bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the Mechanical and Tribological Properties of Sputtered a:SiC Thin Films
Authors: Scharf T. W. , Inturi R. B. , Barnard J. A. 
Published: April 2011

AbstractD.C. magnetron sputtering from a CVD β-SiC target has been utilized to deposit amorphous SiC thin films on various substrates (Coming 7059 glass, unoxidized Si (111), and sapphire). The approximately 1 μm thick films were grown under various Ar sputtering pressures and flow rates. In situ annealing during deposition in vacuum and ex situ post-deposition annealing in air, both at 500°C for two hours, were implemented to determine their effects on the properties of the films. The mechanical properties were assessed via nanoindentation. An accelerated sphere-on-flat(tape) wear tester was administered to measure the wear volume losses and resultant wear rates under 0.1 and 0.2N loads, a 0.024m/s tape speed, and a 1mm ruby sphere diameter. An atomic force microscope (AFM) established the wear scar volume losses as well as the surface arithmetic roughness (RA) and root mean square roughness (RMS) of the films. The amorphous microstructure was verified by X-ray diffractometry. There was a decreasing trend in the plastic contact damage resistance, hardness, elastic modulus, and wear resistance of the films with increased amounts of Ar gas pressure; on the other hand, annealing of the lower Ar content films generated an increase in these properties compared to the as-deposited films. Atomic force microscopy revealed a more pronounced change in surface features and roughness for the in situ annealed films.
Isothermal Stress Relaxation in Al, Alcu and A1vpd Films
Authors: Lokker J. P. , Jongste J. F. , Janssen G. C. A. M. , Radelaar S. 
Published: April 2011

AbstractMechanical stress and its relaxation in aluminum metallization in integrated circuits (IC) are a major concern for the reliability of the material. It is known that adding Cu improves the reliability but complicates plasma etching and increases corrosion sensitivity. The mechanical behavior of AlVPd, AlCu and Al blanket films is investigated by wafer curvature measurements. During thermal cycling between 50°C and 400°C the highest tensile stress is found in AlVPd. In a subsequent experiment, the cooling was interrupted at several temperatures to investigate the stress behavior during an eight hour isothermal treatment. Isothermal stress relaxation has been observed in the three types of films and is discussed.
Strain, Structure and Electronic States in MBE Grown (Nb, Ti)O2 Mixed Rutile
Authors: Chambers S. A. , Gao Y. , Thevuthasan S. , Wen S. , Merkle K. L. , Shivaparan N. , Smith R. J. 
Published: April 2011

AbstractWe have grown and characterized epitaxial NbxTi1-xO2 on TiO2(110) and (100) for the purpose of investigating the role of chemically-inequivalent metal atoms on the thermal and photocatalytic properties of TiO2. Our goal is to introduce, in a highly controlled fashion, a Group VA transition metal into the lattice of a Group IVA transition metal oxide without altering the crystallographic structure. So doing would alter the electronic structure in interesting and potentially useful ways by the addition of one valence electron per substituted metal atom. However, strain builds in the film as more Nb is added at a rate which depends on the crystallographic orientation of the growth direction. Films grown along (110) can accommodate Nb mole fractions as high as ˜0.3 without forming misfit dislocations, whereas those grown along (100) are limited to ˜10 at. % Nb. Nb-O bond lengths in NbxTil−xO2 are the same as Ti-O bond lengths in pure TiO2 prior to the onset of dislocation formation. The extra 4d valence electron per Nb atom forms a nonbonding band which is degenerate with bonding states in the valence band region.
Growth, Structure, and Mechanical Properties of Pulsed Laser Deposited TiN/TiB2 Microlaminates
Authors: Kumar Ashok , Inturi R. B. , Ekanayake U. , Chan H. L. , Barnard J. A. 
Published: April 2011

