bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Processing Method on the Grain Boundary Character Distribution and Network Connectivity
Authors: Schwartz Adam J. , Kumar Mukul , King Wayne E.
Published: April 2011

There exists a growing body of literature that correlates the fraction of “special” boundaries in a microstructure, as described by the Coincident Site Lattice Model, to properties such as corrosion resistance, intergranular stress corrosion cracking, creep, etc. Several studies suggest that the grain boundary character distribution (GBCD), which is defined in terms of the relative fractions of “special” and “random” grain boundaries, can be manipulated through thermomechanical processing. This investigation evaluates the influence of specific thermomechanical processing methods on the resulting GBCD in FCC materials such as oxygenfree electronic (ofe) copper and Inconel 600. We also demonstrate that the primary effect of thermomechanical processing is to reduce or break the connectivity of the random grain boundary network. Samples of ofe Cu were subjected to a minimum of three different deformation paths to evaluate the influence of deformation path on the resulting GBCD. These include: rolling to 82% reduction in thickness, compression to 82% strain, repeated compression to 20% strain followed by annealing. In addition, the influence of annealing temperature was probed by applying, for each of the processes, three different annealing temperatures of 400, 560, and 800°C. The observations obtained from automated electron backscatter diffraction (EBSD) characterization of the microstructure are discussed in terms of deformation path, annealing temperature, and processing method. Results are compared to previous reports on strainannealed ofe Cu and sequential processed Inconel 600. These results demonstrate that among the processes considered, sequential processing is the most effective method to disrupt the random grain boundary network and improve the GBCD.
Dynamic Embrittlement: Quasi-Static Interfacial Decohesion
Authors: Mcmahon C. J. , Bassani J. L. , Mishin Y.
Published: April 2011

In a surprising variety of cases, interfaces in normally ductile materials can undergo timedependent
brittle cracking under the influence of a tensile stress, either applied externally or existing as an internal residual stress. The connecting feature in all these cases is the presence of a surface-adsorbed element that is highly mobile in comparison to the constituent elements of the material. As in the phenomena of diffusion creep and diffusive growth of cavities at high temperatures, the driving force for this cracking is the work done by the tensile stress when a surface atom enters the solid. At temperatures below about 0.5 Tm of the solid, this occurs mainly along grain boundaries. Examples of systems that have been studied in some detail include cracking of alloy steels by sulfur, Cu-Sn alloys by tin, and nickel-based alloys by oxygen. Because the cracking involves diffusive penetration along grain boundaries, the rate of cracking is highly sensitive to grain-boundary structure and composition, and these variables offer opportunities to control the problem. We are aiming at a quantitative understanding of the effects of grain-boundary structure, stress, and temperature on this phenomenon by crack-growth experiments on bicrystals, by atomistic modeling of the stress-driven diffusion, and by micromechanical modeling of the events occurring at the tip of a growing crack.
Angle-Resolved XPS Studies of Interfacial Bonding States in Silicon oxynitrides Fabricated Using Different Thermal Methodologies
Authors: Dang Sanjit Singh , Takoudis Christos G.
Published: April 2011

Silicon oxynitride films, fabricated by direct thermal growth and annealing in N2O or NO, were analyzed by Angle-Resolved X-ray Photoelectron Spectroscopy (ARXPS). It is seen that for the samples processed in N2O, N is bonded as Si3N4 only, irrespective of whether the fabrication was done on bare Si or on an oxide pre-grown in O2. But the films processed in NO depict additional bonding arrangements, namely, non-stoichiometric SiOxNy, (Si-)2-N-O, and Si-N(-O)2. These bonding states are found to be concentrated in a higher proportion above the oxynitride/substrate interface. Further, it is seen that annealing of a pre-grown oxide in NO for 30 min incorporates the same bonding states as by direct growth in NO for as long as 120 min. Also, a critical N concentration (between 1.9% and 2.3%) is required for the incorporation of the Si-N(-O)2 structure, observed at 400.7 eV. Besides enhancing the overall understanding of the progress of silicon oxynitridation process in N2O and NO, these findings can help significantly towards developing process-property relationships for incorporation of N with the desired bonding state(s) at specific positions within an oxynitride film.
Low-Temperature Bonding of Ceramics by Sol-Gel Processing
Authors: Barbé C.J , Cassidy D.J. , Triani G. , Latella B.A. , Mitchell D.R.M. , Day A. , Short K. , Bartlett J.R. , Woolfrey J.L. , Collins G.A.
Published: April 2011

Sol-gel bonding was produced between smooth, clean substrates of silicon and polycrystalline alumina by spin-coating solutions containing partially hydrolysed silicon alkoxides. The two coated-substrates were assembled and the resulting sandwich was fired at temperatures ranging from 300 to 600°C. The coatings and bonded substrates were investigated using SEM, TEM and micro-indentation. For silicon wafers, an optimum water-to-alkoxide molar ratio of 10 and hydrolysis water pH of 2 was found. Such conditions led to relatively dense films (>90%), resulting in bonds with a fracture energy of 3.5 J/m2, which is significantly higher than those obtained using hydrophilic wafer bonding (typically 1.5 J/m2).

