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Docmentation of newly developed methods to assess material compatibility in refrigeration and air-conditioning applications. Final report, 1 October 1993--31 August 1994

Description: This document summarizes the experimental methods used during the materials compatibility and lubricants research program (MCLR). The MCLR program was jointly sponsored by the U.S. Department of Energy and the air-conditioning and refrigeration industry. The individual projects were managed by the Air-Conditioning and Refrigeration Technology Institute. The projects presented in this report are: Chemical and Thermal Stability of Refrigerant/Lubricant Mixtures with Metals, Miscibility of Lubricants with Refrigerants, Compatibility of Refrigerants and Lubricants with Motor Materials, Compatibility of Refrigerants and Lubricants with Elastomers, Compatibility of Refrigerants and Lubricants with Engineering Plastics and Sealed Tube Comparisons of the Compatibility of Desiccants with Refrigerants and Lubricants.
Date: August 1, 1994
Creator: Hawley, M.
Partner: UNT Libraries Government Documents Department

COMPREHENSIVE STRUCTURAL STUDY OF PRE-AND POST-HEAT TREATED COMPRESSION MOLDED POLYURETHANE SAMPLES OF VARYING COMPOSITION STUDIES BY SCANNING PROBE TECHNIQUES

Description: Only a limited number of structural studies have been performed on polyurethanes using scanning probe techniques to determine both the microstructure and the corresponding distribution of hard and soft segments within samples. This type of information is needed to better understand the mechanical properties of these materials and to facilitate modeling. In order to address these issues, we have fabricated a series of compression molded segmented poly(ester urethane) samples with hard (HS) to soft segment ratios from 19 to 100%. Samples were examined using scanning probe phase imaging techniques to obtain the topography and corresponding distribution of hard domains before and after heating at 100 C. A number of significant differences were observed between the pre- and post-heat treated samples. Variations in structure and heat-induced morphological changes were directly related to HS content. Fine strand- or fibril-like structures were most prominent in the 23 and 19% HS sample but first appeared at 30% HS. Harder, thicker elongated structures dominated the surface of the 100% HS sample and were seen to a limited extent on all samples, especially after annealing and quenching. The 23% HS sample surface structure depended on quenching rate and time after treatment.
Date: March 1, 2001
Creator: HAWLEY, M.; ORLER, E. & AL, ET
Partner: UNT Libraries Government Documents Department

The influence of surface morphology and oxide microstructure on the nucleation and growth of uranium hydride on alpha uranium

Description: While the bulk kinetics of the uranium-hydrogen reaction are well understood, the mechanisms underlying the initial nucleation of uranium hydride on uranium remain controversial. In this study, the authors have employed environmental cell optical microscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy, (AFM) in an attempt to relate the structure of the surface and the microstructure of the substrate with the susceptibility and site of hydride nucleation. Samples have been investigated with varying grain size, inclusion (carbide) concentration, and thermal history. There is a clear correlation to heat treatment immediately prior to hydrogen exposure. Susceptibility to hydride formation also appears to be related to impurities in the uranium. The oxidized surface is very complex, exhibiting wide variations in thickness and topography between samples, between grains in the same sample, and within individual grains. It is, however, very difficult to relate this fine scale variability to the relatively sparse hydride initiation sites. Therefore, the surface oxide layer itself does not appear to control the sites where hydride attack is initiated, although it must play a role in the induction period prior to hydride initiation.
Date: December 31, 1998
Creator: Hanrahan, R.J. Jr.; Hawley, M.E. & Brown, G.W.
Partner: UNT Libraries Government Documents Department

STM and x-ray diffraction temperature-dependent growth study of SrRuO{sub 3} PLD thin films

