bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role Of Thermomechanical Energy In Diffusion Kinetics And Crystallinity Of Mechanically Alloyed Titanium Aluminides
Authors: Dahl Laura , Shepler Mark , Nash Alexis S.
Published: March 2011

Mechanical alloying, MA, is an amorphization technique which involves a solid state reaction below the crystallization temperature. This technique is capable of producing a more homogeneous and fine microstructure with improved mechanical properties. Amorphization of Titanium aluminide binary system, in the range of 45–65 at % Al is possible under optimized milling conditions since in this range the mixture has a large negative heat of mixing. This system is considered suitable for human implant applications for its light-weight, wear resistance, corrosion resistance, strength-to-weight ratio and biocompatibility.
Interfacial Structure and Evolution in Mesotaxial CoSi2/Si Heterostructure
Authors: Hull S. R. , Hsieh Y. F. , White A. E. , Short K. T.
Published: March 2011

We describe the evolution and microstructure of Si/CoSi2/Si (100) and (111) heterostructures formed by Co+ ion implantation into Si substrates (“mesotaxy”), followed by high temperature annealing. It is shown that the CoSi2 precipitate nucleation and ripening process, and eventual coalescence into buried layers, is controlled by interfacial structure and energetics. Understanding and control of these processes allows for the first time synthesis of otherwise almost identical CoSi2 buried layers with either twinned or untwinned CoSi2/Si(111) interfaces.
Interfacial Structures of MoSi2-Mo5Si3 Eutectic Alloys
Authors: Kung H. , Chang H. , Gíbala R.
Published: March 2011

Script lamellar microstructures which occur in certain intermetallic eutectic alloys, such as in the Mo-Si system, may provide desirable mechanical properties. Arc-melted specimens of MoSi2-Mo5Si3 eutectic alloys which exhibit the interlocking lamellar phases were examined in this study. We have observed, by conventional transmission electron microscopy (TEM), an orientation relationship between the MoSi2 and the Mo5Si3 phases, (110)[001]1-2 ‖ (330)[110]5-3, which is consistent with the crystallographic coordinate transformation matrix. High resolution transmission electron microscopy (HRTEM) discloses the interfacial dislocations to be of <100> and 1/2<111> types and the interfaces are regularly faceted. A shear fault which may be consisting of antiphase boundary (APB)-coupled 1/6<331> superpartial dislocations was observed in MoSi2 grain near the interface. Crack propagation paths suggest that the eutectic has a strong, low energy interface which is consistent with the observations of a low index orientation relationship between the two phases and the faceted interfacial structures.
Comparison of Different Thickness Measurements of Oxide Films on Silicon
Authors: Kao Shou-Chen , Doremus Robert H.
Published: March 2011

The thermal oxidation of silicon in dry oxygen is examined with three different thickness measurements: Ellipsometry, transmission electron microscopy and step-profile measurements. The oxidation kinetics follow a linear-parabolic relationship throughout the measured thickness range. Previous deviations from linear-parabolic behavior result from inaccurate ellipsometer measurements of film thickness for films thinner than 0.05 /zm.
The Role of Chemical Interactions in the Stability of Artificial Metallic Superlattices
Authors: Sluiter M. , Turchi P.E.A.
Published: March 2011

Atom by atom deposition techniques, such as magnetron sputtering, make possible the synthesis of artificial superlattices with composition modulations in one dimension on an atomic scale[1]. Generaily, elastic effects (lattice mismatch) and chemical affinity (ordering or clustering tendencies are recognized as the most important driving forces for the thermodynamic stability of such materials. In this study the chemical aspect of stability will be examined using a formalism based on first-principles electronic structure calculations developed originally for bulk alloys. The formalism has been applied to a number of systems with fee and bec transition metals as constituents. In some cases the stability of artificial superlattices was found to depend in a rather surprising and unexpected way on the direction and wavelength of the composition modulation.
The Control of Interfacial Reactions Via Length Scales of Ultrathin-Film Modulated Composites
Authors: Fister Loreli , Novet Thomas , Grant Christopher A. , McConnell John , Johnson David C.
Published: March 2011

Interfaces are difficult to probe because the volume of the interfacial region is exceedingly small compared with the bulk. Our approach is sequentially to deposit thin (5–50Å) elemental layers to create a unique initial reactant. Due to the short modulation length, the interfaces constitute a large fraction of the total composite. Composites modulated below a critical repeat unit length are found to evolve into homogeneous amorphous alloys. Composites modulated above this critical distance behave like bulk diffusion couples. The layered nature of the starting reactant permits the evolution of the interfacial structure to be followed in a quantitative manner using x-ray diffraction. Distinct differences in the evolution of the interfaces above and below the critical distance are observed. This approach to studying interfaces also permits the direct and selective synthesis of crystalline compounds. Nucleation is the rate-limiting step in the formation of a crystalline material from an amorphous alloy, and the phase formed is strongly influenced by the stoichiometry of the homogeneous amorphous alloy. Results from studies of molybdenum-selenium and iron-silicon ultrathin-film composites will be discussed.
Characterization of Pd/V Multilayer Structures by High-Angle Annular Dark-Field Microscopy and High Resolution Tem
Authors: Liu J. , Cheng Y. , Lewen G. D. , Stearns M. B.
Published: March 2011