Poly-crystalline alumina substrates were similarly bonded at 600°C; the opt imised silica sol-gel chemistry yielded interfaces with fracture energy of 4 J/m2.
Selective Area Growth of Magnetic Garnet Crystals by Liquid-Phase Epitaxy
Authors: Yokoi H. , Mizumoto T.
Published: April 2011

Selective area growth of magnetic garnet crystals was studied by liquid-phase epitaxy. The garnet layers grown on Ti-masked substrates were analyzed under a scanning electron microscope, and by X-ray diffraction measurements, energy-dispersive X-ray analysis and reflection high-energy electron diffraction. Narrow stripes in the Ti mask were designed to form waveguides by one-step growth. The light waves could be guided within the waveguide fabricated by selective area liquid-phase epitaxy.
Effect of Electric Field on Metal Induced Lateral Crystallization of Amorphous Silicon
Authors: Singla Shivani , Poon M.C. , Chan M. , Qin M. , Chan W.Y. , Yuen C.Y. , Ko P.K. , Wong H.
Published: April 2011

The effects of electric field on the rate of metal induced lateral crystallization (MILC) of amorphous silicon were investigated. Nickel silicide, which is known to be a key species for the low temperature crystallization, was driven by an electric field. As a result, the crystallization velocity of EMILC was much faster than that of conventional MILC methods. Directional crystallization of amorphous silicon thin film was successfully achieved by applying a DC field during heat treatment. The crystallization was performed at different temperatures (500-625°) by employing a thin layer of nickel (30°). The directionality of the resulting crystallization depended on the polarity of the electric field. The lateral crystallization velocity was three to four times faster than MILC when an electric field of 53.5V/cm was applied.
Mesoscopic characterization of the optical property of antiphase boundaries in CuPt-ordered GaInP2
Authors: Ohno Y. , Takeda S.
Published: April 2011

We have developed an apparatus for polarized cathodoluminescence (CL) spectroscopy combined with transmission electron microscopy (TEM), that enables us to obtain simultaneously structural data in higher spatial resolution by TEM and polarized luminescence spectra by CL of the same microscopic area. The polarized-CL/TEM method is very useful to study the optical properties of low-dimensional microstructures in semiconducting materials. We have applied the method to examine the optical property of antiphase boundaries in CuPt-ordered GaInP2 and found, for the first time, the polarized light emission from the APBs whose habit planes are parallel to the (T11) and (1T0) atomic planes.
Depth-Resolved Microspectroscopy of Porous Silicon Multilayers
Authors: Manotas S. , Agulló-Rueda F. , Moreno J. D. , Martín-Palma R. J. , Guerrero-Lemus R. , Martínez-Duart J. M.
Published: April 2011

We have measured micro-photoluminescence (PL) and micro-Raman spectra on the cross section of porous silicon multilayers to sample different layer depths. We find noticeable differences in the spectra of layers with different porosity, as expected from the quantum confinement of electrons and phonons in silicon nanocrystals with different average sizes. The PL emission band gets stronger, blue shifts, and narrows at the high porosity layers. The average size can be estimated from the shift. The Raman phonon band at 520 cm−1 weakens and broadens asymmetrically towards the low energy side. The line shape can be related quantitatively with the average size by the phonon confinement model. To get a good agreement with the model we add a band at around 480 cm−1, which has been attributed to amorphous silicon. We also have to leave as free parameters the bulk silicon phonon frequency and its line width, which depend on temperature and stress. We reduced laser power to eliminate heating effects. Then we use the change of frequency with depth to monitor the stress. At the interface with the substrate we find a compressive stress in excess of 10 kbar, which agrees with the reported lattice mismatch. Finally, average sizes are larger than those estimated from PL.
Optical Characterization of Ion Implanted SIC
Authors: Williams E. K. , Ila D. , Poker D. B. , Hensley D. K.
Published: April 2011

We present the preliminary results of our investigation of producing nanoclusters of gold and tin in 6H-SiC. In this work we study the changes in the linear optical properties as a function of ion fluence and post-implantation heat treatment. The optical absorption is complemented by micro-Raman spectroscopy to investigate lattice damage and recovery. We implanted 1.0 MeV Au and 120 and 160 keV Sn into the Si face of SiC at 30 or 500°C followed by annealing at various temperatures. Using optical absorption spectrophotometry, we determined the location of the absorption band for each metal nanocluster in SiC. Elevated temperature implantation greatly reduced optical absorption due to ion implantation induced defects. Using Mie theory, we determined the index of refraction in the implanted volume and estimated the size of the Au nanoclusters as 5 nm in diameter. Rutherford backscattering analysis of the oxide layer grown during annealing showed an increase of 20 percent in on the implanted side. It was found that the Au clusters occurred only in the oxide layer.
Photo-Induced Current Spectroscopy in Undoped Cvd Diamond Films
Authors: Borchi E. , Bruzzi M. , Lombardi L. , Menichelli D. , Miglio S. , Pirollo S. , Sciortino S. , Serafini D.
Published: April 2011

Combined TSC and PICTS measurements have been used to determine the activation energies (Et) and capture cross-sections (σ) of the trap levels inside the bandgap of CVD diamond in the energy range 0.4−0.7 eV. High temperature TSC analysis has been performed to determine the trap parameters in the energy range from 0.9 to 1.3 eV. A fieldmap in the Et−σ plane has been obtained from the combination of the TSC and PICTS data depicting the regions corresponding to two isolated trap levels and to a continuous distribution of states. The concentrations of defects have been calculated from the TSC signals and the measurement of the charge collection efficiency of the diamond samples.
Microvoids in Polycrystalline Cvd Diamond
Authors: Mcnamara Karen M.
Published: April 2011

