bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Ftir Investigations of Polymer Surface Modification in Downstream Microwave Plasma Etching
Authors: Leu Jihperng , Jensen K.F. 
Published: March 2011

AbstractIn situ Fourier transform infrared (FTIR) reflection-absorption spectroscopy investigations of etching of thin polyimide and poly(methyl methacrylate) films (200-1500Å) in downstream microwave NF3/O2/Ar plasmas are reported. Etch rates and surface chemistry are monitored as a function of gas phase composition, plasma treatment conditions and time. NF3/Ar plasma treatment leads to significant surface fluorination characterized by the formation of aliphatic fluorine compounds (CFx), acyl fluorides, benzoyl fluoride, and polyfluorinated benzene. Addition of oxygen to the etching gas reduces the degree of surface fluorination and modifies the chemical structure. The absorption bands due to CFx structures decrease gradually while polyfluorinated benzene rings and benzoyl fluoride are absent for NF3/O2 mixtures with more than 20% oxygen. The effect of humidity on the plasma-modified polymers is studied by comparing infrared spectra collected in situ with those after air exposure. For NF3/O2 plasma-treated polyimides significant changes are observed while samples fluorinated in NF3 show no changes after exposure to air overnight. The FTIR data are supplemented by XPS analysis.
Moisture Intrusion in Sio2/Epoxy Interfaces
Authors: Takahashi Ken M. 
Published: March 2011

SummaryIn-situ interfacial impedance measurements were used to study the effects of moisture at 80 °C on the interface between oxidized silicon and a diglycidyl ether of bisphenol A (DGEBA) epoxy cured with diethylene triamine (DETA). Using two electrode configurations, admittances attributable to bulk and interfacial conduction processes were distinguished. Bulk impedance measurements followed Randles behavior; conduction in the bulk epoxy was ionic, and was diffusion controlled at low frequencies. Equivalent circuit models were used to demonstrate that an apparent interfacial conduction process was caused by distributed current leakage into the silicon subphase, not a true interfacial conduction path that would indicate water adsorption or interfacial aggregation. However, transitions in diffusivity and bulk epoxy permittivity behavior above a 70-80% relative humidity threshold were observed. Effective epoxy permittivity (∈c) jumped to values indicative of a water cluster induced Maxwell-Wagner relaxation. The humidity threshold corresponds to a level that has been associated with adhesion loss in epoxies. It appears that epoxy adhesion losses result from bulk epoxy property changes at high humidity rather than interfacial bond displacement or delamination.
Morphology of Lignin-Polyurethane Blends
Authors: Feldman D. , Lacasse M.A. 
Published: March 2011

AbstractThe morphology of blended polyurethane (PU) sealants was studied by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The PU was modifided by mechanical mixing with various amounts of Lignin (L) to achieve a homogeneous blend. Specimens were subjected to control (C), accelerated weathering (AW), and natural weathering (NW) conditions. Results obtained from SEM analysis reveal an even distribution of L particles in the PU matrix. Furthermore, the SEM photomicrographs clearly emphasize the differing morphologies of the constituent phases. They also depict the differences in surface texture between control and aged specimens. The DSC analysis shows that the two phases are immiscible which is in agreement with observations by microscopy.
Effect of Oxygen Plasma Treatments on Polypropylene-Epoxy Interfacial Strength
Authors: Occhiello E. , Morra M. , Morini G. , Garbassi F. 
Published: March 2011

AbstractThe effect of oxygen plasma treatment on adhesion and surface properties of polypropylene (PP) was assessed. An oxygen rich modified PP layer, immiscible with bulk PP, was formed by the treatment. Contact angle measurements showed that macromolecular motions led with time to rearrangements of the surface layer drastically decreasing its wettability, while its composition, measured by XPS, remained unaffected.The shear strength of PP-epoxy joints increased after plasma treatment. The locus of failure was found to occur at the PP/epoxy interface for untreated PP, within PP in the case of oxygen-plasma-treated samples, close to the modified PP/bulk PP interface. This result suggests that the plasma treament improves the interaction at the PP/epoxy interface, but weakens the mechanical strength of the surface layer thereby creating a weak point at the modified PP/bulk PP interface.
Study of Nanophase TiO2 Grain Boundaries by Raman Spectroscopy
Authors: Melendres C. A. , Narayanasamy A. , Maroni V. A. , Siegel R. W. 
Published: March 2011

