bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hrxrd Study of the Strain Properties of MBE-Grown ZnSe and ZnSTe on GaAs
Authors: Sou I.K. , Mou S.M. , Chan Y.W. , Xu G.C. , Wong G.K.L. 
Published: April 2011

ABSTRACTWe have studied the structural properties of MBE-grown ZnSe/GaAs and ZnSTe/GaAs heterostructures using high resolution X-ray diffraction (HRXRD). The transition from pseudomorphic to partially and then fully relaxed strained layers is observed as a function of ZnSe layer thickness. The critical thickness for the on-set of strained relaxation for ZnSe on GaAs(001) is determined to be between 1600 and 1850 Å. Using a simulation program based on the dynamical theory, the poisson's ratio of ZnSe is accurately determined to be v=0.380±0.002. A set of ZnSl-xTex epilayers with 0 ≤ × ≤ 1 was grown on GaAs by MBE for the first time. A linear dependence of the lattice constant upon Te composition is found, which agrees well with the Vegard's Law. The characteristic behaviors of inclination between the layer and substrate planes as a function of layer thickness has been studied on both ZnSe/GaAs and ZnSTe/GaAs systems. The atomic planes of both ZnSe and ZnSTe layers are observed to tilt from those of the GaAs substrate.
The influence of tellurium interdiffusion on the optical properties of MOVPE-grown ZnSe-ZnTe superlattices
Authors: Aulombard R.L. , Briot O. , Briot N. , Cloitre T. , Gwl B. , Sallese J.M. , Gailhanou M. , Bonard J.M. 
Published: April 2011

ABSTRACTWe have used low pressure MOVPE to grow a series of short-period ZnSe-ZnTe strained-layer superlattices onto either ZnSe or ZnTe buffer layers. Typical superlattice periods range from 2 to 6.5 nm with constant ZnSe thickness of 2 monolayers. X-Ray diffraction analyses have shown that the superlattices are free-standing if grown on a ZnSe buffer but lattice matched to ZnTe if grown on ZnTe buffer layers. The luminescence emitted by the free standing samples has been studied using both the photoluminescence technique at low temperature and cathodoluminescence at higher temperature, for improved pumping. Our samples exhibit a complicated temperature dependence similar to the behaviour of ZnSeTe alloys where exciton self-trapping to tellurium gives strong photoluminescence bands labelled SI and S2. A high temperature, high energy feature is observed and is associated with the fundamental superlattice transition. The energy position of this structure suggest a high value of the ZnSe/ZnTe valence band offset, in the range 1200-1400 meV.
Influence of Substrate Preparation on the Two-Stage MOCVD of CdTe on (001)GaAs
Authors: Cheng T.T. , Aindow M. , Jones I.P. , Hails J.E. , Graham A. , Giess J. , Williams D.J. , Astles M.G. 
Published: April 2011

ABSTRACTA TEM study of the initial nucleation layers for the two-step growth of CdTe on 2°-off (001) GaAs substrates by MOCVD is presented. When the substrates are degreased and etched in the usual manner, the initial deposits are oriented with their axes parallel to those of the substrates. When the substrates are, instead, prepared by thermal etching at 545-585°C, the initial deposits contain both (001) and (111)-oriented grains. When these polycrystalline initial deposits are heated to the “bulk” growth temperature, epitaxial regrowth occurs giving a single crystal film with a very distinctive anisotropic defect microstructure. Possible reasons for these effects are discussed.
Modelling of the Texture Formation in Electro-Deposited Metal Films
Authors: Li D. Y. , Szpunar J. A. 
Published: April 2011