Description: SrRuO{sub 3} (SRO) has recently found a number of applications in different fields, e.g. as a buffer layer for the growth of high temperature superconductor (HTS) YBa{sub 2}Cu{sub 3}O{sub 7-x} films and as a bottom electrode for ferroelectric or high dielectric constant thin film capacitors and nonvolatile data storage. The growth of high crystallinity SRO films with good structural and electrical properties is the prerequisite for each of these applications. In this paper we describe the affect of one growth parameters temperature (T), on the crystalline quality, epitaxial substrate relationship and resulting electrical properties. SRO films were deposited on LaAlO{sub 3} single crystal substrates by pulsed laser deposition at substrate temperatures (T{sub s}) ranging from room temperature (RT) up to 800{degrees}C with a nominal film thickness of 150 nm range. The resulting films were characterized by x-ray diffraction, 4-point transport, and STM. The films` microstructures, as revealed by STM, evolved from polygranular at RT to a layered plate-like structure at higher deposition temperatures, T{sub s}, Increasing T{sub s} was marked first by increasing grain size, then a stronger orientational relationship between film and substrate, finally followed by the development of increased connectivity between grains to an extended island or condensed layered state. The transition from polygranular to layered structure occurred at T{sub s} > 650{degrees}C. Increased conductivity paralleled the changes in microstructure. The surfaces of all of the films were relatively smooth; the oriented films are suitable for use as conductive templates in multilayer structures.
Date: December 31, 1996
Creator: Hawley, M.E.; Jia, Q.X. & Brown, G.W.
Partner: UNT Libraries Government Documents Department

Iron oxide mineral-water interface reactions studied by AFM

Description: Natural iron mineral surfaces have been examined in air by atomic force (AFM) and scanning tunneling (STM) microscopies. A number of different surface features were found to be characteristic of the native surface. Even surfaces freshly exposed by crushing larger crystals were found to have a pebbly surface texture caused by the presence of thin coatings of what might be surface precipitates. This finding is interpreted as evidence for previous exposure to water, probably through an extensive network of microfractures. Surface reactions on the goethite crystals were studied by AFM at size resolutions ranging from microns to atomic resolution before, during, and after reaction with distilled water and 0.lN HCl. Immediate and extensive surface reconfiguration occurred on contact with water. In one case, after equilibration with water for 3 days, surface reprecipitation, etching and pitting were observed. Atomic resolution images taken under water were found to be disordered. The result of surface reaction was generally to increase the surface area substantially through the extension of surface platelet arrays, present prior to reaction. This work is being done in support of the site characterization project at Yucca Mountain.
Date: July 1, 1994
Creator: Hawley, M.E. & Rogers, P.S.Z.
Partner: UNT Libraries Government Documents Department

The effect of temperature, growth kinetics, and substrate on the microstructure of RF off-axis sputter deposited YBa{sub 2}Cu{sub 3}O{sub 7} thin films

Description: YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) thin films were grown on single crystal substrates by RF off-axis sputter deposition under different growth condition, systematically varied to change the kinetic and thermodynamic processes that determine both the film microstructure and its crystallographic orientation. The effect of substrate temperature, position, and material, total chamber pressure, and RF power on the final film structure was examined. The growth matrix was bounded by temperatures from 640 to 780C, pressures from 50 to 200 mtorr, and power from 50 to 100 watts. Higher growth rates were achieve by increasing the power setting, lowering the total pressure, and moving the substrate farther into the plasma. Care was taken to stay within these parametric stability limits defining the 123-YBCO growth regime. The resulting films were characterized, primarily, by scanning tunneling and atomic force microscopy, x-ray diffraction, and eddy-current measurements. At the extremes of the growth conditions used in this study, ex-situ examination of the films revealed that they spanned the extremes from all c-axis normal to all a-axis normal material, with mixed a-/c-axis normal material in between extremes in deposition parameter limits, with the mixed films containing a-axis material overlaying a c-axis layer. Smooth single orientation films, suitable for multilayer device structure, could be routinely obtained by controlled growth. Highest surface roughness measurements were usually due to incomplete or non uniform a-axis coverage on c-axis films. Combined data obtained from different studies showed that lower temperatures and higher rates favored a-axis growth under the conditions used in these studies. The YBCO films were more unstable to a cross-over from c-axis to a-a-axis growth when deposited on NdGaO{sub 3} and LaAIO{sub 3} than on SrTiO{sub 3}. Under conditions favoring c-axis perpendicular growth, higher temperatures and rates resulted in rounder islands.
Date: July 1, 1995
Creator: Hawley, M.; Houlton, R.J.; Garzon, F.H. & Raistrick, I.D.
Partner: UNT Libraries Government Documents Department

Substrate and growth related microstructural and magnetic properties in La{sub 0.67}Sr{sub 0.33}MnO{sub 3} thin films