The structures of e-beam evaporated Pd/V multilayer thin films, which were fabricated at different substrate temperatures, have been characterized by high-angle annular dark-field microscopy and high resolution electron microscopy techniques. X-ray scattering and crosssectional electron microscopy showed that both the Pd and V layers are composed of small textured crystallites with dominant orientations of Pd (111) and V (110). It is found that Pd/V multilayers with high chemical modulation can be fabricated at substrate temperatures around 350 K and at a deposition rate of 0.2 nm/s. Here high-angle annular dark-field microscopy has been shown to provide direct information about the compositional variation of the interlayers of these ML.
High Resolution Electron Microscopy Observations About The Interface Structure In A Ti/TiN Multilayer Material
Authors: Ning X. G. , Guo L. P. , Huang R. F. , Gong J. , Yu B. H. , Wen L. S. , Ye H. Q.
Published: March 2011

The interface structure in a Ti/TiN multilayer material has been investigated by high resolution transmission electron microscopy (HRTEM). It was shown that the α-Ti and β-TiN layers consisted of many cylindrical crystals growing along the close packed directions normal to the surface of a stainless steel. There existed specific orientation relationship at the Ti/TiN interfaces without transition layers: (111)TiN ‖ (001)Ti, [110]TiN ‖ [100]Ti. However there was no such orientation relationship at the Ti/TiN interfaces with TixN (x >1) transition layers.
Microstructural Evolution Of Ti/Ni AND Ni/Ti Bilayer Thin Films
Authors: Haftek E. , Tan M. , Waknis A. , Barnard J. A.
Published: March 2011

The growth and microstructural evolution of sputtered Ti/Ni and Ni/Ti bilayer thin films have been investigated as a function of Ti and Ni layer thicknesses in as-deposited and annealed states (280°C for 60 minutes) by transmission electron microscopy (TEM). The Ti layer thickness was varied systematically from 4.9 to 29.4 nm while the Ni thickness was varied from 3.2 to 19.2 nm. Carbon coated Cu TEM grids were used as substrates. Microstructural characteristics of the bilayers were found to be deposition sequence dependent. Ti/Ni bilayers exhibit a finer microstructure than N/T especially for the thicker films. Intergranular cracking is observed in the Ti/Ni sequence. In both deposition sequences the presence of Ni promotes the crystallization of Ti in the as-deposited state. By contrast, single layer Ti films deposited under the same sputtering conditions remain amorphous up to 9.8 nm thick. The Ti{002} electron diffraction ring is present in all of the bilayers even those with the thinnest Ti layers. Additional Ti rings, {010} and {011}, develop in bilayers with thicker Ti layers. In both bilayer systems a tensile stress parallel to the film plane is present in the Ni layer. Annealing removes structural defects and relieves the stress. A large increase in Ni{111} spacing can be attributed to dissolution of Ti atoms into the Ni lattice. Annealing also produces evidence of grain growth, intermetallic compound formation, and amorphization in both Ti/Ni and Ni/Ti samples.
Low-Temperature Device-Quality SiO2/Si (100) Interfaces Prepared By A Combined Remote Plasma Oxidation-Deposition Process
Authors: Yasuda T. , Ma Y. , Lucovsky G.
Published: March 2011

Gate-quality SiO2/Si(100) interfaces were reproducibly fabricated using a two-step remote plasma-assisted oxidation/thin-film deposition processing sequence at temperatures between 200 and 300°C. The pre-deposition oxidation creates approximately 0.5nm of SiO2, and produces an SiO2/Si interface with a midgap trap density of ∼1.3×1010cm−2eV−1. The MOS capacitors prepared by this technique have properties comparable to those with thermal oxides grown at 850–1050°C. These capacitors also show a longer minority-carrier life time in the underlying Si than samples prepared using other pre-deposition treatment methods.
The Properties of Twinning Dislocations in Alpha-Titanium Simulated With A Many-Body Interatomic Potential
Authors: Bacon David J. , Serra Anna
Published: March 2011

Computer simulation of the atomic structure and movement of twinning dislocations in four twin boundaries in the h.c.p. metal α-Ti is described. These dislocations have the form of steps on the twin boundary, and whereas some have cores which are very widely spread over the interface, others are only an interatomic spacing or so across. These configurations are determined mainly by whether or not atomic shuffles are required to restore the h.c.p. crystal structure when the dislocation is introduced. The mobility of the dislocations is also controlled by the same effect, and is found to correlate well with experiment.
Alloy Effects And Extended Solubilities In Binary Mixtures Of Nanometer-Sized Fe-Cu Crystals
Authors: Eckert J. , Birringer R. , Holzer J. C. , Krill C. E. , Johnson W. L.
Published: March 2011

Binary mixtures of Fe-Cu powders in the range of 10–95 at.% Fe have been prepared by mechanical alloying and investigated by x-ray diffraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The final grain sizes of the powders vary between 6 and 20 nm, and depend on the composition of the material. Indications for the formation of single-phase alloys with up to 60 at.% Fe in Cu and 20 at.% Cu in Fe have been found although the Fe-Cu system exhibits only vanishingly small solid solubilities under equilibrium conditions. Between 60 at.% and 80 at.% Fe a two-phase region of fee and bec solid solutions exists. Alloy formation is discussed with respect to the thermodynamic conditions of the material. The influence of the large grain boundary fraction, as well as the role of internal strains and stored enthalpies introduced by ball milling, is critically assessed.
Synthesis And Characterization Of Ball-Milled Nanocrystalline Fcc Metals
Authors: Eckert J. , Holzer J. C. , Krill C. E. , Johnson W. L.
Published: March 2011

