bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of Rapid Thermal Annealing on LPCVD Polysilicon Films for Piezoresistivity
Authors: Kleimann P. , Berre M. Le , Barbier D. , Pinard P. 
Published: April 2011

AbstractPolycrystalline silicon is used as a transducing material in pressure microsensors. Its piezoresistive properties are strongly dependent on the processing steps and its properties -which define the sensor characteristics- vary sharply with temperature. LPCVD boron implanted polysilicon thin films have been annealed by RTA at 1100°C or below under conditions ensuring a uniform dopant distribution accross the film thickness. The resistivity as well as the gauge factor have been measured and compared with other authors' results. The gauge factor has been measured using the clamped beam technique between room temperature and 200°C with a specially designed apparatus. Technological parameters such as the Temperature Coefficient of Resistance (TCR) and the Temperature Coefficient of the Gauge Factor (TCK) are deduced as a function of doping. It appears that such coefficients do not satisfactorily describe the resistivity and gauge factor behavior at high temperature.
Damageless Magnetron Sputtering Deposition of SnO2:Sb Thin Films with Compensation Methods
Authors: Shin Sung Ho , Song Kug-Hyun , Park Kwang Ja , Ishida Tadashi , Tabata Osamu 
Published: April 2011

AbstractPhenomena and solving methods for damage of Sb-doped SbO2 thin films deposited by RF magnetron sputtering have been investigated by observing in the main the positional difference of film electrical resistivity. A ring plate mask was used to disperse the energetic particles and sputtering parameters were controlled such a manner that effects by the parameters were compensated each other. By the control, positional differences in resistivity and XRD patterns of the films could be reduced to a minimum value; The films became nearly uniform ones.
Microstructure and Electrical Properties of Zinc Films on InP
Authors: Kamiinska E. , Piotrowska A. , Barcz A. , Kasjaniuk S. , Mizera E. , Dynowska E. 
Published: April 2011

AbstractThe interactions between thin films of Zn and (100)InP were analysed with secondary ion mass spectrometry, X-ray diffraction and transmission electron microscopy. Zn was found to penetrate the native oxide on InP surface during deposition, and to form an ohmic contact when deposited on n-type InP. Under heat treatment Zn protrudes into InP, and beneath Zn/InP interface a tetragonal Zn3P2 phase lattice matched to InP grows.
Optical and Electrical Real-Time Characterization of the Color-Switching Process in Thin Film Electrochromic Devices
Authors: Martí J. , Gimeno S. , Lousa A. , Bertran E. 
Published: April 2011

AbstractMultilayer structures for electrochromic devices have been produced using vacuum evaporation and electrochemical deposition, and have been optically and electrically characterized by real time measurements. The deposited structures consist of a five layer stack comprising a transparent electrode (indium tin oxide) on glass substrates, an electrochromic active layer (W03), an electrolyte, a complementary electrochromic film (prussian blue) acting as a reservoir for the active layer, and a second transparent or reflecting electrode. In order to determine the process dynamics, real time transmittance and reflectance spectral analysis on the visible range have been performed using a multiple analysis system (OMA), during colorswitching of the device, in coordination with electrical characterizations of the switching process by current and charge transfer measurements. These measurements were performed as a function of time and of the driving voltage, and provide a means of determining the structural parameters of the device through the switching time and the current transient.
Microstructure and Activity of Thin Films for a Microelectronic Gas Sensor
Authors: Patel Sanjay V. , Dibattistam Michael , Gland John L. , Schwank Johannes W. 
Published: April 2011

AbstractScanning force microscopy is used to study the structure of various sensing films after chemical and thermal treatments. An example chemical modification of the sensing film can be achieved by heating a Pt/Ti sensing film in an oxygen environment. 1 With Pt acting as a catalyst, the Ti can become partially oxidized, resulting in a Pt/TiOx film which has different electronic properties than a metallic film. By further oxidizing the film, an insulating layer of TiO2 may be achieved. Or as in the case of hydrogen sensing, the Pt/TiOx film may revert to a more metallic state via the reduction of TiOx. The chemical interactions of these sensing films may be associated with large scale microstructural changes. The sensing activity and the structure of Ti, Pt/Ti, and Au/Ti films to gases such as hydrogen, and propylene has been studied. These chemical and morphological changes can be monitored by measuring the resistance of the thin sensing films. Pt/Ti films were found to have the best response to hydrogen (200 ppm) and propylene (150 ppm), while Au/Ti films showed weaker response to propylene (500 ppm) and CO (1000 ppm). The Pt/Ti films also showed shifts in temperature with changing propylene concentration possibly due to catalytic combustion.
X-ray Diffraction and Modelling Studies of Multilayer SnO2 Thin Film Gas Sensors
Authors: Depero L. E. , Perego C. , Sangaletti L. , Sberveglieri G. 
Published: April 2011