AbstractRaman spectra have been recorded for as-consolidated nanophase TiO2 samples with differing grain sizes and on samples annealed in air at a variety of temperatures up to 1273 K. The nanophase samples with the smallest grain size, about 12 nm average diameter, could have 15-30% of their atoms in grain boundaries; nevertheless, the strong Raman-active lines representative of the rutile structure were found to dominate all of the observed spectra, independent of grain size and annealing treatment. These lines were quite broad in the as-consolidated nanophase samples, equally in 12 nm and 100 nm grain-size compacts, but sharpened considerably upon annealing at elevated temperatures. The Raman data give no indication of grain-boundary structures in nanophase TiO2 that are significantly different from those in conventional polycrystals. However, defect structures within the grains, which anneal out at elevated temperatures, are evidenced by changes in the Raman spectra.
Fluorinated Monomolecular Assemblies: Model Systems to Probe Chemical Interactions at the Polymer-Metal Interface
Authors: Chau Lai-Kwan , Porter Marc D. 
Published: March 2011

AbstractMonomolecular assemblies of n-perfluorocarboxylic acids [CF3 (CF2)nnCOOH,n=-6,7, and 8] have been adsorbed at silver by spontaneous adsorption from dilute alcoholic solutions. Infrared reflection spectroscopy indicates that the monolayers form by the reactive chemisorption of the carboxylic acid to a carboxylate salt. Ellipsometrically-determined film thicknesses increase linearly with an increase in the perfluorocarbon chain length. Contact angle measurements indicate that the packing density of the films increases with increasing chain length, resulting in an interface with a low surface free energy. The structure and properties of these interfaces are compared to those for monolayers of n-alkanoic acids. The potential utility of such assemblies to probe fundamental chemical and physical interactions at polymer-metal interfaces are also discussed.
Adhesion of Copper to Polytetrafluoroethylene
Authors: Kim Yong-Kil , Chang Chin-An , Schrott A.G. , Andreshak J. , Cali M. 
Published: March 2011

AbstractAn enhancement of the adhesion between copper and polytetrafluoroethylene (PTFE) has been studied. Thin-films of copper were electron-beam deposited on the surface of the polymer substrates. Peel test measurements showed that, without any treatment of the substrates, the adhesion was poor with a peel strength of 1-2 g/mm. A pronounced enhancement of the adhesion has been obtained when the fluorocarbon substrates were treated by either an ultraviolet (UV) irradiation, an ion-beam presputtering prior to the metal deposition, or heat treatments after the deposition. Among the treatments employed, the ion-beam sputtering was the most effective in improving the adhesion. The roles of the treatments and possible reasons for the enhanced adhesion are discussed in conjunction with the studies of interface morphology and chemistry using Scanning Electron Microscopy, Rutherford Backscattering Spectroscopy, and X-ray Photoelectron Spectroscopy.
The Aspects of Thermal Anneal to Intrinsic Stress and Hicrostructure of Multilayer Thin Films
Authors: Yang C. H. , Chen P.C. 
Published: March 2011

AbstractAdhesion degradation mechanism at the interface of a multilayer thin film was studied as a function of annealing temperature. The multilayer thin films employed for current investigation of the temperature effect were constructed by sputtering 500 Å Cr and 10K Å Cu on both sides of kapton. A steady decrease of adhesion strength was found as a result of increasing the annealing temperature from 150°C to 350°C. Thin film and interfacial properties in association with degradation of adhesion were characterized by several techniques, including intrinsic stress measurement, Auger, TEN and SIMS. Several changes were observed by elevating the annealing temperature. It was found that the intrinsic stress in each layer changed. Both Cu and Cr grain size increased with the annealing temperature. The interface at kapton and metal became more defined. The Cu atoms were found to become mobile and diffused into Cr and kapton layer after a 350 degree annealing. In addition, a change of molecular orientation and chemistry in kapton near the interface was observed by SIMS and XPS studies. A combination of these factors resulted in a decline of adhesion strength.
Measurement of Micromechanical Properties Using Atomic Force Microscope with Capacitative
Authors: Neubauer Gabi , Cohen Sidney R. , McClelland Gary M. 
Published: March 2011

