bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropic Organic/Inorganic Resists: A Novel Concept for Electron Proximity Effect Reduction
Authors: Merhari Lhadi , Li Henry H. , Gonsalves Kenneth E.
Published: April 2011

Electron projection lithography is considered to be one of the best candidates for sub-100 nm production circuits. One of the major problems that hinders its development is not related to machine fabrication issues but to electron proximity effects which stem from fundamental electron-polymer interactions. During the past two decades, efforts to reduce the electron proximity effects have essentially focused on the optimization of the resist exposure by means of dose modulation correction programs. We propose a novel approach where the structure of the resist can be tailored so that controlled anisotropy is introduced to laterally constrain the electron scattering. This novel approach does not require the use of high-voltage electron beams nor the processing of a large amount of data, which is a significant economic advantage. Some concepts for the synthesis of these anisotropic resists are discussed and the preliminary example of iron oxide nanorods aligned in poly(methylmethacrylate) (PMMA) is studied.
On the Influence of Applied Fields on Spinel Formation
Authors: Korte C. , Farrer J. K. , Ravishankar N. , Michael J. R. , Schmalzried H. , Carter C. B.
Published: April 2011

Interfaces play an important role in determining the effect of electric fields on the mechanism of the formation of spinel by solid-state reaction. The reaction occurs by the movement of phase boundaries but the rate of this movement can be affected by grain boundaries in the reactants or in the reaction product. Only by understanding these relationships will it be possible to engineer their behavior. As a particular example of such a study, Mgln2O4 can be formed by the reaction between single-crystal MgO substrate and a thin film of In2O3with or without an applied electric field. High-resolution backscattered electron (BSE) imaging and electron backscattered diffraction (EBSD) in a scanning electron microscope (SEM) has been used to obtain complementary chemical and crystallographic information.
Adhesion Properties of Cellulose Films
Authors: Zhang Xiujuan , Young Raymond. A.
Published: April 2011

The adhesion properties were evaluated for untreated and modified cellulose (cellophane) films. Several functional groups were introduced on the film surfaces by plasma based treatments. All the films were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM was employed to study the adhesion properties using both standard silicon nitride tips as well as self-assembled monolayer (SAM) modified gold coated tips containing a variety of specific functional groups. The acetone extracted cellulose films, which are rich in –OH groups, were used as substrates. The adhesion force detected with –COOH terminated AFM tips (∼ 34.8 nN) was much larger than that with –CH3 terminated AFM tips (∼16.7 nN), which was attributed to the hydrogen bonding between –COOH and –OH functional groups. The adhesion force of –NH2 terminated AFM tips on the acetone extracted cellulose film was higher at 42.92 nN. However, after surface modification of the cellulose films with argon and oxygen based plasma treatments, the adhesion force were decreased to 17.4 and 19.4 nN respectively as a result of greatly enhanced surface roughness. Hydrazine plasma treatment also was used to introduce –NH2 groups on the film surfaces, and the strongest adhesion behavior was observed with AFM tips terminated with -COOH groups on the aminated film due to acid-base interaction. The argon and oxygen plasma treatment greatly increased the surface roughness, resulting in poor adhesion properties. Both surface roughness and chemical modification of the cellophane films affected the adhesion properties as measured by AFM force curves.
Observations of Interaction Between Magnetic Domain Wall and Grain Boundaries in Fe-3wt%Si Alloy by Kerr Microscopy
Authors: Kawahara K. , Yagyu Y. , Tsurekawa S. , Watanabe T.
Published: April 2011

Magnetic domain structures in Fe-3wt%Si alloy have been observed by a Kerr microscopy to understand the interaction between the magnetic domain wall and grain boundaries. It was found that the domain structures in the vicinity of the grain boundary depend on the misorientation angle; the high angle random boundary disturbs the magnetic domain structure more than the low angle boundary. In addition to the misorientation angle, magnetic domain structures were affected by the inclination of the grain boundary plane. Moreover, dynamic observations of rearrangement of the magnetic domain structure during magnetization revealed that grain boundaries could act as the sink and/or the source for magnetic domains.
Integranular Fracture: The Effect of Grain Boundary Orientation and Crack Growth Directions
Authors: Kysar Jeffrey W.
Published: April 2011

