bluuebunny/crossref_metadata_2025_split huggingface dataset:
Universality of Dielectric Response as an Aid to Diagnostics
Authors: Jonscher Andrew K 
Published: April 2011

ABSTRACTThe advent of frequency response analysers and the formulation of the universality of dielectric responses have between them greatly enhanced the usefulness of dielectric measurements as a diagnostic tool. The available frequency range was extended to between eight and twelve decades, making it possible to determine spectra with some precision. In addition, we now have a much more complete understanding than was available previously of the significance of various spectral shapes. For charge carrier systems the universal approach is based on the fractional power law of frequency dependence of the real and imaginary components of the susceptibility , where the exponent falls in the range O < n < 1. Values of n close to unity correspond to low-loss behaviour, values close to zero to very lossy processes dominated by low-frequency dispersion (LFD). Examples will be presented of both extremes and an indication will be given of the theoretical significance of these results. A brief discussion will be given of the physical principles of low-loss dielectrics showing “flat” or frequency-independent χ and of the opposite limit of LFD. It will be shown how the presence of universality simplifies the analysis of data and their interpretation.
Very Low Loss Ceramic Dielectric Resonator Materials
Authors: Alford N McN , Penn S J , Templeton A , Wang X , Filhol P , Klein N , Zuccaro C. , Gallop J C 
Published: April 2011

ABSTRACTThe huge increase in the use of microwave communications places severe constraints on the operating performance of the microwave filters. Dielectric resonators are a very attractive option as they can be prepared with very low dielectric loss, moderately high dielectric constant and a low temperature coefficient of the resonant frequency. In filters they possess very low intermodulation products and are capable of handling high power. Certain dielectric oxide single crystals display very low loss at microwave frequencies and on cooling the loss is generally observed to drop. The Q of sapphire at 10 GHz exceeds 107 at low temperatures of around 10K. However, single crystals are expensive and the purpose of this research is to explore inexpensive, sintered polycrystalline alternatives. By very careful attention to purity, processing and microstructure Q values approaching those of single crystals have been achieved. The loss of polycrystalline ceramics of Al2O3, Ba(Mg1/3Ta2/3)O3 (BMT) and Zr0.875Sn0.25Ti0.875O4 (ZTS) has been studied. Alumina, Al2O3 has been studied as a model material for dielectric loss. Theory predicts that the loss in single crystal sapphire should follow a T5 dependence. However at low temperatures the loss is dominated by extrinsic losses due to crystal imperfection, residual dopant atoms, dislocations and other lattice defects and the T5 dependence does not hold. In polycrystalline alumina the intrinsic loss is immediately masked by these extrinsic losses, even at room temperature, and a simple T dependence is observed. Results on polycrystalline alumina show that a Q of > 5×104 at 10 GHz and at room temperature are possible and Q's well in excess of 105 at 10 GHz and 77 K can be achieved.
Impedance Spectroscopy of Nanocrystalline Y-Stabilized Tetragonal Zirconia
Authors: Mondal P. , Hahn H. 
Published: April 2011

ABSTRACTImpedance Spectroscopy, X-Ray Diffraction and High Resolution Scanning Electron Microscopy have been used to study the effect of extremely fine grain size on electrical properties such as dc-conductivity and activation energies in nanocrystalline Y-stabilized tetragonal zirconia. The samples were prepared from powders produced by the Inert Gas condensation method. X-Ray Diffraction was used to characterize phase and average grain size of the sample. In addition, grain size and microstructure of the sample was examined using High Resolution Scanning Electron Microscopy. With Impedance Spectroscopy relaxations of O−2-ions in the lattice and in the grain boundaries could be resolved. The dc-conductivities of the lattice and the grain boundaries were deduced from the data. The activation energies for ac- and dc-conductivity of the lattice and grain boundary relaxation are reported.
Stability and Conductivity of Gd2((Mo1/3Mn2/3)xTi1-x)2O7
Authors: Sprague J. J. , Porat O. , Tuller H. L. 
Published: April 2011