AbstractStructural studies have been carried out on SnO2 multilayer thin film grown by the Rheotaxial Growth and Thermal Oxidation method on A120 3 substrates. A preliminary analysis of the X-ray diffraction patterns shows that, in addition to the Sn0 2 cassiterite phase, a strong contribution from an orthorhombic Sn02 phase is present.In the case of the 3-layer film, the orthorhombic phase is structurally and microstructurally stable after an annealing up to 32 h at 400 'C. The cation coordination is similar to that found in cassiterite, but the chains of edge-sharing [SnO6]8- octahedra run in a zig-zag fashion along the [100] direction, each straight unit containing four octahedra. The relationship between the two phases is discussed on the basis of structural simulations including twinning planes in the crystal structure.
Morphology and Domain Structure of Unsupported PbTiO3Thin Films Prepared by Sol-Gel Process
Authors: Lu C. J. , Ren S. B. , Shen H. M. , Wang Y. N. 
Published: April 2011

AbstractThe morphology and domain structure of unsupported PbTiO3thin films with fine grains (>200 nm) were investigated by TEM technique. The unsupported PbTiO3thin films were successfully prepared by sol-gel process onto NaCI substrates and followed by dissolving away the substrates. Electron diffiraction patterns showed that the unsupported PbTiO3thin films had slight <110> preferred orientation perpendicular to the film surfaces. Grain size and morphology vary significantly with the thickness of the films or the annealing temperatures. Even though the grain size is rather small (40–180 nm), the domains are clearly visible. Most of the grains show single domain, while some irregular and curved domain walls appear only in a small portion of the fine grains. The number of single-domained grains increases with decreasing grain size. Almost all domain walls observed are 90° walls.
Composition Control of Lead or Bismuth Based Ferroelectric Thin Films Prepared by Sputtering Method
Authors: Yamakawa K. , Trolier-McKinstry S. , Dougherty J. P. 
Published: April 2011

AbstractComposition control in lead or bismuth based ferroelectric thin films was studied for rf magnetron, dc magnetron and ion beam sputter depositions with metal or oxide targets. For room temperature depositions, (1) control of the target surfaces, (2) suppression of harmful effects from negative ions and (3) control of oxygen content in the films were significant. The surface of the lead target gradually degrades and alters the lead flux extracted from the target. At low pressures resputtering from the film occurs by negative oxygen ions. It is necessary to put more oxygen into the films in the sputter depositions with metal targets and the ion beam sputter depositions. For high temperature depositions, a composition self control was observed for films deposited in excess lead environments.
A Microstructural Model of the Electrical Failure of an Interconnect Resulting from Flux Divergences
Authors: Rickman J. M. , Smith D. A. , Nichols C. S. 
Published: April 2011

AbstractA simplified microstructural model of an interconnect is considered in order to develop a criterion for failure due to void production induced by electromigration. The kinetics of growth of individual voids at grain triple junctions are calculated and the time dependence of the change in conductance of an interconnect estimated from the time dependence of the total volume of voids produced. It is found that the time to failure increases with increasing grain size, i.e., decreasing density of sites for flux divergence, consistent with observations.
Representation of Finite Cracks by Dislocation Pileups: An Application to Atomic Simulation of Fracture
Authors: Shastry Vijay , Farkas Diana 
Published: April 2011