Intergranular fracture is a common failure mechanism for which many issues remain to be resolved. In this study we investigate intergranular fracture behavior of specially oriented symmetric tilt bicrystals of aluminum as well as the fracture behavior of a crack along the interface of a copper-sapphire bicrystal. We begin by describing briefly the structure of a symmetric tilt grain boundary which leads to a discussion of the types of issues related to intergranular fracture that can be addressed with symmetric tilt grain boundaries. We then discuss in detail one of these issues, that of the directional dependence of fracture, and present results of finite element simulations of a copper-sapphire bicrystal specimen that exhibits the directional dependence of fracture. The simulations account for the single crystal nature of the constituents and use a cohesive-zone model, for which the grain boundary energy can be varied, to simulate the fracture process along the interface. The directional dependence of fracture emerges from the simulations for a broad range of parameters in the constitutive models of both the single crystal constituents as well as the interfacial cohesive-zone.
Creep in Polycrystalline Aluminum
Authors: Briant C. L. , Davidson D. L.
Published: April 2011

This paper presents a study of creep in polycrystalline aluminum. The sample was deformed in a scanning electron microscope and local strain was measured by analyzing micrographs taken during the test. EBSP was used to examine grain curvature and recrystallization The results showed that tensile strain developed during the test. The strain was not constant but varied both spatially and with time. Significant grain boundary migration occurred during the test, and near a triple point a grain with a completely new orientation was formed.
Grain Boundary Microstructure Dependent – Intergranular Fracture in Polycrystalline Molybdenum
Authors: Tsurekawa Sadahiro , Watanabe Tadao
Published: April 2011

The intergranular brittleness in polycrystalline materials is a source of serious problem in material processing and practical applications. To obtain a fundamental knowledge of improvement in the brittleness, we have examined the relationship between fracture behaviour and grain boundary (GB) microstructures in polycrystalline molybdenum. Quantitative analyses of GB microstructures were performed by orientation microscopy (OIM), and followed by 4-points bending tests at 77K. Thereafter, crack propagation was analyzed in connection with GB microstructures. We found the fracture stress depends on the grain size in similar manner to the Hall-Petch relation. In addition, the Hall-Petch relation also depends on the grain boundary character distribution (GBCD). The fracture stress increases with increasing the frequency of low σ GBs at constant grain size. Conversely, random GBs seem to act as weak intrinsic defects and the interconnection among them may give rise to premature failure. Therefore, the connectivity of random GBs probably becomes important as well as the GBCD to suppress the intergranular fracture.
Interfacial Engineering for Optimized Adhesion in Polymeric Composite Materials
Authors: Drzal Lawrence T.
Published: April 2011

Fiber-matrix adhesion is a variable to be optimized so that optimum composite mechanical properties can be achieved in polymer matrix composites. The contemporary view of adhesion rests on an “interphase” model in which not only the actual chemical and physical interactions between fiber and matrix are considered but also the structure and properties of both the fiber and the matrix in the region near the interface. The optimum design methodology starts with the specification of the fiber and matrix from a structural consideration. Once the constituents are selected, the focus is on the creation of a beneficial fiber-matrix “interphase”. This region where the fiber and matrix interact has to be designed for both “processing” and “performance”. Although no quantitative algorithm is available for interphase optimization, various thermodynamic principles coupled with experimental data can be used to qualitatively design the optimum interphase. Examples will be presented to illustrate how this interface can be engineered with surface treatments and sizings or coatings to insure thorough wetting, protection of the fiber, chemical bonding between fiber and matrix, toughness and desirable failure modes.
Inclined Substrate Deposition by Evaporation of Magnesium Oxide for Coated Conductors
Authors: Bauer Markus , Metzger Ralf , Semerad Robert , Berberich Paul , Kinder Helmut
Published: April 2011

Biaxially textured MgO buffer layers were deposited on metal substrates using “inclined substrate deposition” (ISD). The influence of the substrate inclination angle, deposition rate, and film thickness on the texture is shown. Scanning electron microscopy reveals columnar growth. We developed a growth model to explain the texturing. To test this model we have carried out 3D Monte-Carlo simulations. We find that the preferred orientation arises from mutual shadowing of the columns and directional surface diffusion due to their initial momentum.