Small angle light scattering has been used to quantitatively study microvoids in polycrystalline CVD diamond. Guinier's approximation was used to calculate the average radius of gyration of these defects for diamond films made by both DC arc-jet and microwave CVD assuming a spherical defect geometry. Values of the radius of gyration varied between approximately 1 and 5 μm and were found to correlate with the thickness, relative transmission and thermal conductivity measured for the films. Some inconsistencies were observed between microwave and DC arc-jet materials which may be related to fundamental differences in the growth processes. This represents the first quantitative analysis of such defects in polycrystalline films and holds great promise for improving our understanding of the diamond CVD processing and properties.
Photoemitters Based on Glass - ITO Structures
Authors: Olesik J.
Published: April 2011

The sample was a silicon glass with conducting films (ITO) evaporated by reactive ion sputtering on its both sides. The internal electric field was created by applying a negative polarizing voltage Upol, to field electrode. The investigations were performed in the vacuum of the order 10−6 Pa. As a result of applying Upol and illumination, photoelectrons are released and enter electron multiplier. The electrons create voltage pulses in the multiplier which are recorded in the multichannel pulse amplitude analyzer. The amplitude spectra were measured for unilluminated samples and illuminated by a quartz lamp.

Energy analysis of emitted electrons was performed by the retarding field method. Measurements of electrons energy in field induced emission showed that about 80% o electrons have energy up to 10 eV but some electrons of higher energy are also detected. The described effects can be modeled with support of the electron effects occurring during the intrinsic discharges in gases. Theoretical molecular dynamics simulations have shown that SnO4 tetrahedral interacting with SiO4 clusters of the glass substrate play central role in the observed nonlinear photoinduced changes.
Energy behavior with magnetic field of negatively charged magnetoexcitons in quantum wells and heterojunctions
Authors: Munteanu F. M. , Kim Y. , Perry C. H. , Rickel D. G. , Simmons J. A. , Reno J. L.
Published: April 2011

We present the results of the magneto-photoluminescence measurements performed on modulation doped GaAs/AlGaAs heterostructures in high magnetic fields (up to 60T) and low temperatures (0.37−1.5K). With increasing magnetic field we observe the formation of the triplet and singlet states of negatively charged magneto-excitons (X−) in addition to the neutral exciton (X0). Their behavior with field strongly depends on the sample geometry. In the case of a modulation doped quantum well (QW) with a well-width of 200A, the and states cross at a magnetic field of about 40T, whereas for a modulation-doped single heterojunction (SHJ) these states show no crossing over the whole range of available fields.
STM-Light Emission From Metal Deposited Semiconductor Surfaces
Authors: Yamamoto N. , Kagami S. , Minoda H.
Published: April 2011

Light detection system combined with a UHV-scanning tunneling microscope (STM) was applied to the study of silver films deposited on Si(111) surfaces. Photon maps clearly show single atom height steps and terraces on an Ag(111) surface with high spatial resolution of nanometer scale. Chemical reaction on the Ag surface with residual gas was clearly revealed in the photon map. In the photon map of the thin Ag film of 2˜3 ML in thick, no contrast appears between the terraces, and a characteristic bright contrast appears at the single atom height steps. The local plasmon model does not readily explain those contrasts.
Optical properties of Si nanowires on a Si {111} surface
Authors: Ozaki N. , Ohno Y. , Takeda S.
Published: April 2011

We have investigated optical properties of straight silicon nanowires by means of in-situ cathodoluminescence spectroscopy in a transmission electron microscope. The nanowires, grown on a Si{111} surface via vapor-liquid-solid growth mechanism, have no structural defects such as kink, and the diameter and growth direction are controlled by varying the growth conditions. We have found that the nanowires emit intense light. These lines have not been observed in other kinds of Si nanostructures such as porous Si.
Synchrotron x-ray Study of Elastic Phase Strains in the Bulk of an Externally Loaded Cu/Mo Composite
Authors: Wanner A. , Dunand D.C.
Published: April 2011

High-energy, high-flux x-rays from a third-generation synchrotron source were used to measure average elastic strains in the bulk of 1.5 mm thick composites consisting of a copper matrix reinforced with 7.5 vol.% molybdenum particles. From the evolution of lattice strains in both phases during uniaxial tensile deformation, the internal load transfer between phases and reinforcement damage were characterized during elastic and plastic deformation of the composite. The graininess of the diffraction rings, which is related to the Bragg peak broadening, was quantified as a function of applied stress and related to plastic deformation in the matrix.
In Situ XAFS of the LixNi0.8Co0.2O2 Cathode for Lithium-Ion Batteries
Authors: Kropf A. J. , Johnson C. S.
Published: April 2011

The layered LiNi0.8AsCo0.2O2 system is being considered as a new cathode material for the lithium-ion battery. Compared with LiCoO2, the standard cathode formulation, it possesses improved electrochemical performance at a projected lower cost. In situ x-ray absorption fine-structure spectroscopy (XAFS) measurements were conducted on a cell cycled at a moderate rate and normal Li-ion operating voltages (3.0-4.1 V). The XAFS data collected at the Ni and Co edges approximately every 30 min. revealed details about the response of the cathode to Li insertion and extraction. These measurements on the LixNi0.8AsCo0.2O2 cathode (0.29<×<0.78) demonstrated the excellent reversibility of the cathode's short-range structure. However, the Co and Ni atoms behaved differently in response to Li insertion. This study corroborates previous work that explains the XAFS of the Ni atoms in terms of a Ni3+ Jahn-Teller ion. An analysis of the metal-metal distances suggests, contrary to a qualitative analysis of the x-ray absorption near-edge structure (XANES), that the Co3+ is oxidized to the maximum extent possible (within the Li content range of this experiment) at x = 0.47 ± 0.04, and further oxidation occurs at the Ni site.
Experimental Investigations of the Interaction of SO2 with MgO
Authors: Freitag Andrea , Rodriguez J. A. , Larese J. Z.
Published: April 2011