Nanocrystalline fee metals (Al, Cu, Ni, Pd, Rh, Ir) have been prepared by ball milling. The development of the microstructure is investigated by x-ray diffraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The final grain sizes range from 6 to 22 nm and scale with the melting point and the bulk modulus of the elements: metals with higher melting point and bulk modulus have a smaller final grain size. From this a general relation between the deformation mechanism during ball milling and the ultimate grain size achievable by this technique is inferred. With decreasing grain size the lattice strain is enhanced and deformation enthalpies of up to 40 % of the heat of fusion are stored in the material. The contributions of the lattice strain and of die excess enthalpy of the grain boundaries to the stored enthalpies are critically assessed. The kinetics of grain growth are investigated by mermal analysis. The activation energy for grain boundary migration is derived from a modified Kissinger analysis and estimates of the grain boundary enthalpy are given.
Structural Relaxations At Metal / Metal Oxide Interfaces
Authors: Mader W.
Published: March 2011

Recent work is reviewed on the structure of metal/metal oxide interfaces in model systems with well defined orientation relationships and boundary inclination. Structural relaxations established upon interface formation may be described as misfit dislocations which can be investigated using conventional and high resolution TEM. The conditions for obtaining informations at an atomistic scale using HRTEM are critically discussed. Specifically, geometrical restrictions are found to be critical in HRTEM study of {111} interfaces in fee metal -fee oxide systems. Different misfit dislocation networks at {100} interfaces in fee metal - fee oxide systems were observed which may be correlated to the relative strength of metal-anion and metal-cation bonds at the interface. In strongly interacting systems misfit dislocations can possess an equilibrium stand-off distance from the interface. In the system Nb-Al2O3 the interface is shown to be coherent by the registry of atomic columns adjacent to the interface. In this configuration energy is minimized by unbroken strong interfacial bonds and misfit localization in the elastically softer metal.
Metal-Oxide Interfacial Structures Produced By Internal Oxidation
Authors: Lu P. , Tung I.-C. , Cosandey F.
Published: March 2011

Interfaces in Cu/MgO, Pd/MgO, Pd/Al2O3, Ni/NiAl2O4 and Ni/Al2O3 systems produced by internal oxidation have been studied by transmission electron microscopy. For the Cu/MgO system, the MgO particles, with a cube-on-cube orientation with respect to Cu matrix, are faceted with principal faces parallel to {111} lattice planes of Cu and MgO. For the Pd/MgO system, the MgO particles, with a cube-on-cube orientation with Pd matrix, are faceted with interfaces parallel to the {100} and {111} lattice planes of MgO and Pd. Additional plate-like MgO particles with main facets parallel to {111} lattice planes possess a twin orientation relationship with the Pd matrix. Interfaces in Cu/MgO and Pd/MgO systems are all partially coherent with interfacial misfit dislocations. For the Pd/Al2O3 system, various transition oxide phases such as η, δ, and θ-Al2O3 and stable α-Al2O3 phase have been observed. The [1100] direction of α-Al2O3 is parallel to the [110] direction of Pd and the (0001) plane of α-Al2O3 is parallel or nearly parallel to the (110) plane of Pd. The NiAl2O4 spinel phase and Al2O3 phases are formed in Ni-Al alloys under two different oxidation conditions. The NiAl2O4 particles have a plate-like morphology with a cube-on-cube orientation relationship with the Ni matrix, while Al2O3 particles are randomly oriented.
Experimental Determination Of Relaxation Of Interphase Interfaces In Oxide Eutectics
Authors: Dravid Vinayak P. , Ravikumar V. , Dhalenne G. , Revcolevschi A.
Published: March 2011

Interphase interfaces in the directionally solidified eutectics.(DSEs) of NiO-ZrO2(CaO), NiO-Y2O3 and MnO-ZrO2 have been investigated using a variety of TEM techniques. The unique lamellar morphology of the DSEs allows characterization of interfaces and identification of relaxations along multiple directions, aiding visualization of interface structure in three dimensions. Possible low energy interface orientations were identified through examination of facets. The low energy interface planes almost invariably correspond to polar surfaces of adjacent crystals. An attempt has been made to experimentally identify the variety of interfacial relaxation mechanisms using a variety of analytical TEM techniques and only HRTEM results are summarized in this paper. It was found that most of the DSE systems exhibit very little relaxation and possess tight interface cores.
TEM Study of (015) Growth Twins in The Bi-Sr-Ca-Cu-O Superconductors Obtained by Melt Quench Technique
Authors: N Ohnishi , M Sankararaman , H Sato
Published: March 2011

A new type of twin structure is found to exist quite commonly in the Bi2Sr2CaCu2O8+δ superconductor obtained by annealing melt quenched amorphous precursors. From transmission electron microscopy and electron diffraction, the twinning plane is determined to be the (015) plane (disregarding the period of incommensurate modulation in the b-direction). Further, the twin boundary is found to be coherent with a specific coincidence condition. The analysis of the morphologies indicates that the twins nucleate at the early stages of the grain growth in these materials.
Simulation of Y-Ba-Cu-0 Epitaxial Growth and Microstructure Formation
Authors: Burmester C. P. , Wille L. T. , Gronsky R.
Published: March 2011

