bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidation Resistant Ceramic Composites: How Weak Interfaces Became Designed Failure Processes
Authors: Kerans Ronald J. 
Published: April 2011

ABSTRACTInterest in ceramic composites arises from their potential for dramatically improved damage tolerance, as compared to monolithic ceramics, while delivering similar high-temperature properties. The remarkable toughening effect resulting from the proper combination of brittle phases is dependent upon the failure process developing in a particular way; matrix cracks must deflect into fiber debonding cracks that run in or near the fiber/matrix interface and permit some relative displacement. In early composites the requirements for crack deflection and good composite behavior seem to have been almost fortuitously satisfied by native C layers; however, the most productive uses of ceramic composites are dependent upon the development of fiber coatings that not only promote the desired interfacial failure, but also satisfy the additional requirement of being oxidation resistant. Though conceptually simple, the management of a failure process—specifically, predetermining the progress of cracks on a very local level—places a very demanding and unprecedented requirement on the materials designer. Historically, the details of fracture events were of interest principally for insight into means of avoiding them. The composite problem imposes the new requirement that we design to promote a special kind of fracture, and control post-fracture fiction within a certain range. This truly is a higher level of sophistication than heretofore attained, and its complexities have deterred many investigators from seriously addressing the problem. Nevertheless, there has been progress both in depth of understanding and in actual achievement of viable systems. Moreover, very interesting properties of several families of materials have been uncovered. These issues will be outlined and discussed in more detail with the objective of developing a broad view of the lessons learned and opportunities revealed.
Interface Characterization Using the Automated-EBSP Technique
Authors: Sutliff John A. 
Published: April 2011

ABSTRACTThe use of the electron back scattering pattern (EBSP) technique of electron diffraction (also referred to as EBSD and BKD) to study microstructure continues to gain popularity in the materials characterization community. The technique's ability to rapidly measure lattice orientation with good relative accuracy provides a statistically powerful tool for investigating the misorientation character of interfaces. It is certainly possible to gather basic misorientation data on thousands of interfaces in only a couple of hours. This invited talk will discuss the detection and characterization of interfaces in polycrystalline materials using the automated-EBSP technique with specific discussion of sub-grain and twin boundaries in deformed and/or annealed materials. This paper will also attempt to demonstrate with data from γγ' Ni-base superalloys that the process of acquiring, with high accuracy, all the spatial, orientation, and chemical information associated with boundaries during an extended data acquisition is a substantial experimental challenge. Combining quantitative image analysis of traditional high-resolution scanning electron micrographs with the EBSP data can help correct some of the distortions commonly encountered in EBSP data.
Control of Grain Boundary Microstructures in Liquid-Phase Sintered Alumina
Authors: Ravishankar N. , Carter C. Barry 
Published: April 2011

ABSTRACTThe elimination of the grain boundary liquid in liquid-phase sintered materials is examined for the case of anorthite liquid in alumina grain boundaries. It is shown that under suitable conditions the liquid can exude from the grain boundary to the free surface. The proposed driving force is provided by the difference in energies and wetting behavior of the grain boundary and the free surface at high temperatures. The results emphasize the importance of the crystallography of the boundary and the nature of free surfaces (i.e., the surface energies) on the exudation behavior.
Temperature Effect on Vapor Phase Etching of Ground Silicon Substrate and Surface Morphology
Authors: He Yifei , Zakaluk Gregory 
Published: April 2011

AbstractWe have been using the low-cost method of fabrication of epitaxial wafer for discrete devices for many years. This low-cost operation is done by eliminating the conventional but costly polishing procedure, instead of using grinding, cleaning and etching processes prior to epitaxy growth. The etching step is needed to remove any residual grinding scratches and possible remaining contamination. In this study, etching is accomplished with HCl gas at a temperature range from 1120 to 1150 °C, at atmospheric pressure. The surface analysis and inspection techniques were used to test residual grinding scratch removal and point defect density. It is found that the temperature effect on the etch rate is small, but the surface morphology with ground pattern is very sensitive to the etching temperature. The study revealed the presence of regions of temperature which the silicon surface has a minimum of grinding scratches and little etch pits. The etching temperature has strong effect on the substrate surface thereby strongly impacting subsequent epitaxial layer morphology. The different morphologies and their temperature dependence can be explained on the basis of the thermodynamics of the surface and role of surface diffusion and evaporation.
SOI Formation from Amorphous Silicon by Novel Gain Enhancement Method
Authors: Yuen C.Y. , Poon M.C. , Chan M. , Qin M. , Chan W.Y. , Shivani S. , Ko P.K. 
Published: April 2011

