bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interfacial Interactions in Silica Reinforced Silicones
Authors: Aranguren Mirta I. , Macosko Christopher W. , Thakkar Bima , Tirrell Matthew 
Published: March 2011

AbstractThe study of the type and strength of the filler-polymer linkages is of great importance in understanding the reinforcement of elastomers. Silicone rubbers are weak elastomers and the addition of reinforcing fillers is essential in order to obtain useful, strong materials. The best reinforcing filler for these elastomers are fumed silicas. These fillers, like reinforcing carbon blacks, have very complex structures. Both have fractal characteristics, small particles fused together forming open aggregates that can cluster by physical forces. Silicas have sometimes more complex structures than carbon blacks, but have a better understood surface chemistry. Interactions between polydimethylsiloxanes and silica surfaces have been studied using heat of adsorption measurements of mostly low molecular weight analogs or inferring the strength of the adsorption by the shift of particular peaks in the infrared spectrum [1]. Here we will present a new technique that measures directly the strength of the adsorption of the polymer segments onto glass and between themselves. It also allows for comparison of the strength of such bonds with the strength of a polymer entanglement “link”.
Interfacial Effects of Plasma Treatment on Fiber Pull-Out
Authors: Gaur Umesh , Davidson Theodore 
Published: March 2011

AbstractSurface modification of organic reinforcement fibers by exposure to certain plasmas appears to have considerable potential as a means for improving the performance of composites. Such treatments can change fiber surface properties, leaving the core of the fiber virtually unaffected so that the mechanical properties of the fibers remain unaltered. Previous studies [1–5] have shown that plasma treatment of polymeric fibers can modify surface energetics and that the acid/base characteristics of a fiber surface can be altered by exposure to plasmas of acidic or basic gases. Although several publications [6,7] have reported that the mechanical properties of composites reinforced with plasma-treated fibers are enhanced, there has been no direct evidence to show the impact of fiber surface plasma treatment on interfacial shear strength.
The Effects of Fiber Surface Treatments by a Cold Plasma in Carbon Fiber/Bismaleinide Composites
Authors: Chang Tao C. , Jang B. Z. 
Published: March 2011

AbstractThe effects of plasma treatments on the physical and chemical characteristics of carbon fiber surface and on the mechanical properties of carbon fiber/bismaleimide (BMI) resin composites were investigated. Scanning tunneling microscopy (STM), scanning electron microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and wettability measurements were applied for fiber surface characterization. Oxygen plasmas were found to be effective in enhancing the interfacial adhesion between carbon fiber and BMI matrix. Possible mechanisms of interfacial adhesion promotion were suggested and discussed.
Interphase Behavior in Cyclic Fatigue of Monofilament Composites
Authors: Schadler Linda S. , Figueroa Juan C. , Laird Campbell 
Published: March 2011

AbstractMacroscopic properties of fiber reinforced composites are dependent on the micromechanics of the filament-matrix interphase. We present here some preliminary results of our studies aimed at understanding the behavior of the interphase when the composite is subjected to cyclic tensile loading. We have used carbon/polycarbonate mono-filament composites as a model system for studying the effects of loading direction (axial and transverse), frequency, and amplitude. The interphase was varied by etching the filament surface. Damage was characterized by fiber matrix debonding, reduction in interphase stress transfer efficiency, and changes in the locus of failure as determined by SEM fractography.
Plasticity During Fracture of the Au/Al2O3 Interface
Authors: Reimanis Ivar E. 
Published: March 2011

AbstractAu/Al2 O3 interfaces are created by bonding highly textured Au films (25 pm thick) to single crystal A12 O3. Mechanical tests are done under the optical microscope to examine the effect of plastic deformation on the energy of fracture of the interface. Fracture occurs at the interface and is accompanied by plastic deformation in the Au. The relatively large value for the fracture energy measured (50-70J/m2) is attributed to the plastic deformation in the Au. It is also observed that fracture occurs subcritically due to stress corrosion at fracture energies from 10-20J/m2. Topographic features on the fracture surfaces are characterized and discussed briefly.
A Critical Evaluation of the Use of the Microbond Method for Determination of Composite Interfacial Properties
Authors: Haaksma Rebecca A. , Cehelnik Marilyn J. 
Published: March 2011