High resolution adsorption isotherms, temperature programmed desorption (TPD), x-ray diffraction (XRD) and x-ray absorption near edge spectroscopy (XANES) methods were used to investigate the interaction of SO2 with high quality MgO powders. The results of these investigations indicate that when SO2 is deposited on MgO in monolayer quantities at temperatures near 100K both SO3 and SO4 species form that are not removed by simply pumping on the pre-dosed samples at room temperature. TPD and XANES studies indicate that heating of pre-dosed MgO samples to temperatures above 350 °C is required for full removal of the SO3/SO4 species. XANES measurements made as a function of film thickness indicate for coverages near monolayer completion that the SO4 species form first.
Structural Characterization Using Synchrotron Radiation of Oxide Films and Multilayers Grown by MOCVD
Authors: Dubourdieu C. , Lindner J. , Audier M. , Rosina M. , Weiss F. , Sénateur J.P. , Hodeau J.L. , Dooryhee E. , Bérar J.F.
Published: April 2011

Synchrotron radiation at the European Synchrotron Radiation Facility has been used to characterize oxide thin films and multilayers grown by metal organic chemical vapor deposition (MOCVD). Reflectometry measurements were performed in the low angle region to get information on the quality of film/substrate and film/film interfaces of the heterostructures. The experimental data were compared to simulated spectra. High angle diffraction experiments were performed on superlattices of (BaTiO3/SrTiO3)15 and (La2/3Sr1/3Mn03/SrTiO3)15. The multilayers are oriented with the [001] direction perpendicular to the substrate plane. The 001 diffraction peaks were recorded up to the 008 one. The satellite peaks observed for both types of multilayers indicate the good coherence over the whole stacking. For the (BaTiO3/SrTiO3)15 systems, the diffraction peaks were particularly well resolved even for the highest order (008 peak), showing excellent epitaxial quality with abrupt interfaces for periods up to 16 nm.
High Spatial Resolution Strain Measurements Within Bulk Materials by Slit-Imaging
Authors: Lienert U. , Martins R. , Grigull S. , Pinkerton M. , Poulsen H.F. , Kvick Å.
Published: April 2011

High energy synchrotron radiation is employed for residual strain measurements from local gauge volumes within the bulk of polycrystalline materials. The longitudinal spatial resolution is defined by placing a narrow imaging slit behind the sample and recording the intensity distribution on a position sensitive detector. It is shown that the sample to slit distance can be increased without sacrificing longitudinal resolution by applying a reconstruction technique. Hence, space is provided for large samples and sample environments. The reconstruction technique is described and validated by measuring the residual strain profile of a shot-peened Al sample. A longitudinal gauge length of 95 üm is achieved at 52 keV with a sample to slit distance of 10 cm.
X-ray phase contrast imaging study of activated carbon/carbon composite
Authors: Kobayashi Kenji , Izumi Koichi , Kimura Hidekazu , Kimura Shigeru , Ohira Tomoaki , Saito Takashi , Kibi Yukari , Ibuki Takashi , Takai Kengo , Tsusaka Yoshiyiki , Kagoshima Yasushi , Matsui Junji
Published: April 2011

We have obtained the x-ray phase contrast images of the activated carbon/carbon (AC/C) composite used as electrodes in an electric double-layer capacitor (EDLC). To improve the spatial resolution, the beam size of x-ray transmitted from a sample were expanded by using asymmetric Bragg diffraction (asymmetric factor b) of analyzer crystal. Since the analyzer crystals were placed in (+, -) arrangements in both vertical and horizontal directions, the total magnification factor was 1/b2 for each direction. By using the 511 asymmetric Bragg diffraction of Si (100) analyzer with an asymmetric factor of 0.207, we could obtain the magnification factor of about 23.3. We applied this optical system to the AC/C composite. The phase contrast image corresponding to the carbon particles with the diameter of about 10 μm could be detected with the spatial resolution of 5 μm. Furthermore, we also obtained realtime images of bubble formation and movement during the overcharging of an EDLC with the time resolution of 30 frames number per second.
Growth Twins in YbxY1−xAl3(BO3)4 and NdxGd1−xAl(BO3)4 Crystals Observed by White-Beam Synchrotron Radiation Topography
Authors: Hu X.B. , Wang J.Y. , Guo M. , Zhao S.R. , Gong B. , Wei J.Q. , Liu Y.G.
Published: April 2011