The results of systematic computer simulations of the deposition and growth of Y-Ba-Cu-0 thin films is reported. The deposition process is modeled by means of a three-step Monte Carlo simulation incorporating one sorption deposition mode and two modes of film annealing addressing surface and bulk diffusion. The simulation is used to investigate the evolution of surface morphology and film microstructure, growth rate anisotropy, and the dependence of film texture on deposition parameters. Characteristic defects and surface morphologies observed by simulation are found to be in good agreement with those observed experimentally. It is observed that surface kinetics can dominate the evolution of film microstructure.
Defect Structures in Epitaxially Grown InAs Films on InP Substrates
Authors: Ballal A. K. , Salamanca-Riba L. , Partin D. L. , Heremans J. , Green L. , Fuller B. K.
Published: March 2011

In this paper we study the lattice-mismatch induced defect structures of InAs films grown on semi-insulating InP substrates using metal organic chemical vapor deposition. The defect structure studies were carried out on films of equal total thicknesses but for different duration for nucleation of a layer of InAs deposited at low temperature on the substrate. Misfit strain is caused by the inherent lattice mismatch of approximately three percent and this is partially relieved by the generation of misfit dislocations at the film/substrate interface. Transmission electron microscopy studies show the presence of an intrinsic strain and the generation of thermal etchpits at the heteroepitaxial interface. Our studies show that there is a direct correlation between the density of dislocations generated at the film/substrate interface and the duration of nucleation of the film on the substrate. Dislocation densities at the surface of the InAs films and at the heteroepitaxial interface differed by almost two orders of magnitude. High resolution electron microscopy reveals abrupt and sharp interfaces in films with thick nucleation layers and also confirms that the lattice mismatch is partially accommodated by the generation of misfit dislocations at the film/substrate interface.
Measurement of Viscoelastic Stress Relief in Patterned Silicon-on-Insulator Composite Structures With Raman Spectroscopy
Authors: Létavic T. J. , Maby E. W. , Gutmann R. J. , Petruzzello J.
Published: March 2011

Raman spectroscopy has been utilized to measure room-temperature residual strain in the active device layer of laser-recrystallized silicon-on-insulator (SOI) composite structures. The SOI composite structures were fabricated on synthetic fused-silica substrates, and the composites contained a phosphosilicate glass (PSG) layer to provide high-temperature stress relief. Conventional masking and etching techniques were used to selectively pattern the polycrys-talline silicon layer into isolated square islands prior to recrystallization. The biaxial in-plane stress in recrystallized films was calculated from the measured strain-induced first-order Stokes Raman wavenumber shifts, and the results indicate that 200- μm-square recrystallized silicon islands have significantly lower in-plane stress values than continuous recrystallized silicon films. These measurements provide a preliminary confirmation of the dependence of the time constant for viscoelastic stress relief on the in-plane pattern dimension.
Eigenstresses in Anisotropic Films
Authors: Auricchio Ferdinando , Ferrari Mauro
Published: March 2011

A closed-form solution for a macroscopically homogeneous, fully anisotropie layer subject to non-uniform through-thickness eigenstrain is presented, and employed in determining the three-dimensional deformation and stress states of a thermally loaded ceramic film with microstructure-induced macroscopic anisotropy. The resultant stress field is compared with those that could be deduced by experimental determination of the curvature and the classical structural theories.
Tribological Properties of Superhard PVD Coatings
Authors: Knotek O. , Löffler F.
Published: March 2011

In order to advance the development of extremely hard coatings, new homogeneous and metastable films were prepared by magnetron sputter ion plating (MSIP) and arc ion plating (AIP) in the DC. or RF. mode.

In the present study coatings in the systems Ti-B-C-N, Si-C-N and amorphous carbon coatings (ADLC) were investigated and compared with other hard coatings. Multicomponent layers of different compositions and structures were deposited by varying the reactive gases methane (CH4) and nitrogen (N2) and the dominant process parameters (e. g. C/V-characteristic of the cathode, substrate bias).

X-ray diffraction studies of the Ti-B-C-N coatings revealed either an amorphous structure or crystallization in a hexagonal lattice. The ADLC and Si-C-N coatings were always amorphous. Electron microprobe analysis and auger electron spectroscopy were used to determine the coating compositions.

The tribological properties were determined by a ball on disc tribometer (e.g. friction coefficent), a pin on disc tribometer and a special abrasive wear test.
Metal Reinforced Diamond Composite Films
Authors: Tsai C. , Nelson J. , Gerberich W. , Heberlein J. , Pfender E.
Published: March 2011

A three-step process for producing a composite diamond film is presented. Plasma deposited diamonds are reinforced by an electroplated metal binder and the diamonds regrown to produce a continuous, strongly adhered diamond film on molybdenum and tungsten substrates. Microscratching and pin-on-disk testing indicate that the composite films are more adherent than plasma deposited diamonds alone.
The Indentation Properties of Amorphous Boron Coatings Synthesized by Plasma-Enhanced CVD
Authors: Cooper C. V. , Shuskus A. J.
Published: March 2011