ABSTRACTA composite solid state electrochemical device, with (Gd1-xCax)2Ti2O7 serving as the electrolyte and Gd2(Ti1-xMox)2O7 (GT-Mo) as the anode has recently been proposed. The latter exhibits high levels of mixed conduction under reducing atmospheres, but decomposes at high Po2. We have recently succeeded in extending the stability limits of the GT-Mo to higher Po2 with the addition of Mn. In this study, we report on the conductivity and stability of Gd2((Mo13Mn2/3)xTi1-x)207 (GMMT) as a function of Po2, T, and composition utilizing impedance spectroscopy and x-ray diffraction. The addition of Mn extends the stability region of the material to Po2 = 1 atm with little change in the magnitude of the conductivity. Defect models explaining the dependence of the conductivity on oxygen partial pressure are presented. Preliminary results from the use of an electronic blocking sandwich cell used to isolate the ionic conductivity of GMMT are also presented.
Formation of Dislocations in NiAl Single Crystals Studied by In Situ Electrical Resistivity Measurement
Authors: Sun Y. Q. , Hazzledine P. M. , Dimiduk D. M. 
Published: April 2011

ABSTRACTThis paper reports experiments in which in situ electrical resistivity measurements were used to monitor the formation of dislocations in initially dislocation-free NiAl single crystals. The electrical resistivity is found to exhibit an abrupt jump at the onset of plastic yielding. This is interpreted to result from an abrupt nucleation of a massive density of dislocations at the yield point.
In-situ Characterization of Laser Deposited Fe/Ag Multilayers by a Combination of Time-of-Flight, Rheed and Resistance Measurements
Authors: Fähler Sebastian , Weisheit Martin , Krebs Hans-Ulrich 
Published: April 2011

ABSTRACTFe/Ag multilayers, prepared by pulsed laser deposition (PLD) using KrF radiation, were characterized in-situ by RHEED (diffraction of high energetic electrons) and resistance measurements during deposition, and by X-ray diffraction after deposition. While the x-ray diffraction experiments give indications for sharp interfaces, the in-situ investigations clearly show an asymmetry of the structural behaviors at the interfaces and mixing effects on a nm scale, especially as soon as Fe is deposited on Ag. Time-of-flight (TOF) measurements performed with a Faraday cup show that during PLD in ultrahigh vacuum ions are deposited with kinetic energies of more than 100 eV. The results are modeled and discussed with respect to implantation and mixing effects due to the high kinetic energy of the deposited particles during PLD.
In Situ Plasma Characterization of Laser-Ablated BaxSr1-xTiO3
Authors: Venizelos D. T. , Sengupta S. , Sausa R. C. 
Published: April 2011

ABSTRACTHigh speed imaging and emission spectroscopy are used to characterize the plumes generated from the ablation of bulk barium strontium titanium oxide material in vacuum and 30–60 mTorr of O2 using a pulsed 248-nm laser with fluences ranging from 5–8 J/cm2. High speed imaging reveals that in vacuum the leading edge of the plume expands normal to the substrate surface with a velocity of 19.7 km/sec. The ratio of distance traveled to the plume's radius is ˜ 2 at the early stages of the expansion and 3.2 at the later stages near the substrate. Similar observations are observed when the plume expands in 30 mTorr of O2 for times less than 2.0 μsec. However, at times greater than 2.0 μsec the plume's expansion is retarded due to collisional momentum transfer and reactions with the background gas. This effect is more pronounced when the plume expands in 60 mTorr of O2. Blast wave theory is used to model these results. Time-resolved emission spectroscopy of Ba(I) lines in the 735–770 nm region reveals that the plume' electron temperatures, Te, in a vacuum expansion range from 18000±2000 K at 0.1 μsec to 15000±1500 K at 2.0 /μsec. In contrast, in 30 mTorr of O2 the values of Te range from 17000±2000 K at 0.1 μsec to 4000±500 K at 8.0 μsec. At 0.1 μsec the plume's electron density is estimated as 1.7±0.4 × 1017 cm−3 in both vacuum and 30 mTorr of O2. We also determine the Stark broadening of the Ba(I) line at 746 nm to be 0.5±0.1 Åat an electron temperature of 1 eV and an electron density of 1017 cm−3.
In situ Monitoring of the Effects of Gas Mixtures on Ion Beam Depositions of Diamond-Like Carbon Films
Authors: Wu R. L. C. , Lanter W. , Monreal R. , Kosel P. B. , Miyoshi K. 
Published: April 2011