AbstractThe microbond method has been applied with increased frequency to characterize interfacial adhesion in fiber reinforced composites. Nevertheless, a number of serious questions remain regarding the interpretation of experimental data. This paper addresses material and experimental variables in the microbond test procedure including the cure behavior of thermoset test specimens, matrix heterogeneity, locus of failure in test specimens and load application techniques. The theoretical basis for the method is examined by viewing experimental results in terms of existing theoretical interpretations of interfacial failure. Conclusions are presented regarding the limitations and the potential of the microbond method for determining fiber/matrix adhesive bond strength.
Transmission Electron Microscopy Studies of Silicon Nitride / Silicon Carbide Interfaces
Authors: Kleebe H. J. , Corbin N. , Willkens C. , Rühle M. 
Published: March 2011

AbstractMicrostructural investigations of HIP'ed silicon nitride reinforced with silicon carbide whiskers were performed using a 400 kV high resolution analytical transmission electron microscope. Two different whisker sources as well as uncoated and carbon coated whiskers were evaluated for their effectiveness in improving mechanical properties.This paper focuses on microstructural and microchemical analysis of interface and grain boundary regions within the composites. Combined HREM and AEM investigations reveal that variations in fracture toughness are mainly influenced by the microstructural and chemical development of the interface. Fracture toughness can be related to the surface chemistry of the reinforcements.
Fibre-Matrix Reaction Zones in Model Silicon Carbide-Titanium Aluminide Metal-Matrix Composites
Authors: Baker D. R. , Doorbar P. J. , Loretto M. H. 
Published: March 2011

AbstractThe reactions between coated SiC continuous fibres and TiAl, Ti3A1, or Ti3A1 + β matrices, have been investigated using optical metallography, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), with chemical information obtained by energy dispersive x-ray analysis (EDX) and electron energy loss spectroscopy (EELS).Similar sequences of phases were found in all the composites; carbides based on TiC and TixAIC (x=2,3) and titanium silicides based on Ti5Si3 forming in narrow bands outside of the complex carbides. The occurrence of individual phases can be related to published phase diagram information. However, the sequences in which the reaction products occur within the reaction zones cannot be fully rationalised from the present results.
The Study of the Dislocation Structure and Energy of NiO-Pt Interfaces
Authors: Shieu F.-S. , Sass S. L. 
Published: March 2011

AbstractThe dislocation structure of Pt-(001)NiO interfaces was studied using electron microscopy and electron diffraction techniques. Specimens were produced by hot pressing polycrystalline Pt films on to thin NiO single crystals, and bulk Pt single crystals on to bulk NiO single crystals. The polycrystalline Pt specimens were used to determine the favored orientation relationships between the NiO and Pt, while the bulk NiO-Pt specimens were used to study the detailed structure of the interface. Three categories of orientation relationships were identified: exact epitaxy with (001)Pt ║ (001)NiO, [110]Pt ║ [110]NiO; small rotations away from exact epitaxy about the common [001] direction; high index planes of Pt parallel to (001) of NiO. Theoretical calculations of the expected dislocation structures of interfaces with the first two orientation relationships were made using a Bollmann-type analysis. The experimental observations and theoretical predictions were shown to be in good agreement. The energies of the interfaces having the first two orientation relationships were shown to be similar which is believed to be the reason why they both occur.
Growth of Monocrystalline Cosi2 on Cosi2 Seeds in (100)Si
Authors: Maex Karen 
Published: March 2011

ABSTRACTGrowth of monocrystalline CoSi2 on top of (100) Si has been obtained by silicidation of deposited Co films on Si/CoSi2/Si heterostructures formed by ion implantation. The layers are of excellent crystalline quality and the CoSi2/Si interface is atomically flat. The required implanted dose can be reduced, since epitaxial silicidation is possible starting from aligned CoSi2 precipitates in the Si.
Temperature Dependent Current-Voltage Characteristics of TiSi2/n+/p-Si Shallow Junctions
Authors: Shah Bhupen , Ravindra N.M. 
Published: March 2011

ABSTRACTModelling of temperature dependent current-voltage characteristics of TiSi2/n+/p-Si shallow junctions has been presented here. The formation of shallow pn junctions, by ion implantation of As+ through Ti films evaporated on p-Si substrates has been performed in these experiments. The temperature dependent factors such as band gap narrowing, intrinsic carrier concentration, mobilities and diffusivities are considered in the model.
Properties of Ohmic Contacts to Heterojunction Transistors
Authors: Harrison H. Barry 
Published: March 2011