Amorphous boron coatings, ranging in thickness from 4 to 15 μm, have been synthesized via plasma-enhanced chemical vapor deposition using an rf plasma coil having serpentine rather than helical geometry for inductive coupling of the plasma. The power input to the rf coil has been established at five discrete levels ranging from 50 to 200 W during deposition from diborane onto Ti-6Al-4V substrates at 450°C. Deposition rates have been found to depend significantly on coil input power, reach in a saturation level of 15 μm/h at 100 W and higher but decreasing markedly with lower coil power levels. The amorphous nature of the coatings has been confirmed by selected area electron diffraction of extracted particles. Vickers and ultralow-load indentation experiments have been performed on boron coatings in cross-sectional and plan orientations, respectively. The ultralow-load hardnesses of the coatings deposited at all power levels exhibited relative independence from deposition power and ranged from 11.5 to 14.6 GPa. Vickers indentation in cross section produced hardnesses which were significantly greater than those using ultralow loading and an inconsistent dependence on deposition power.
Characterisation of Pointed Indentation Fracture of Thin Silica Films on a Ductile Substrate.
Authors: Samandi M. , Bell T. J. , Swain M. V.
Published: March 2011

Observations are presented of the indentation of amorphous silica films of different thickness on mild steel substrates. The films were prepared by sol—gel dip coating and sintering at 500° C. Indentation of the films with a Berkovich indenter using an ultra micro—indentation hardness system (UMIS) revealed a critical load for the fracture of the thin films. The variation of the fracture load was characterised by a Weibull analysis that gave a mean fracture load and a Weibull modulus. The latter was found to be nearly independent of film thickness whereas the former varied with the square of the thickness.
In Situ Study of Isothermal Strain Relaxation in Si-Ge Heteroepitaxial Films Using Substrate Curvature Measurements
Authors: Gillard Véronique T. , Noble David B. , Nix William D.
Published: March 2011

Understanding die kinetics and mechanisms of strain relaxation in Si-Ge heteroepitaxial films is pertinent to several device applications. In this paper we present a method for determining the evolution of the mobile dislocation density with time during the course of strain relaxation taking place in an isothermal annealing experiment.

Wafer curvature measurements using a laser scanning technique are used to determine the elastic strain after growth in films of variable thickness and to follow the strain relaxation during isothermal annealing experiments. By coupling the strain relaxation measurements with previous TEM measurements of dislocation velocities in this system, the mobile threading dislocation density and its evolution with time are determined.
The Critical Thickness of Layers Subject to Anisotropic Misfit.
Authors: Beanland Richard
Published: March 2011

It is well known that it becomes energetically favourable for misfit dislocations to be introduced into strained epitaxial layers above a certain ‘critical’ layer thickness, hc. To date, theoretical calculations of hc have only been made for cases of isotropie misfit - i.e. cases where the misfit is the same for every direction in the interface. Using a new formulation of the Frank-Bilby equation and the concept of coherency dislocations, it is now possible to treat cases of anisotropie misfit, such as silicon on sapphire (SOS). The method used to obtain the critical thickness is described, and values of hc and equilibrium dislocation density are given for various materials systems.
Strain Shift Coefficients for Phonons in Si-Ge Heterostructures
Authors: Baribeau J.-M. , Lockwood D. J.
Published: March 2011

Strain shift coefficient measurements for longitudinal optical phonons in molecular beam epitaxy grown metastable pseudomorphic Si1−xGex layers on (100) Si (0 < x < 0.35) and Ge (0.80 < x < 1) are reported. Strain in partially relaxed annealed specimens was obtained by double-crystal x-ray diffractometry and the corresponding strain phonon shift was measured by Raman scattering spectroscopy. For epilayers grown on Si it was found that the epilayer Si-Si phonon frequency varies linearly with strain. The magnitude of the strain shift coefficient b however showed a small composition dependence varying from b ≈ -700 cm-1 at x = 0 to b ≈ -950 cm-1 at x = 0.35, corresponding to a stress factor τ = 0.40 + 0.57x: + 0.13x2 cm-1/kbar. For the Ge-Ge vibration mode in epilayers grown on Ge, b decreased from ∼-425 cm-1 at x = 1 to ∼-500 cm-1 at x = 0.8, corresponding to a stress factor τ ≈ 0.52 – 0.14x - 0.08x2 cm-1/kbar.
Structure and Mechanical Properties of Fe/Zr Multilayers.
Authors: Vlassak Joost J. , Nakayama Takenori , Konno Toyohiko J. , Nix William D.
Published: March 2011

Iron zirconium multilayer films have been prepared by sputter deposition and studied using x-ray diffraction, high-resolution transmission electron microscopy and Nanoindenter techniques. The composition-modulation wavelength was varied between 0.8 and 92 nm. For modulation wavelengths greater than 4 nm the multilayers are crystalline with amorphous interfaces; for smaller wavelengths the samples are entirely amorphous. It was not possible to obtain layered structures with wavelengths smaller than 0.8 nm.