AbstractLarge grain (> 10 um) poly-Si film has been formed from nickel Metal Induced Lateral Crystallization (MILC) and subsequent high temperature annealing. The fabricated thin film transistors (TFT) have near SOI performance. The new technology has good potential to provide low cost SOI substrates, multi-layer devices and other novel applications.
Homogeneity of Thermally-Annealed Lightly Fe-Doped SI InP
Authors: Avella M. , Jimenez J. , Fornari R. , puente E. De La 
Published: April 2011

AbstractLightly Fe-doped semiconducting InP samples have been rendered semi-insulating by thermal annealing and subsequently studied by Hall effect, Scanning Photocurrent (SPC) and Scanning Photoluminescence (SPL). Hall measurement shows that the semi-insulating conversion is generally associated to an improvement of the mobility. SPL and SPC measurements show that the distribution of both electrically active iron and compensation ratio is homogeneous after annealing. The cooling rate was seen to influence the compensation ratio.
Micro-Raman Study of Charge Carrier Distribution and Cathodoluminescence Microanalysis of Porous gap Membranes
Authors: Tiginyanu I. M. , Kalceff M. A. Stevens , Sarua A. , Irmer G. , Monecke J. , Cojocari O. , Hartnagel H. L. 
Published: April 2011

AbstractPorous layers and free-standing membranes were fabricated by anodic etching of n-GaP substrates in a sulphuric acid solution. Micro-Raman analysis of the interaction between the longitudinal optical phonons and plasmons in porous membranes allowed us to obtain specific information about the electro-optical properties of microstructured GaP. In particular, apart from the carrier exhausted areas surrounding the pores, the existence of conductive regions was demonstrated. A comparative analysis of the secondary electron and panchromatic cathodoluminescence (CL) images evidenced an increase in the emission efficiency caused by porosity. Data concerning the spectral distribution of CL in bulk and porous samples are presented.
Study of GaSb Junction Devices by Cathodoluminescence and Scanning Tunneling Spectroscopy
Authors: Hidalgo P. , Méndez B. , Piqueras J. , Dutta P. S. 
Published: April 2011

AbstractGaSb p-n junctions formed by Zn diffusion in Te-doped n-GaSb single crystalline wafers have been characterized by cathodoluminescence (CL) microscopy and by scanning tunneling spectroscopy. CL plane-view observations of the Zn diffused side enable to study the homogeneity of the diffusion treatment. Spectra recorded by current imaging tunneling spectroscopy (CITS) in the n and p sides of the junction, clearly show the respective conductive behaviour and provide information on the local surface band gaps. Results are related to the diffusion profile measured by secondary ion mass spectrometry (SIMS).
Nondestructive Analysis of Current Gain of InP/InGaAs Heterojunction Bipolar Transistor Structures using Photoreflectance Spectroscopy
Authors: Sugiyama Hiroki , Watanabe Noriyuki , Watanabe Kazuo , Kobayashi Takashi , Wada Kazumi 
Published: April 2011

AbstractInP/InGaAs heterojunction bipolar transistor (HBT) wafers grown by metal-organic vapor phase epitaxy (MOVPE) have been characterized by photoreflectance (PR) spectroscopy. The intensity of PR signals from the InP emitter and InGaAs collector layers of the HBT wafers decreased with increasing emitter growth temperature and showed a linear positive correlation with the HBT current gain. On the other hand, the intensity of PR signals from the n-InP single layers scarcely changed with increasing InP growth temperature. The change in the PR intensity of the emitter and collector layers is expected to reflect the crystal quality of the adjacent InGaAs:C base layer, which determines the HBT current gain. Thus, the present PR method is eminently suitable for the nondestructive analysis of the current gain of InP/InGaAs HBT wafers.
Investigation of Deep Levels in GaP Liquid Phase Epitaxial Layers on Substrates with Vapor Pressure Heat Treatment
Authors: Yu T. J. , Suto K. , Nishizawa J. 
Published: April 2011