ABSTRACTThe electrical and physical properties of the contact between the active channel of high electron mobility transistors (HEMT’s) and the source or drain contacts play an important role in determining the transistor characteristics. This paper considers electrical models that may be applied to the various techniques now available to form these Interconnections. Results of electrical (and some physical) studies with regard to these systems are then discussed and compared where possible with predictions made using the electrical models. The comparisons show that the electrical models provide a useful base to identify the important parameters in these interconnections.
Controlled Modifications in the Electrical Properties of Metal/GaAs Junctions
Authors: Eizenberg M. 
Published: March 2011

ABSTRACTControlled modifications in the electrical properties of metal/GaAs junctions were obtaind by a few different approaches. The first approach is based on modifications induced by solid state reactions occurring between the metal and GaAs substrate, resulting in compound formation and component redistribution. The characteristics of such contacts can further be modified when the contact metal is alloyed with another metal or with a dopant. The second approach is based on modifying the doping level of the near surface region of the GaAs. Here an enhancement of the barrier height was obtained by heavily counter doping the top GaAs region by recoil implantation of Mg from a Mg thin film irradiated by As− ions. The correlations between the electrical properties of the junctions and the physical processes taking place using the above mentioned approaches are discussed.
Rbs Analysis of Intermixing in Annealed Samples of Pt/Ti/Iii-V Semiconductors
Authors: Savin W. , Weir B. E. , Katz A. , Chu S. N. G. , Nakahara S. , Harris D. W. 
Published: March 2011

ABSTRACTLow resistance Pt/Ti nonalloy contacts to GaAs, GaP, In As, InGaAs, and In Alas have been studied using Rutherford Backscattering. The samples were studied by comparing an as deposited structure to samples annealed at temperatures between 300°C and 600°C for 30 s. For all samples intermixing of the Pt and Ti was observed to start at 350°C. The Ti/HI-V semiconductor interface mixing was strongest for As when it was present, but In and Ga also strongly intermixed for anneals of 4S0°C and above.
Thermally Stable, Low Resistance Indium-Based Ohmic Contacts to n and p-Type GaAs
Authors: Murakami Masanori , Hallali P.-E. , Price W. H. , Norcott M. , Lustig N. , Kim H.-J. , Wright S. L. , LaTulipe D. 
Published: March 2011

ABSTRACTRecently, thermally stable, low resistance In-based ohmic contacts to n-type GaAs have been developed in our laboratories by depositing a small amount of In with refractory metals in a conventional evaporator, followed by rapid thermal annealing. By correlating the interfacial microstructure to the electrical properties, InxGa1-xAs phases grown epitaxially on the GaAs were found to be essential for reduction of the contact resistance (Rc). This low resistance was believed to be due to separation of the high barrier (φb) at the metal/GaAs contact into two low barriers at the metal/InxGa1-xAs and InxGa1-xAs/GaAs interfaces. In this paper the effects of the In concentration (x) in the InxGa1-xAs phases and addition of dopants to the contact metal are presented. High In concentration is desirable to reduce the φb at the metal/InxGa1-xAs interface. Such contacts were prepared by sputter-depositing InAs with other contact elements, but the low Rc values were not obtained. The reason was explained to be due to an increase in the φb at the InxGa1-xAs/GaAs interface due to the formation of misfit dislocations. However, addition of a small amount of Si to the contact metals reduced significantly the Rc value. This contact demonstrated excellent thermal stability: no deterioration was observed at 400°C for more than 100 hrs. In addition, the use of this Ni(Si)InW contact metal allowed us to fabricate the low resistance ohmic contacts by one-step (simultaneous) annealing for “implant-activation” and “ohmic contact formation”, which simplifies significantly GaAs device fabrication process steps. For p-type ohmic contacts, low resistance contacts were fabricated by depositing the same NilnW contact material to p-type GaAs. This contact was also thermally stable during subsequent annealing at 400°C. Within our knowledge this is believed to be the first demonstration of low resistance, thermally stable ohmic contact fabrication using the same materials for both n and p-type GaAs.
Mn–In–Co, Mn–Pt and Mn–In–Pt Based Contacts to p–GaAs
Authors: Kalkur T. S. , Lu Y. C. , Rowe M. 
Published: March 2011