AbstractThe elastic displacement field solution of a semi-infinite crack in an anisotropic body, calculated using a complex variable approach due to Sih and Liebowitz, is usually used by atomistic simulations of fracture. The corresponding expression for the displacement field of a finite crack is numerically cumbersome since it involves multiple square roots of complex numbers. In this study, displacement field of the crack is calculated by superposing the displacements of dislocations in an equivalent double pileup, equilibrated under mode I conditions. An advantage of this method is its extensibility to atomistic studies of more complex systems containing multiple cracks or interfaces. The pileup representation of the finite crack is demonstrated as being equivalent to its corresponding continuum description using the example of a double ended crack in α-Fe, loaded in mode I. In these examples, the interatomic interaction in α-Fe is described by an empirical embedded atom (EAM) potential.
Dislocation Kink Motion - Ab-Initio Calculations and Atomic Resolution Movies
Authors: Spence J. C. H. , Kolar H. R. , Huang Y. , Alexandera H. 
Published: April 2011

AbstractThe results of recent ab-initio, relaxed, computations for the energy barrier to the motion of a kink on a 30° partial dislocation in silicon are summarised. The electronic structure and charge density are given. We suggest that the shearing motions involved with ductility and kink motion are controlled by the band structure energy involving valence electrons, whereas the tensile forces involved in fracture depend on both ion-ion and valence forces. Experimental atomic resolution TEM images of dissociated dislocation lines in silicon are discussed. These are formed using “forbidden reflections” with the dislocation lines lying on (111), normal to the electron beam. For images of samples at 600 C recorded at video rates, differences between successive frames reveal the motion of individual kinks, from which the kink velocity and migration energy can be estimated.
An Ab Initio Investigation of a Grain Boundary in a Transition Metal Oxide
Authors: Dawson I. , Bristowe. P. D. , Payne M. C. , Lee M-H. 
Published: April 2011

AbstractWe have used ab initio total energy plane wave pseudopotential methods to perform the first completely ab initio investigation of the atomic and electronic structure of a grain boundary in a transition metal oxide. The ∑ = 15 (210)[001] tilt boundary in rutile TiG2 is studied using the conjugate gradients iterative minimisation technique for performing total energy calculations within the LDA and pseudopotential approximations. The stability of the experimentally observed translation state of the boundary is confirmed, and some insight is gained into its electronic structure.
Cu-Au Alloys Using Monte Carlo Simulations and the BFS Method for Alloys
Authors: Bozzolo Guillermo , Good Brian , Ferrante John 
Published: April 2011

AbstractSemi empirical methods have shown considerable promise in aiding in the calculation of many properties of materials [1,2]. Materials used in engineering applications have defects that occur for various reasons including processing [3]. In this work we present the first application of the BFS (Bozzolo, Ferrante and Smith) method for alloys [1] to describe some aspects of microstructure due to processing for the Cu-Au system (Cu-Au, CuAu3 , and Cu3Au). We use finite temperature Monte Carlo calculations, in order to show the influence of ’heat treatment‘ in the low-temperature phase of the alloy. Although relatively simple, it has enough features that could be used as a first test of the reliability of the technique. The main questions to be answered in this work relate to the existence of low temperature ordered structures for specific concentrations, for example, the ability to distinguish between rather similar phases for equiatomic alloys (CuAu I and CuAu II, the latter characterized by an antiphase boundary separating two identical phases).
Some Computer Simulations of Semiconductor Thin Film Growth and Strain Relaxation in a Unified Atomistic and Kinetic Model
Authors: Madhukar A. , Yu W. , Viswanathan R. , Chen P. 
Published: April 2011

AbstractAn overview is provided of an evolving atomistic and kinetic model of semiconductor growth that unifies the main features of strain relaxation in low and high lattice misfit heteroepitaxy. The model reveals a kinetic pathway for dislocation formation during growth with little or no energy cost at low misfits, thus providing a way out of the longstanding dilemma of too high dislocation nucleation energies predicted by classical theories of the equilibrium behaviour of a fixed number of particles at low misfits. The essential kinetic processes underlying the model are identified on the basis of comparison of the predictions of kinetic Monte-Carlo simulations of growth with real-time or in-situ data obtained in such experiments as reflection high-energy electron diffraction (RHEED) and scanning probe microscopy (SPM). Relative significance of these atomistic kinetic processes is shown to naturally lead to strain relaxation via defect initiation at low misfits while maintaining smooth surface morphology or at high misfits change to 3-dimensional morphology while initially maintaining coherence. The potential role of steps in providing sources for defect formation is examined through molecular dynamics simulations of Ge overlayers on Si (001) stepped surfaces.
Embrittlement of Cracks at Interfaces.
Authors: Emeritus Robb Thomson , Carlsson A. E. 
Published: April 2011

