bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Magnetic CoZrNb Seed Layers on Pd/Co Multilayers
Authors: Morris Jonathan C. , Liu Wenhong , Lairson Bruce M. 
Published: April 2011

ABSTRACTPd/Co multilayers are candidates as perpendicular magnetic recording media. A softmagnetic underlayer can both improve crystallographic orientation and reduce the magnetostatic energy of recorded domains. Pd/Co multilayers have been deposited onto silicon nitride by DC magnetron sputtering with and without CoZrNb (CZN) seed layers. Cross-sectional transmission electron microscopy shows that the CZN layer imposes a columnar grain structure on the multilayer film through epitaxy. Seeded multilayers have columnar 200Å grains that begin at the CZN interface and extend through the film thickness. In contrast, the grains in unseeded multilayers are not columnar. X-ray rocking curves on the (111) Pd/Co peak show that the CZN seed layer improves the (111) crystallographic texture of the multilayer film. We observe a correspondence between FWHM rocking curve widths in the CZN and the subsequently deposited multilayer. The CZN seeding produces changes in perpendicular hysteresis loops, which are attributed to an exchange interaction and a change in the multilayer amicrostructure due to seeding.
Structural and Chemical Characterisation of Ni/Ti Multilayers with TEM
Authors: Leifer K. , Buffat P.A. , Böni P. , Clemens D. , Friedli H.P. , Grimmer H. , Anderson I.S. 
Published: April 2011

ABSTRACTNi/Ti multilayers were prepared by argon sputtering. We observe changes of latticeparameter, strain, grain size and texture depending on the single layer thickness and thepressure of the sputter gas. Moreover the quality of the layers can be improved by including impurities during the growth of the Ni and the Ti layers. Generally the results show that such additions lead to more planar layers and to structural changes within the individual layers. Although we observe hexagonal Titanium in the as-deposited films, some of the specimens which were prepared for TEM observation reveal an fcc-Ti structure.The chemical composition of the layers has been investigated in a field emission microscope using a probe diameter of nmmC. omposition profiles were determined by evaluating EELS spectra taken at each point in an automated scan, In this way it was possible to determine residual concentrations of Ni in Ti layers lower than 0.5%. In the samples studied the interface width appears to be of the order of 4-5nm and the concentration profiles of Ni—Ti interfaces appear to be different from those of the Ti—Ni interfaces.
Measuring Enthalpies of Formation Using Thick Multilayer Foils and Differential Scanning Calorimetry
Authors: Weihs T.P. , Barbee T.W. , Wall M.A. 
Published: April 2011

ABSTRACTThe exothermic, solid state reaction of Al and Zr has been studied in thick AL/Zr multilayers using Differential Scanning Calorimetry and X-ray diffraction. The multilayersamples were magnetron sputter deposited into highly textured alternate layers of Al and Zr with nominal composition A13Zr. The samples used in this study were 47μm thick with a 427Å period. When samples were isochronally scanned from 25º to 725ºC, a large exotherm at ˜350ºC was followed by one or two smaller exotherms at ˜650ºC. The first exotherm is dominated by a diffusionbased reaction of Al and Zr that produces two phases in isochronal scans: amorphous AI-Zrand cubic A13Zr, and two additional phases in isothermal anneals: A12Zr and tetragonal AI3Zr. The exothermic heat from this multi-phase reaction is measured using isochronal scans and isothermal anneals, and the heat flow is analyzed using a l-D diffusion based model. An average activation energy and a diffusion constant are determined. In the isothermal scans, the total exothermic heat increases linearly with √ime, and layer thicknesses vary linearly with heat.
A Model of Superlattice Yield Stress and Hardness Enhancements
Authors: Chu XI , Barnett Scott A. 
Published: April 2011

ABSTRACTA model is presented that explains the yield stress and hardness enhancements that have been observed in superlattice thin films. The predicted strength/hardness enhancement increased with increasing superlattice period, Λ, before reaching a saturation value that depended on interface widths. The results indicate that superlattice strength/hardness depends strongly on interface widths and the difference in shear moduli of the two components for Λ values below the maximum, and on the average shear modulus for larger Λ.
Enhanced Hardness and Stress-Driven Delamination in Fe/Pt Multilayers
Authors: Daniels B.J. , Nix W.D. , Clemens B.M. 
Published: April 2011