ABSTRACTThe texture formation during the electrodeposition process was simulated using a Monte Carlo technique. The simulation uses a two dimensional hexagonal lattice to map the microstructure of the deposit. The criteria for the texture formation was based on the minimization of the system’s free energy. The anisotropy of surface-energy was taken into account. Since a metal’s surface energy is influenced by hydrogen adsorption, the texture of metal deposits may vary with hydrogen co-deposition.
A Microstructural Comparison of Cu(In,Ga)Se2 Thin Films Grown from CuxSe and (In,Ga)2Se3 Precursors
Authors: Gabor Andrew M , Tuttle J. R. , Albin D. S. , Matson R. , Franz A. , Niles D. W. , Contreras M. A. , Hermann A. M. , Noufi R. 
Published: April 2011

ABSTRACTWe fabricated CulnSe2 and Cu(In,Ga)Se2 thin films by two different pathways using physical vapor deposition. In the first we formed a Cu-Se precursor and then reacted it with a flux of (In,Ga) + Se. These films had large grains but were too rough for optimal device performance. In the other pathway, we first formed a smooth precursor of (In,Ga)2Se3 and then exposed it to a flux of Cu+Se. We overshot the optimal film composition to allow recrystallization of the film by a secondary CuxSe phase. We then consumed the excess CuxSe in a third stage deposition of (In,Ga) + Se. The recrystallization step increased the grain sizes, and the resulting films remained smooth. Photovoltaic solar cells made from these films have produced the highest total-area efficiencies of any non-single-crystal, thin-film solar cell.
A Unified Approach to Grain Boundary Diffusion and Nucleation in Thin Film Reactions
Authors: Coffey K. R. , Barmak K. 
Published: April 2011

ABSTRACTAn alternative model is proposed to extend the conventional view of diffusion under a concentration gradient in a grain boundary phase of width δ. The conventional model is well developed and readily applied to the thickening kinetics of polycrystalline product phases in binary diffusion couples, however it is not readily extended to other phenomena of interest in thin films, i.e., the nucleation and growth of the product phase crystallites prior to formation of a product phase layer. In the alternative model presented here, non-equilibrium thermodynamics is used to define the chemical potentials, μi, for each atomic specie in the grain and interphase boundaries of a polycrystalline diffusion couple. The chemical potential difference for each specie between the bulk phases of the diffusion couple is partitioned between the driving force for grain boundary diffusion and that for interfacial reaction. This partition leads to a characteristic decay length that describes the spatial variation of μi. Numerical calculations of μi are used to show that boundary diffusion favors heterogeneous nucleation. Product nucleation in thin film reactions is seen to be similar to precipitation from a bulk solid solution.
Orientation Imaging of the Microstructure of Polycrystalline Materials
Authors: Adams Brent L. 
Published: April 2011

ABSTRACTRecent developments, coupling the scanning electron microscope with image processing and crystallographic analysis, now make it possible to automatically index many thousands of lattice orientations exposed on section planes in polycrystalline materials. Backscattered Kikuchi diffraction patterns obtained from high-gain SIT and CCD cameras are analyzed using the Hough transformation (Cartesian coordinates - polar coordinates) in order to identify diffraction band widths and interplanar angles. From this basic information local lattice orientation can be determined. Information from raw data sets (in excess of 100,000 single orientations in some examples) can be used to construct orientation imaging micrographs which emphasize certain aspects of the exposed field of lattice orientations. Thus, features of the spatial placement of lattice orientation (including grain boundary misorientation, microtexture, and connectivity of the microstructure) are readily studied. In this paper these techniques are reviewed, and recent explorations of the connectivity of grain boundary misorientation structure are presented for an interesting nickel-chromium-iron alloy.
The Thermal Stability of Ti-Al-C Pvd Coatings
Authors: Knotek O. , Löffler F. , Wolkers L. 
Published: April 2011

