Single crystal heteroepitaxial ferroelectric films are desired for non-linear optical applications to maximize the electro-optic coefficient and minimize waveguide losses. In this study, lithium tantalate films were deposited on (0001) sapphire from lithium hexaethoxytantalate by chemical beam epitaxy. Characterization showed that films had nearly stoichiometric composition, epitaxial orientation, and a high degree of crystalline perfection. However, the films exhibited high optical waveguide losses. Additional characterization by TEM revealed that the films had a two dimensional grain structure with epitaxial variants related by translation and a twin orientation to the substrate. To better understand the nature of the heteroepitaxial growth of lithium tantalate on (0001) sapphire, a model was developed to explain the observed epitaxial orientations, misfit dislocation networks, and grain boundary structures of lithium tantalate on (0001) sapphire.

We examine the influences of spontaneous atomic ordering and the associated subvariant domain structure on the transient photoconductivity in epitaxial Ga0.47In0.53As films grown by MOCVD on InP 2°-<110>. Ultra-high frequency photoconductivity decay is used to measure carrier lifetimes in ordered and disordered material following excitation with a YAG laser. Ordered material shows an extended lifetime of 18–186 gis that decreases with incident power. Strongly ordered material showed two CuPt-B subvariants in TEM diffraction patterns and images. Ordering in the first 0.5 μm of growth consists of a fine, interwoven structure with the subvariants closely associated. The subvariants then segregate into imperfectly ordered columnar superdomains that form a mosaic in the film plane with numerous order/order interfaces. In addition, order/disorder interfaces form within and adjacent to the partially ordered superdomains. We attribute the extended transient photoconductivity lifetime in ordered samples to trapping effects that result from the subvariant domain structure.

We have recently reported the observation of CuAu-I, CuPt, and Cu3Au ordered structures in the diluted magnetic semiconductor Zn1−xFexSe grown by molecular beam epitaxy for different values of the Fe concentration. In the present work, we grew a series of samples with identical Fe composition (x=0.5) but for a range of growth temperatures (from 250 °C to 450 °C). By using transmission electron microscopy, ordering along the <001> and <110> directions was observed in both electron diffraction patterns and cross-sectional high-resolution lattice images corresponding to the CuAu-I ordered structure of Zn0.5Fe0.5Se. However, this ordered structure coexists with a tetragonal FeSe structure and forms large, well defined faceted domains. At the higher growth temperature, the number of faceted domains increases as observed by atomic force microscopy. Pure FeSe films were also grown at different temperatures for comparison. The influence of substrate preparation before film growth is also discussed.

Surfactant epitaxy has been expected to be a powerful method to improve thin film growth from three dimensional island mode to layer-by-layer growth one. Supposing that Pb is the surfactant and Ni is the substrate and deposition metal, we have investigated how the surfactant atoms segregate on surface by computer simulations using the modified embedded atom method. To verify the effect of Pb on the homoepitaxial growth of Ni, we have performed a series of experiments on the growth of Ni on Ni(100) surface with and without Pb using reflection high energy electron diffraction (RHEED). It was clearly found that Pb induced layer-by-layer growth of Ni metal film. The result of the dependence of the growth behavior on the thickness of Pb layer suggests that there is the most suitable thickness of a surfactant layer which is not always the monolayer.

The phenomenon of surfactant-mediated growth has been successfully simulated by means of a molecular dynamics method using two-dimensional model atoms interacting via a Lennard-Jones potential. Surfactant atoms were placed on a substrate, and then film atoms were deposited. Under adequate experimental conditions, the surfactant atoms could stay at the growing surface by exchanging their positions with the deposited atoms. Effects of various conditions on the morphology of the film surface were precisely investigated by the simulations.

We have investigated the generation process of crystalline defects in GaP layers grown on Si substrates (GaP/Si) by molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). Transmission electron microscopy observations revealed that a regular network of misfit dislocations was generated in GaP/Si by MEE. On the other hand, threading dislocations as well as interfacial misfit dislocations were observed in GaP/Si by MBE. Moreover, stacking faults were generated in high density at the hetero-interface of GaP/Si by MBE. The density of stacking faults was drastically reduced by MEE.

We have investigated the influence of substrate misorientation on facet formation in selective area metalorganic chemical vapor deposition (MOCVD) on GaAs (001) vicinal substrates. Macroscopic steps several hundred angstroms high were generated on the epitaxial layer over triangular voids where the voids were formed using the conditions of the reverse–mesa–shaped facets. AFM observations revealed that the macroscopic steps were formed by the combined effects of the growth rate enhancement and the development of the exact (001) crystallographic surface. Through removing the growth rate enhancement effect from the experiment results, it could be expected that the exact (001) surface developed only on the side for which the (001) surface was exposed because the surface energy of a low index plane was lower than that of a misoriented high index plane.

