Dense epitaxial LiNbO3 thin films without any misoriented plane on sapphire substrates were obtained with a sol-gel process utilizing 2-methoxyethanol based metal alkoxide precursors without pre-hydrolysis and rapid thermal annealing. Epitaxial LiNbO3 films annealed at 700°C were transparent and showed refractive indices close to bulk single crystal values. Epitaxial and transparent LiTaO3 films crystallized successfully on sapphire substrates with single orientations with the present process. X-ray rocking curve full widths at half maximum of epitaxial LiNbO3 and LiTaO3 films on sapphire (110) substrates and annealed at 700°C were less than 0.4 degree.

Potassium niobate, KNbO3, possesses high nonlinear optical coefficients making it a promising material for frequency conversion into the visible wavelength range. While epitaxial thin films of KNbO3 have been reported [1,2], only limited data exists concerning the optical loss mechanisms and nonlinear optical properties of these films. In this study, epitaxial thin films of KNbO3 have been grown using ion beam sputter deposition and evaluated in terms of their microstructures and optical properties. Characterization of the microstructures of these films includes the in-plane epitaxial relationship to the substrate. The relationships between the growth parameters and microstructures developed to the indices of refraction and the optical losses (absorption and scattering) are discussed.

Crystalline quality of BaMgF4 films grown on Pt/MgO, Si, and GaAs substrates either by solid phase crystallization (SPC) or by molecular beam epitaxy (MBE) has been investigated. In the SPC method, the films are deposited typically at 300°C in amorphous state and subsequently crystallized at temperatures higher than 500°C. It has been found from X-ray diffraction analysis that (010)-oriented films are grown on the three substrates by the SPC method, while that (011)- and (120)-oriented films are grown on respective (100)- and (111)-oriented substrates of Si and GaAs, when the MBE method is used at substrate temperatures around 500°C. These results show that the spontaneous polarization which is generated along a-axis of a BaMgF4 crystal, is not parallel to the film surface, only when the films are grown on (111) substrates by MBE.

Ferroelectric and dielectric properties were measured for BaTiO3 thin films prepared by metalorganic chemical vapor deposition which were highly a-axis textured. No ferroelectric hysteresis was observed from the as-deposited BaTiO3 films on Pt coated MgO. Upon applying an electric field exceeding a threshold electric field, Et, ∼ 50 - 100 kV/cm, a ferroelectric hysteresis was observed. A spontaneous polarization Ps ≥ 15 μC/cm2 was measured for the textured films.

Epitaxial formation of KNbO3 films on several substrates was examined. The films were prepared by a sol-gel process using potassium ethoxide and niobium pentaethoxide. Hetero-epitaxial KNbO3 films with (100) orientation were successfully obtained both on MgO (100) and SrTiO3 (100) substrates by heat treatments above 700°C, while polycrystalline KNbO3 were formed on Si (111) substrates. Higher temperatures and extended soaking time promoted the grain growth of KNbO3 and KNbO3 films with improved surface morphologies (smoother surfaces) could be obtained by controlling heat treatment parameters.

Insulating BaTiO3 thin films were obtained on titanium coated silicon wafers using a novel low temperature technique. They were produced hydrothermally by introducing the substrate in a 0.25M Ba(OH)2 solution inside an autoclave and heating in the 200- 250°C range for 8 hours. This treatment delivered smooth pinhole-free films on the Ti with thicknesses ranging from 35nm (200°C) to 45nm (250°C), with grains in the 100- 300nm diameter range in all films. The films exhibited a dielectric constant up to 227, a breakdown field of 70MV/m, and a dc resistivity of 4.106Ωm.

KNbO3 thin films have been deposited from K(OMe)/Nb(OMe)5 sols onto (100) MgO substrates. Microstructural changes were observed relative to stoichiometry, aging, and the hydrolysis temperature. The production of single phase, oriented films has been demonstrated, and was found to be strongly dependent on process conditions. The films were characterized by XRD, TEM, SEM, EDS, and Raman spectroscopy.

Epitaxial Pt(001) thin films have been grown on MgO(001) substrates using dc magnetron sputtering with an Ar/O2 mixture at 700°C. The width (FWHM) of the rocking curve of the Pt(002) peak is between 0.16° and 0.20°, which is only 0.05° wider than that of the MgO (002) peak of the cleaved substrate. The film surface roughness is about 1 nm (rms) for a 240 nm thick Pt film. No grain structure could be observed using SEM. In contrast, the films deposited at 700 °C with pure Ar, have both Pt(111) and Pt(001) oriented growth, as shown by XRD Θ - 2 Θ scans, with the Pt(111) peak having the largest intensity. BaTiO3 epitaxial films have also been deposited on Pt(001)/MgO(001). The width (FWHM) of the rocking curve of the BaTiO3(200) peak is 0.4°. The surface morphology of the epitaxial BaTiO3(100) thin films on Pt(001)/MgO(001) is featureless. XRD pole figure measurements on Pt/BaTiO3/Pt trilayer shown a very good in-plane alignment of all layers. The epitaxial growth relationship was also confirmed by TEM electron diffraction and cross-section imaging. The Pt/BaTiO3/Pt epitaxial trilayer could serve as a prototype for ferroelectric capacitors and may be able to improve the electrical properties of the capacitors.