ABSTRACTMn–In–Co, Mn–In–Pt and Mn–Pt metallizations are used to form ohmic contact on Be-implanted rapid thermally annealed GaAs. The rapid thermal alloying of contact metallizations are performed in A.G. Associates Heat pulse system in nitrogen atmosphere in the temperature range of 350°C to 800°C for 5 seconds. The contacts were found to be ohmic at an annealing temperature of 450°C. The In–Mn–Co metallization showed higher minimum contact resistivity (5 × 10−4 ohm.cm2 ) than In–Mn–Pt metallization (1.5 × 10−5 ohm.cm2 ) for an annealing temperature of 700°C and time 5 seconds. The surface morphologies of In–Mn–Pt metallizations were smooth even after alloying at 700°C for 5 seconds. The Auger analysis shows outdiffusion of Ga and As into the contact metallization and negligible indiffusion of In and Mn into GaAs.
Alloying behavior of the Ni/In/Ni/n-GaAs Ohmic Contact
Authors: Jan Chia-Hong , Swenson Doug , Austin Chang Y. 
Published: March 2011

ABSTRACTThe interactions between Ni and Ni/In/Ni thin-films and GaAs were studied by SEM, SAM and AES. The presence of a molten phase was observed for both contacts after annealing at 820°C for 3 minutes. This behavior was rationalized in terms of the presence of a ternary eutectic reaction in the gallium-nickel-arsenic system. DTA confirmed the existence of the reaction:at 810°C. In the case of Ni/In/Ni, melting was thought to occur because of the segregation of indium metal to the contact surface and the subsequent melting of the nearly ternary interfacial region. Upon further cooling the formation of NiGa, NiAs, InxGa1−xAs and an unspecified compound Ni-In was believed to occur. The contact was shown to be either sintered or alloyed, depending upon processing conditions.
Investigation of Thin Pd-Ge Layer Formation Using Synchrotron Vacuum Ultraviolet Photoemission Spectroscopy
Authors: Meissner P. L. , Bravman J. C. , Kendelewicz T. , Miyano K. , Spicer W. E. , Woicik J. C. , Bouldin C. 
Published: March 2011

ABSTRACTThe formation of Pd-Ge layers was studied as a function of deposition and annealing using synchrotron Ultraviolet Photoemission Spectroscopy (UPS). Pd depositions ranging in thickness from 0.5 monolayers (ML) to 44 ML were examined in-situ on Ge (111) cleaved in ultra-high vacuum. The primary reaction components appear to be Pd2Ge and PdGe. Comparison of bulk and surface sensitive Ge 3d core levels for even the highest coverages indicates that Ge segregates to the surface at room temperature. Such low temperature segregation suggests that Ge can diffuse via a rapid diffusion mechanism.
Taper Etchable Neon-Sputtered Molybdenum Film
Authors: Kato Kinya , Wada Tsutomu 
Published: March 2011

ABSTRACTTaper etchable molybdenum (Mo) films are successfully obtained by neon (Ne) sputter deposition. Mo films several hundred nanometer thick are deposited using an RF planar magnetron sputtering system. After photolithography, the Ne-sputtered Mo films are etched with a hydrogen peroxide solution. Films deposited in low pressure Ne show an excellent tapered edge with a taper angle of less than 45°, which can eliminate the step-coverage problem. However, higher-pressure Ne-sputtered films and films sputtered in argon (Ar) show steep edge profiles .Ne-sputtered Mo films show a drastic change in characteristics depending on the gas pressure. The internal stress is strongly compressive for lower pressures and becomes tensile for higher pressures. According to RHEED patterns, lower pressure sputtered film shows a <110> orientation including a halo which indicates the existence of an amorphous-phase, but higher pressure sputtered films show clear <111> orientations. TEM observations confirm the structural change. Higher pressure Ne-sputtered film and Ar-sputtered film show columnar structures, but low-pressure Ne-sputtered film shows the disordered structure.Taper etchability of the low-pressure Ne-sputtered Mo films is considered to be due to the structural change, especially the included amorphous-phase.
Role of Interface-States in the Reverse Bias Aging of Gaas Schottky Barriers
Authors: Christianson K. A. 
Published: March 2011