Soft magnetic properties and microstructure evolutions of FeTaNC films were investigated, and compared with those of FeTaN and FeTaC films. Effects of substrate species (glass vs. CaTiO3) on the magnetic properties were also investigated. Co-addition of N and C enhances the grain refinements and soft magnetism compared with N or C only addition. Good soft magnetic characteristics of coercivity of 0.17 Oe, permeability of 4000 (5 MHz), and magnetic flux density of 17 kG can be obtained in the FeTaNC films with the relatively wide process ranges. While these values appear to be similar to those of FeTaN films on glass substrate, the most distinctive difference between FeTaNC and FeTaN (or C) films is the effects of substrate. Whereas FeTaNC films show good magnetic characteristics on both glass and CaTiO3 substrates, FeTaN (or C) films show substantial degradation on the CaTiO3 substrate.

Platinum silicide films, with a typical thickness of several hundred Å, prepared on n-type Si(100) wafers by UHV mnagnetron sputter deposition followed by rapid thermal annealing, have been studied by Si L2,3-edge X-ray absorption near edge structure (XANES) using both total electron and total fluorescence yield detection. Samples of various annealing times were studied. XANES provides information on the electronic structure and morphology of the samples. By utilizing the sampling depth difference between the two detection methods, we can clearly see XANES data from each layer (eg. surface oxide, silicide) in the sample and can estimate the thickness of the oxide layer.

Ga0.47In0.53As films are grown by metal-organic chemical vapor deposition (MOCVD) on InP substrates and are lattice-matched to the latter. Studies have shown that by varying growth temperature and lattice orientation, some ordering of the metal sublattice is produced. In this work, we studied the excess carrier lifetimes in ordered and disordered films using an ultra-high frequency photoconductive decay measurement technique (UHFPCD). Excitation was provided by a Q-switched YAG laser (1.064 μs wavelength) with pulses of about 5 ns full width half maximum (FWHM). The transient photoconductive decay (PCD) signals varied markedly with the degree of ordering of the specific film. As description of the experimental results of these UHFPCD measurements follow.

We have observed spontaneous, lateral composition modulation in tensile InAlAs alloy films grown as short-period superlattices on InP (001). We have analyzed these films using transmission electron microscopy, x-ray reciprocal space mapping, and polarized photoluminescence spectroscopy. We find the growth front is nonplanar, exhibiting ∼2nm deep cusps aligned with the In-rich regions of the compositionally modulated films. In addition to the measured 15nm wavelength modulation in the [110] direction, a modulation of 30nm wavelength is seen in the orthogonal [110] direction. The photoluminescence from the modulated layer is strongly polarized and red shifted by 0.22eV.

CaO thin films were grown on (001) MgO single crystal substrates by a chemical solution deposition method to study the influence of a relatively high lattice mismatch (14%) on the epitaxial growth. In order to minimize an influence of a different crystal structure and chemistry between film and substrate, film and substrate were chosen to have the same structure (NaCl) and a similar chemistry. The films were heat treated until they broke up into single crystal islands on the MgO substrate. X-ray pole figure analysis and TEM observations of the CaO-films showed that most of the grains had a single out-of-plane orientation (111)CaO || (001)MgO, corresponding to two non-redundant, symmetry related in-plane variants [1 10](111)CaO || [110](001)MgO and [110](111)CaO || [110](001)MgO. A near coincidence site lattice (NCSL) model could be constructed for the interface, suggesting good lattice and charge matching for the observed orientation relations. The mechanisms and energetics leading to the experimentally observed orientation relations are discussed.

A series of ZnCdSe epitaxial films containing various amounts of Cd were grown on InP (001) substrates using DEZn, DMCd and DESe in the temperature range of 350 to 450°C. The composition and structure of the films were studied by EDX and high resolution X-ray diffraction techniques. It was found that Cd rich films were obtained at low while Zn rich films at high growth temperatures. Double-crystal rocking curves of the films showed that the Cd rich films have substantially fewer defects than similar films grown on GaAs. This improvement in structure is attributed to the closer match of the lattice parameters of lnP and ZnCdSe. The independent determination of composition and structure allowed us to measure the degree of relaxation of the films. We found that even for films whose thickness far exceeds the critical thickness, complete relaxation is not achieved.

Perovskite-phase lead zirconate titanate (PZT) thin films were fabricated at 4751C by the electron cyclotron resonance (ECR) plasma enhanced DC magnetron multi-target reactive sputtering method on Pt/Ti/SiO2/Si and Pt/SiO2/Si substrates. Stoichiometric perovskite PZT films were readily obtained on Pt/Ti/SiO2/Si substrates because Ti atoms which were out-diffused to the Pt surface facilitated Pb incorporation by forming lead titanate at the early stage of deposition process. Activation of oxygen by ECR plasma facilitated the oxidation reaction and Pb incorporation into the film. Thus perovskite-phase PZT can be obtained on the Pt/SiO2/Si substrate.

The transformation of silicon oxide thin films at room-temperature by UV-photons provided by a Xe2* incoherent excimer lamp (λ = 172 nm, Δλ = 14 nm) was studied. Films were produced at low-temperature (T = 260 °C) by ArF laser-induced CVD (LCVD) in parallel configuration from a silane/nitrous oxide/argon gas mixture. The silicon oxide films were irradiated in several consecutive steps to follow-up the modifications with the illumination time. Rutherford backscattering (RBS), infrared (IR) and X-ray photoelectron (XPS) spectroscopies, ellipsometry, and elastic recoil detection analysis (ERDA) were used to characterize the effects of the irradiation on the structure, composition, density, and hydrogen content.