ABSTRACTA quadrupole mass spectrometer and a total ion-current measuring device have been utilized to monitor the ion compositions of gas mixtures of CH4/H2 and CH4/H2/O2 during the deposition for quality control and process optimization. An ultra high vacuum system using a 20 cm diameter RF excited (13.56 MIfz) ion gun and a four-axis substrate scanner has been developed for deposition of diamond-like carbon films for electrical, optical, and tribological applications. At a constant RF power of 179W, the mass spectra of gas mixture CH4/H2 (1:2.5) showed the most abundant ion is CH3+. Addition of O2 to the ion source has been found to affect the adhesion, deposition rate, and physical and chemical properties of the DLC films. By use of a mass spectrometer with and without the electron beam, the degree of ionization of CH4 was calculated to be about 10%. As the concentration of O2 was increased, all hydrocarbon ions decreased and H3O+ increased, resulting in a decrease in the film growth rate and an increase in etching of Si and glass substrates. In general, the optical bandgap, adsorption coefficients and refractive index decreased as oxygen concentration increased. Raman spectra showed the G-peak position shifted toward the graphitic peak with narrow peak width as oxygen concentration increased. At ultra high vacuum, the coefficient of friction increased with increased adhesion on substrates as oxygen was increased.
Real-Time Feedback Control of Thermal CL2 Etching of GaAs Based on In-Situ Spectroscopic Ellipsometry
Authors: Parent T. , Heitz R. , Chen P. , Madhukar A. 
Published: April 2011

ABSTRACTIn-situ, real-time, spectroscopic ellipsometry (SE) is utilized to study thermal chlorine etching of GaAs in an all ultra-high-vacuum interconnected growth and etching system. In the low temperature (between ˜40°C and ˜120°C) range, the etch rate is found to exhibit an Arrhenius dependence on substrate temperature with an activation energy of 11.6Kcal/mole and to be proportional to essentially the square root of the chlorine pressure. An SE feedback based real-time etch process control algorithm is developed and successfully implemented on the basis of the above noted input - output relation derived from the experimental data base.
Nano-Scale Viscoelastic Properties of Polymer Materials
Authors: Asif S. A. Syed , Pethica J. B. 
Published: April 2011

ABSTRACTThe AC force modulation technique in nano indentation has been extended to study the dynamic viscoelastic properties of polymer materials. The frequency and temperature dependent loss and storage modulus, the time-temperature superposition, the mechanical relaxation and the activation energy for the relaxation process can all be directly measured from nano scale contact. The results obtained for PMMA and Polyisoprene are in good agreement with the reported literature results obtained from conventional dynamic testing. The technique is likely to be of particular value for polymer thin films.
Aging Effects on the Durability of Tantalum Nitride Films
Authors: Moody N. R. , Medlin D. , Boehme D. , Norwood D. 
Published: April 2011

ABSTRACTIn this study, nanoindentation and nanoscratch testing were used to determine the effects of annealing and long term aging on the properties and fracture resistance of thin tantalum nitride resistor films on aluminum nitride substrates. These films were sputter-deposited to a thickness of 440 nm. Some films were left in the as-deposited condition while others were annealed or annealed and then aged. X-ray diffraction revealed that sputter deposition created high compressive residual stresses in the as-deposited films which were partially relieved by annealing. Subsequent aging of the annealed films had no effect on residual stress levels. Nanoindentation showed that mechanical properties were unchanged after annealing and after annealing and aging. However, nanoscratch testing showed that annealing markedly reduced the susceptibility to catastrophic failure with no further changes discernible after aging.
Curves of Elasto-Plastic Deformation of Thin Coatings Obtained in Depth-Sensing Indentation Experiments
Authors: Dub S. N. 
Published: April 2011

ABSTRACTA method to obtain curves of elasto-plastic deformation of materials in depth-sensing indentation tests is proposed. Elasto-plastic deformation curves of thin films and brittle materials have been received at room temperature using this method.
Quantitative Measurement of the Effect of Annealing on the Adhesion of Thin Copper Films Using Superlayers
Authors: Kriese M. D. , Moody N. R. , Gerberich W. W. 
Published: April 2011