Description: Ambient observation of magnetic domain structures by magnetic force microscopy (MFM) in La{sub 0.67}Sr{sub 0.33}MnO{sub 3} films has not yet been clearly correlated with stresses induced by kinetic or thermodynamic growth processes or the compressive (LaAlO{sub 3}) or tensile (SrTiO{sub 3}) nature of the film-substrate lattice mismatch. Although domain-like magnetic structures have been seen in some as-grown films and related to substrate-induced stress and film thickness, no magnetic structure has been seen for other films grown under similar conditions on the same pair of substrates. In this study the authors have grown films over a range of temperatures by pulsed-laser deposition, using the above substrates, to determine the relationship between growth and stress-induced magnetic structures. Results from scanning tunneling, atomic force, and magnetic force microscopies, measurements of temperature-dependent magnetization and structure-dependent coercivity show the relationship between growth and magnetic properties. Maze-like domain structures, with separations between 150 nm and 200 nm, were only observed for the thicker films grown at the highest temperature, 800 C. Application of an in-plane magnetic field converted these domain structures to stripe-like domains whose spacing and out of plane component decreased as the field was increased.
Date: December 31, 1998
Creator: Hawley, M.E.; Brown, G.W.; Kwon, C. & Jia, Q.
Partner: UNT Libraries Government Documents Department

Growth-related magnetic and physical structures in CMR films

Description: Scanning tunneling microscopy (STM), atomic force microscopy (AFM), and magnetic force microscopy (MFM) have proven to be powerful tools for revealing property-sensitive structures in magnetic materials. With the renewed interest in perovskite films as materials for read-heads in high density magnetic data storage, the same challenges faced by high temperature superconductor (HTS) film fabrication are repeated for these materials. To begin addressing these challenges, we used vapor phase epitaxy to fabricate La (Sr, Ca,) based manganate films on single crystal perovskite substrates under different conditions and characterized them with scanning probe microscopies, x-ray diffraction, and temperature-dependent magnetization and resistivity measurements (M(T) and {rho}(T)). The as-grown films were polygranular with grain sizes increasing with increasing temperature (T). The post-deposition annealed films consisted of coalesced layers with improved transport properties. The room temperature magnetic structure of the Sr-based films appeared to be related to defects and/or strain.
Date: September 1, 1997
Creator: Hawley, M.E.; Brown, G.W. & Hundley, M.F.
Partner: UNT Libraries Government Documents Department

Scanning probe microscopy competency development

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project collaborators developed an ultra-high vacuum scanning tunneling microscope (UHV-STM) capability, integrated it with existing scanning probe microscopes, and developed new, advanced air-based scanning force techniques (SPMs). Programmatic, basic, and industrially related laboratory research requires the existence of SPMs, as well as expertise capable of providing local nano-scale information. The UHV-STM capability, equipped with load-lock system and several surface science techniques, will allow introduction, examination, and reaction of surfaces prepared under well-controlled vacuum conditions, including the examination of morphology and local bonding associated with the initial stages of film growth under controlled growth conditions. The resulting capabilities will enable the authors to respond to a variety of problems requiring local characterization of conducting and nonconducting surfaces in liquids, air, and UHV.
Date: December 31, 1998
Creator: Hawley, M.E.; Reagor, D.W. & Jia, Quan Xi
Partner: UNT Libraries Government Documents Department

Effect of carrier gas on the surface of morphology and mosaic dispersion for GaN films by low-pressure MOCVD

Description: Low-pressure metal-organic chemical vapor deposition (MOCVD) has been used to deposit unnucleated and self-nucleated GaN thin films on (00.1) sapphire substrates. For the self-nucleated films, initial layers were grown at 540{degrees}C using trimethylgallium and ammonia as elemental sources and either nitrogen or hydrogen as the carrier gas. Using these same gas phase conditions, overlayers on native (00.1) sapphire substrates or the GaN-nucleated (00.1) sapphire substrates were deposited at 1025{degrees}C. The surface morphology and mosaic dispersion of these unnucleated and self-nucleated GaN thin films have been surveyed by a combination of real space images from atomic force microscopy and reciprocal space intensity data from X-ray scattering measurements. As expected, the unnucleated GaN films show a large-grained hexagonal relief, typical of three-dimensional island growth. However, the self-nucleated films are shown to be dense mosaics of highly oriented islands, emblematic of a more two-dimensional growth.
Date: December 31, 1995
Creator: Kistenmacher, T.J.; Wickerden, D.K.; Hawley, M.E. & Leavitt, R.P.
Partner: UNT Libraries Government Documents Department