AbstractHard coatings of TiN and TiB2 have many interesting properties such as high thermal and electrical conductivity, high melting point, good thermodynamic stability and combination of these properties make them an interesting prospect for a wide range of tribological and electronic applications. It is understood that artificial multilayer structures have shown anamolously high hardness and modulii making them likely candidate for future protective coatings. Single layer of TiN, TiB2, and TiB2/TiN microlaminates coatings with varying thickness have been deposited on Si (100) and oxidized Si(111) substrates by in-situ pulsed laser deposition method. These films are deposited at 10 Hz repetition rate of excimer laser (λ = 248 nm). Our preliminary results show that elastic modulii and hardness values of multilayered coatings are superior than monolithic coatings of either of the two constituent materials. The coatings have been characterized by X-ray diffiractometer and AFM techniques. Detailed results have been presented to correlate the effect of microlaminate thickness on the mechanical properties.
Fracture of Thin Synthetic Diamond Films
Authors: Drory M. D. 
Published: April 2011

AbstractLarge residual stresses in diamond coatings may result in film failure through splitting, delamination and substrate failure. In addition, the CVD diamond growth environment may degrade the substrate mechanical properties. These issues are examined for diamond-coating of a tool steel alloy. Diamond growth was achieved on the steel substrate with the use of a titanium interlayer. Embrittlement of the Ti interlayer was not evident, however the substrate hardness was severely degraded.
High Resolution Synchrotron X-Ray Diffraction Tomography Of Large-Grained Samples
Authors: Piotrowski D.P. , Stock S.R. , Guvenilir A. , Haase J.D. , Rek Z.U. 
Published: April 2011

AbstractIn order to understand the macroscopic response of polycrystalline structural materials to loading, it is frequently essential to know the spatial distribution of strain as well as the variation of micro-texture on the scale of 100 μm. The methods must be nondestructive, however, if the three-dimensional evolution of strain is to be studied. This paper describes an approach to high resolution synchrotron x-ray diffraction tomography of polycrystalline materials. Results from model samples of randomly-packed, millimeter-sized pieces of Si wafers and of similarly sized single-crystal Al blocks have been obtained which indicate that polychromatic beams collimated to 30 μm diameter can be used to determine the depth of diffracting volume elements within ± 70 μm. The variation in the two-dimensional distribution of diffracted intensity with changing sample to detector separation is recorded on image storage plates and used to infer the depth of diffracting volume elements.
Pb Induced Layer-by-Layer Growth and the Dependence on an Amount of Surfactant in the Growth of Ni on Ni(100) Surface
Authors: Iwanami M. , Kamiko M. , Matsumoto T. , Yamamoto R. 
Published: April 2011

AbstractSurfactant 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.
Changes in Structure and Composition of Silicon Oxide Thin Films Induced by Ultraviolet Illumination
Authors: Parada E. G. , González P. , León B. , Pérez-Amor M. , Silva M. F. DA , Soares J. C. , Fernández A. , González-Elipe A. R. 
Published: April 2011

AbstractThe 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.
Structure and Magnetic Properties of Epitaxial Ordered FePd (001) Thin Films
Authors: Gehanno V. , Marty A. , Gilles B. 
Published: April 2011

AbstractEquiatomic FePd (001) thin films have been deposited by Molecular Beam Epitaxy on a Pd (001) surface. We show that the degree of chemical order in the epitaxial layer is highly dependant on the temperature of deposition thus leading to a drastic change in the magnetic properties. At 25°C, while the RHEED oscillations reveal a layer by layer growth, the structural study demonstrates that the disordered phase has grown. In that case, the easy magnetization axis lies in the plane of the layer. At 350°C, the RHEED oscillations show that the growth proceeds bilayer by bilayer. We find that the tetragonal L10 ordered phase is stabilized with its 4-fold symmetry axis along the growth direction and this results in a perpendicularly magnetized thin film. The Transmission Electron Microscopy study reveals the presence of twins and antiphase boundaries in the ordered film.
Tem Study of Strain Compensated InP/GaAs/GaP/GaAs Superlattice Structures
Authors: Rusakova I. , Bensaoula A. H. , Bensaoula A. 
Published: April 2011