YBa2Cu3O7 (YBCO) films deposited on the ISD buffer layers are highly textured. The ab-planes of the YBCO are tilted with respect to the surface by typically 25° towards the direction of MgO vapor incidence. Therefore, the critical current density jc is anisotropic with up to 8 × 105MA/cm2 in one direction and 4 × 105MA/cm2 in the other. For tape coating the MgO deposition direction can be chosen so that the high jc is along the tape.
Ion Beam Induced Growth Structure of Fluorite Type Oxide Films for Biaxially Textured htsc Coated Conductors
Authors: Iijima Y. , Kimura M. , Saitoh T.
Published: April 2011

Biaxially aligned film growth by dual-ion-beam sputtering method were studied for fluorite type (Zr0.85Y0.15O1.93(YSZ), Hf0.74Yb0.26O1.87, CeO2), pyrochlore type (Zr2Sm2O7), and rare-earth C type (Y2O3, Sm2O3) oxides on polycrystalline Ni-based alloy substrates. Cube-textured (all axes aligned with a <100> axis substrate normal) films were obtained for fluorite and pyrochlore ones by low energy (<300 eV) ion bombardment at low temperatures (< 300 °C). Besides, cube textured Y2O3 films were obtained in far narrow conditions with a quite low energy (150 eV)-ion bombardment at the temperature of 300°C. The assisting ion energy dependence was discussed in connection with lattice energies for these oxide crystals.
Growth and Structural Characterization of Sr2TiO4: Chemical Control Over the Terminating SrTiO3 Surface.
Authors: Salvador P. A. , Mercey B. , Perez O. , Haghiri-Gosnet A. M. , Doan T.-D. , Raveau B.
Published: April 2011

Thin films of Sr2TiO4 were grown using pulsed laser deposition (PLD) and laser-MBE on [100]-SrTiO3single crystal substrates. Films grown by standard PLD display only a single peak in the X-ray diffraction spectra, corresponding to the (006) peak of the K2NiF4 parent structure. Using a Laser-MBE, controlled two-dimensional growth and RHEED intensity oscillations can be routinely obtained. The period of the RHEED intensity oscillations was confirmed to correspond to the deposition of one-half the unit cell. In contrast to PLD-grown films, the (004) and (006) peaks are observed in XRD spectra for the Laser-MBE-grown films. The intensity of the (004) peak is discussed and modeled with respect to in-plane disorder arising from substrate step-edges and out-of-plane film-substrate structural mismatches. That a single, half unit-cell can be deposited allows one to "flip" the terminating surface of SrTiO3 in a controlled and simple manner from a pure TiO2 layer to a SrO layer. Experimental evidence of the importance of such surface control is given for the SrCuO2 structural stability.
Instabilities and Point Defects at Step-Free Si(001) and (111) Terraces During High Temperature Annealing
Authors: Lee Doohan , Blakely Jack M.
Published: April 2011

In this paper we describe observations on the stability of extremely large Si(001) and (111) terraces that are formed by a technique described previously. Following annealing at high temperature and quenching, a series of concentric pits of monoatomic depth are observed with spacing between successive pits of the order of several microns; pits do not form on (111) until the terraces get extremely large. The occurrence of small islands or small pits on the terraces of quenched samples gives information on the majority point defect at the annealing temperature. On (001) samples that are slowly cooled from the annealing temperature, it is observed that pairs of atomic steps have formed on the large terrace; we believe that these result from the tendency of the surface to minimize the strain energy associated with the (2 × 1) reconstruction.
Structural and Electrical Characterization of Si-Modfet Structures Grown at High Rates by Lepecvd
Authors: Rosenblad C. , Kummer M. , Müller E. , Dommann A. , Künel H. Von
Published: April 2011