ABSTRACTPolycrystalline Fe/Pt multilayers of varying bilayer period, Λ, were sputter deposited onto SiO2 at room temperature. Film structure was characterized by x-ray diffraction, hardness was determined using nanoindentation, and stresses were examined with wafer curvature. The Fe layers were shown to be predominantly {110} oriented while the Pt layers were mostly {111} oriented. The hardnesses of these multilayer films were enhanced over the rule of mixtures value by a factor of almost 3 and exhibited a dependence on Λ which was similar to that previously observed in epitaxial Fe(001)/Pt(001) multilayers. The hardnesses of the polycrystalline multilayers were higher than those of the epitaxial multilayers, presumably due to grain boundary strengthening in these films. Film stress was large (∼1.5 GPa) and compressive, resulting in buckling-driven delamination of the film from the substrate for films with 40≤Λ≤100 Å. Delamination occurred in the “telephone cord” morphology and was observed in real time. A qualitative discussion of our observations of this delamination mechanism is presented.
Beryllium-Based Multilayer Structures
Authors: Stearns D. G. , Skulina K. M. , Wall M. , Alford C. S. , Bionta R. M. , Makowiecki D. M. , Gullikson E. M. , Soufli R. , Kortright J. B. , Underwood J. H. 
Published: April 2011

ABSTRACTMultilayer (ML) structures composed of Mo-Be, Ru-Be and Rh-Be with bilayer periods of - 6 nm have been grown using dc magnetron sputter deposition. The ML microstructure has been characterized using x-ray diffraction and high-resolution transmission electron microscopy, and the normal incidence reflectivity has been measured at soft x-ray wavelengths.
Tem Study of Crystallization of a-SiC in Contact With Silver
Authors: Zh Nanchang , Sinclair Robert 
Published: April 2011

ABSTRACTMetal mediated crystallization of an amorphous phase has been found in many systems, in which eutectic phase diagrams are formed. It is interesting to know if an amorphous phase containing two elements, which can form compound, can react and form a crystalline compound at a low temperature in contact with metals. In this paper we studied the Ag/Sil−xCx system by transmission electron microscopy(TEM). It was foundthat amorphous silicon carbide was crystallized into cubic SiC at about 800°C in areas containing Ag. The silver diffused and segregated into the a-SiC phase upon annealing. The silver grains in the original deposited layer as well as those segregated act as nucleation sites for the crystallization of β-SiC. A nucleation temperature as low as 800°C was observed.
XPS, AES and Leed Studies of The Interaction Between The Si(100) 2×1 Surface and Cadmium Deposited at Room Temperature
Authors: Santucci S. , Nardo S. Di , Lozzi L. , Passacantando M. , Picozzi P. 
Published: April 2011

ABSTRACTVery thin films of cadmium, with a mean thickness between 1 Å and 500 Å, were deposited by thermal evaporation in ultra-high-vacuum on a Si(100) 2×1 surface held at room temperature. In situ X-ray Photoelectron Spectroscopy and Auger Electron Spectroscopy were performed in order to investigate the interaction between the silicon substrate and the deposited cadmium. In samples with deposited mean thickness up to 3 Å, cadmium and silicon are found to be strongly interacting. In fact both XPS and AES spectra show evident changes in shape and energy position leading to the conclusion that a chemical compound between Cd and Si is formed. No diffusion between cadmium and silicon is observed, so the cadmium atoms deposited after the first 3 Å show a bulk character. The analysis of the first derivative intensity of the Si L23VV and Cd M5N45N45 Auger signals, varying the amount of deposited Cd, indicates the formation of islands in the early stage of the Cd growth. These islands show an amorphous structure as observed by using the LEED spectroscopy.
Electrical Properties of (Zn, Mn) Containing Multilayer Metallizations to p-Type InGaAs/InP
Authors: Leec Patrick W. , Reeves Geoffrey K. , Zhou Wei 
Published: April 2011