AbstractA new UHV atomic force microscope for the study of micromechanical properties is described. A capacitance technique is used, which enables simultaneous measurement of forces perpendicular and parallel to the surface (i.e., load and friction), and has low noise down to frequencies below 0.1 Hz. Preliminary results for Ir- and W-tips sliding on graphite and silicon, respectively, demonstrate the capabilities of this new instrument.
Design, Development, and Applications of Novel Techniques for Studying Surface Mechanical Properties
Authors: Miyoshi Kazuhisa 
Published: March 2011

AbstractThis paper reviews the author's research of the adhesion, friction, and micromechanical properties of materials and presents examples of the results. The ceramic and metallic materials studied include silicon carbide, aluminum oxide, and iron-base amorphous alloys. The design and operation of a torsion balance adapted for study of adhesion from the Cavendish balance are discussed first. The pull-off force (adhesion) and shear force (friction) required to break the interfacial junctions between contacting surfaces of the materials were examined at various temperatures in a vacuum. The surface chemistry of the materials was analyzed by x-ray photoelectron spectroscopy. Properties and environmental conditions of the surface regions which affect adhesion and friction - such as surface segregation, composition, crystal structure, surface chemistry, and temperature were also studied.
Fracto-Emission from Interfacial Failure
Authors: Dickinson J. T. 
Published: March 2011

AbstractFracto-Emission is the emission of particles and photons during and after fracture of materials. The observed emission includes electrons, negative and positive ions, neutral species in both ground states and in excited states, and visible photons. This emission can often serve as a sensitive probe of crack growth and may prove to be a useful tool for investigating molecular and microscopic events accompanying crack growth and for studying the details of failure modes in a variety of materials. Interfacial failure provides unique fracto-emission signals due to the extensive charge separation accompanying separation of dissimilar materials. Here we present the results of several recent studies of interfacial failure involving a variety of materials and relate them to electronic and mechanical processes accompanying failure.
Elastic Properties of Grain Boundaries in Copper
Authors: Adams James B. , Wolfer Wilhelm G. , Foiles Stephen M. 
Published: March 2011

AbstractThe elastic constants of a Σ5 (100) twist grain boundary are calculated on a monolayer-by-monolayer basis, and the elastic behavior is shown to differ by up to an order of magnitude from bulk-like behavior. This unusual elastic behavior is found to be similar to that of uniaxiallystrained crystals, since the grain boundaries themselves are regions which are strained (expanded) in one direction.
Role of the Interface in the Adhesion of Cu to SiO2
Authors: Kellock Andrew J. , Baglin John E.E. 
Published: March 2011

AbstractThe adhesion of thin evaporated Cu films directly to SiO2 is generally poor. The adhesion can be improved by a variety of treatments, ranging from a pre-deposition Ar ion bombardment of the substrate, to post deposition bombardments with ion beams, photons or electrons. Also, if a thin layer of partially oxidized Cr is deposited onto the SiO2 prior to Cu deposition, the Cu adheres more strongly. The intrinsic mechanism responsible for these adhesion improvements remains to be understood.We have attempted to characterize the interface of these structures by a combination of Rutherford Backscattering Spectrometry (RBS) and an adhesion peel test to determine the role each treatment plays in the adhesion process.
Precipitation at Grain Boundaries in Irradiated Austenitic Fe-Cr-Mn Alloys
Authors: McCarthy J. M. 
Published: March 2011

AbstractIn previous work, the phase stability of Fe-Cr-Mn alloys during irradiation was investigated in a study that included simple binaries, simple ternaries and commercially produced alloys. These low activation alloys are being considered for fusion reactor service in the first wall and in other structural applications subject to high neutron doses. In addition to phase instabilities observed within the grains, grain boundaries were susceptible to varying levels of precipitation dependent upon alloy composition, displacement dose and irradiation temperature. This paper describes the grain boundary microstructures that developed in these Fe-Cr-Mn alloys during irradiation.
An Arxps Investigation of the Initial Growth of Aluminum Films on the (0001) Face of Sapphire.
Authors: Arbab Mehran , Chottiner Gary S. , Hoffman R. W. 
Published: March 2011