Microstructures and electrical properties of SrRuO{sub 3} thin films on LaAlO{sub 3} substrates

Description: Conductive SrRuO{sub 3} thin films have been deposited using pulsed laser deposition. Structure and microstructure of this system were studied using XRD, SEM, and scanning tunneling microscopy. Electrical properties of these films were measured. The film deposited at 250{degree}C is amorphous-like, showing semiconductor-like temperature dependence of electric conductivity. Film deposited at 425{degree}C is crystalline with very fine grain size (100 {approximately} 200{angstrom}), showing both metallic and semiconductor-like temperature dependence of the electrical conductivity. Film deposited at 775{degree}C shows reisistivity of 280 {mu}{Omega}{center_dot}cm at RT and resisdual resistivity ratio of 8.4. Optimized deposition conditions were determined. Possible engineering applications of SrRuO{sub 3} thin films are discussed. Bulk and surface electronic structures of SrRuO{sub 3} are calculated using a semi-empirical valence electron linear combination of atomic orbitals, and they are used to understand the electrical properties of the films.
Date: March 1, 1996
Creator: Chu, F; Mitchell, T.E.; Hawley, M; Landrum, G; Jia, Q.X. & Wu, X.D.
Partner: UNT Libraries Government Documents Department

Microstructural study of CMR films as a function of growth temperature as-deposited and annealed

Description: The properties encompassed by the family of complex metal oxides span the spectrum from superconductors to insulating ferroelectrics. Included in this family are the new colossal magneto-resistive perovskites with potential applications in advanced high density magnetic data storage devices based on single or multilayer thin films units of these materials fabricated by vapor phase deposition (PVD) methods. The realization of this potential requires solving basic thin film materials problems requiring understanding and controlling the growth of these materials. Toward this end, we have grown La{sub 0.7}Ca{sub 0.3}MnO{sub 3} and La{sub 0.7}Sr{sub 0. 3}MnO{sub 3} on LaAIO{sub 3} single crystal substrates by pulsed laser and RF sputter deposition at 500 to 900 C and annealed at over 900 C for about 10 hours. The evolution of the microstructure of these films was studied by scanning probe microscopies and transmission electron microscopy (TEM). Results of SPM characterization showed that at the lower end of the growth temperature range, the as-grown films were polygranular with grain size increasing with temperature. The 500 C as-grown films appeared to be amorphous while the 750 C film grains were layered with terrace steps often one unit cell high. In contrast, films grown at 900 C consisted of coalesced islands with some 3-D surface crystals. After annealing, all films had coalesced into very large extended layered islands. The change in microstructure was reflected in a decreased resistivity of coalesced films over their unannealed granular precursors. Previous reported work on the growth of La{sub 0. 84}Sr{sub 0.16}MnO{sub 3} and La{sub 0.8}Sr{sub 0.2}CoO{sub 3} grown demonstrated the sensitivity of the microstructure to substrate and deposition conditions. Films grown on an ``accidental`` vicinal surface grew by a step flow mechanism.
Date: December 1995
Creator: Hawley, M. E.; Wu, X. D.; Arendt, C. D.; Adams, M. F.; Hundley & Hefner, R. H.
Partner: UNT Libraries Government Documents Department

Thin film ionic conductors based on cerium oxide

Description: Fluorite and perovskite structure cerium oxide based ceramics are a class of materials that may exhibit good oxygen ion and/or protonic conductivity. The authors have successfully deposited thin films of these materials on a variety of substrates. Interesting orientation relationships were noticed between cerium oxide films and strontium titanate bi-crystal substrates. Near lattice site coincidence theory has been used to study these relationships.
Date: December 1, 1994
Creator: Haridoss, P.; Hellstrom, E.; Garzon, F. H.; Brown, D. R. & Hawley, M.
Partner: UNT Libraries Government Documents Department

Temperature-dependent growth of LaAlO{sub 3} films on YBa{sub 2}Cu{sub 3}O{sub 7} C-axis films for multilayer structures