Strain relaxed graded SiGe buffer layers have been grown by low energy plasma enhanced chemical vapour deposition (LEPECVD). Due to the low ion energies involved in LEPECVD, exceptionally high plasma intensities can be applied without any ion damage of the epitaxial layers. Transmission electron microscopy and X-ray reciprocal space mapping show that relaxed buffer layers grown at rates exceeding 5 nm/s are of a comparable quality to buffer layers grown by standard techniques at much lower rates. Low temperature electric transport measurements on remotely doped tensilely strained Si quantum wells synthesized by LEPECVD show that also good electrical quality is achieved.
SPM Characterization of Substrate Surfaces Prepared for Carbon-Related-Film Deposition
Authors: Narumi Kazumasa , Yamamoto Shunya , Naramoto Hiroshi
Published: April 2011

Abstracts

Variation of surface steps on sapphire (0001) and (1120) substrates processed with thermal annealing in air or a reducing environment at 1000 to 1400°C for 1 to 10 hours were investigated with an atomic force microscope (AFM). The annealed (0001) surfaces consist of atomically smooth and large terraces and atomic-height steps, whose configurations strongly depend on annealing conditions. On the (1120) surfaces, where crystallographic misorientation is almost an order of magnitude larger than that of the (0001) surfaces, step height and terraces increase in size with the longer annealing time and higher annealing temperature. Characteristic step figures due to the symmetry of atomic arrangement were observed on the (0001) surface.
Porous SiC Substrate Materials for High-Quality Epitaxial and Bulk Growth
Authors: Mynbaeva M. , Savkina N. , Zubrilov A. , Seredova N. , Scheglov M. , Titkov A. , Tregubova A. , Lebedev A. , Kryzhanovski A. , Kotousova I. , Dmitriev V.
Published: April 2011

The main unsolved problem in SiC technology is a high density of defects in substrate materials (micropipes and dislocations) propagating into device structures and causing device failure. Recently, significant progress in defect density reduction in semiconductor materials has been achieved using epitaxial lateral overgrowth techniques. In this paper, we describe a novel technique, which shows a high potential for defect reduction in epitaxial and bulk SiC. This technique is based on nano-scale epitaxial lateral overgrowth (NELOG) method, which employs porous substrate materials. Usually, the pores are from 50 to 500 nm in size and epitaxial material overgrowing these pores, forms continues high-quality layer. It is important that the NELOG method does not require any mask. This technique may be easily scaled for large area substrates.

In this work, SiC layers were grown on porous SiC by sublimation method, which is widely used for both epitaxial and bulk SiC growth. Porous SiC substrates were formed by surface anodization of SiC commercial wafers. It was shown that SiC layers grown on porous SiC substrates have smooth surface and high crystal quality. The surface of overgrown material was uniform and flat without any traces of porous structure. X-ray topography indicated significant defect density and stress reduction in SiC grown on porous material. Photoluminescence measurements showed a reduction of deep level recombination in SiC.
Micro-Raman Characterization of Arsenic-Implanted Silicon: Interpretation of the Spectra
Authors: Lavine James P. , Tuschel David D.
Published: April 2011

Raman spectra were measured on arsenic-implanted silicon with micro-Raman spectroscopy in the backscattering mode and with macro-Raman spectroscopy. A peak is observed between 505 and 510 cm−1 with 488 and 514.5 nm excitation. This peak and a related peak from the substrate at about 520 cm−1 are seen in selected regions of the implanted samples when the implant dose is above 2 × 1014 As/cm2. These features may be due to a long room temperature anneal, as they are absent in recently prepared samples. Possible explanations for the features are presented.
Scanning Tunneling Microscope-Induced Luminescence Studies of Defects in GaN Layers and Heterostructures
Authors: Evoy S. , Harnett C. K. , Keller S. , Mishra U. K. , DenBaars S. P. , Craighead H. G.
Published: April 2011