Both the hardness and the elastic modulus were measured as a function of composition-modulation wavelength by means of continuous indentation testing. The elastic modulus shows some variation with wavelength; the average value being 131 GPa. The hardness increases sharply when the modulation wavelength decreases below 4 nm. We attribute this increase to die crystalline to amorphous transition that occurs in these films at this wavelength.
Zero Creep Measurements of the Interfacial Free Energy of Ag/Ni Multilayers
Authors: Josell D. , Spaepen F.
Published: March 2011

The free energy γAgNi associated with an interface between layers of silver and nickel has been experimentally determined. Creep tests were conducted on multilayer thin films to determine the load at which the length of the film neither shrank nor stretched. The interfacial free energy was obtained from this zero creep load and microstructural data using a specific model for the grain boundary diffusional creep in multilayers.
Strain Analysis in PbTe/PbMnTe Superlattices by X-Ray Diffraction
Authors: Koppensteiner E. P. , Krenn H. , Frank N. , Bauer G.
Published: March 2011

The strain tensor components of the PbTe and PbMnTe constituent layers of three superlattices grown on (111) oriented BaF2 substrates are determined from an X-ray analysis. Symmetric (222) and asymmetric (426), (224), (244) Bragg reflections were analysed and a generalization of the Hornstra-Bartels model is used, assuming that the SL (superlattice) can be simulated accordingly. Since in the multilayers also the satellites of the symmetric and asymmetric reflections have been considered the strain tensor components were determined with an accuracy of 1.5×10-4. Consequently the Mn-content of the PbMnTe layers could be determined with an accuracy of ± 0.03%.
Stress Calculations in Thin Films and Multilayers Using Distributions of Infinitesimal Dislocations.
Authors: ĢrilhÉ Jean , Junqua Nicole
Published: March 2011

Distributions of infinitesimal dislocations have been used to determine stress components near lateral surfaces of strained multilayers. The nucleation of misfit dislocations at these surfaces are discussed.
Tensile Stress-Strain Properties of a-C:H (Diamond-Like Carbon) thin Films
Authors: Garrett Paul D. , Daniels Brian K.
Published: March 2011

Fundamental mechanical properties of a-C:H (amorphous or “diamond-like” carbon, DLC) thin film coatings have been investigated. Coatings were deposited by a methane-argon RF plasma on polycarbonate films. Tensile stress-strain behavior of the coated polymer was studied using an extensometer to monitor strain. The differences in moduli between uncoated and coated samples were used to calculate apparent coating moduli, which varied from 1 GPA to 82 GPa. The mode of failure was observed via in-situ optical microscopy during deformation. Intrinsic bond strength of the coating/substrate interface was estimated from crack spacings in the deformed coating.
Electromigration in Aluminum Based Interconnects of VLSI-Microcircuits, with and without Preceding Stress-Migration Damage
Authors: Korhonen M. A. , Børgesen P. , Li Che-Yu
Published: March 2011

In the narrow, confined metal interconnects used in the chip level, electromigration flux is resisted by the evolution of mechanical stresses in the interconnects. Recently there has been a growing concern on the effects of preceding stress-migration on the subsequent electromigration damage. We present here an electromigration model, which is able to address the effects of stress-migration and mechanical stresses on electromigration lifetime.
Effect of Hydrogen on Thin Cu/Ti and Cu Films
Authors: Apblett Christopher A. , Ficalora Peter J.
Published: March 2011

Thin films of Cu and Cu on Ti were prepared by sputtering films onto SiO2 substrates. The films were annealed at temperatures between 350 and 400°C in vacuum and hydrogen ambiente. The stress was measured in-situ during the anneals. The stress in vacuum initially was compressive, then became tensile and remained so. The stress in hydrogen started in compression and remained so throughout the anneal. The origin of these stresses is explained as a result of compound formation. In vacuum anneals, TiCu forms during the compressive stage with an activation energy of 1.7 eV, then TiCu3 forms during the tensile stage with an activation energy of 2.5 eV. In hydrogen, a single compound, TiH2, forms under the Cu with an activation energy of 0.93 eV.

Studies on the Cu films indicate that hydrogen reduces the incremental stress formed in the films during annealing. A possible explanation is presented for the stress change in that hydrogen has been shown to assist in annealing dislocations. Experimental evidence of an instantaneous change in the stress state upon the introduction of a new ambient is also presented.
Ceramics as Engineering Materials: Structure-Property-Processing
Authors: Kent Bowen H.
Published: March 2011

Ceramic materials are currently being used in many applications and account for about $26 B of the U.S. economy in low value-added products (glass, refactories, cement, whitewares, etc.) and nearly $4 B of high value-added components (chip carriers, waveguides, capacitors, cutting tools, etc.). There are many new applications of ceramics in high technology engineering systems which will result in significant growth of the ceramics business if the materials research triad Structure-Property-PROCESSING moves from the laboratory to the manufacturing plant. Each component can be classified by function (e.g., thermal, mechanical, electromagnetic, optical, biological, and nuclear); configuration (e.g., film, monolith, composite, porous, and single crystal); or processing route (e.g., powder processing, glass forming, and crystal growth). The opportunities are greatest for those components which have a well established processing science base or an unique fabrication method.