ABSTRACTWhile (Ti,Al)N coatings are well known and established in wear applications like drilling and milling, the corresponding TiC based metastable system Ti-Al-C is not well examined. This paper investigates the phase stability and the phase transition behaviour of post-deposition heat-treated Ti-Al-C coatings. The samples were annealed in a temperature range from 600–1400 °C in a high vacuum furnace. The influence of deposition parameters like coating compositions via the Ti/Al ratio and the metal/metalloid ratio on the properties were investigated. Another very important parameter in this investigation is the carbon carrier gas. Examined gases were methane, ethane, ethylene and ethine. The changes in microhardness, lattice parameters and particle sizes were analysed with respect to their temperature dependence.The phase formation depends on the target composition and on the reactive gas. A formation of a metastable (Ti,Al)C phase can be observed. A higher C:H ratio of the reactive gas leads to better incorporation of carbon into the coating. An Al-loss independent of the coating composition begins 1000 °C. The microhardness increases with higher annealing temperature and decreases with higher Al-content.
The Effects of Cross Hatch Angle (CHA) on Magnetic Properties and Read/Write Characteristics of CoCrPtTaB Thin Film Media
Authors: Chen Ga-Lane , Do H. , Yeh T.-A. , Sivertsen J. M. , Judy J. H. 
Published: April 2011

ABSTRACTCross-hatch type texturing has been widely used to replace circumferential texturing in the thin film media industry for optimizing tribology performance. However, higher “cross hatch angle” (CHA) may degrade magnetic performance. The relationship between texturing cross hatch angle (CHA) and magnetic properties and their effects on the read/write characteristics of sputtered thin film media are discussed in this paper. As the CHA increases, both the orientation ratio (OR) and the squareness ratio “S(c)/S(r)” decrease. The film with the highest OR is located at CHA=90, which has the lowest media noise. The medium has highest signal/noise ratio when CHA is equal to 90. PW50 can decrease as much as 4 nanoseconds as CHA increases to 730. By calculating a ratio of the intensity of Cr (110) + CoCrPtTaB (0002) to the intensity of Cr (200), we are able to correlate the intensity ratio to magnetic properties and read/write characteristics.
The Microstructure of Sputtered Co-Cr Magnetic Recording Media
Authors: Pundt Astrid , Busch Ralf , Michaelsen Carsten 
Published: April 2011

ABSTRACTWith the increase of magnetic storage capacity in view, sub grain decomposition in Co-Cr magnetic recording material is examined with the field ion microscope / atom probe (FIM/AP) on a nanometer scale. Concentration variations in sputtered 50 nm Co-20at% Cr and 3 μm Co-22at% Cr films are analysed. Layers with up to 50 nm thickness are sputtered directly onto tungsten FIM tips. FTM-tips of layers with up to 3 μm thickness are prepared by a lithography and etching technique. The measurements show decomposition on the scale of a few nanometers. The concentration amplitudes vary between 11 at% Cr and 42 at% Cr within 50 nm films. Within 3 μm films the concentration varies from about 10 at% Cr to 30 at% Cr. Furthermore, at grain boundaries 3–4 nm precipitates of about 40 at% Cr are observed. The observed concentrations depend on substrate temperature. The compositional inhomogeneity can be explained by a miscibihty gap in the hep phase solid solution which is induced by magnetism at low temperatures.
Stress, Microstructure and Magnetic Properties of Thin Sputtered Co Alloy Films
Authors: Ross C. A. , Ranjan R. , Chang J. 
Published: April 2011

ABSTRACTThe internal stress and magnetic properties have been measured for cobalt alloy films deposited using a range of sputter conditions. The sputter conditions affect the internal stress and the microstructure, both of which contribute to the magnetic properties of the films. Stress influences the magnetic properties via magnetostriction, while the microstructural effect on coercivity comes primarily from the degree of separation and size of the grains in the film. The effect of stress on coercivity was investigated separately by applying external stresses to the films, and magnetostriction coefficients were derived for different alloys. The change in coercivity with sputter parameters indicates that in alloys such as Co77Ni7Cr4Pt12, the microstructure has the dominant effect on coercivity.
Effects of Substrate Temperature on Magnetic and Crystallographic Properties of Co-Cr-Pt/Cr Films Deposited by Laser Ablation
Authors: Ishikawa Akira , Shiroishi Yoshihiro , Sinclair Robert 
Published: April 2011