We present the scanning tunneling microscope-induced luminescence (STL) imaging of defects in optoelectronic materials. Resolution is first discussed using cross-sectional images of InGaAs/GaAs quantum dots. Proof of concept is then provided through the nanometer-scale imaging of GaN layers and quantum wells. The expected λ=356±25 nm range dominates the low temperature STL of GaN. Mapping of luminescence shows circular non-emitting areas around threading dislocations. Extent of dark areas suggests a hole diffusion length of Ld=30–55 nm, in agreement with reported values. The expected λ=450±35 nm range dominates the STL from a buried InGaN/GaN multiple quantum well. Imaging reveals 30–100 nm wide smooth fluctuations of luminescence.
Optical Absorption and Luminescence Study of the Effect of Thermal Treatments on the Porous Silicon Surface
Authors: Plugaru R. , Craciun G. , Bercu M. , Rams J. , Piqueras J.
Published: April 2011

The evolution of the cathodoluminescent emission bands of porous silicon at 420–480 nm, 540 nm and 640 nm under oxidizing and inert atmosphere annealings has been investigated and correlated to the structural reconstruction of the porous silicon surface during the treatments. Dry oxidation at low temperature of 450°C determines a less defected bonding interface structure of the growing oxide matrix comparatively with an oxidation treatment at 1000°C. The optical absorption band at 883 cm−1 observed in the 1000°C oxidized porous silicon is correlated to the presence of the interface defect centers. The quenching of the 540 nm and 640 nm emission bands in the high temperature oxidized porous silicon results from nonradiative transitions in the associated defect levels.
Confocal Micro-Raman Characterization of SiC Epilayers
Authors: Liu Ran
Published: April 2011

The large visible optical penetration depth makes it difficult to isolate the Raman signals of SiC epilayers from those of the substrates such as SiC, sapphire and Si when visible laser lines are used. In this work, confocal micro-Raman was used to characterize 3C, 4H and 6H SiC layers on different substrates with enhanced lateral resolution (˜ 0.8 μm) and depth resolution (˜ 2 μm). Both lateral and depth variation of the free electron concentration and scattering time were measured from n− SiC epi layers on n+ SiC substrates and from H+ implanted SiC. A defect mode induced by oxidation process was also analyzed as function of the depth and the lateral position.
Internal Spatial Modes and Local Propagation Properties in Optical Waveguides Measured Using Near-Field Scanning Pptical Microscopy
Authors: Goldberg Bennett B , Ünlü M. Selim , Rhodes Greg Vander
Published: April 2011

Near-field scanning optical microscopy has been used to measure the internal spatial modes and local properties controlling optical wave propagation in glass/silica buried waveguides. The period of the observed standing modes provides a direct measure of the effective index, which combined with the measured transverse modal shape and decay constants, determines the values of all spatial components of the wave vector.

Typically, small fluctuations in the material properties of structures can prevent proper operation as well as accurate diagnostic device modeling. The NSOM local probe measurements provide a means of detailed characterization, and defects in processing and their affects on performance are readily identified. We have also developed a technique that can obtain information about the locations of remote dielectric interfaces based upon the rate of change in the phase of the standing wave as a function of wavelength. Finally, experimental results addressing the issue of perturbation of the NSOM probe on the measurement of the local field shows a weak but measurable perturbation, and the dependence on aperture and material parameters will be discussed.
Characterization of Mixed-Metal Oxides Using Synchrotron-Based Time-Resolved x-ray Diffraction and x-ray Absorption Spectroscopy
Authors: Rodriguez José A. , Hanson Jonathan C. , Brito Joaquín L. , Maiti Amitesh
Published: April 2011