AbstractThe (0001) face of α-Al2O3 and the initial growth of ultra-thin aluminum, films deposited on this surface were studied by a combination of low energy electron diffraction, angle resolved x-ray photoelectron spectroscopy and thermal desorption techniques. At high temperatures, the (0001) face of α-Al2O3 reconstructs to form a (√31×√31)R±9° structure which remains stable at lower temperatures, as evidenced by IEED. ARXPS shows that the annealed sanple retains its bulk composition up to the solid-vacuum interface.Thin Al films were deposited on the above surface by in situ evaporation. ARXPS results indicate a uniform growth of the initial monolayer of aluminum. Further growth (<3 A°) deviated fr the layer by layer adsorption mechanism.
Novel Approach for High Resolution Tem Studies of Ceramic-Ceramic Interfaces
Authors: Datye Abhaya K. , Paine Robert T. , Narula Chaitanya K. , Allard Lawrence F. 
Published: March 2011

AbstractCeramic coatings on oxides can be studied by high resolution transmission electron microscopy (HRTEM), with minimal sample preparation, if the substrate consists of nonporous particles of simple geometric shape. Interfaces suitable for ‘end-on’ examination by HRTEM can be readily obtained without any necessity for ion-beam thinning. All the interface orientations that are thermodynamically stable are available for examination from a single sample. This technique is of general applicability and can be used for studies of metal-ceramic and ceramic-ceramic interfaces. We have examined the nature of boron nitride interfaces with oxides such as MgO, TiO2 and Al2O3 and find that BN appears to wet the oxide surface and form tough, adherent coatings. The hexagonal crystalline BN grows with the (0001) planes always being locally parallel to the oxide surface in every instance.
Deep-Level Dominated Current-Voltage Characteristics of Novel Semiconductor Heterostructures
Authors: Das K. 
Published: March 2011

AbstractCurrent-voltage characteristics of Au contacts formed on buried implanted oxide silicon-on-insulator structures and molecular beam epitaxially grown GaAs on (1012) sapphire and silicon-on-sapphire substrates indicate that the dominant transport mechanism in these films is space-charge-limited current conduction in the presence of deep-level states. The deep-level parameters, determined using an analysis of the current-voltage characteristics, appear to be sensitive to the nature of crystallographic defects present in the grown layers. Conduction in the GaAs film on SOS was dominated by one discrete state located ~ 0.28eV below the conduction band-edge, which is close to the El center uniquely observed in the molecular beam epitaxially grown GaAs-on-Si. Discrete levels are also observed in annealed buried implanted oxide silicon-on-insulator films. In contrast, the GaAs films deposited directly on (1012) sapphire substrates and rapid-thermally annealed high-dose As implanted buried oxide SOI films appear to have a continuous distribution of states. The distributed states in GaAs films deposited directly on sapphire probably arise from the electrical activity of the double-position boundaries present in this material system.
Surface Structure of Sulfur Coated GaAs
Authors: Fujisaki Yoshihisa , Goto Shigeo 
Published: March 2011

AbstractSurface structure of (NH4)2S treated GaAs. is investigated using PL (PhotoLuminescence), XPS (X-ray Photoelectron Spectroscopy) and RHEED (Reflection of High Energy Electron beam Diffraction). The data taken with these techniques show the strong dependence upon the crystal orientations coming from the stabilities of chemical bonds of Ga-S and As-S on GaAs crystals. The greater enhancement of PL intensity, the clearer RHEED patterns and the smaller amount of oxides on (111)A than (111)B implies the realization of a more stable structure composed mainly of the Ga-S chemical bond.
Evidence for Strong Trapping by Ionized Donors of Free Excitions in Excited States for High Purity GaAs and AlGaAs
Authors: Zemon S. , Lambert G. 
Published: March 2011

AbstractStriking increases in the intensity of donor-related, photoluminescence transitions are observed in undoped (1014-1015 cm-3) GaAs for excitation energies (Ee) in the vicinity of the band-gap energy (Eg). The enhancement has maxima at Ee consistent with excitation of the n=2 and 3 states of the free exciton (Xn=2,3) and appears to be correlated to the concentration of ionized donors, suggesting that the effects are related to capture of electron-hole pairs by ionized donors through trapping of Xn=2,3. The enhancement decreases monotonically as Ee increases to values as much as 12 meV above Eg.
Optical Absorption of Deep Defects in Neutron Irradiated Semi-Insulating GaAs.
Authors: Manasreh M. O. , Pearah P. J. 
Published: March 2011