Thirty years of research have shown that the critical physical/chemical properties are strongly related to the structure on one or more levels: few angstroms - crystal structure and phases; 10–100 Å - boundary or grain boundary layers or phases; 1 μm - microstructure (grain size, porosity, interpenetrating phases, etc.); and macro-structure including joining, shape and dimensional tolerances. The major focus of this overview relates to issues of reliability and reproducibility in processing polycrystalline ceramics and the relationship between processing and the control of the structure and properties. Examples considered are those of high value-added components where design and functionality justify improved material characteristics.
UV Photoemission Study of Defect States in Polyethylene Films
Authors: Pong W. , Brandt D. , Sato A. , Imaino W. , Farrow M.
Published: March 2011

Photoemission from evaporated Polyethylene films was measured in the spectral region between 6 and 11 eV. A significant increase in photoemission yield was observed after the films were exposed to O2 and to air containing ozone and ions from a diffuse glow discharge at reduced pressures. The enhancement can be attributed to oxygen and ozone reacting with the defects in the evaporated polyethylene films, which are unsaturated carbon double bonds in the polyethylene chain. For the ozonized polymer films deposited on gold substrates, the photoelectron spectra show a relatively high density of occupied states at 6.8 ± 0.3 eV below the vacuum level of the polymer and a photoemission threshold of 3.8 ± 0.3 eV. The implication of the results to contact charging of polyethylene is discussed.
The Effect of Ionizing Radiation on Nickel-Doped MgO.
Authors: Boldú J. L. , Muñoz P. E. , Tsang K. L. , Abraham M. M. , Chen Y.
Published: March 2011

Defect and impurity valence changes induced by γ irradiation of nickel- doped MgO crystals are studied using magnetic resonance and optical techniques.
Photoplasticity in HgCdte
Authors: Galligan J. M. , Pellegrino J. , Manzur T.
Published: March 2011

A time delay has been observed in HgCdTe in the photoplastic response of these crystals. Both the magnitude of the time delay and the total change in stress, Δσ, are dependent on the wavelength of the light. These observations provide a basis for establishing that the photoplastic process is a dynamic one, in contrast to prior treatments of the problem as a static process. Solution of the kinetics associated with this time delay allow us to show the dynamical character of photoplasticity.
Dynamic Consolidation of Ceramic Powders: Practicalities, Problems, and Prospects
Authors: Gourdin William H.
Published: March 2011

I present an assessment of the technological potential ofshock wave consolidationof ceramic powders as a technique for producing well-bonded, uniform, crack-free monoliths. Current compaction methods are briefly reviewed and the characteristics of the consolidated material are presented. The shock and release histories experienced by powder compacts in simple compaction assemblies are complex and I conclude that such simple assemblies are unlikely to yield structurally sound bodies. Control of the stress history over the entire loading cycle is necessary if the tensile stresses which develop during release are to be reduced to acceptable levels. Such exacting control is difficult to achieve, and becomes increasingly difficult as the peak stresses are increased. The powder must therefore be sufficiently plastic at moderate stresses to permit densification and bonding of the compact without destruction of the compact during release. Not all ceramic powders will satisfy this criterion. Local microstructural modification, including interfacial melting, is limited by the fine particle sizes and large surface areas of many ceramic powders. Production of cohesive, crack-free bodies thus depends upon a complex interplay between shock history, material properties, and powder characteristics which is poorly understood. I conclude that the technology of dynamic consolidation of ceramic powders will be difficult to develop and will have limited applications.
Fast Diffusion of Iron in Single Crystal Rutile and Iron Doped Rutile
Authors: Sasaki J. , Peterson N. L. , De Jonghe L. C.
Published: March 2011

Tracerdiffusioncoefficients of Fe, DFe*in single crystals of rutile and of 0 –2.0% Fe doped rutile were measured. The oxygen pressure dependence of DFe* in pure rutile showed complicated behavior. The values of DFe* may consist of contributions from Fe2+ions diffusing by an interstitial mechanism and from Fe3+ions diffusing by an interstitialcy mechanism in cooperation with tetravalent titanium interstitial ions, Tii. The value of DFe* in Fe doped rutile attains a saturation value when the Fe content reaches about 0.1%, D*Fedecreases drastically when the Fe content exceeds about 0.35%. Complex impedance measurements ofelectrical conductivityindicate the existence of ionic conduction for Fe doped rutile containing less than 0.35% of Fe. The small ionic conductivity relative to the values of D*Fesuggests that only a small fraction of the iron ions are highly mobile. Above 0.35% Fe, the observed drastic decrease in D*Femay result from the formation of a shear structure In highly doped rutile.
Recent Advances in Solid-State Laser Materials
Authors: Moulton Peter F.
Published: March 2011

After some years of relatively little activity, the field of solid-state lasers has again become an important research area. Laser operation has been demonstrated in new combinations of laser-active ions and host crystals to provide wavelength-tunable output and the promise of greatly improved efficiency. This paper will discuss several currently interesting classes of laser materials: divalent-transition-metal-doped, rutile- and perovskite-structured fluoride crystals such as Co:MgF2 and V:KMgF3 , Ti3+-doped materials including Ti:A12O3 and a variety of large-lattice-size garnet crystals doped with Cr3+ and/or Nd3+.
Lightguide Technology Review and Status
Authors: Safi M. A.
Published: March 2011

Remarkable progress has been made in the lightguide technology over the past ten years. The realization of low loss optical fibers approaching intrinsic material limit and long life semiconductor lasers has stimulated rapid deployment of lightwave communication systems. Within the past five years the world wide fiber production capacity has grown from a few thousand to over one million kilometers per year. The impetus for this phenomenal growth can also be traced to recent advances in computer technology allowing low cost processing and storage of a great deal of complex information. This combination of information processing and transmission technologies is bringing a host of new services such as voice, data and visual communications, CATV, videotex and facsimile transmission, over the same network. One could therefore expect an accelerating growth in deployment of lightwave communication systems.
On the Role of Schottky Disorder on the Stability and Structure of (100) Twist Grain Boundaries in Nio
Authors: Wolf D.
Published: March 2011