AbstractThis paper presents a synopsis of already published work for cracks on interfaces and new results on the effect of changing the chemistry of the atoms at the interface. Once the appropriate cut-off for the oscillatory singularity in the interface analysis is determined, the physics of the crack is determined in terms of an appropriate driving force for a particular event of interest, and a lattice resistance to the event. Analytic approximations are available for the driving forces, and the lattice resistance is determined on the basis of a block construction for the lattice. We show that for the case where the chemical bonding at the interface is different from that in the matrix, the same ideas are applicable, provided the different chemistry is incorporated correctly in the lattice resistance construction.
Mixed Mode Interface Toughness Of Metal / Ceramic Joints
Authors: Wei Yueguang , Hutchinson John W. 
Published: April 2011

AbstractA mechanics study of the interface toughness of joints comprised of ceramic substrates joined by a thin ductile metal layer is carried out for arbitrary combinations of mode I and mode II loading. The crack lies on one of the metal/ceramic interfaces, and the mechanism of separation at the crack tip is assumed to be atomic decohesion. The SSV model proposed by Suo, Shih and Varias is invoked. This model employs a very narrow elastic strip imposed between the substrate and the ductile layer to model the expected higher hardness of material subject to high strain gradients and possible dislocation-free zone in the immediate vicinity of the crack tip. The criterion for crack advance is the requirement that energy release rate at the crack tip in this narrow elastic strip be the atomistic work of fracture. The contribution of plastic dissipation in the metal layer to the total work of fracture is computed as a function of the thickness and yield strength of the layer and of the relative amount of mode II to mode I. Ductile joints display exceptionally strong thickness and mixed mode dependencies.
The Non-Linear Behaviour Of A Model Related To The Fracture Of Composite Materials
Authors: Varone Alberto , Meloni Franco , Ginesu Francesco , Aymerich Francesco 
Published: April 2011

AbstractThe fracture of a fibre reinforced graphite peek polymer is considered when dynamic load is applied. The energy-time diagram shows various critical points during cyclic tensile loading. A quantitative analysis based on the study of the fractal dimension of the chaotic attractor in the representative phase space will allow us to individuate the physical parame ters responsible of the stability range of the material. A new simple model has been derived and successfully tested from a non-linear chaotic scheme. The present approach appears very promising for a future interdisciplinary study for evaluating the physical response of real massive materials under stress.
On The Response Of Dynamic Cracks To Increasing Overload
Authors: Gumbsch P. 
Published: April 2011

AbstractOne of the most interesting questions in the dynamics of brittle fracture is how a running brittle crack responds to an overload, i.e. to a mechanical energy release rate larger than that due to the increase in surface energy of the two cleavage surfaces. To address this question, dynamically running cracks in different crystal lattices are modelled atomistically under the condition of constant energy release rate. Stable crack propagation as well as the onset of crack tip instabilities are studied.It will be shown that small overloads lead to stable crack propagation with steady state velocities which quickly reach the terminal velocity of about 0.4 of the Rayleigh wave speed upon increasing the overload. Further increasing the overload does not change the steady state velocity but significantly changes the energy dissipation process towards shock wave emission at the breaking of every single atomic bond. Eventually the perfectly brittle crack becomes unstable, which then leads to dislocation generation and to the production of cleavage steps. The onset of the instability as well as the terminal velocity are related to the non-linearity of the interatomic interaction.
Scaling And Universality In Real Cracks
Authors: Daguier Pascal , Bouchaud Elisabeth 
Published: April 2011

AbstractThe morphology of fracture surfaces in complex metallic alloys is analysed. The simultaneous use of Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) allows the measurement of the universal roughness exponent ζ┴ = 0.78 over five decades of lengthscales (0.5 nm - 0.5 mm). Furthermore, a small lengthscales regime (lnm - 1 μm) is shown to be characterised by a roughness index ζ┴QS ≃ 0.5.On the other hand, cracks fronts stopped during their propagation at pinning microstructural obstacles in two different metallic alloys is analysed, and their “in-plane” roughness index is determined for the first time. In the case of the 8090 Al-Li alloy, which has a very anisotropic microstructure, the roughness of the tensile crack front propagating along the grains length is equal to ζ ≃ 0.60. On the other hand, the roughness of the purely three-dimensional fatigue crack front in the Superα2 Ti3Al-based alloy is equal to ζ ≃ 0.54.
Atmospheric Pressure Chemical Vapor Deposition of 3C-SiC
Authors: Russell Michael W. , Freitas Jaime A. , Berry Alan D. , Butler James E. 
Published: April 2011