ABSTRACTThe effects of the substrate temperature on the magnetic properties and crystal structure of Co89Cr7Pt4/Cr films deposited by laser ablation were studied. A pulsed KrF excimer laser with a wavelength of 248 nm was focused on ablation targets in a vacuum chamber. The laser irradiation energy was estimated to 10 J/cm2. Cr underlayer and Co89Cr7Pt4 films were successively deposited on the Si substrate at a rate of 0.012 nm/pulse. At a substrate temperature lower than 350 °C, an in-plane coercivity of 30 nm thick CoCtjPu film deposited on 50 nm thick Cr underlayer was 50∼150 Oe showing no significant influence by the substrate heating. The coercivity at 450 °C, however, increased to 800 Oe showing a maximum at this temperature. X-ray diffraction analyses showed that the magnetic films formed at lower than 350 °C have fcc-Co phase, while the films deposited at 450 °C had hep-Co phase with the c-axis oriented parallel to the substrate. At temperatures higher than 450 °C, the coercivity decreased concomitant with a disappearance of the oriented hep-Co phase. The grain size of the films increased from 10 nm to 20∼30 nm by increasing the substrate temperature. The increase of coercivity is probably due to annealing effects resulting in the grain growth of Cr underlayer and the phase transformation of the magnetic films to form the hep-Co phase.
Effect of Interlayers Upon Texture and Magnetic Properties in Co Alloy Multilayer Films for Longitudinal Magnetic Recording
Authors: Visokay M. R. , Kuwabara M. , Saffari H. , Hayashi H. , Sinclair R , Onishi Y. 
Published: April 2011

ABSTRACTCoCrNi bilayer films with Cr, Ti and Zr interlayers were deposited by DC magnetron sputtering onto ultra densified amorphous carbon substrates and characterized using cross-section transmission electron microscopy and vibrating sample magnetometry. The films are polycrystalline with a columnar microstructure. In the Cr interlayer case there is layer-to-layer epitaxy throughout a given column. Magnetic measurements snowed a simple in-plane easy axis magnetic hysteresis loop. In the Zr and Ti interlayer cases epitaxy within a column was lost beginning with the first CoCrNi/(Zr/Ti) interface, resulting in a magnetic layer consisting of two crystallographically unrelated CoCrNi films. Magnetic measurements revealed a complex step-structure hysteresis loop for this case. Annealing the Zr interlayer film led to a significant growth of the amorphous layer due to a solid state amorphization reaction between the Zr and CoCrNi, which was accompanied by a decrease in the saturation magnetization.
Giant Magnetoresistance Studies of NiFe-Based Spin-Valve Multilayers
Authors: Lin Chien-Li , Sivertsen John M. , Judy Jack H. 
Published: April 2011

ABSTRACTThe giant magnetoresistance in FeMn exchange-biased NiFe-based multilayer spin-valve structures prepared by rf-diode sputtering technique were studied. Experiments were performed on samples with different thicknesses of each layer in these multilayers. The magnetic properties were measured using a vibrating sample magnetometer and the giant magnetoresistance was measured using an in-line four-point magnetoresistance probe. A magnetoresistance of 6.5% in a magnetic field of less than 15 Oe was obtained in a Cu(30Å)/FeMn(150Å)/NiFe(50Å)/Co(15Å)/ Cu(20Å)/Co(15Å)/NiFe(60Å) multilayer structure at room temperature. Annealing experiments of these multilayers were performed to study the thermal stability during the recording head fabrication processes. No degradation in the magnetoresistance has been found for annealing these films at 230°C up to four hours.
The Geometry of Grain Disappearance in Thin Polycrystalline Films
Authors: Townsend S. J. , Nichols C. S. 
Published: April 2011