Experiments are described showing the utility of synchrotron-based time-resolved x-ray diffraction (TR-XRD) and x-ray absorption near-edge spectroscopy (XANES) for characterizing the physical and chemical properties of mixed-metal oxides that contain Mo and a second transition metal (Fe, Co or Ni). TR-XRD was used to study the transformations that occur during the heating of a FeMoO4/Fe2(MoO4)3 mixture and the α⇒β phase transitions in CoMoO4 and NiMoO4. The Mo LII- and O K-edges in XANES are very useful for probing the local symmetry of Mo atoms in mixed-metal oxides. The results of XANES and density-functional calculations (DMo13, DFT-GGA) show large changes in the splitting of the empty Mo 4d levels when going from tetrahedral to octahedral coordinations. XANES is very useful for studying the reaction of H2, H2S and SO2 with the mixed-metal oxides. Measurements at the S K-edge allow a clear identification of S, SO2, SO3 or SO4 on the oxide surfaces. Changes in the oxidation state of molybdenum produce substantial shifts in the position of the Mo LII- and MIII-edges.
Anomalous Ultra-Small-Angle X-ray Scattering From Evolving Microstructures during Tensile Creep
Authors: Jemian P. R. , Long G. G. , Lofaj F. , Wiederhorn S. M.
Published: April 2011

Ultra-small-angle x-ray scattering provides quantitative and statistically significant information on the size distribution of electron density inhomogeneities with dimensions between ≈100 Å and ≈5 μm. All sizes are sampled simultaneously with a single experiment, removing the possibility of observational bias. In a material such as commercial silicon nitride, where the inhomogeneities are due to populations of intergranular secondary phases and voids of similar dimensions, the scattering contains contributions from each individual population. A single USAXS scan cannot separate overlapping populations of scatterers due to the different contrasts of the microstructural components. Anomalous USAXS (A-USAXS) is an elementspecific contrast variation method to vary the scattering contribution from one of the populations while holding that of the other populations fixed. To follow the size evolution under tensile creep of both the cavities and the Yb disilicate secondary phases, A-USAXS data was measured near the Yb LIII absorption edge. Creep cavity and disilicate size distributions were each determined as a function of deformation.
Attenuation- and Phase-Contrast Microtomography Using Synchrotron Radiation for the 3-D Investigation of Specimens Consisting of Elements With Low and Medium Absorption
Authors: Beckmann F. , Bonse U.
Published: April 2011

Attenuation- and phase-contrast microtomography using synchrotron radiation is applied to different samples demonstrating the advantages and limits of the two different contrast mechanism. Photon energies in the range of 8-25 keV and 60-100 keV are used. Scanning techniques employing a 2-dim. x-ray detector allow for investigation of larger specimens at high spatial resolution.
X-ray Topography Study of Surface Damage in Single-Crystal Sapphire
Authors: Black D. , Polvani R. , Medicus K. , Burdette H.
Published: April 2011

X-ray diffraction topography was used to investigate the relationship between subsurface damage, near-surface microstructure, and fracture strength in a series of sapphire modulus of rupture (MOR) bars which had been fabricated to proof test fabrication processes. The strength of the bars was determined by failure in four point bending. The tensile surface of the bars was also examined using optical microscopy and non-contacting surface profilometry. Both show that the bars have good surface finish, with a typical RMS roughness of 0.7 nm. No correlation was found between RMS surface finish and fracture strength. Although the bars appeared to be indistinguishable, topographs taken prior to fracture testing revealed that they are of two distinct types. Type 1 has an oriented microstructure consisting of a pattern of linear features running the length of the bars. Type 2 was typical of well-polished sapphire, containing individual dislocations and occasional damage from handling. We attribute the Type 1 microstructure to fabrication damage that was not removed by subsequent processing and/or polishing. Fracture strength data showed that the Type I (damaged) bars had strengths less than 70 % of the bars without damage. Topography is sensitive to near-surface damage that can be correlated to fracture strength. Neither low magnification optical microscopy nor conventional surface finish statistics could be correlated to strength.
Dislocation motion around loaded notches in ice single crystals
Authors: Cullen D. , Hu X. , Baker I. , Dudley M.
Published: April 2011