ABSTRACTThe specific contact resistance, pc, of Au/Zn/Au, Ni/Zn/Ni/Au, Pd/Zn/Pt/Au and Pd/Mln/Sb/Pd/Au contacts to p-In0.47Ga0.53As/ InP has been measured as a function of layer thickness of Zn or Mn. All of the as-deposited contacts were ohmic, with pc = 1−2 × 10−5 Ω cm2. Increasing thickness of the Zn layer above 200 Å in the Au/Zn/Au contacts resulted in a minor decrease in pc while producing no change in the Ni/Zn/Ni/Au metallization. For the as-deposited Pd/Mn/Pd/Au contacts, the value of pc was independent of thickness of the Mn layer but differences in pc emerged at annealing temperatures of ≥ 250°. The analysis of these structures by RBS has shown an extensive intermixing of the metal layers at an annealing temperature of 450 °. In the Pd/Zn/Pt/Au contacts, the value of pc was reduced to a minimum value of 8 × 10−6 Ω cm2 by annealing at a temperature of 500 °. An examination of the Pd/Zn/Pt/Au configuration by RBS has shown that the Pt layer acted as a barrier for the indiffusion of the Au.
The Influence of a-Si:H/Substrate Interface on Electronic Properties Of Me-a-Si:H - Substrate Structures
Authors: Budaguan B.G. , Aivazov A.A. , Meytin M.N. 
Published: April 2011

ABSTRACTWe have performed the investigations of temperature dependencies of dark conductivity σd(T) in a-Si:H films deposited on different substrates (glass, oxynitride, polyimide film) at the temperature range of 20 °C to 250 °C. The temperature dependence of dark conductivity of a-Si:H on glass and oxynitride demonstrates the “kink” at 80 –160 °C. This “kink” wasn't observed in σd(T) measurements of a-Si:H on polyimide. It has been shown that the appearance of “kink” is connected with substrate material, value of applied electric field and its polarity. The relaxation nature of the “kink” is also suggested. Two transport mechanisms of charge carriers are proposed - transport via material bulk and transport via a-Si:H/substrate interface. It is shown that “kink” occurs when transport via interface becomes predominant. The mathematical simulation of this process is also presented.
The Preparation of Crystalline NbSe2/TiSe2 Superlattices from Modulated Elemental Reactants
Authors: Noh Myungkeun , Thiel James , Johnson David C. 
Published: April 2011

ABSTRACTThree new crystalline NbSe2/TiSe2 superlattice compounds with 43.472±0.005A, 80.66±0.03A and 117.9±0.1Å unit cells in thec direction were prepared through controlled crystallization of Ti/Se/Nb/Se superlattice reactants with different compositional layer thicknesses. Theta-theta and rocking curve data were collected using a theta-theta diffractometer to study the evolution of the initially layered reactants into the crystalline superlattices as a function of temperature. Low angle diffraction data demonstrates that the initial layered reactant contracts in the c-axis direction upon initial annealing and suggests that the interfaces become smoother during this initial interdiffusion. High angle rocking curve diffraction data shows the development of caxis oriented NbSe2fTiSe2 crystal growth perpendicular to the substrate surface. Theta-theta scans show a gradual decrease of the (001) diffraction linewidths of the growing compound as a function of annealing time and temperature indicating an increase in the c-axis domain size. High quality caxis oriented TiSe2/NbSe2 crystalline superlattices result from annealing at the relatively low temperature of 500ºC. The rational synthesis of intergrowth compounds from superlattice reactants as described herein will permit the tailoring of physical properties as a function of compositional layer thicknesses and nativeproperties of the parent compounds.
Some Characteristics of X-Ray Multilayered Thin Films Made with A Plasma Controlled System
Authors: Cilia M. , Yakshin A. , Trambly H. , Vidal B. 
Published: April 2011

ABSTRACTMultilayered structures with small periods were fabricated using RF-magnetron sputtering device. The conditions of deposition and small changes in the plasma during all deposition period was investigated by optical emission spectroscopy. We studied influence of different parameters (pressure, power, sputtered material) to emission lines corresponding to the working gas Ar and W or Si. Structure and properties of multilayers were estimated, using transmission electron microscopy (TEM) and small-angle x-ray (1.54 Å) scattering techniques. The results was compared with emission line intensities of Ar, W and Si and self-bias data written for each layer with computer during multilayer fabrication. Wediscuss X-ray reflection properties of multilayers fabricated under our conditions and correlation of emission spectroscopy analysis data with another parameters of plasma (self-bias).
Residual Stress in Diamond and Amorphous Carbon Films
Authors: Ager Joel W. 
Published: April 2011