AbstractWe fabricated GaP liquid phase epitaxial layers with temperature difference method under controlled vapor pressure (TDM-CVP), successively to GaP substrate annealing at growth temperature (1133K) under various phosphorus vapor pressures around the optimum one (150 torr) for stoichiometric crystallization of GaP. Photocapacitance (PHCAP) and photoluminescence measurements have been carried out for characterizing GaP substrate crystals and the LPE layers and for revealing the mechanism of defect formation. Over one order of magnitude decrease of deep level densities in PHCAP has been observed after substrate crystals are annealed. Compared to the layers on substrates without heat treatment, similar tendency of deep level density deduction has been found in GaP LPE layers on heattreated substrates. In photoluminescence measurements, an obvious decrease of 700nm-band intensity from heat-treated substrates, as well as increases of green band intensities from GaP LPE layers on heat treated substrates, have been observed at 77K. Phosphorus interstitial is suggested to be possibly related to the origin of deep level centers in the GaP substrate crystals. It is considered that during the process of heat treatment at growth temperature, under the optimum phosphorous pressure, the defects in GaP substrate crystals reach an equilibrium state, so that their diffusion to the growth layer decreases greatly.
Interplay of charge, orbital and magnetic order in Pr1−xCaxMnO3
Authors: Zimmermann M. v. , Hill J.P. , Gibbs Doon , Blume M. , Casa D. , Keimer B. , Murakami Y. , Tomioka Y. , Tokura Y. 
Published: April 2011

ABSTRACTWe report resonant x-ray scattering studies of charge and orbital order in Prl−xCaxMnO3 with x=0.4 and 0.5. Below the ordering temperature, To=245 K, the charge and orbital order intensities follow the same temperature dependence, including an increase at the antiferromagnetic ordering temperature, TN. High resolution measurements reveal, however, that long range orbital order is never achieved. Rather, an orbital domain state is formed. Above To, the charge order fluctuations are more highly correlated than the orbital fluctuations. We conclude that the charge order drives the orbital order at the transition.
Synchrotron Small Angle X-ray Scattering Study of Melt Crystallized Polymers
Authors: Georgiev Georgi , Dai Patrick Shuanghua , Oyebode Elizabeth , Cebe Peggy , Capel Malcolm 
Published: April 2011

ABSTRACTIn this paper we report a synchrotron small angle x-ray scattering (SAXS) study of development of structure in semicrystalline Poly(Ether Ether Ketone), (PEEK) and an 80/20 blend with amorphous Poly(Ether Imide) (PEEK/PEI). Samples were treated to dual stage melt crystallization scheme involving initial isothermal crystallization at T1 followed by a second isothermal period at T2 (T1 < T2). Intensity of small angle scattering was measured in real-time. Structural parameters characterizing the lamellar thickness, 1c, long period, L, and SAXS invariant were deduced from the one-dimensional electron density correlation function assuming an ideal, two-phase structural model.
Plastic Deformation and Recrystallization Studied by the 3-D x-ray Microscope
Authors: Jensen D. Juul , Kvick Å. , Lauridsen E.M. , Lienert U. , Margulies L. , Nielsen S.F. , Poulsen H.F. 
Published: April 2011

ABSTRACTA newly developed synchrotron instrument – the so-called 3D X-ray microscope – is presented. The instrument is placed at the Materials Science beamline at ESRF and dedicated to local μm scale structural characterization within bulk materials. In this paper, emphasis is onin situstudies of thermomechanical processing. The potential of the instrument for characterization of single nuclei and grains is described and discussed based on both first results and planned experiments.
Raman Characterization of Composition and Strain in Si1−xGex/Si Heterostructures
Authors: Liu Ran , Tillack B. , Zaumseil P. 
Published: April 2011