ABSTRACTNanoindentation at loads from 100 to 750 mN was used to measure the interfacial adhesion energy of sputtered copper thin-films, for which the release of elastic strain energy drives delamination. The as-sputtered films were of four thicknesses, nominally 225 nm, 400 rn, 600 nm and 1000 nm, and were deposited onto Si/SiO2 wafers; one wafer of each two-wafer run was annealed at 600°C for 2 hrs in a nitrogen atmosphere. Subsequently, a nominally 700 nm thick sputtered superlayer of tungsten was deposited over all wafers. The tungsten overlayer was used to promote delamination at the copper-SiO2 interface. The energies for fracture ranged from 1 to 80 J/m2, increasing with increased indentation depth, and a trend of higher adhesion energy for annealed films. The large values of adhesion energy with respect to the thermodynamic work of adhesion are attributed primarily to plasticity and/or void nucleation within the copper film, which appears to be strongly influenced by the constraint of an overlayer.
Fatigue Strength Of Thin Films By Means Of Impact Tester
Authors: Lugscheider E. , Knotek O. , Wolff Christian , Bärwulf Stephan 
Published: April 2011

ABSTRACTMachine parts like rolling bearings or gears are stressed during operation in a changing mechanical strain. This causes wear by impacts and wear by rolling which is marked by the so called surface ruin. The appearance of surface fatigue is based upon structural transformation, cracking and cracking-growth processes and ends with the separation of debris particles caused by the above mentioned permanent changing strain /1/. The final stage, which is equivalent to the component failure, is the so called ‘pitting’ on the technical surface, which is characteristically named ‘surface fatigue’.The impact tester is used for detailed research about failure mechanisms of thin films. Statements about the adherence of hard material coatings under dynamic compressive stress can be made using this test method, due to the possibility to simulate some effects of rolling strain. Therefore a hard metal ball strikes with a frequency of up to 50 Hz onto the surface. The altitude stress can be varied to get a detailed evaluation of fatigue strength under reversal strain.Selected hard material coatings were analized after testing with the described method applying an impact force of 300 N, 500 N and 700 N. In the framework of this presentation MSIP (Magnetron-Sputter-lon-Plating) coatings on titanium- and chromium basis were used. The fatigue defects and the results of this study will be discussed depending on structure and morphology of thin films.
Grain Impingement and Intrinsic Stresses in CVD Diamond
Authors: Nijhawan S. , Rankin J. , Walden B. L , Sheldon B. W. 
Published: April 2011

ABSTRACTIntrinsic stresses in polycrystalline CVD diamond films have been related to restructuring at grain boundaries. It is speculated that reducing the interfacial energy induces an elastic tensile strain. There appears to be a correlation between the evolution of macroscopic stresses in the entire sample and localized, non-homogeneous stresses in the microstructure based on Raman Spectroscopy and x-ray diffraction pole figures. A multistep processing sequence developed previously can help reduce these stresses substantially, by using an intermediate annealing step when the diamond grains are partially coalesced. Our results suggest that small changes in the film microstructure due to annealing can reduce both homogeneous and non-homogeneous stresses.
Annealing Effects On The Microstructure Of Electrodeposited Cu/Ag Multilayered Nanocomposites
Authors: Kong Dan , Zhai Qing , Ebrahimi Fereshteh 
Published: April 2011

ABSTRACTTEM was used to investigate the annealing effects on the microstructure of two electrodeposited Cu/Ag multilayered nanocomposites with bi-layer thickness values of 110nm and 330nm, respectively, as well as electrodeposited pure copper. It was found that silver layers limited the lateral growth of columnar copper grains and possibly acted as sites for nucleation of new copper grains in the as-deposited composites. The refinement of copper grains in this condition is one reason for the much higher strength of these materials in comparison to pure copper. Annealing at 100 °C did not change the microstructure significantly. After annealing at 150 °C, recrystallization occurred in all samples. The degree of recrystallization was dependent on the extent of internal stresses. Recrystallization was complete in the 110nm bi-layer thick composite, which had the highest internal stresses owning to its large Cu/Ag interfacial area. The recrystallization and growth of copper grains can be one reason for the drastic drop of the composites yield strength after annealing at 150°C
Structure And Mechanical Properties Of Reactive Sputter Deposited Tin/Tan Multilayered Films
Authors: Soe W.-H. , Kitagaki T. , Ueda H. , Shima N. , Otsuka M. , Yamamoto R. 
Published: April 2011

