in Ba and Sr observed in the deposited BST (x=0.5) films. Films deposited from compensated targets have higher dielectric constants than films deposited from stoichiometric targets. Donor/acceptor dopants have also been added to the BST target (Mn, W, Fe ≤4 mol.%) to further improve the dielectric properties. The relationship between the dielectric constant, the dielectric Q, the change in dielectric constant with electric field is discussed.

Single phase BaxSr1−xTiO3 (x=0.5 and 0.6) thin films (∼5000Å thick) have been deposited onto (100) MgO single crystal substrate with (Ba,Sr) compensated and/or (Mn,Fe,W) doped targets using pulsed laser deposition (PLD). The room temperature capacitance (C) and dielectric Q (1/tanδ) have been measured at microwave frequencies of I to 20 GHz as a function of electric field (0-80kV/cm). Microstructural defects associated with cation and anion vacancies have been observed in BaxSr1−xTiO3 films. Compensation of the ablation target with excess Ba and Sr tends to increase the dielectric constant and the dielectric Q. A film deposited with (Ba,Sr) compensated target has been obtained with 25% tuning, where % tuning is defined as {(C(0)-C(E))/C(O))×100, and dielectric Q of ∼ 100 at room temperature (1 — 10 GHz) for DC bias field (E=67 kV/cm). A further increase in the dielectric Q is observed by the addition of donor/acceptor dopants such as Mn, Fe, and W (Q≈100-240). The effects of (Ba, Sr) compensation and (Mn,Fe,W) doping on the film structure and dielectric properties are discussed.

Single phase Bao0.5Sro0.5TiO3 films with three different thicknesses (40, 80, and 160 nm) have been deposited onto MgO substrates by pulsed laser deposition (PLD). The lattice parameters for the thin film have been measured using x-ray diffraction. The deposited films all show a significant tetragonal distortion. The in-plane lattice parameters for all film thickness are always larger than surface normal lattice parameters for as-deposited films. Films (80 and 160 nm) annealed at 900, 1100, and 1200 °C for 6 hours after deposition show reduced tetragonal distortion compared to as-deposited films. Further, tetragonal distortion of annealed films with thicknesses of 80 and 160 nm were reduced with decreasing annealing temperature from 1200 °C to 900 °7, while that with a thickness of 40 nm is increased with decreasing annealing temperature. This result indicates that the stress due to lattice mismatch and thermal expansion difference changes as a function of film thickness.

Ferroelectrics are known to be excellent materials for nonlinear optics. Miniaturization of circuits using these materials requires an optimization of structural and morphological properties of thin films, to minimize optical losses. The first condition is the use of epitaxially grown thin films. The second one is the optimization of the morphological properties, in particular the roughness at the air/film and film/substrate interfaces must be the lowest possible.

The aim of this work is to study the effect of the deposition atmosphere on these properties for PLT thin films grown on (0001) A12O3 and (001) SrTiO3.

A low temperature metal-organic decomposition process for depositing LiNbO3 thin films on diamond/Si(100) substrates is reported. X-ray diffraction studies show that the films are highly textured polycrystalline LiNbO3 with a (012) orientation. Scanning electron microscopy analyses reveal that the LiNbO3 thin films have dense, smooth surface without cracks and pores, and adhere very well to the diamond substrates. The grain size in the LiNbO3 thin films is in the range of ∼0.2-0.5 μm. The effect of the processing procedures on the surface morphology of the LiNbO3 films is investigated. Possible reasons for the elimination of microcracks in the LiNbO3 films are discussed.

With sol-gel processing and rapid thermal annealing (RTA), crack-free PbTiO3 and PbZr1−xTixO3(x=0.2-0.8) ferroelectric thin films were prepared on Si(100) and Pt/Ti/SiO2/Si(100) substrates respectively. Results from x-ray diffraction (XRD) show that the films are single perovskite phase structure. Scanning electron microscopy (SEM) was used to determine the grain sizes of the thin films. Energy dispersive spectroscopy (EDS) of x rays was used to analyze the composition of the films. From infrared reflection spectroscopy in the wavelength region of 40-700 cm−1 at 300K, the vibrational mode frequencies in PbTiO3 thin films on silicon substrates were obtained at the wavenumbers of 79, 155, 206, 298, 344, 461, 520 and 621 cm−1. Among these phonon modes, the modes at 298 and 461 cm−1 have not been reported before. The infrared optical constants and the thickness of PZT thin films on Pt/Ti/SiO2/Si(100) substrates were directly measured in the wavelength region of 2-12μm by an automatic wavelength swept infrared spectroscopic ellipsometer. These constants include: refractive index (n), extinction coefficient (k), thickness of the films and absorption coefficient (α). Possible correlation among the processing, microstructure and optical properties of the thin films were discussed.