ABSTRACTOptically transparent SiC deposits were grown via atmospheric pressure chemical vapor deposition (APCVD) on graphite substrates from methyltrichlorosilane (MTS) in hydrogen in a cold-walled, RF-induction furnace. Structural morphology was examined by scanning electron microscopy and correlated to substrate temperature, MTS/H2 ratio, and hydrogen flow. Photoluminescence revealed that high quality cubic material was grown. The PL spectra exhibited a zero phonon line (2.3787 eV) attributable to an exiton bound to a neutral nitrogen donor, in addition to TA, LA, TO, and LO phonon replicas. Observed broadening and splitting of the PL spectral lines was associated with the morphological habit and internal strain of individual crystallites. In addition, the PL spectra for samples grown at higher MTS/H2 ratios and low H2 flows exhibited weak shoulders on the low energy side of the five-line spectra which might be associated with nonstoichiometric defects such as Si interstitials or C vacancies.
Adhesion of ZrN And SiC Thin Films on Titanium and Nickel Alloys
Authors: Gruss K. A. , James R. D. , Davis R. F. 
Published: April 2011

ABSTRACTChemically inert ceramic coatings are currently being investigated to extend the lifetime of metallic components operating in severe environments. Polycrystalline ZrN and amorphous SiC coatings were deposited by cathodic arc evaporation and by PACVD, respectively, on Titanium Grade 12 and Incoloy 825 metal substrates. The structure of the coatings was verified by SEM and XRD. Residual stress analyses were performed on the ZrN coatings via XRD using the sin2 φ method. Compressive stresses of 3.7 GPa and 2.5 GPa were calculated in the ZrN on the Incoloy and Titanium substrates, respectively. Studies of the interfacial chemistry via AES revealed chemically abrupt interfaces. Scratch tests were employed to assess the critical load for interfacial failure and fracture mechanisms for the various coating systems. Critical loads, charaterized by a kidney-shaped crack patterns found in the scratch tracks, occurred at 12 N for ZrN on Titanium and 20 N for ZrN on Incoloy. Interfacial failure of SiC on Titanium was dominated by brittle fracture of the SiC coating at 3N loads.
Processing and Mechanical Properties of SiC-Metal Interpenetrating Composites
Authors: Hozer Leszek , Chiang Yet-Ming , Ivanova Svetlana , Bar-On Isa 
Published: April 2011

ABSTRACTIn this paper we demonstrate a liquid exchange process to introduce a ductile metal reinforcement phase in the amount of 10–30 vol. % into reaction-bonded silicon carbides (RBSCs). Immersion of RBSC in pure Al or Al-Si melts enables diffusional replacement of secondary phase silicon with metal. The Al and Al-Si exchanged composites show improvement in fracture toughness (single edge precracked beam technique) to 6–7 MPa·m1/2 as compared to 3–4 MPa·m1/2 in otherwise similar siliconized silicon carbide. Increased fracture strength (four point flexure) was also observed after the liquid exchange process.
The Reaction of NH3 With TiN: Implications for CVD
Authors: Schulberg Michelle T. , Allendorf Mark D. , Outka Duane A. 
Published: April 2011

ABSTRACTSince NH3 is an important component of TiN chemical vapor deposition (CVD) processes, understanding the NH3/TiN surface interaction is crucial to developing a model for the overall reaction. Temperature programmed desorption experiments show that NH3 adsorbs molecularly on amorphous TiN surfaces. Chemisorption occurs at only ∼5% of the surface sites, with an activation energy for desorption of 24 kcal/mol. The sticking probability into this state is 0.06 at 100 K. In addition, NH3 adsorbs with high probability into a multilayer state with an activation energy for desorption of 7.3 kcal/mol, similar to that found in other systems. NH3 does not dissociate on TiN. Under CVD conditions, however, the reactivity of NH3 on TiN may increase and surface reactions may play a part in film growth.