ABSTRACTTiN/TaN multilayers were grown by reactive magnetron sputtering on WC-Co sintered hard alloy and MgO(100) single crystal substrates. Multilayer structure and composition modulation amplitudes were studied using x-ray diffraction method. Hardness and elastic modulus were mea- sured by nanoindentation tester. For bilayer thickness (Λ) larger than 80 A˚, hardness are lower than rule-of-mixtures value of individual single layers, and increased rapidly with decreasing Λ, peaking at hardness values ≈33% higher than that at A=43 Å. As a result of analysis the inclination of applied load for indenter displacement on P-h curve (ΔP/Δh), this paper exhibits that the en- hancement of the resistance to dislocation motion and elastic anomaly due to coherency strains are responsible for the hardness change.
Evaluation of Residual Stresses in Thin Films by Means of Micro-Raman Spectroscopy
Authors: Mizuhara Kazuyuki , Takahashi Shinichi , Kurokawa Jyunichi , Morita Noboru , Yoshida Yoshitaro 
Published: April 2011

ABSTRACTThe effects of temperatures on the stress evaluation of boron doped silicon in solid and film forms are investigated. Several techniques, such as fluid cooling to eliminate the temperature raise and/or simultaneous observation of Stokes and anti Stokes peaks to compensate the temperature effects, are applied. The advantages and disadvantages of each method and the abilities and limits of these techniques are discussed.
On The Measurement Of Residual Stress In Thin Films
Authors: Zhao Z. B. , Hershberger J. , Yalisove S. M. , Bilello J. C. 
Published: April 2011

ABSTRACTThis work reports a comparative study on three curvature based techniques for stress measurement in thin films, including double crystal diffraction topography (DCDT), profilometry, and laser scanning technique (LST). These techniques measure different physical quantities. In the former case, the curvature of crystal lattice planes is assessed while in the latter two cases, the curvature of physical surface of a sample is measured. The current experiments use these three techniques to determine the quantities of interest for a variety of films deposited on Si (100) wafers. In general, profilometry and LST produce similar results on surface curvature. For specimens where the residual stresses produces large curvatures of both types (lattice curvature and surface curvature), the results by DCDT and LST agree fairly well. When small to moderate curvatures are present, the two methods deviate to varying degrees on absolute curvatures. Nevertheless, DCDT and LST generally yield similar results on differential curvatures, i.e., the stress induced curvature differentials. When proper consideration is taken for the inherent limits of each technique, both DCDT and LST can be used as valid procedures for stress measurement in thin film-substrate systems.
Determination Of Temperature Dependent Unstressed Lattice Spacings In Crystalline Thin Films On Substrates
Authors: Cornella G. , Lee S. , Kraft O. , Nix W. D. , Bravman J. C. 
Published: April 2011

ABSTRACTX-ray strain analysis via Generalized Focusing Diffractometry (GFD) [1], and the concurrent need for accurate values of the unstrained lattice parameter, are discussed. A new method for determining the unstrained lattice parameter without knowledge of the elastic constants of the sample material is described. Stress measurements at varying temperatures, and extraction of the coefficient of thermal expansion from these measurements, are demonstrated for aluminum and gold films.
Residual Stress Generation During Constrained Sintering Of Layered Ceramic Thin Film Structures
Authors: Busso E. P. , Travis R. P. , Chandra L. 
Published: April 2011

ABSTRACTThis work investigates the sintering kinetics and residual stresses which develop in thin layered ceramic structures when sintered on a rigid substrate. A continuum constitutive framework to model the evolution of the microstructure and stresses in the sintering layers under non-isothermal conditions is presented. The sintering model is used to investigate the constrained sintering behaviour of layered ceramic structures used in solid oxide fuel cells (SOFC). Samples of a 50 μm thick SOFC film were screen-printed on a fully dense yttriastabilised zirconia substrate and then sintered at temperatures ranging from 1100°C to 1300°C. Measured values of relative density and average grain size are compared with model predictions. A correlation between residual stresses extracted from curvature measurements and analytical predictions revealed these stresses to have been mostly relieved during the subsequent cooling by microcrack formation.
Computer Simulation of Stress Distribution in Amorphous SiO2 Thin Films
Authors: Kogure Y. , Doyama M. 
Published: April 2011

ABSTRACTA molecular dynamics simulation of amorphous SiO2 thin films has been made to investigate the structure and internal stress. The atomic configuration of the amorphous structure is investigated through the radial distribution function and the distribution of Si-O-Si bond angles. Distribution of internal stress through the specimen is evaluated from the volume and the shape of the SiO4 tetrahedron, which is the elementally unit of amorphous SiO2.