AbstractTwo defects were observed in thermal neutron irradiated semi-insulating liquid-encapsulated Czochralski (LEC) GaAs materials by using the infrared absorption technique. The first defect was observed before thermal annealing and it has a broad peak at ~0.83 eV. The second defect was observed after annealing the sample at 250 °C for 15 min. The latter defect is an EL2 - like defect, but is thermally unstable at 400 °C with a concentration of about an order of magnitude larger than [EL2] observed in as grown LEC materials. Both defects were found to photoquench with white light or 1.1 eV monochromatic light at 9 K and thermally recovered at 150 K. The concentration of the EL2 - like defect is reduced from 8.5×1016cm3 after annealing the sample at 300 °C for 15 min to 2×1016cm-3 after annealing at 400 °C for 15 min. This defect becomes unquenchable after the latter annealing conditions. An explanation for this behavior is offered.
New, Germanium - Related Defect in Neutron - Irradiated Gallium Phosphide
Authors: Barczynska J. , Goldys E. 
Published: March 2011

AbstractGaP crystals were irradiated with thermal neutrons with a fluence 1.4 * 10 19 neutrons / cm2 . The isochronal annealing at temperatures up to 800°C resulted in n - type conductivity of irradiated samples. After 800°C anneal 10% of transmuted Ge atoms become neutral donors. Simultaneously the absorption spectrum shows a broad band centered at 1 eV. The similar feature is observed in photoconductivity. The origin of the absorption band is discussed. The band is most likely due to germanium - related defect.
Anomalous Luminescence Properties of GaAs grown by Molecular Beam Epitaxy
Authors: Szafranek I. , Plano M.A. , McCollum M.J. , Jackson S.L. , Stockman S.A. , Cheng K.Y. , Stillman G.E. 
Published: March 2011

AbstractA shallow acceptor-like defect labeled “A” is frequently incorporated in molecular beam epitaxial GaAs. We report here anomalous photoluminescence effects that are induced by this defect. With increasing concentration of the “A” defect: (1) neutral and ionized donor-bound exciton peaks disappear almost completely even for donor concentration as high as 7×1014 cm-3 and compensation ratio ND/NA≈0.3; (2) a new, sharp line emerges at 1.5138 eV, and (3) the relative intensity and line shape of the free exciton transition change dramatically. These observations are discussed in the perspective of previous reports, where similar effects were, in our opinion, misinterpreted.
Infrared Studies of the Double Acceptor Zinc in Silicon
Authors: Dörnen A. , Kienle R. , Thonke K. , Stolz P. , Pensl G. , Grünebaum D. , Stolwijk N.A. 
Published: March 2011

AbstractIn the present paper, optical absorption studies on the neutral charge state of the double acceptor zinc in silicon are presented. Measurements were carried out in the mid infrared (MIR) and in the near infrared (NIR) region. The MIR absorption spectra show the excitation series of an effective-masslike hole, from which the Zn° level position is calculated to be at Ev + 319. 1 meV. A splitting of the ground state into 3 sublevels is assigned to hole-hole coupling and crystal-field splitting. Absorption spectra obtained in the NIR are interpreted in terms of an A° X-type bound exciton.
Luminescence Due to Mn Doped GaP
Authors: Monteiro Teresa , Pereira Estela 
Published: March 2011

AbstractIn n-type GaP doping with Mn gives rise to a deep centre due to Mn+2. Its luminescence occurs in the near infrared.The behaviour of this centre is studied as a function of temperature and the thermal quenching of the luminescence interpreted as due to a non-radiative process to the ground state. The behaviour of another band that appears upon doping with Mn is also discussed.
Generation and Dissociation of Iron-Boron Pairs in Silicon
Authors: Suezawa Masashi , Sumino Koji 
Published: March 2011

AbstractThe generation and dissociation processes of Fe-B pairs in Si crystal are investigated by means of the measurements of electron paramagnetic resonance of Si crystals of various B concentrations doped with Fe. Fe-B pairs are generated due to annealing of the crystals at temperatures around 300 K obeying to the first order reaction kinetics. The activation energy for pair generation is determined to be about 0.65 eV which is almost equal to the migration energy of Fe impurity in a Si crystal. Fe-B pairs are found to be dissociated at tempeatures higher than 150°C leading to the precipitation of Fe.