AbstractIn this work, we investigate the effects that alternating stress has on the structural quality of chemical beam epitaxy grown InP/GaAs/GaP/GaAS superlattices. Grown on GaAs (100), InP has a lattice mismatch of +3.9% whereas that of GaP grown under the same conditions is -3.7%. We have shown in previous work [1] that it is possible to use the principle of strain balancing to achieve highly coherent, electronically active, structures. We use TEM to first evaluate the critical thickness of GaP/GaAs and InP/GaAs heterolayers, then proceed with an extensive structural study of strain compensated structures. Misoriented substrates were also chosen to intentionally induce dislocations, allowing us to observe their structure without changing the overall strain conditions.
Characterization of Co-Cr-Mo Alloys Used in HIP Implant Articulating Surfaces
Authors: Varano R. , Bobyn J. D. , Yue S. 
Published: April 2011

AbstractThe microstructure, crystallography and mechanical properties of a wrought (ASTM F-1537) Co-Cr- Mo hip implant alloy were studied in this work. The effects of carbon content, heat treatment and room temperature compression on the above characteristics were also analyzed. Metallography of the asreceived material revealed the presence of ‘twins’ in a relatively fine microstructure with some randomly distributed grain boundary carbides. Heat treatment of the specimens produced a coarser microstructure, more uniformly distributed grain boundary carbides and annealing twins. Neutron diffraction of the specimens, which were deformed at room temperature, exhibited an increase in the volume fraction of the more stable Co-hexagonal closed-packed (HCP) crystal structure, due to a strain-induced transformation (SIT) from the metastable Co-face-centered cubic (FCC) crystal structure. It was also seen that the higher C specimens, as well as the heat treated specimens, possessed a lower volume fraction of the HCP phase. It was found, through shear punch testing, that the deformed specimens exhibited higher mechanical properties without any significant losses to the ductility of the material.
The Synthesis and Superconducting Behavior of Crystalline Superlattices: (TiSe2)m(NbSe2)n
Authors: Noh Myungkeun , Johnson David C. 
Published: April 2011

AbstractA series of kinetically stable, crystalline superlattices containing an integral number of intergrown TiSe2 and NbSe2 layers have been synthesized by controlled crystallization of elementally modulated reactants. Theta-theta and rocking curve data were collected to study the evolution of the initially layered reactants into the crystalline superlattices as a function of temperature. Nucleation of the dichalcogenide structure occurs upon annealing at temperatures above 200°C with the c-axis oriented perpendicular to the substrate surface. The [00l] diffraction linewidths decrease with increased annealing time and temperature suggesting growth of the c-axis domain size. High quality c-axis oriented dichalcogenide crystalline superlattices result from extended annealing at the relatively low annealing temperature of 500°C. The large number of well resolved [00l] Bragg diffraction peaks confirm the well developed crystal structure of the product superlattices in this direction. Four probe electrical conductivity measurements were used to determine the variation of the superconducting critical temperature as a function of the number of TiSe2 and NbSe2 layers in the superlattice.
Mixed Mode Fracture in Electronic Packages
Authors: Soboyejo W. O. , Sinha V. , Kenner V. 
Published: April 2011

AbstractIn this paper, mixedmode (mode I + mode II) fracture toughness data are presented for the prediction of molding compound (silica filled epoxy resin) failure. The stresses necessary to cause the package cracking under mixed mode loading are experimentally determined. Measured toughness values are presented as a function of modemixity and temperature
Microstructure and Reliability of Sputter Deposited
Cr-Crcu-Cu thin Films for Flip-Chip Applications
Authors: Zhang Na , Mcnicholas Mark , Colvin Neil 
Published: April 2011