ABSTRACTBoth diamond and amorphous carbon films can contain substantial residual stresses (up to 10 GPa and higher) due to a combination of thermal and intrinsic effects. Residual stresses in the films limit the maximum thickness to which films can be grown and can lead to weakening and/or failure of the film/substrate interface. In addition, a quantitative measurement of the residual stress in the film is required for an accurate determination of the film/substrate interface fracture toughness. Spectroscopic measurements of residual stresses in diamond and amorphous carbon films based on frequency shifts of Raman-active phonon modes are presented. The spatial resolution of the technique is 1 μm in the lateral direction. In transparent materials such as single crystal diamond, stress profiles with 10 μm resolution in the axial direction can be measured. Examples of such stress profiles are presented for natural and CVD-grown single crystals. Raman measurements of thermal stress in thin polycrystalline diamond films on metal substrates are presented. Initial, spatially resolved measurements of large, compressive intrinsic growth stresses in high-hardness amorphous carbon films grown by ion beam techniques are presented. The accuracy of the Raman residual stress measurement depends on the film structure and is ±60 MPa for single crystal diamond, ±120 MPa for polycrystalline diamond, and ±500 MPa for hard amorphous carbon.
Local Stress Assessment of CVD Diamond with Micro-Raman Spectroscopy Up To 1200K
Authors: Chen Li-Chyong , Chen Kuei-Hsien , Lai Yen-Liang , Wu Jin-Yu 
Published: April 2011

ABSTRACTRaman spectra in CVD diamond films were measured at room temeprature and at high temperatures up to 1200 K. With micron spatial resolution, variations of Raman line from different crystals in the same sample were observed. Both single-peak and multiple-peak analyses were used to assess the stress distribution within the CVD diamond film. In addition, the evolution of Raman line position, line width, and line intensity was monitored as a function of annealing temperature and isothermal holding time. Both (100) and (111) CVD diamond crystals were studied. The detailed evolution of the Raman line width was found to depend on the crystallographic orientation. The temperature dependence of the Raman spectra for CVD and natural diamonds are compared.
Fracture, Fatigue and Indentation Behavior of Pyrolytic Carbon for Biomedical Applications
Authors: Ritchie R. O. , Dauskardt R. H. , Gerberich W. W. , Strojny A. , Lilleodden E. 
Published: April 2011

ABSTRACTThe fracture, fatigue and indentation properties of pyrolytic carbon, both as a monolithic material and as a coating on a graphite substrate, are described in light of its use for biomedical implant applications, specifically for the manufacture of mechanical heart valve prostheses. From the perspective of determining properties that are important for the prediction of safe structural lifetimes in such prostheses, it is found that by traditional engineering standards, pyrolytic carbon has low damage tolerance, i.e., fracture toughness values between 1 and 3 MPa√m and susceptibility to subcritical crack growth by both cyclic fatigue and stress-corrosion cracking (static fatigue). Subcritical crack-growth rates are evaluated in simulated physiological environments for both through-thickness “long” cracks, and for physically “small” surface cracks, the latter measurements being performed for cracks initiated at hardness indents. The unusual deformation characteristics of indentation in pyrolytic carbon are described based on instrumented microhardness indentation and scanning probe microscopy (AFM/STM) studies.
Threshold Crack Size in A Pyrolytic Carbon for no Growth Under Cyclic Stress
Authors: Ling M A , Sines George H. , Gilpin C. Barclay 
Published: April 2011

ABSTRACTIn this work, the fracture toughness of monolithic pyrolytic carbon and sandwich composites of this carbon on a graphite substrate were measured by a disk-shaped compact specimen and by using a tensile specimen. On this material, a large number of specimens that had small cracks induced by a Vickers diamond indenter were tested under cyclic stress. The existence of a true threshold stress intensity factor range for non-propagation of the cracks was demonstrated. Statistical confidence on pre-cracked specimens was obtained through testing a large number of specimens to a very long lifetime of the order of 109 cycles.
Fracture Toughness and Subcritical Crack Growth in CVD Diamond
Authors: Kant A. , Drory M. D. , Ritchie R. O. 
Published: April 2011