ABSTRACTForward bias capacitance has been used to examine the Au/W/GaAs and Au/Pt/Ti/GaAs Schottky barriers present in power microwave MESFET devices to see if interface-state generation plays any role in the previously reported reverse bias barrier height aging process. If a constant carrier capture cross-section is assumed, forward bias capacitance has shown that for samples strongly susceptible to aging (i.e. the Au/W/GaAs samples in this study) interface-state generation is taking place during the aging process. The validity of the constant capture cross section assumption has been tested by examining the I-V properties. For those samples whose reverse I-V properties were not dominated by thermionic-field emission, similar increases in interface-state densities were evaluated from the I-V characteristics for the degraded samples.
Thermal Stability of a1-pt Thin Films/Gaas for Self-Aligning Gate Contacts
Authors: Wilk G. D. , Blanpain B. , Olowolafe J. O. , Mayer J. W. , Zheng L. R. 
Published: March 2011

ABSTRACTSeveral compositions of Al-Pt thin films have been co-evaporated on GaAs substrates to study the stability of the alloys at high-temperature anneals. The Al concentration in the alloys ranges from 45 at.% to 70 at.%, and we show that the films meet thermal stability requirements imposed by GaAs self-aligning gate technology for compositions between AlPt and Al2Pt.
Electrical Properties and Schottky Barriers of Metal-Semiconductor Interfaces
Authors: Aboelfotoh M.O. 
Published: March 2011

ABSTRACTThe electrical properties of metal/Si(100) and metal/Ge(100) interfaces formed by the deposition of metal on both n-type and p-type Si(100) and Ge(100) have been studied in the temperature range 77-295 K with the use of current- and capacitance-voltage techniques. Compound formation is found to have very little or no effect on the Schottky-barrier height and its temperature dependence. For silicon, the barrier height and its temperature dependence are found to be affected by the metal. For germanium, on the other hand, the barrier height and its temperature dependence are unaffected by the metal. The temperature dependence of the Si and Ge barrier heights is found to deviate from the predictions of recent models of Schottky-barrier formation based on the suggestion of Fermi-level pinning in the center of the semiconductor indirect band gap.
Requirements of Electrical Contacts to Photovoltaic Solar Cells
Authors: Gessert T.A. , Coutts T.J. 
Published: March 2011

ABSTRACTThe importance of contacts to photovoltaic solar cells is often underrated mainly because the required values of specific contact resistance and metal resistivity are often thought to be relatively modest compared with those associated with very large scale integration (VLSI) applications. However, due to the adverse environmental conditions experienced by solar cells, and since many of the more efficient cells are economically advantageous only when operated under solar concentration, the requirements for solar cell contacts are sometimes more severe. For example, at one-sun operation, the upper limit in specific contact resistance is usually taken to be 10−2 Ω-cm2. However, at several hundred suns, this value should be reduced to less than 10−4 Ω-cm2. Additionally, since grid line fabrication often relies on economical plating processes, porosity and contamination issues can be expected to cause reliability and stability problems once the device is fabricated. It is shown that, in practice, these metal resistivity issues can be much more important than issues relating to specific contact resistance and that the problem is similar to that of providing stable, low resistance interconnects in VLSI. This paper is concerned with the design and fabrication of collector grids on the front of the solar cells and, although the discussion is fairly general, it will center on the particular material indium phosphide. This III-V material is currently of great importance for space application because of its resistance to the damaging radiation experienced in space.
Pd-Ge-Au Ohmic Contacts to GaAs: Reliability and Failure Analysis.
Authors: Kazior T. E. , Hieslmair H. , Brooks R. C. 
Published: March 2011

ABSTRACTWe report on experiments that were performed to evaluate the temperature stability and long term reliability of non-alloyed Pd-Ge-Au ohmic contacts on N-type GaAs. Low resistance contacts (≈1×10−6Ωcm2) were obtained for samples that were sintered in a conventional furnace or flash sintered in a graphite susceptor. Elevated temperature storage (≈4000 hours at 280°C) showed improved contact stability when compared to Ni-AuGe-Ni-Au control samples. Gateless MESFETs subjected to bias temperature stress measurements (Ids ≈300-350mA/mm, 2000–4000 hours at 200°C) showed no significant change in device current. This result is in contrast to devices with Ni-AuGe-Ni-Au ohmic contacts which exhibited a 6–27% decrease in current under the same test conditions. Failure analysis reveals significant electromigration and Au diffusion in the drain fingers of devices with Ni-AuGe-Ni-Au contacts. In contrast, devices with Pd-Ge-Au contacts show no electromigration or Au diffusion in the GaAs.