ABSTRACTHigh quality epitaxial Sil−xGex/Si (x= 0.09 to 0.27) samples were studied with polarized Raman scattering technique. The LO (longitudinal optical) -TO (transversal optical) phonon mode splitting due to the tetragonal strain imposed by the lattice mismatch between Sil−xGexand Si was observed for the first time in such structures. In contrast to the case of uniaxial stress, the biaxial stress induces a larger strain frequency shift for the LO mode than for the TO mode. The phonon strain shift coefficient for the LO mode was found to be 1010 cm−1, which is larger than most of the values reported in the literatures, and almost composition independent throughout the range ofx≤0.27. We argue that the smaller LO strain shift coefficients indicate that the Sil−xGexfilms used in previous work were partially relaxed.
Real-Time optical Characterization and Control of Heteroepitaxial GaxIn1−xP Growth by P-Polarized Reflectance
Authors: Dietz N. , Ito K. , Lauko I. , Woods V. 
Published: April 2011

ABSTRACTThe characterization and control of thin film growth processes requires improved methods of characterization and understanding of decomposition pathways and surface reaction kinetics under steady-state epitaxial growth involving organometallic precursors. In this contribution we present the application of p-polarized reflectance spectroscopy (PRS) for real-time monitoring and control of pulsed chemical beam epitaxy (PCBE) during low temperature growth of epitaxial Ga1−xInxP heterostructures on Si(001) substrates by PCBE, where the growth surface is sequentially exposed to organometallic precursors. During the pulsed precursor supply the surface reaction kinetics can be followed by analyzing a periodically in composition and thickness modulated surface reaction layer (SRL), which is captured in the PR-signals as a fine structure that is superimposed to the interference fringes caused due to the underlying growing film. The optical response is linked to the growth process via a reduced order surface kinetics (ROSK) model and integrated as a control signal in the implementation of filter and control algorithms for closed-loop controlled growth of epitaxial Ga1−xInxP heterostructures on Si(001) substrates. The control concept has been applied for thickness and compositional graded multi-heterostructure GaxIn1−xP epilayers and validated by ex-situ post-growth analysis, showing superior tracking of composition and thickness targets under closed loop controlled conditions compared to films grown using pre-designed source injection profiles (open-loop conditions).
Development of Nondestructive Method for Prediction of Crack Instability
Authors: Schroeder J. L. , Eylon D. , Shell E. B. , Matikas T. E. 
Published: April 2011

ABSTRACTA method to characterize the deformation zone at a crack tip and predict upcoming fracture under load using white light interference microscopy was developed and studied. Cracks were initiated in notched Ti-6A1-4V specimens through fatigue loading. Following crack initiation, specimens were subjected to static loading during in-situ observation of the deformation area ahead of the crack. Nondestructive in-situ observations were performed using white light interference microscopy. Profilometer measurements quantified the area, volume, and shape of the deformation ahead of the crack front. Results showed an exponential relationship between the area and volume of deformation and the stress intensity factor of the cracked alloy. These findings also indicate that it is possible to determine a critical rate of change in deformation versus the stress intensity factor that can predict oncoming catastrophic failure. In addition, crack front deformation zones were measured as a function of time under sustained load, and crack tip deformation zone enlargement over time was observed.
Atomic-Scale Structure of the Si-SiO2 and SiC-SiO2 Interfaces and the Origin of Their Contrasting Properties
Authors: Buczko Ryszard , Pennycook Stephen J. , Pantelides Sokrates T. 
Published: April 2011

ABSTRACTOne of the reasons for the dominance of Si in microelectronics is the quality of the Si-SiO2 interface. In contrast, development of SiC-based MOSFETs for power applications is hampered primarily by poor carrier mobility at the SiC-SiO2 interface. Here we review recent calculations that elucidate the reasons of the contrasting properties of the two interfaces. In the case of Si, the interface energy is in fact lower when the interface is abrupt and smooth because of the intrinisic geometry of the Si (001) surface and the softness of the Si-O-Si angle. However, two energe ically degenerate phases are possible, leading to domain boundaries, that are the cause of subcxide bonds, steps, and dangling bonds. In principle, these effects may be avoidable by low-temperature deposition. In contrast, the geometry and bond lengths of SiC surfaces are not suitable for abrupt and smooth interfaces, requiring the existence of a nonstoichiometric interlayer that may be the cause of the reduced mobility.
Mesoscopic Transport in Broken Down Ultrathin SiO2 Films
Authors: Miranda E. , Suñe J. , Rodriguez R. , Nafria M. , Aymerich X. 
Published: April 2011