Synchrotron X-ray topography has been used to study dislocation behavior around a notch in single crystal ice during in-situ deformation at a constant strain-rate of 1 × 10−8s−1 and a temperature of -8 °C. During deformation a dislocation depleted zone (DDZ) formed above the notch. Modeling the interaction between basal plane dislocation loops and the notch stress field suggested that this DDZ arose from dislocations gliding completely through the specimen.
X-ray Spectro-Microscopy and Micro-Spectroscopy in the 2100 eV to 12000 eV Region (Invited)
Authors: Mölders N. , Schilling P.J. , Schoonmaker J.M.
Published: April 2011

An x-ray microprobe beamline was recently developed and commissioned at the Center for Advanced Microstructures and Devices (CAMD), Louisiana State University. It achieves a moderate horizontal and vertical focal spot size of 18.8 µm × 7.0 µm (σ), respectively. The beamline and end-station are designed and optimized to perform (i) spatially-resolved x-ray fluorescence spectroscopy (spectro-microscopy) using the broad intense spectrum of the white synchrotron radiation, and (ii) spatially-resolved x-ray absorption spectroscopy (micro-spectroscopy) in the energy region of 2100eV to 12000 eV. These dual capabilities enable K-edge measurements and mapping, in non-vacuum conditions, of low-Z elements down to Cl, S, and P that are of both environmental interest and technological importance. In this paper, an application of this novel synchrotron tool to elucidate the elemental distribution (microstructure) and chemical state (speciation) of Mn, Cl, S, and P-containing particulates emitted from automobile engines burning methylcyclopentadienyl manganese tricarbonyl- (MMT-) added fuel will be discussed in detail. Future opportunities of this microbeam technique in materials science and materials characterization will also be outlined.
Extracellular Iron-Sulfur Precipitates From Growth ofDesulfovibrio desulfuricans
Authors: Antonio Mark R. , Tischler Monica Lee , Witzcak Dana
Published: April 2011

We have examined extracellular iron-bearing precipitates resulting from the growth ofDesulfovibrio desuyfuricansin a basal medium with lactate as the carbon source and ferrous sulfate. Black precipitates were obtained whenD. desulfuricanswas grown with an excess of FeSO4. WhenD. desulfuricanswas grown under conditions with low amounts of FeSO4, brown precipitates were obtained. The precipitates were characterized by iron K-edge XAFS (x-ray absorption fine structure),57Fe Mössbauer-effect spectroscopy, and powder x-ray diffraction. Both were noncrystalline and nonmagnetic (at room temperature) solids containing high-spin Fe(III). The spectroscopic data for the black precipitates indicate the formation of an iron-sulfur phase with 6 nearest S neighbors about Fe at an average distance of 2.24(1) Å, whereas the brown precipitates are an iron-oxygen-sulfur phase with 6 nearest O neighbors about Fe at an average distance of 1.95(1) Å.
Giant Magnetoresistance Imaging for NDE of Conductive Materials
Authors: Boltz E. S. , Albanna S. G. , Stallings A. R. , Spooner Y. H. , Abeyta J. P.
Published: April 2011

Traditional coil-based eddy-current sensors are severely limited in their ability to detect small buried defects, defects under fasteners and deeply buried cracks and corrosion. TPL has developed eddy-current sensors and arrays based on the use of Giant Magnetoresistance (GMR) sensor elements. GMR offers high sensitivity, very wide bandwidth and low noise from DC to over 1 GHz. Coupled with the ability to fabricate GMR sensors with micron-level dimensions, these new eddy-current sensors offer an ideal technology for inspections requiring high spatial resolution and low-frequency, deeply-penetrating fields.
Characterization of Hydrogen in Concrete by Cold Neutron Prompt Gamma-Ray Activation Analysis and Neutron Incoherent Scattering
Authors: Paul Rick L. , Chen-Mayer H. Heather , Lindstrom Richard M. , Blaauw Menno
Published: April 2011