Description: Fabrication of ultra smooth films, free of micro-shorts, is essential to the development of High Temperature Superconducting (HTS) thin film devices. One such example is a SNS junction consisting of two HTS layers separated by a uniformly smooth continuous barrier material. Other schemes under consideration require multilayer structures of up to 5 - 7 epitaxially grown layers of complex oxide material. Successful fabrication of such devices necessitates understanding the epitaxial growth of polycrystalline oxide films on polycrystalline film templates. Toward this end we have developed a set of deposition parameters that produce high quality epitaxial insulating layers suitable for HTS device applications. All films in this study were grown by off-axis RF magnetron sputter deposition. LaAlO{sub 3} films were deposited over MgO grown YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) c-axis thin films at temperatures ranging from 200 to 700C and on virgin substrates at 600C. Atomic Force Microscopy, eddy current measurements, and x-ray diffraction techniques were used to monitor the effect of growth conditions on the resulting film crystallinity, nanostructure, and electrical properties. Ex-situ interrupted growth characterization of these materials has yielded new insight into the processes that control the growth mechanism and resulting microstructure. All films were polycrystalline. Below 600C, LaAlO{sub 3} films were not epitaxial while films grown at 650C showed some <200> orientation. The shape of the underlying YBCO film is most clearly evident for the film grown at 400C. Surface roughness depended on the appearance of crystals on the film surface. The superconducting properties of the underlying YBCO film required O{sub 2} annealing prior to deposition of the LaAlO{sub 3} layer.
Date: January 1, 1995
Creator: Hawley, M. E.; Houlton, R. J.; Raistrick, I. A. & Garzon, F. H.
Partner: UNT Libraries Government Documents Department

Characterization of Si(100) homoepitaxy grown in the STM at low temperatures

Description: We explore the growth of low-temperature bulk-like Si(100) homoepitaxy with regard to microscopic surface roughness and defects We characterize films grown at different temperatures up to 500K in-situ by means of an effusion cell added to our UHVSTM. The development of novel architectures for future generation computers calls for high-quality homoepitaxial (WOO) grown at low temperature. Even though Si(100) can be grown crystalline up to a limited thickness: the microstructure reveals significant small-scale surface roughness and defects specific to low-temperature growth. Both can he detrimental to fabrication and operation of small-scale electronic devices.
Date: January 1, 2002
Creator: Grube, H. (Holger); Brown, G. W. (Geoffrey W.); Pomeroy, J. M. (Joshua M.) & Hawley, M. E. (Marilyn E.)
Partner: UNT Libraries Government Documents Department

Plastic behavior of Cu/Ni multilayers

Description: In order to study the plasticity in Cu-Ni multilayers deposited on single crystals of nanoindentation measurements, and by the transmission of well characterized dislocations from the underlying substrate by tensile deformation of Cu single crystals. Various multilayers were deposited by physical vapor deposition with layer thicknesses varying between 1,000 and 20 Angstroms (for a total thickness between 0.8 and 1 {micro}m). Two types of experiments were designed. The first one aimed at injecting, in a controlled way, some dislocations from the substrate into the multilayers; the second type of experiment concerned the structure of the multilayer surface after having plastically pushed the material away from a nanoindenter. This communication reports the results from the nanoindentation measurements, as well as the observations of slip on the surface. The authors observed through the injection of dislocations by nanoindentation that the multilayers increase in strength with refinement of the layer structure but at thicknesses below 35 {angstrom} exhibits a softening behavior. Also observation of the upheaval around the nanoindent showed an evolution from slip lines to more spread plasticity with refinement of the layer structure.
Date: December 31, 1998
Creator: Verdier, M.; Hawley, M.; Nastasi, M.; Kung, H.; Niewczas, M. & Embury, J.D.
Partner: UNT Libraries Government Documents Department

Structure versus properties in High-temperature superconductors

Description: This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). High-temperature superconductors (HTS) have crystal structure that make them a distorted subset of Perovskite materials. The complexity of the superconductors arising from the large number of elements that they possess gives us all sorts of imperfect regions in our materials, and these regions tend to show Perovskite-like properties. This project sought to expand our fundamental understanding of high-temperature superconductors by combining experimental and theoretical studies of this class of novel materials. The research objectives were to interrelate structural and superconducting properties of HTS materials to further understand parameters influencing their behavior in important power and electronic applications.
Date: October 1, 1996
Creator: Smith, J.L.; Chou, F; Foltyn, S.; Hammel, P.C.; Hawley, M.; Johnson, D. et al.
Partner: UNT Libraries Government Documents Department