Growth twins in Ybx Y1−xAl3(BO3)4 (YbYAB) and NdxGd1−xAl3(BO3)4 (NGAB) crystals were observed by white-beam synchrotron radiation topography combined with chemical etch. It was found that growth twins in YbYAB crystals are of inversion types in which two twinned pairs have the central inversion relationship. This kind of twinning was visible in x-ray topography not by ‘domain contrast’ but by ‘boundary contrast’ stemming from the kinematical x-ray diffraction at the boundary. Growth twins in NGAB crystals are of 1800 rotation types in which the twofold symmetric operation axis is parallel to the [0001] axis. This kind of twinning often shows black-and-white contrast in x-ray topography which originates from the different structure factors between twinned pairs. In addition. the formation mechanisms of growth twins are discussed.
The Structure of Actinide Ions Exchanged into Native and Modified Zeolites and Clays
Authors: Wasserman Stephen R. , Soderholm L. , Giaquinta Daniel M.
Published: April 2011

x-ray absorption spectroscopy (XAS) has been used to investigate the structure and valence of thorium (Th4+) and uranyl () cations exchanged into two classes of microporous aluminosilicate minerals: zeolites and smectite clays. XAS is also employed to examine the fate of the exchanged cations after modification of the mineral surface using self-assembled organic films and/or exposure to hydrothermal conditions. These treatments serve as models for the forces that ultimately determine the chemical fate of the actinide cations in the environment. The speciation of the cations depends on the pore size of the aluminosilicate, which is fixed for the zeolites and variable for the smectites.
EXAFS and Raman Studies of PTMGn:MCl2 and PTMG/PEGn:MCl2 Complexes (M = Co, Zn)
Authors: Furtado C.A. , Porto A.O. , Silva G.G. , Silva R.A. , Alves M.C. Martins , Schilling P.J. , Tittsworth R.
Published: April 2011

Extended x-ray absorption fine structure (EXAFS) and Raman spectroscopy measurements have been performed in a series of liquid polymer electrolytes prepared using poly(tetramethylene glycol) (PTMG), and copolymer poly(tetramethylene glycol/poly(ethylene glycol) (PTMG/PEG), as matrices, and ZnCl2or COCl2 as dopants in the concentration range of n = 30 to 90, where n is the molar ratio of Oxigen/Metal cation. EXAFS results have shown the presence of Co-O and Co-Cl coordination shells for PTMG/CoCl2 and PTMG/PEG/CoCl2 systems. Zn-based systems have shown only Zn-Cl bonds in all the concentration range studied. The presence of ZnCl2 and COCl2 species was confirmed by Raman measurements, by the presence of bands characteristic of CI-Zn-Cl and Co-Cl stretching modes.
Synchrotron-Based Studies of Transition Metal Incorporation into Silica-Based Sol-Gel Materials
Authors: Mountjoy G. , Pickup D.M. , Holland M.A. , Wallidge G.W. , Newport R.J. , Smith M.E
Published: April 2011

Previous structural studies on titania- and zirconia-silica xerogels have shown the occurrence of homogeneous mixing at low metal content, and phase separation at high metal content. The use of additional, complementary, synchrotron-based methods can contribute to a fuller structural description of these materials. We present new x-ray absorption near edge structure (XANES) and SAXS results for (ZrO2)x(SiO2)1-x, xerogels and compare them with previous results for (TiO2)x(SiO2)1-x xerogels. Significant differences between (TiO2)x(SiO2)1. and (ZrO2)X(SiO2)1-x xerogels are observed in the affects of heat treatment on the coordination of homogeneously mixed metal atoms, and in the development of phase separated metal oxide regions.
Non-Destructive Dielectric Assessment of Water Permeation in Composite Structures
Authors: Boinard P. , Boinard E. , Pethrick R.A. , Banks W.M. , Crane R.L.
Published: April 2011

Over the last ten years, the application of high frequency dielectric spectroscopy techniques for the assessment of composite structures has been investigated. Novel approaches to assess non-destructively the evolution during ageing of adhesively bonded carbon fibre reinforced plastic (CFRP) structures and bulk glass fibre reinforced plastic (GRP) structures are presented in this paper and the results are critically assessed.

The applicability and limitations of dielectric measurements, in both frequency and time domain, to the monitoring of water ingress at 30°C and 60°C are examined. The correlation between gravimetric and high frequency dielectric spectroscopy data demonstrates the suitability of the techniques regarding the assessment of water uptake in composites structures and illustrates its potential as a non-destructive evaluation (NDE) technique. The dielectric time domain response (TDR) study of adhesively bonded structures indicates a new way to assess such structures. The approach for frequency domain analysis of bulk GRP using a coaxial probe technique indicates the potential portability of the technique for in-situ measurements.
Nondestructive Damage Evaluation of Electro-Mechanical Components Using a Hybrid, Computational and Experimental Approach
Authors: Furlong C. , Pryputniewicz R. J.
Published: April 2011

With the electronic industry being one of the most dynamic, in terms of new technologies, electronic packages have to be designed and optimized for new and ever more demanding applications in relatively short periods of time. This, in turn, indicates a need for effective quantitative testing methodologies. In this paper, a novel hybridized use of nondestructive, noninvasive, remote, full field of view, quantitative opto-electronic holography techniques with computational modeling is presented. The hybridization is illustrated with a representative application, which shows that the combined use of opto-electronic holography techniques and computational modeling provides an effective engineering tool for nondestructive study of electro-mechanical components.
Non-Destructive Evaluation of Mechanical Properties of Magnetic Materials
Authors: Kankolenski Kevin P. , Hua Susan Z. , Yang David X. , Hicho G. E. , Swartzendruber L. J. , Zang Z. , Chopra Harsh Deep
Published: April 2011