AbstractThe Cr‐CrCu‐Cu metal scheme, as a terminal multistructure metallization for flip chip applications, has been investigated utilizing PVD sputter deposition varying the conditions of deposition power and temperature, and film thickness. A modified Controlled Collapse Chip Connection (C4) process was utilized in order to evaluate the aforementioned deposition of the Cr‐CrCu‐Cu multilayers and the effect of film microstructure on the parameters of shear strength and thermal cycle reliability. Thermal cycle reliability results proved to be a function of both the CrCu alloy and the Cu overlayer thickness. Transmission electron microscopy (TEM) cross‐sections of the Cr‐CrCu‐Cu multilayers suggests that the columnar grain structure of the CrCu layer may provide a sacrificial thermal diffusion barrier between the PbSn alloy solder balls and the Al bond pads during the thermal‐cycle tests.
Selective Growth of GaN and Al0.2Ga0.8N on GaN/AlN/6H-SiC (0001) Multilayer Substrates Via Organometallic Vapor-Phase Epitaxy
Authors: Nam O. H. , Bremser M. D. , Ward B. L. , Nemanich R. J. , Davis R. F. 
Published: April 2011

ABSTRACTThe selective growth of GaN and Al0.2Ga0.8N has been conducted on stripe and circular patterned GaN/A1N/6H-SiC(0001) multilayer substrates. Growth morphologies on stripe patterns changed with the widths of stripes and the flow rate of TEG. No ridge growth was observed along the edges of the stripe patterns, and the (0001) top facets were very smooth. Uniform hexagonal pyramid arrays of undoped GaN and Si-doped GaN were successfully grown on 5μm circular patterns. Field emission measurement of a Si-doped GaN hexagonal pyramid array exhibited a turn-on field of 25V/μm for an emission current of 10.8nA at an anode-to-sample distance of 27μm.
The Effect of Hydrogen on the Molecular-Beam-Epitaxy Growth of GaN on Sapphire Under Ga-Rich Conditions
Authors: Buczkowski S. L. , Yu Zhonghai , Richards-Babb M. , Giles N. C. , Romano L. T. , Myers T. H. 
Published: April 2011

ABSTRACTNucleation and growth of GaN under Ga-rich conditions by molecular beam epitaxy using a nitrogen rf plasma source is shown to result in both a smoother GaN surface and a reduced inversion domain content. In addition, preliminary results of the dramatic effect of atomic hydrogen on growth kinetics for Ga-rich growth are presented.
Impact of Growth Temperature, Pressure, and Strain on the Morphology of GaN Films
Authors: Fujii H. , Kisielowski C. , Krueger J. , Leung M. S. H. , Klockenbrink R. , Rubin M. , Weber E. R. 
Published: April 2011

ABSTRACTGaN films grown on sapphire at different temperatures are investigated. A Volmer-Weber growth mode is observed at temperatures below 1000K that leads to thin films composed of oriented grains with finite size. Their size is temperature dependent and can actively be influenced by strain. Largest grains are observed in compressed films. It is argued that diffusing Ga ad-atoms dominate the observed effects with an activation energy of 2.3 ± 0.5 eV. Comparably large grain sizes are observed in films grown on off-axes sapphire substrates and on bulk GaN. This assures that the observed size limitation is a consequence of the 3D growth mode and not dependent on the choice of the substrate. In addition, the grain size and the surface roughness of the films depend on the nitrogen partial pressure in the molecular beam epitaxy (MBE) chamber,most likely due to collisions between the reactive species and the background gas molecules. This effect is utilized to grow improved nucleation layers on sapphire.
Nano-Tubes in GaN
Authors: Liliental-Weber Z. , Chen Y. , Ruvimov S. , Swider W. , Washburn J. 
Published: April 2011

ABSTRACTFormation of vertical hollow nano-tubes in GaN grown on different substrates using different growth methods is described. These defects are shown to be of several different types, some related to threading dislocations, but others originating at tubular inversion domains, or crystal inhomogeneities. Kinetic mechanism based on slow growth rate on polar {0111} surfaces is proposed to explain the origin of these defects.
Inversion Domain Boundaries in GaN Grown on Sapphire
Authors: Romano L. T. , Northrup J.E. 
Published: April 2011