Sub-micron sized metal oxide particles were formed via aerosol decomposition using single-source mixed metal-organic precursors specifically designed to decompose at low temperatures. The advantage of these single-source precursors over mixtures of individual precursors is that each particle contains a fixed stoichiometry and molecular level homogeneity. Furthermore, the loss of volatile intermediates (such as PbO) may be avoided. Aerosol processing routes can produce uniform sub-micron sized powder that can be sintered at low temperatures for various thin film and membrane applications. The single-source precursors were prepared in pyridine by reaction of divalent metal α-hydroxycarboxylates of general empirical formula A(O2CCMe2OH)2 (where A = Pb, Ca, Sr, Ba; Me = methyl) with metal alkoxides (for example, Ti(O-i-Pr)4) with the elimination of two equivalents of alcohol. These species were then hydrolyzed in solution and yellow powders were isolated by removal of the pyridine solvent in vacuo. These powders were dissolved in water and used to prepare mixed metal oxide powders via spray pyrolysis. Phase-pure submicron-sized particles of PbTiO3 and BaTiO3 were produced at temperatures of 600-900 °C. The particles were hollow, ranged in size from 0.1 to 1 μm and consisted of 30-50 nm crystallites.

The use of single-source mixed metal-organic precursors specifically designed for the formation of crystalline perovskite phase mixed metal oxide powders has been investigated. Pyridine solutions of divalent metal α-hydroxycarboxylates of general empirical formula A(O2CCMe2OH)2 where A = Pb, Ca, Sr, Ba; Me = methyl, were designed to react with metal alkoxides, for example, Ti(O-i-Pr)4, with the elimination of two equivalents of alcohol to form species with fixed A:B stoichiometry of 1:1 according to the equation: A(O2CCMe2OH)2 + B(OR)4 → A(O2CCMe2O)2B(OR)2 + 2HOR. Hydrolysis of these compounds in pyridine produces clear solutions which on removal of the solvent in vacuo, yield yellow powders. These powders readily dissolve in ethanol to give solutions from which thin films can be formed either by dip-coating or spin coating. The crystallization behavior, composition and ferroelectric properties of these films is discussed. The crystallization of the films generally required substantially higher temperatures compared to powders obtained from the same precursor solutions.

PZT films were etched in an ECR microwave reactor with RF polarization.The etch rate was evaluated using various gas mixtures including combinations of two of the following: C12, NF3, SF6 and HBr. The etch rate was measured as a function of the percentage of one gas in the mixture. Other parameters investigated included gas pressure, bias voltage on the electrode and substrate temperature.Results of the effect of temperature show that etch rates are higher on high temperature substrates than on low temperature substrates. A mixture of C12 and SF2 provided a PZT etch rate of 750 Å / min on a substrate, at approximately 100 °C. We evaluated the resultant etch profile and surface roughness

The microstructure of lead zirconate titanate (PZT) thin films prepared by a sol-gel technique was investigated using transmission electron microscopy (TEM) and transmission electron diffraction. We investigated the microstructure of three sets of thin films with different chemical compositions: PZT 53/47 films with no excess PbO; with excess PbO; and PZT 65/35 with no excess PbO. All samples were fired for 30 minutes at temperatures ranging from 400C to 700C. Incorporation of excess PbO in the 53/47 film fired at 450C resulted in polycrystalline perovskite grains with an average grain size of less than 0.1 μm. Grain boundaries are decorated by 5-10 nm diameter precipitates possibly caused by the segregation of remnant pyrochlore or excess PbO. The films have high values of dielectric constant (up to 2500) when fired at 700C. PZT 65/35 fired at 700C consists of two distinct phases: a fine-grained matrix of pyrochlore, and 10-μm diameter rosettes of perovskite. The correlations between the compositions, the microstructure of the films, and their processing conditions on the one hand, and ferroelectric properties on the other are discussed.

Much interest in the area of ferroelectric thin films has been generated by the recent developments in unique property observation for these materials. As deposition methods move toward potential commercialization, the importance of chemically and thermally stable at use temperature, high vapor pressure and purity, readily available and economically competitive sources for the requisite group 2 elements will emerge. This presentation entails an initial overview of the presently utilized compounds, their advantages and disadvantages. New group 2 CVD precursors have been developed based both on inter- and intramolecular stabilization of cyclopentadienides, alkoxides and β-diketonates. Recent results on the coordination environment around the central metal atom have offered insight into the next generation of polydentate, monoanionic ligand design. Specific details are discussed for the metal complexes of “scorpion-tail” β-diketoethers. Results of comparison studies between these new precursors and earlier compounds are presented as a model for designing future sources.