A magnetic-based non-destructive evaluation (NDE) method, which employs Barkhausen effect and measurement of the hysteresis loops, is used to correlate the magnetic and mechanical properties of ultra low carbon (ULC) steel. In particular, the NDE method was used to detect small deviations from linearity that occur in the stress-strain curve well below the 0.2% offset strain, and which generally defines the yield point in materials. Results show that three parameters: jumpsum and jumpsum rate (derived from the Barkhausen spectrum), and the relative permeability (derived from the B-H loops) varies sensitively with small permanent strains, and can be related to the plastic deformation in ULC steels. Investigation of micromagnetic structure revealed that plastic deformation leaves a residual stress state in the samples; the associated magneto-elastic energy makes the favorable easy axis of magnetization in a given grain to be the one that lies closest to the tensile axis. The consequence of this realignment of domains is that wall motion becomes intergranular in nature (as opposed to intragranular in unstrained samples). As a result, the more complex grain boundaries instead of dislocations, become the dominant pinning sites for domain walls. These observations provide a microscopic interpretation of the observed changes in the measured magnetic properties.
Non-Destructive Evaluation of 304 Stainless Steels Using a Scanning Hall-Sensor Microscope: Visualization of Strain-Induced Austenite-Phase Breakdown
Authors: Oota A. , Miyake K. , Sugiyama D. , Aoki H.
Published: April 2011

Using a scanning Hall-sensor microscope with an active area 50pμm × 50μm, we succeeded in visualizing a breakdown of paramagnetic austenite-phase in 304 stainless steels induced by a plastic strain at room temperature, resulting from a transformation to ferromagnetic martensite-phase. Magnetic images of spontaneous magnetic fields on a surface of strained sample show the degree and the place (and/or the extent) of phase breakdown. Furthermore, the images nearly agree with the calculated results for the principal shear stress rather than the principal stress under plastic deformation, indicative of the driving force of this breakdown. The study should open a way for non-destructive evaluation of 304 stainless steels.
Quantitative Measurement of Local Carrier Concentration of Semiconductor From Displacement Current-Voltage Curve Using a Scanning Vibrating Tip
Authors: Majima Yutaka , Oyama Yutaka , Iwamoto Mitsumasa
Published: April 2011

A new scanning probe method for evaluating the local carrier concentration of semiconductors is presented. The distance between a semiconductor surface and a vibrating tip is changed sinusoidally, and is adjusted to as small as a few nm across which tunneling current IT flows between the semiconductor surface and the vibrating tip. Displacement current ID due to the change in electric flux from the semiconductor surface to the vibrating tip flows periodically in accordance with the vibration of the tip. IT also flows when the distance becomes minimum. Both IT and ID flow simultaneously when a d.c. tip voltage V is applied, and these two currents are separated by using a two-phase lock-in amplifier. ID-V curve is analyzed by taking into account two-dimensional electric flux profile under the tip. In the tip voltage range within which majority carriers are accumulated, ID-V curve is extrapolated by a straight line. On the contrary, the slope of the curve decreases as the tip voltage is reduced from the voltage range of the accumulation, indicating that the majority carriers are depleted at the center of the Si surface. The theoretical ID-V curves are in good agreement with the measurement in the tip voltage region where the majority carriers are both accumulated and depleted. The local carrier concentration is able to be determined by makingthe theoretical ID-V curve fit the experimental results without contacting the semiconductor surface.
Monitoring Silicon Quality From Diffusion Furnaces Using In-Line Measurements
Authors: Stoker Matt , Catmull Kelvin , Horner Greg , Letherer Brian
Published: April 2011

Carrier lifetimes provide an excellent indication of the concentration of impurities and defects in semiconducting materials. This paper describes a non-contact technique for measuring generation and recombination lifetimes. This technique, which is incorporated into the KLATencor Quantox system, provides a highly sensitive method for monitoring the formation of defects or incorporation of impurities in silicon wafers during processing. Several applications of these measurements are investigated, such as monitoring the effects of various thermal cycles on the formation of a high-lifetime denuded zone near the wafer surface and monitoring diffusion furnace contamination after a quartz change.
Optimization of x-ray Techniques for Nondestructive Characterization of Single Crystal Turbine Blades
Authors: Winter J.M. , Lipetzky K.G. , Green R.E.
Published: April 2011

This paper describes nondestructive x-ray characterization techniques which detect macroscopic and microscopic defects, determine the overall crystallographic perfection, and detect any unwanted secondary crystals both on the external surface as well as in the interior of single crystal blades. The method of Asymmetric Crystal Topography for diffraction imaging the surfaces of single crystal turbine blades and the method of White Beam Transmission Topography for diffraction imaging through the thickness of single crystal turbine blades are both discussed and illustrated with representive diffraction images (topographs). It is clear that the images gained from these methods have a capability for providing information about the details of crystalline perfection (or lack thereof) in nickel-based alloy single crystal turbine blades. Such information can provide considerable leverage for the crystal grower to help in adjusting processing variables to enhance quality of a critical product. And the same methods of topography can conceiveably provide tools for evaluating the finished product in a way which has not been available to date.
Nondestructive Characterization of GaN Films Grown at Low and High Temperatures
Authors: Yana C.H. , Yao H.W. , Hove J.M. Van , Wowchak A.M. , Chow P.P. , Han J. , Zavada J.M.
Published: April 2011