Recent calculations on (100) coincidence-site lattice (CSL) twist boundaries in the NaCl structure have shown that without point defects these boundaries are only marginally stable. Following an earlier suggestion that point defects are the likely source for the considerable stability of these boundaries observed experimentally for Mgo and NiO, Tasker and Duffy have shown recently that the creation of a Schottky pair can, indeed, stabilize a (100) twist boundary in NiO. In this article a variety of configurations in which one or more Schottky pairs have been created in the perfect CSL or anti-CSL unit cell are investigated. It is concluded that many metastable structures may exist which differ mainly with respect to their different interfacial mass densities and the relative translation of the two halves of the bicrystal.
Characterisation of Thin Lattice Mismatched Heteroepitaxial Layers by XRD
Authors: Halliwell Mary A. G.
Published: March 2011

Many advanced III - V devices require highly strained heteroepitaxial layers less than 25 nm in thickness, with tight specifications on both the layer thickness and composition. In many cases the layers required are close to the critical thickness.

The growth conditions for these thin layers are often extrapolated from established conditions for thicker layers. This method can result in layers which have the incorrect thickness and composition because of the transients which occur as growth commences. To minimise this problem it is desirable to establish growth conditions for layers which are as close to device requirements as possible. X-ray diffraction is capable of measuring layer thicknesses and compositions non-destructively. The minimum measurable layer thickness is usually within a small factor (typically 0.5 to 5 times) of device requirements.

A single x-ray rocking curve is required to determine the thickness and composition of an unrelaxed (strained) layer. At least two rocking curves are required when relaxation is present. This paper discusses the appropriate choice of measurement conditions for a given sample.
Dynamical X-Ray Diffraction Studies of Interfacial Strain in Superlattices Grown by Molecular Beam Epitaxy
Authors: Vandenberg J. M. , Chu S. N. G. , Hamm R. A. , Panish M. B. , Ritter D. , Mancrander A. T.
Published: March 2011

Dynamical X-ray diffraction studies have been carried out for lattice-matched InGaAs/InP superlattices grown by modified molecular beam epitaxy (MBE) techniques. The (400) X-ray satellite pattern, which is predominantly affected by the strain modulation, was analyzed. The strain and thickness of the actual layers including the presence of strained interfacial regions were determined.
Relaxation of Mismatched InxAl1−xAs/InP Heterostructures
Authors: Bennett Brian R. , del Alamo Jesús A.
Published: March 2011

We have investigated the relaxation of intentionally mismatched layers of InxAl1−x-As on InP. The layers were grown by MBE and characterized by double-crystal x-ray diffraction (DCXRD) and variable azimuthal angle ellipsometry. Measurements of DCXRD epitaxial layer peak width show high crystalline quality for layers up to five times the Matthews-Blakeslee critical layer thickness. For thicker layers, relaxation occurs with a change in crystal symmetry from tetragonal to orthorhombic. We attribute this to an asymmetry in misfit dislocation density. Ellipsometry reveals optical anisotropy for mismatched layers in compression, but not in tension.
A Grazing Incidence X-Ray Reflectometer for Rapid Nondestructive Characterization of Thin Films and Interfaces
Authors: Loxley N. , Monteiro A. , Cooke M. L. , Bowen D. K. , Tanner B. K.
Published: March 2011

We describe a novel instrument dedicated to making rapid angular-dispersive grazing incidence X-ray reflectivity measurements. A novel, automatic, optical technique for rapid specimen alignment, is incorporated into the control software. We discuss the information content of diffuse scattering data collected in non-standard modes. Examples of data are presented showing the application to the characterization of semiconductors and metal multilayers. The technique is shown to be particularly powerful for measurement of the thickness of epitaxial films of AlGaAs on GaAs less than 50 nm thick and where high resolution X-ray diffraction becomes impracticable. We demonstrate that, as the method is insensitive to dislocation density, high quality data can be taken rapidly from heavily relaxed multilayers. Minimum criteria for adequate information content in the data are explored and the effect of specimen curvature is examined.
Carrier Mobility and Active Layer Sheet Measurements of Compound Semiconductors
Authors: Denenberg David , Blew Austin
Published: March 2011

This paper describes a compact production line microwave (approx. 10 GHZ) active layer sheet resistivity carrier mobility measurement instrument based on the invention from IBM Watson Labs by Dr. Norman Bras lau. [1]

The Measurement techniques and compound semiconductor wafer measurements will be described.
Growth of GaAs, InxGa1−xAs, and AlxGa1−xAs on GaAs (111)B Substrates by Molecular Beam Epitaxy
Authors: Yang K. , Schowalter L. J. , Laurich B. K. , Smith D. L.
Published: March 2011

We have studied the growth of GaAs, InxGa1−xAs, and AlxGa1−xAs on on-axis GaAs (111)B substrates by MBE. RHEED patterns are used to identify different growth conditions. Using the optimized growth parameters, GaAs and Al0.3Ga0.7As films with surface defect densities (observed under an optical microscope) of less than 50 cm−2 were routinely achieved. No significant differences in surface morphology and carrier concentration were found between As4 and As2 if their mass fluxes are the same. A Hall mobility of 30,000 cm2V−1s−1 at 77 K was obtained for a GaAs film with a free electron concentration of 2×1015cm−3.