Under the UV illumination the as-deposited film evolves from a suboxide film (SiO1.6) to a stoichiometric silicon dioxide (SiO2), and its originally strained structure changes towards a relaxed tetrahedral configuration. The UV irradiation is able to anneal at room temperature the silicon oxide films breaking the Si-H bonds and incorporating new SiO and hydroxyl groups in a relaxed network. The hydrogen does not effuse out, but remains in the film as molecular hydrogen and/or forming silanol or water groups.

Polycrystalline zirconia layers have remarkable low thermal conductivity and thermal expansion coefficient, high melting temperature and mechanical properties which are objects of interest in materials science. In this work thin polycrystalline zirconia films were obtained by two different excimer laser treatment ways. In the first one, pulsed laser deposition (PLD) is used to obtain directly as-deposited polycrystalline layers from a sintered, partially stabilized zirconia target. In the second one, excimer laser irradiation is used to crystallize previously electron gun-deposited amorphous zirconia films. Reflection high energy electron diffraction(RHEED) and low angle X-ray diffraction(LAXRD)-techniques were used to study the structure evolution of both types of films. In both cases, it is shown that cubic polycrystalline films are readily obtained.

Sintered alumina ceramics are recognized as important industrial materials. For many of their applications however, a suitable pretreatment is required aiming at improving the ceramic surface properties. Since excimer lasers have recently proved to be efficient in ceramic processing, a detailed investigation of sintered alumina surface modifications upon excimer irradiation has been performed. In a previous work the results of low-angle X-ray diffraction analysis reveal emergence of the alumina gamma-phase within the upper 10nm of the material. This presence is further demonstrated by the XPS-study reported here. The photoelectron data are compared with information obtained by optical methods.

Electron diffraction investigations carried out on flash evaporated mercury zinc sulphide films with mercury concentration ( atomic percentage, x ) in the range 0.16 ≤ x ≤ 0.84 grown on freshly cleaved single crystal KCl substrates maintained at temperatures (Ts) between 65°C and 225°C indicate the films grow as single phase ternary alloy films with b.c.c. structure. Presence of a single phase alloy of the type HgxZn1−xS in the films is corroborated by a single absorption edge observed in the optical absorption measurements. The lattice parameter varies between 5.26Å and 4.52 Å as ‘x’ is varied between 0.16 and 0.84. The lattice parameter is observed to decrease slightly with increase of Ts for all compositions. The average grain size is observed to increase between 0.020 microns and 0.058 microns with increase of Ts in all films. Results of room temperature d.c. resistivity measurements show the resistivity to decrease with increase in mercury concentration ‘x’ in the films at a given Ts; ( for ‘fs=225°C, ρ(x=0.16) = 100.6 Ω-cm and ρ(x=0.84) = 10−0.4 Ω-cm ). The resistivity of films with a particular mercury concentration is, however, observed to increase with increase in the substrate temperature; ( for x=0.84 film, typical resistivity values are, ρ(Ts = 65 C) =10−2 Ω-cm and ρ(Ts = 225 C) = 10−0.4 Ω-cm). The observed resistive behavior of the films hints towards predominant grain boundary conduction in the films.

Fluorine doped tin oxide thin films were prepared from solutions with high fluorine contents using the spray pyrolysis technique; the resulting films were studied by electron and X-ray diffraction methods; the resonant nuclear reaction (RNR) method was used to determine the final concentration of fluorine atoms in our films for different doping levels. Also, electrical and optical properties of SnO2:F films were measured and correlated with deposition and structural parameters obtained from X-Ray diffraction and electron microscopy studies.

Zinc oxide (ZnO) thin films have been grown by radio frequency sputtering on glass, Al, Au and R cut sapphire substrates. Microstructures of the ZnO / substrate interface have been observed by transmission electron microscope. The purpose of this study is to elucidate the crystal growth mechanism of ZnO thin films using various substrates that have different crystallinity and crystal structures. An amorphous layer with a thickness of about 5 nm is observed at the ZnO/glass interface, and c axis orientation perpendicular to the substrate is observed on this amorphous layer. Mianstructurts at the ZnO/buffer metal interface, on the other hand, are significantly different from those of ZnO/glass interface. A thick amorphous layer of about 15 nm is observed at the ZnO/Al interface, presumably consisting of Al2O3 interface layer material. ZnO thin film grown on Au buffer layers is distinctly different from both ZnO on glass and Al. No amorphous layer is formed at the ZnO/Au interface, and c axis orientation begins directly from the Au surface. Epitaxially grown ZnO thin film is confirmed on a R-cut sapphire substrate. These results dearly demonstrate that ZnO thin films prepared by radio frequency sputtering are strongly influenced by the substrate surface crystallinity at the topmost layer of the substrate.