GaN films grown on GaAs and sapphire substrates by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) at both low and high temperatures (LT and HT) were characterized by Raman scattering and variable angle spectroscopic ellipsometry (VASE). Optical phonon spectra of GaN films are obtained through back-scattering geometry. Crystal quality of these films was qualitatively examined using phonon line-width. Phonon spectra showed that the HT GaN has wurtzite crystal structure, while LT GaN and GaN/GaAs have cubic-like structures. Thickness nonuniformity and defect-related absorption can be characterized by pseudo dielectric functions directly. Surface roughness also can be determined by using an effective-medium approximation (EMA) over-layer in a VASE analysis. Anisotropic optical constants of GaN, both ordinary and extraordinary, were obtained in the spectral range of 0.75 to 6.5 eV with the consideration of surface roughness, through the small and large angles of incidence, respectively. The film thickness of the GaN was accurately determined via the analysis as well.
Effects of Reverse Biased Floating Voltage at Source and Drain During High-Field Electron Injection on the Performance of NMOSFETS
Authors: Jarwal R. K. , Misra D.
Published: April 2011

We have examined the effects of reverse biased floating voltage at the source and drain junctions during constant current high-field electron injection on the performance of NMOSFETs. Device parameter degradation was studied when electrons were injected from both gate and substrate. Hole trapping and electron trapping (observed from threshold voltage degradation) were found to be enhanced with reverse biased floating voltage for devices subjected to substrate injection. On the other hand, damages in the devices subjected to gate injection were found to be minimal dependent on reverse biased voltage. Increase in current density due to reduction in effective channel length is believed to be the cause of modified device characteristics. Transconductance degradation for both substrate injection and gate injection was found to have minimal dependence on reverse biased voltage. An asymmetry in the distribution of electron traps at the gate-oxide and substrate-oxide interfaces was observed.
Dielectric Properties of Bi2Ti2O7 Thin Films With (111) Orientation
Authors: Wang Zhuo , Huang J. , Wang S.W. , Hong X.X. , Hou Y. , Wang M. , Shang S.X. , Wang H. , Hu X.B. , Wang Yuguo
Published: April 2011

Bismuth titanate thin films have been prepared on silicon by metalorganic decompositionMOD) technique with bismuth nitrate and titanium butoxide as source materials. The growth procedure of the Bi2Ti2O7 thin films is discussed in this paper. The surface morphology of the Bi2Ti2O7 film was investigated by using Electric Force Microscope (EFM), and the crystallization of the films was studied by x-ray diffraction (XRD). Bismuth titanate thin film prepared on (100) silicon substrate showed strong (111) orientation. Its dielectric properties and the current-voltage (I-V) characteristics were measured. The dielectric constant of the Bi2Ti2O7 thin films vs. frequency, in the temperature range of 100-800 °C, were studied. The dielectric constant and the dielectric loss for Bi2Ti2O7 are 118 and 0.07 respectively at 100KHz. For the Bi2Ti2O7 films with 0.4µm in thickness annealed at 580 °C for 40 minutes, their leakage current density is 4.06×10−7 A/cm2 at an applied voltage of 15V.

The ferroelectric phase transition has been observed distinctly and the Curie temperature was determined for the Bi2Ti2O7 ceramic films. Capacitance vs. temperature was measured from 27-800 at 1KHz, 100KHz, 100KHz and 1MHz.
Low-Temperature Direct-Oxidation of Si Using Activated Oxygen Generated by Tungsten Catalytic Reaction
Authors: Kudo Manabu , Izumi Akira , Matsumura Hideki
Published: April 2011

Ultra-thin silicon dioxide films can be formed at temperatures as low as 220°C by direct oxidation of Si, using active oxygen species generated by tungsten catalytic reaction in a catalytic chemical vapor deposition (Cat-CVD) system. The structural and electrical properties of such a films are investigated. It is found that the density of Si atoms in intermediate oxidation states and the density of films determined from etch rate in dilute HF solution were comparable to those of the films by a conventional thermal oxidation at 900°C. The electrical properties, breakdown electric field and leakage current were also comparable to those of thermally oxidized films.
Structural, Optical and Electrical Characteristics of Silicon Carbon Nitride
Authors: Chen L. C. , Wu C. T. , Wen C.-Y , Wu J.-J. , Liu W. T. , Liu C. W.
Published: April 2011

Dielectric layers of thin silicon carbon nitride (SiCxNy) films have been prepared by ion beam sputtering deposition (IBD). For submicron metal-insulator-Si (MIS) based device applications, a dielectric of low interface roughness, increased capacitance/area with lower leakage on decreasing scale is highly desirable. We address these aspects for the IBD SiCxNy films on p-type Si and present their structural, optical and electrical characteristics as a function of the deposition conditions. Ultraviolet-visible transmittance and spectroscopic ellipsometry were employed to study the optical properties of the SiCxNy films. For electrical measurements, Al gate electrodes were fabricated on SiCxNy films to form metal-nitride-silicon (MNS) diodes. Characteristic I-V and photoconductivity measurements of the MNS are presented.
Study of Stress-Induced Leakage Current in Thin Oxides Stressed by Corona Charging in Air: Relationship to GOI Defects
Authors: Wilson M. , Lagowski J. , Savtchou A. , Marinskiy D. , Jastrzebski L. , D'amico J.
Published: April 2011

Corona charging in air combined with non-contact oxide charge measurement with a contact potential difference probe provides an unique possibility for fast monitoring of electron tunneling characteristics without preparation of MOS capacitors. It has also been found tha corona charging of thin oxides in the tunneling range is very effective in generating stressinduced leakage current. In this work we demonstrate the sensitivity of the corona stressinduced leakage current magnitude to gate oxide integrity defect density. The experimenta results cover three of the most common gate oxide integrity defects, namely: 1 – the defect induced by heavy metals (Fe.Cu) at a practically important low concentration range of 1×1010 to 1×1011 atoms/cm3: 2 – the defects originating from interface roughness and 3–the defects related to crystal originated particles.