ABSTRACTDuring grain growth, shrinking columnar grains in thin-film polycrystalline microstructures eventually reach sizes comparable to the film thickness. Due to surface drag, the sides of such grains may bow inward rather than remaining fiat through the bulk of the film. The grain boundaries delimiting such small shrinking grains may become unstable long before the surface of the shrinking grain reaches zero area. We report simulation results demonstrating such an instability in the limit of infinite surface drag. This may lead to extremely rapid disappearance of 4- or 5- sided grains, such as have been recently observed in in situ hot-stage TEM experiments on aluminum thin film polycrystals.
Interfaces in Ferroelectric Metal Oxide Heterostructures
Authors: Ramesh R. , Lee J. , Keramidas V. G. , Fork D. K. , Ghonge S. , Goo E. , Auciello O. 
Published: April 2011

ABSTRACTRealization of a viable nonvolatile ferroelectric thin film memory technology hinges on the successful solution of the reliability problems associated with the ferroelectric capacitor concurrent with the integration of these materials with the appropriate Si-CMOS based drive electronics. This integration process introduces a variety of structural, chemical, ionic and electronic interfaces in the memory elements. In this paper, the influence of some of the interfaces on the ferroelectric properties and on the process integration is discussed.
The Effect of Layer Thickness on Polycrystalline Zirconia Growth in Zirconia-Alumina Multilayer Nanolaminates
Authors: Scanlan C. M. , Wiggins M. D. , Gajdardziska-Josifovska M. , Aita C. R. 
Published: April 2011

ABSTRACTThe mechanical properties of zirconia are known to be a function of phase composition. We show here that a nanolaminate geometry can be used to control the phase composition of zirconia films. The experiment consisted of growth of nanoscale multilayer films (nanolaminates) of polycrystalline zirconia and amorphous alumina by reactive sputter deposition on Si (111) and fused silica substrates. The films were characterized using x-ray diffraction and high resolution electron microscopy. The results show that both monoclinic (m) and tetragonal (t) zirconia polymorphs were formed in the zirconia layers. Most crystallites are oriented with either close-packed {111}-t or {111}-m planes parallel to the substrate. The volume fraction of tetragonal zirconia, the desired phase for transformation-toughening behavior, increases with decreasing zirconia layer thickness. Nanolaminates with a volume fraction of tetragonal zirconia exceeding 0.8 were produced without the addition of a stabilizing dopant, and independent of the kinetic factors that limit tetragonal zirconia growth in pure zirconia films.
Texture and Phases in Oxide Films on Zr-Nb Alloys
Authors: Lin Y. P. , Woo O. T. , Lockwood D. J. 
Published: April 2011

ABSTRACTOxide films, 0.2-2.0 μm in thickness on Zr-2.5Nb and 11 μm thick on Zr-20Nb alloys, formed in steam at 673 K, have been examined using TEM, XRD and Raman spectroscopy. Columnar grains of mostly monoclinic Zr02 in oxide films on Zr-2.5Nb exhibit a dual texture: a fibre mode with an axis close to the 102m pole and a [001]m growth mode with an orientation relationship [100]m // [4510]α and (010)m // (0001)α with the α-Zr metal. In both modes, “tetragonal” (and/or cubic) ZrO2 was present. Raman spectroscopy differentiated two non-cubic “tetragonal” forms of ZrOz within the [001]m growth texture. In thin oxides (0.5 μm or less), this corresponds to the tetragonal ZrO2 observed in ceramic zirconia and is characterised by a Raman band near 260 cm−1. The 278 and related 438 cm−1 Raman bands observed here in some oxide films (and in other Zr corrosion oxides) are attributed to a separate, non-cubic phase structurally related to the tetragonal ZrO2. The intensities of the 278 and 438 cm−1 bands are dependent not only on the amount of this modified-tetragonal phase but also on the oxide texture (related to the metal texture) and the beam orientation. The lack of Raman response from the “tetragonal” ZrO2 within the fibre mode of texture indicates either a low volume fraction or a cubic-like structure. For oxide on Zr-20Nb, XRD and Raman spectroscopy show a mixture of monoclinic and “tetragonal” ZrO2; the Raman results indicate the “tetragonal” ZrO2 has a high crystal symmetry or nearly cubic structure.
Computer Simulation of Strain Energy and Surface- and Interface-Energy on Grain Growth in Thin Films
Authors: Carel R. , Thompson C. V. , Frost H. J. 
Published: April 2011