ABSTRACTInversion domain boundaries (IDBs) in GaN grown on sapphire (0001) were studied by a combination of high resolution transmission electron microscopy, multiple dark field imaging, and convergent beam diffraction. Films grown by molecular beam epitaxy (MBE), metalorganic vapor deposition (MOCVD), and hydride vapor phase epitaxy (HVPE) were investigated and all found to contain IDBs. Inversion domains (IDs) that extended from the surface to the interface were found to be columnar with facets on the {10–10} and {11–20} planes. Other domains ended within the film that formed IDBs on the (0001) and {1–102} planes. The domains were found to grow in clusters and connect at points along the boundary.
High Resolution X-ray Diffraction Analysis of GaN-Based Heterostructures Grown by OMVPE
Authors: Goorsky M.S. , Polyakov A.Y. , Skowronski M. , Shin M. , Greve D.W. 
Published: April 2011

ABSTRACTWe demonstrate the use of triple axis diffraction measurements, including Φ scans (in which the sample is rotated about an axis perpendicular to its surface) to assess the crystal perfection of wurtzite GaN layers on sapphire grown using different pre-nitridation growth treatments by or-ganometallic vapor phase epitaxy. The Φ scans determine the in-plane misorientation angles between the crystallites and hence provide information on the edge dislocation density. Using glancing incidence (1014) and (1015) reflections, we determined that the misorientation among the GaN crystallites decreases with increasing layer thickness and that the pre-nitridation conditions control the initial level of misorientation. Triple axis ω and ω-2θ scans around the (0002) reflection did not show a systematic trend with increasing layer thickness. However, layers grown without a pre-nitridation step tended to exhibit higher values of both mosaic spread and strain. The appropriate asymmetric reflections for GaN-based Φ scan measurements are determined using structure factor calculations, which are presented here.
Free and Bound Excitons in GaN Epitaxial Films
Authors: Meyer B.K. 
Published: April 2011

ABSTRACTWe report on photoluminescence experiments on hexagonal GaN epitaxial films grown on 6H-SiC and sapphire substrates by organo-metallic and hydide vapor phase epitaxy. At low temperatures we observe free and neutral donor bound exciton transitions which allow to establish properties of the free excitons and localisation energies of the bound excitons involving different shallow donors. From temperature dependent luminescence experiments thermal activation energies are determined which measure the exciton localization and donor binding energies. The localization energies of the excitons scale with the respective donor binding energies (Haynes rule). The inter-impurity transitions of neutral donors are observed in fourier transform infra-red absorption. Three shallow donors with binding energies of 34.7 meV, 55 meV and 58 meV can be seen. We present evidence for the chemical nature of the shallow impurities.
Magnetic Resonance Studies of High-Resistivity GaN Films Grown on Al2O3
Authors: Glaser E. R. , Kennedy T. A. , Wickenden A. E. , Koleske D. D. , Freitas J. A. 
Published: April 2011

ABSTRACTWe have made an attempt to obtain electronic and atomic structure information on the residual defects that exist in high-resitivity GaN epitaxial layers from optically-detected magnetic resonance (ODMR) experiments performed on the broad 3.0 and 2.2 eV photoluminescence (PL) bands observed from these films. The first observation of magnetic resonance on this 3.0 eV band reveals two ODMR signals. The first resonance is sharp (FWHM ∼ 3.5 mT) with g ∼ 1.950 and is assigned to effective-mass (EM) donors based on previous studies. The second feature is much broader (FWHM ∼18 mT) with a donor-like g-value of ∼ 1.977. This new resonance may be associated with partially EM-like donor states located ∼ 54 - 57 meV below the conduction band edge proposed recently to be involved in this 3.0 eV PL band.
Effects of X-ray and γ-ray Irradiation on GaN
Authors: Qiu C. H. , Leksono M. W. , Pankove J. I. , Rossington C. , Haller E. E. 
Published: April 2011

ABSTRACTAs part of the feasibility study of using III-V nitride semiconductors for x-ray and γ-ray detection, the irradiation effects on GaN were investigated. GaN films with very different electrical resistivity and electron concentration were used in the study. The electron mobility, photoconductivity spectra, and photo-luminescence spectra were measured before and after irradiation. An enhanced ημτ product for undoped GaN films and an enhanced blue luminescence for a Zn-doped sample were observed after irradiation.