ABSTRACTA common theoretical framework is presented to model the conduction characteristics of the two main dielectric breakdown modes in ultrathin SiO2 gate oxides, namely the soft and hard breakdown modes. The breakdown paths are considered to behave as mesoscopic quantum point contacts so that the conduction properties are controlled by energy funneling effects. An adiabatic approach to the modelling of these quantum point contacts is adopted to obtain an analytical approximation for the total transmission coefficient. In the limit of small breakdown spot areas, tunneling through a potential barrier associated with the lower electron transversal state at the narrowest part of the constriction explains the soft breakdown characteristics. For larger areas, such a barrier dissapears and conductance quantization is predicted. Experimental results are well explained by the model, including the conductance values after the hard breakdown and the oxide thickness independence of the current-voltage characteristic after the soft breakdown.
Mechanical Properties of Al Thin Films as Measured by Bulge Testing
Authors: Wang Yinmin , Edwards Richard L. , Hemker Kevin J. 
Published: April 2011

AbstractFree-standing rectangular Al thin films have been fabricated using sputter deposition and standard micromachining techniques. Mechanical properties and residual stresses of both asdeposited and annealed Al films were measured by bulge testing. The films were loaded into the plastic deformation regime, and then unloaded and reloaded several times. The pressure and deflection of the thin films were recorded and used to generate stress-strain curves. The planestrain elastic modulus, flow stress and plastic behavior of the Al thin films were used to characterize the mechanical response of these films. The Al films were measured to have a plane-strain modulus that is slightly lower than the literature values for a {111} textured film. The Von-Mises equivalent yield stress was measured to be higher in the annealed films but much more significant strain hardening was observed in the as-deposited films. A plastic hysteresis was observed on unloading and reloading stress-strain curves of the as-deposited Al films but not the annealed films.
Bending Response of a 100nm Thick Free Standing Aluminum Cantilever Beam
Authors: Taher M. , Saif A. , Haque Aman 
Published: April 2011

AbstractA micro instrument is developed to apply force on free standing cantilever samples with suborm thickness. The objective is to study the effect of small thickness on the strength of materials when subjected to bending. The instrument consists of a MEMS actuator, 2mm × 3mm in size, and 20μm deep. It is employed to study an annealed Al cantilever sample, 110nm thick, 2μm wide and 15μm long, fabricated by evaporation. The sample yields at 841M Pa during the first cycle of loading. It is then unloaded and reloaded, when yielding occurs at 1200M Pa. To the best of our knowledge, this is the first reported experiment on free standing submicron metal film subjected to bending.
Residual Stresses in MEMS Structures
Authors: Majumdar B. S. , Cowan W. D. , Pagano N. J. 
Published: April 2011

AbstractThe magnitude and origin of residual stresses in thin polysilicon MEMS structures are discussed in this article. The curvature of polysilicon beams were determined at different temperatures. An accurate method of analysis that avoids the thick substrate approximation is described. The polysilicon beams without an Au layer exhibited temperature-independent curvatures, indicating that their residual stresses were largely process related. Beams with an Au top-coat exhibited a strong temperaturedependent effect, and allowed derivation of a stress-free temperature of 143°C. The technique allowed an independent estimate of the thermal expansion coefficient of polysilicon, namely 2.5×10−6 to 3.1×10−6/°C.
Ion Implantation and Misfit Dislocation Formation in P/P+Silicon
Authors: Feichtinger Petra , Fukuto Hiroaki , Sandhu Rajinder , Poust Benjamin , Goorsky Mark S. 
Published: April 2011

AbstractWe determined that self implantation of pseudomorphically strained silicon epitaxial layers greatly attenuates strain relaxation. We employed highly boron doped 150 mm diameter silicon with a nominally un-doped, 2.5 μm thick epitaxial layer (p/p+). The compressively strained layer (mismatch ≈ 1.5 × 10−4) showed inhomogeneous relaxation after epitaxial growth, with misfits forming only near the wafer periphery. High temperature rapid thermal annealing was employed after ion implantation to study misfit dislocation nucleation and glide. Our results suggest that low dose ion implantation has a potential to reduce misfit dislocation propagation and nucleation in epitaxial thin films.