ABSTRACTThe fracture toughness, stress corrosion and cyclic fatigue properties of polycrystalline chemical vapor deposited (CVD) diamond have been investigated on thick (˜100 to 300 μm) free-standing films. Specifically, the fracture toughness, Kc, of diamond was determined using indentation methods and for the first time by the tensile testing of pre-notched fracture-mechanics type compact-tension samples. Measured Kc values were found to be between 5 and 7 MPa-m1/2 by either method and to be apparently independent of grain size and shape. Studies on subcritical crack growth (i.e., at stress intensities less than Kc) indicated that CVD diamond is essentially immune to stress-corrosion cracking under sustained loads in room air, water and acid environments. Corresponding experiments to examine susceptibility to cyclic fatigue are currently being performed using indentation-precracked cantilever beams cycled in three-point bending.
Diamond Films for Tribomechanical Systems
Authors: Boving H. J. , Hänni W. , Maillat M. , Dan J. P. , Niedermann P. 
Published: April 2011

ABSTRACTProgress made in the field of CVD diamond has enabled to strengthen and diversify mechanical applications of these coatings. Although CVD diamond is presently mainly in the laboratory stage, it is possible to recognize the main applications in the field of tribology as follows: cutting tools, metal working tools, bearings and mechanical components. In these 4 areas diamond films can be beneficial, but there are still several problems related to nucleation, adhesion and surface roughness of the coating, to be solved.
Friction and Wear of Amorphous Hydrogenated Carbon
Authors: Heidger S. L. 
Published: April 2011

ABSTRACTUniform amorphous hydrogenated carbon (a-C:H) films with surface roughnesses ranging between 1 nm and 4 nm were produced by radio frequency self biased plasma enhanced chemical vapor deposition (rf PECVD) on > Silicon substrates using 100% methane precursor gas mixture, rf power densities ranging between 0.11 W/cm2 and 1.07 W/cm2, and pressures ranging between 0.67 Pa and 40 Pa. Reciprocating sliding friction experiments were conducted on the a-C:H films with hemispherical, silicon nitride pins in dry nitrogen and in 60% relative humidity. The coefficients of friction and the wear rates of the a-C:H were very low in dry nitrogen, ranging from 0.03 to 0.05, and from 1.1 × 108 mm3/Nm to 2.3 × 10−6 mm3/Nm, respectively. In 60% relative humidity, the initial coefficients of friction were approximately 0.30. However, the steady state coefficients of friction of the a-C:H films ranged from 0.10 and 0.30, depending on the deposition conditions. The wear rates ranged from 2.0 × 10−9 mm3/Nm to 8.9 x 10−8 mm3/Nm in 60% relative humidity. Raman microprobe spectroscopy and Auger electron spectroscopy (AES) revealed that sliding friction was transforming the a-C:H films into a material primarily composed of sp2 bonded carbon with increasing short range order. Qualitatively, the amount of wear which occurred corresponded to the extent that the structural changes progressed. The a-C:H films were further characterized by scanning electron microscopy (SEM) and surface profilometry.
The Erosive Behaviour of Diamond
Authors: Pickles C S James , Coad E J , Jilbert G H , Field J E 
Published: April 2011

ABSTRACTDiamond exists in many forms including natural diamond, synthetic diamond produced at high temperatures and pressures, polycrystalline diamond composites (PCD's) and most recently chemical vapour deposited (CVD) diamond. The liquid impact behaviour of these materials has been characterised in terms of a single and multiple impact damage threshold velocity which was obtained using a jet technique capable of reaching velocities of 600 m s−1. The multiple impact damage threshold velocity is a highly reproducible parameter which is invaluable in comparing the rain erosion resistances of different materials.The sand erosion resistances of the various forms of diamond have also been evaluated using a specially designed sand blasting apparatus at velocities up to 270 m s-1. The extent of damage is quantified by mass and transmission loss as a function of impact velocity.The results of these experiments reveal that the exceptional mechanical properties of diamond cause it to have an equally exceptional response to erosion.
Vibrational Signatures of Diamond Surfaces
Authors: Köhler Th. , Frauenheim Th. , Porezag D. , Pederson M. 
Published: April 2011

ABSTRACTStable clean and hydrogenated diamond (100) and (111) surface reconstructions found by density-functional molecular-dynamics (DF-MD) are characterized by their vibrational properties. For sufficiently large surface slab supercells we have calculated the surface top-three-layer projected vibrational spectra and reproduced the main features obtained from experiments. The various reconstructions of the diamond surface yield rich spectra of surface modes involving excitations of dimers, trimers and chains. We classify most characteristic surface modes and discuss correlations to peaks observed in surface sensitive experiments. The vibrational spectra represent signatures of the considered surfaces that might be used to understand and to classify as grown diamond surfaces.