High-temperature superconducting thin-film-based electronic devices

Description: This the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project involved optimization of processing of Y123 and Tl-2212 thin films deposited on novel substrates for advanced electronic devices. The Y123 films are the basis for development of Josephson Junctions to be utilized in magnetic sensors. Microwave cavities based on the Tl-2212 films are the basis for subsequent applications as communication antennas and transmitters in satellites.
Date: September 1, 1996
Creator: Wu, X.D; Finokoglu, A.; Hawley, M.; Jia, Q.; Mitchell, T.; Mueller, F. et al.
Partner: UNT Libraries Government Documents Department

Observation of large low field magnetoresistance in ramp-edge tunneling junctions based on doped manganite ferromagnetic electrodes and a SrTiO{sub 3} insulator

Description: The authors report the fabrication of ferromagnet-insulator-ferromagnet junction devices using a ramp-edge geometry based on (La{sub 0.7}Sr{sub 0.3})MnO{sub 3} ferromagnetic electrodes and a SrTiO{sub 3} insulator. The multilayer thin films were deposited using pulsed laser deposition and the devices were patterned using photolithography and ion milling. As expected from the spin-dependent tunneling, the junction magnetoresistance depends on the relative orientation of the magnetization in the electrodes. The maximum junction magnetoresistance (JMR) of 30% is observed below 300 Oe at low temperatures (T < 100 K).
Date: July 1, 1998
Creator: Kwon, C.; Jia, Q.X.; Fan, Y.; Hundley, M.F.; Reagor, D.W.; Hawley, M.E. et al.
Partner: UNT Libraries Government Documents Department

The controlled growth of perovskite thin films: Opportunities, challenges, and synthesis

Description: The broad spectrum of electronic and optical properties exhibited by perovskites offers tremendous opportunities for microelectronic devices, especially when a combination of properties in a single device is desired. Molecular beam epitaxy (MBE) has achieved unparalleled control in the integration of semiconductors at the monolayer-level; its use for the integration of perovskites with similar nanoscale customization appears promising. Composition control and oxidation are often significant challenges to the growth of perovskites by MBE, but we show that these can be met through the use of purified ozone as an oxidant and real-time atomic absorption composition control. The opportunities, challenges, and synthesis of oxide heterostructures by reactive MBE are described, with examples taken from the growth of oxide superconductors and oxide ferroelectrics.
Date: October 1, 1997
Creator: Schlom, D.G.; Theis, C.D. & Hawley, M.E.
Partner: UNT Libraries Government Documents Department

Adsorption-controlled growth of ferroelectric PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} films for nonvolatile memory applications by MBE

Description: Epitaxial PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} thin films have been grown on (100) SrTiO{sub 3} and (100) LaAlO{sub 3} substrates by reactive molecular beam epitaxy (MBE). Titanium is supplied to the film in the form of shuttered bursts each containing a one monolayer dose of titanium atoms for the growth of PbTiO{sub 3} and three monolayers for the growth of Bi{sub 4}Ti{sub 3}O{sub 12}. Lead, bismuth, and ozone are continuously supplied to the surface of the depositing film. Growth of phase pure, c-axis oriented epitaxial films with bulk lattice constants is achieved using an overpressure of these volatile species. With the proper choice of substrate temperature (600--650 C) and ozone background pressure (P{sub O{sub 3}} = 2 {times} 10{sup {minus}5} Torr), the excess of the volatile metals and ozone desorb from the surface of the depositing film leaving a phase-pure stoichiometric crystal. The smooth PbTiO{sub 3} surface morphology revealed by atomic force microscopy (AFM) suggests that the PbTiO{sub 3} films grow in a layer-by-layer fashion. In contrast the Bi{sub 4}Ti{sub 3}O{sub 12} films contain islands which evolve either continuously or around screw dislocations via a spiral-type growth mechanism.
Date: September 1, 1997
Creator: Theis, C. D.; Yeh, J.; Schlom, D. G.; Hawley, M. E. & Brown, G. W.
Partner: UNT Libraries Government Documents Department