We have prepared epitaxially grown SBN thin film with c-axis orientation by an ArF pulsed laser deposition on SrTiO3(100). Pole figures show that the SBN film has a twin structure aligned at ±18.4: with the a-axis of SrTiO3. The epitaxial relationship of SBN<310> //SrTiO3 < 100 > is determined. The lattice mismatch between SBN and SrTiO3 is approximately 0.9%, which contributes to the desirable crystallinity of the SBN thin film. Furthermore, we have tried to form the SBN film with a two-step growth sequence in order to improve surface morphology. The amorphous initial growth region of 5 monolayers (2 nm thickness) is prepared with no substrate heating followed by post-annealing treatment at 720°C and additional growth on the initially crystallized layer. RHEED patterns of the SBN film with the two-step growth sequence have remained streaky throughout the film formation, compared with spotty patterns observed from films prepared by a conventional sequence. Atomic force microscope (AFM) images show that both the initial stage and final stage have extremely flat surfaces of rms≦ lnm which is a remarkably improved figure compared with the roughness rms ≧3nm for the film deposited at 720°C from the initial stage. These results suggest that the two-step growth sequence makes it possible to improve surface morphology to a nanometer level.

The preparation and characterization of thick PLZT films for spatial phase modulator applications are reported. Films were fabricated on LSCO/LAO substrates by a sol-gel technique using multiple heat-treatment parameters. The crystal quality of PLZT 9/65/35 films was investigated by X-ray diffraction and scanning electron microscopy.

The nonlinear optical properties of epitaxial KNbO3 were studied for films grown by metalorganic chemical vapor deposition on different substrates. X-ray diffraction revealed epitaxial KNbO3 with a (110) orientation for layers deposited on single crystal strontium titanate. Whereas, films grown on (100) spinel exhibited a multi-variant structure, consisting of the (110) and (001) orientations. The volume fraction of each crystallographic variant in the film was calculated. Second harmonic generation measurements at 532 nm were performed to determine the ferroelectric domain variants present. The Maker-fringe technique was employed to obtain the effective nonlinear optical susceptibility of the films, which ranged from 0.1 - 1.8 pm/V. The SHG intensity profiles reveal a strong dependence upon substrate type.

The renewed interest in KTa1−xNbxO (KTN) mixed perovskite materials, especially in thin films of a high quality, is connected with their remarkable dielectric properties in the dilute compositions. Off-center Nb ions in the highly polarizable KTaO3 lattice provide a drastic increase in the dielectric peak up to 20 times in comparison with pure KTaO3 and KNbO3. We prepared KTN thin films with several Nb concentrations in the range of 0 ≤ x ≤ 1 by pulsed laser deposition from semented KTaO3, KNbO3 and KNO3 targets. The effect of the substrate and symmetry-breaking defects was studied by micro-Raman spectroscopy. An anomalous residual intensity of the forbidden first-order scattering modes in the cubic paraelectric phase of the KTN films was connected with the formation of polar microregions even far above the bulk Tc value. On the whole, the KTN film behavior shows the existence of specific defects enlarging the perovskite unit cell in the film so that the activity of off-center Nb ions increases in producing larger electric dipoles and extending the precursor phase above Tc.

Electro-Optic Pb0.91gLa0.09Zr0.65Ti0.35O3 (PLZT) thin films are studied for transverse optical modulator applications. PLZT thin films were grown by pulsed laser ablation on MgO and GaAs substrates. Structural characterization by x-ray diffraction, transmission electron microscopy, Rutherford backscattering, and sputter Auger electron profiling indicate polycrystalline, phase pure PLZT with evidence of interdiffusion and approximately 20nm RMS surface roughness.

Single PLZT thin films, grown on MgO substrates with a SrTiO3 (STO) buffer layer, were fabricated into simple modulator structures for electro-optical characterization.

Measurements were performed in normal transmission mode. Application of an oscillating electric field across the PLZT layer produced optical amplitude and phase modulation.

The application of an oscillating electric field of frequency f across the PLZT has been observed to produce f and 2f frequency modulation in both the phase and amplitude of the output light. Theoretical considerations show that this can be attributed to the quadratic nature of the electro-optic effect in PLZT.

Epitaxial PbZr0.52TiO0.48O3/YBa2Cu3O7−x heterostructures on Nd:YAlO3 and MgO substrates were fabricated by KrF pulsed laser deposition. The coercive electric field of the PZT films increased with decrease of the film thickness from 1.2 μm to 0.04 μm, while the magnitude of spontaneous polarization was almost constant in this thickness range. It was found that the dependence of the film thickness d on the coercive electric field Ec was Ecæ d−2/3. This results from that the PZT/YBCO heterostructure has the one dimensional ferroelectric domain growth without non-ferroelectric phase. The polarization of AuIPZT/YBCO/(MgO or YAlO) capacitors can be changed by the applied voltage below 5 V.