At low corona stress fluence, these defects play no role in the tunneling characteristics which follow ideal Fowler-Nordheim characteristics for oxides 50Å or thicker and a contribution from a direct tunneling current for thinner oxides. At high corona stress fluences, gate oxide integrity defects control the magnitude of stress-induced leakage current measured at constan oxide field. It is suggested that the gate oxide integrity role is associated with the enhanced rate of the trap generation during stress. It is noted that the present findings employ a novel methodology for gate oxide integrity monitoring based on corona charging and contact potential difference measurement.
Multi-Million Atom Molecular-Dynamics Simulations of Stresses in Si(111)/Si3N4 Nanopixels
Authors: Bachlechner Martina E. , Omeltchenko Andrey , Walsh Phillip , Nakano Aiichiro , Kalia Rajiv K. , Vashishta Priya , Ebbsjö Ingvar , Madhukar Anupam
Published: April 2011

The stress distribution in Si(111)/Si3N4(0001) and Si(111)/a-Si3N4 nanopixels are studied using molecular dynamics simulations on parallel computers. Bulk Si is described by the Stillinger-Weber potential and Si3N4 is represented by a combination of two- and three-body interactions that include steric, charge transfer, polarizability and covalent forces. The charge transfer at the interface is extracted from self-consistent electronic structure calculations. The molecular dynamics simulations for Si(111)/a-Si3N4 nanopixels involve two pixel sizes: 25nm and 54 nm (the systems consist of 3.7 million and 10 million atoms, respectively). In both systems we find stress domains at the interface, which extend into the silicon substrate. The nature of the stress domains is discussed.
Roles of Primary Hot Hole and FN Electron Fluences in Gate Oxide Breakdown
Authors: Li M. F. , He Y. D. , Ma S. G. , Cho Byung Jin , Lo K. F.
Published: April 2011

In this work, we report the link between the primary hot hole and Fowler Nordheim (FN) electron injections in oxide breakdown mechanism. A simple breakdown model is established. The experimental method is carefully designed to measure the primary hot hole fluence and FN electron fluence separately and accurately. The calculation based on our model is in very good agreement with our experiments. Oxide breakdown is stimulated by a combined effect when the sum of the trap density Dpri activated by primary hot hole injection and the trap density Dn activated by FN electron injection reaches a critical value Dcri. The hole is two orders of magnitude more effective than FN electron in causing breakdown. Since primary hot hole injection may occurs under many realistic device operation in the circuit, existing oxide lifetime projected from conventional TDDB measurement by only applying FN stress is overestimated in many cases. The model demonstrated in this work lays the groundwork in approaching a more appropriate way for predicting the oxide reliability and lifetime.
The Effect of Film Thickness on Stress and Transformation Behavior in Cobalt Thin Films
Authors: Hesemann H. Th. , Müllner P. , Kraft O. , Arzt E.
Published: April 2011

Pure cobalt shows a martensitic transformation from a face-centered-cubic to an hexagonal-close-packed phase. In this work it is chosen as a model-system to investigate the influence of film thickness, film stress and microstructure on the martensitic transformation in thin films.

Co films of 0.2 μm to 3.0 μm thickness were sputter-deposited on Si substrates. This paper presents wafer curvature measurements during temperature cycles of these films and results obtained by focused ion beam microscopy. Upon repeated thermocycling, the martensitic transformation was repeatedly observed in 3 μm thick films, whereas it was not found in 0.2 μm Co films. A stress drop on heating as well as on cooling accompanied the martensitic transformation. It was observed that the stress level at which the transformation occurs can be changed by varying the film thickness or maximum temperature of the temperature cycles. As a result, the martensitic start temperature decreases with increasing stress. It is concluded that the film stress is a critical parameter which strongly affects the martensitic transformation.
In-Situ Characterization of Stress Development in Gelatin Film During Controlled Drying
Authors: Lu Mengcheng , Tam Siu-Yue , Schunk P. Randall , Brinker C. Jeffrey
Published: April 2011

Drying of gelatin films was studied by an in-situ cantilever beam method combined with spectroscopic ellipsometry, enabling measurement of the stress development, film shrinkage and compositional change during the drying process. Experiments are carried out under different drying conditions (such as drying extent variation, drying rate variation). The film experiences stress relaxation that indicates visco-elastic relaxation or plastic deformation happened during drying process. Plastic deformation is verified by carefully reversing the drying process, however, the plastic deformation accompanied by visco-elastic relaxation complicates the case of finding the value of the yield stress.
Micro-Wear Scan Test on the Carbon Overcoats as Thin as 6 NM or Less
Authors: Wu T. W. , Scharf Thomas W. , Zhang Hong , Barnard John A.
Published: April 2011

Nitrogen-doped carbon (CNX) overcoats, ranging from 1 to 6nm in thickness, were deposited on magnetic recording disks by a DC-sputtering process. A critical load, based on the first occurrence of coating damage, was used as a semi-quantitative measure of the mechanical strength of these overcoats. It was found that the critical load decreased in a nearly linear manner with the CNX thickness from 6nm down to ∼2nm regime. However, the 1nm thick CNX coating deviated from this trend with a significant decrease in critical load. High-resolution SEM was employed to find the critical loads as well as to reveal the details of the coating wear morphology and the CNX failure mechanism.