ABSTRACTWe have simulated strain energy effects and surface- and interface-energy effects on grain growth in thin films, using properties of polycrystalline Ag (p-Ag) on single crystal (001) Ni on (001) MgO for comparison with experiments. Surface- and interface-energy and strain energy reduction drive the growth of grains of specific crystallographic orientations. The texture that will result when grain growth has occurred minimizes the sum of these driving forces. In the elastic regime, strain energy density differences result from the orientation dependence of the elastic constants of the biaxially strained films. In the plastic regime, strain energy also depends on grain diameter and film thickness. In p-Ag/(001) Ni, surface- and interface-energy minimization favors Ag grains with (11) texture. In the absence of a grain growth stagnation, the texture at later times is always (111). However, for high enough strains and large enough thicknesses, the strain energy driving force can favor a (001) texture at early times, which reverts to a (111) texture at later times, once the grains have yielded.
Low Temperature Atmospheric Pressure Chemical Vapor Deposition of Group 14 Oxide Films
Authors: Hoffman David M. , Atagi Lauren M. , Chu Wei-Kan , Liu Jia-Rui , Zheng Zongshuang , Rubiano Rodrigo R. , Springer Robert W , Smith David C. 
Published: April 2011

ABSTRACTDepositions of high quality SiO2 and SnO2 films from the reaction of homoleptic amido precursors M(NMe2)4 (M = Si, Sn) and oxygen were carried out in an atmospheric pressure chemical vapor deposition reactor. The films were deposited on silicon, glass and quartz substrates at temperatures of 250 to 450 °C. The silicon dioxide films are stoichiometric (O/Si = 2.0) with less than 0.2 atom % C and 0.3 atom % N and have hydrogen contents of 9 ± 5 atom °. They are deposited with growth rates from 380 to 900 Å/min. The refractive indexes of the SiO2 films are 1.46, and infrared spectra show a possible Si-OH peak at 950 cm−1. X-Ray diffraction studies reveal that the SiO2 film deposited at 350°C is amorphous. The tin oxide films are stoichiometric (O/Sn = 2.0) and contain less than 0.8 atom % carbon, and 0.3 atom % N. No hydrogen was detected by elastic recoil spectroscopy. The band gap for the SnO2 films, as estimated from transmission spectra, is 3.9 eV. The resistivities of the tin oxide films are in the range 10−2 to 10−3 Ω cm and do not vary significantly with deposition temperature. The tin oxide film deposited at 350°C is crystalline cassitterite with some (101) orientation.
Atomic Force Microscopy Study of Nickel Oxide Films Modified by Reactive Element
Authors: Czerwinski F. , Szpunar J.A. 
Published: April 2011

ABSTRACTThe evolution of microstructure of thin oxide films during growth has been quantitatively analysed by atomic force microscopy (AFM). The oxide films were formed in pure oxygen atmosphere at temperatures ranging from 873 to 1173 K on polycrystalline nickel substrates. The substrates were both pure and superficially modified by nanometer-sized dispersions of CeO2. The incorporation of reactive element into the oxide inhibits the growth kinetics and affects the microscopic surface morphology. The extent of this effect depends essentially on the substrate surface microstructure prior to modification and the size of CeO2 particles. A correlation was found between the surface topography and the reduction of oxide growth rate caused by the reactive element.