Single oxides (with titanium or lead) deposited as thin films by low pressure metalorganic chemical vapour deposition were investigated by x-ray diffraction and Raman spectroscopy. Examination of mixed oxides (titanates) and silicates were also carried out using these techniques. The crystallographic nature of these thin films were examined and comparisons made to their bulk counterparts. The deposition and anneal conditions 600 for producing cubic PbTiO3 films are discussed briefly.

Optical excitations for trivalent platinum (5d7, t6e) and trivalent Pb (6s1) ions in lead titanate single crystals have been observed for the first time by electron paramagnetic resonance (EPR). The g and hyperfine coupling, A, tensors of Pt+3 defects were found to be axial: gil∥ = 1.938, g⊥ = 2.478, A∥ = 0.0164 cm−1, and A⊥ = 0.0324 cm−1. Analysis of the EPR spectra by crystal field theory indicates that the Pt+3 ions are in tetragonally distorted (elongated) octahedral sites, strongly suggesting that they substitute for the central Ti+4 ions in the perovskite lattice. Axially symmetric Fe+3 impurities were also observed in the crystals, and they also appear to substitute for the Ti+4 cation. Identification of Pb+3 in these single crystals further shows that holes trapped at Pb+2 ions are an inherent feature of Pb-based perovskite ferroelectrics.

Various dielectric thin films have been studied for electroluminescence display (ELD) application to improve dielectric constant and breakdown voltage. In this work, amorphous BaTiO3 thin films were deposited on indium tin oxide (ITO) - coated glass substrates by atomic layer epitaxy (ALE) using metalorganic precursors. Influences of deposition conditions on microstructure, interface characteristics and dielectric properties are investigated. It was possible to obtain dielectric films with good dielectric properties and textured, flat surface microstructure without defects due to the improvement of qualities of the grown films. These results were examined by XRD, SEM and AES analysis.

We report optical waveguiding in single-crystal, epitaxial (101) oriented rutile (TiO2) thin films grown on (1120) sapphire (α-Al2O3) substrates using the MOCVD technique. The propagation constants for asymmetric planar waveguides composed of an anisotropic dielectric media applicable to these films are derived. Modifications to the prism-film coupling theory for this anisotropic case are also discussed. By application of this model to (101) oriented rutile thin films, we directly obtain values of the ordinary and extraordinary refractive indexes, no and ne, of the rutile thin films as well as film thicknesses. We obtain typical values of the refractive indexes (no=2.5701±0.0005; ne=2.934±0.001) near to those for bulk rutile single crystals indicating the exceptional quality of these films.

The defect structure of BaTiO3 thin films grown on (100) Si was examined using transient photocapacitance spectroscopy. The concentration, optical cross section and associated energy levels of both native and impurity defects in as-grown and annealed BaTiO3 films were evaluated. Deep level defects withpeak energies of Ev+1.8, Ev+2.4, Ev+2.7, Ev+3.0-3.1 and Ev+3.2-3.3 eV were observed in the as-grown films. Upon vacuum annealing, the concentration of the traps at Ev+3.0 and Ev+3.2 eV increased while the concentration of the traps at Ev+ 1.8 and Ev+2.4 eV decreased. The levels at Ev+3.0-3.1 and Ev+3.2-3.3 eV are attributed to oxygen vacancies. The other levels are tentatively ascribed to Fe and Fe related defects.

Ferroelectric (FE) films, especially PZT films, have received increasing attention for microelectronic applications such as ferroelectric memory and high density DRAM. There has been significant progress in the preparation of high quality PZT films involving wet chemical and physical vapor deposition techniques. Metal-FE-metal structures, typified by Pt-PZT-Pt capacitors, are the basic building blocks for the ferroelectric devices. The leakage currents of the capacitors are known to be non-ohmic and exhibit an exponential dependence on applied voltage.

The present paper presents a model based on totally depleted back-to-back Shottky barriers. Predictions based on the model can provide significant new understanding of the FE behavior of thin films. For example, the assumption of total depletion leads to the presence of a built-in field within the film which can explain the ubiquitously higher values of coercive field in FE films than found in bulk ceramics. It will be shown that the agreement between model predictions and actual device I-V characteristics of Pt-PZT-Pt capacitors is very close. Further, the model can also explain the observed hysteresis loop asymmetry and low dielectric constants of films of relaxor FE's, whose dielectric constants are much smaller than those of bulk materials.

A series of sol-gel derived PZT films with various Zr/Ti ratios - namely PT, 0/100 - 20/80, 35/65, 53/47, 65/35, 80/20, 94/6 and PZ, 100/0 - were prepared on platinized Si wafers. Excess PbO was added to the precursor chemistries to compensate for eventual PbO loss and also to aid in obtaining the desired perovskite phase.

It was found that the phase assembly, namely the presence of tetragonal or rhombohedral perovskite phases, plays an important role in determining the fatigue and retention behavior. PT-rich (or tetragonal) films offer better retention characteristics than those observed in PZ-rich (or rhombohedral) or PZT 53/47 films. Films with PZrich compositions tend to exhibit superior fatigue behavior compared with PT-rich films.