A combination of cold neutron prompt gamma-ray activation analysis (PGAA) and neutron incoherent scattering (NIS) has been used for nondestructive characterization of hydrogen as a function of position in slabs of wet concrete of different compositions. Hydrogen was determined by PGAA by scanning each sample across a 5 mm diameter neutron beam in 10 mm increments, and measuring the 2223 keV prompt gamma ray. NIS measurements were performed by scanning the sample across a 5 mm diameter neutron beam at 5 mm increments and detecting scattered neutrons. The measurements demonstrate the feasibility of the techniques for 2D compositional mapping of hydrogen and other elements in materials, and indicate the potential of these methods for monitoring the uniformity of drying concrete.
Photoelastic Imaging of Process Induced Defects in 300mm-Silicon Wafers
Authors: Geiler H.D. , Kürner W. , Storbeck O.
Published: April 2011

Process induced crystal defects in silicon wafers can be detected by their stress fields. The nondestructive photoelasticity based on laser polarimetry is applied to visualize the stress fields of temperture gradient induced lattice defects like sliplines or extended defect areas around boat marks. The quantitative evaluation of the defects allows their characterization by a specific danger potential for further evolution causing upstream problems in IC manufacturing.
In Situ Spectroscopic Ellipsometry for the Real Time Process Control of Plasma Etching of Silicon Nitride
Authors: Rosen I. G. , Parent T. , Fidan B. , Madhukar A.
Published: April 2011

Spectroscopic ellipsometry (SE) is a commonly used non-destructive, non-invasive in-situ sensor for dry etching. SE measures the change in the polarization state of light reflected from a surface. Sample thickness is obtained by fitting a model to the experimental ellipsometry data. In this paper we describe the design, testing and evaluation of an SE based adaptive real time feedback controller for etch rate regulation in CF4/O2 plasma etching of silicon nitride films. The feedback variable is the current etch rate as determined from the in-situ SE measurements of the film's thickness. The controller compensates for drifts in etch rate which occur during a given etch, and adaptively adjusts for the run-to-run variability inherent to plasma processing. Experimental results are presented and discussed.
In Situ Spectroscopic Ellipsometry Study of the Oxide Etching and Surface Damaging Processes on Silicon Under Hydrogen Plasma
Authors: Vargas I.M. , Manso J.Y. , Guzmán J.R. , Weiner B.R. , Morell G.
Published: April 2011

We employed in situ ellipsometry in the monitoring of surface damage to monocrystalline silicon (Si) substrates under hydrogen plasma conditions. These measurements were complemented with spectroscopic ellipsometry and Raman spectroscopy, in order to characterize the surface conditions. It was found that heating the Si substrate to 700°C in the presence of molecular hydrogen produces etching of the native oxide layer, which is typically 10 Å thick. When the already hot and bare silicon surface is submitted to hydrogen plasma, it deteriorates very fast, becoming rough and full of voids. Modeling of the spectroscopic ellipsometry data was used to obtain a quantitative physical picture of the surface damage, in terms of roughness layer t ickness and void fraction. The results indicate that by the time a thin film starts to grow on these silicon surfaces, like in the chemical vapor deposition of diamond, the roughness produced by the hydrogen plasma has already determined to a large extent the rough nature of the film to be grown.
Electrically Based Non-Destructive Microstructural Characterization of All Classes of Materials
Authors: Gerhardt Rosario A.
Published: April 2011

This paper gives a short summary of the background, theory and methodology needed to utilize electrical measurements as a non-destructive method for microstructural characterization. Examples are given for all classes of materials. Details are given for how to detect: (1) pore volume in thermal barrier coatings, (2) formation of surface layers due to moisture adsorption in a wide variety of materials, (3) orientation of fibers and whiskers in ceramic matrix and polymer matrix composites, (4) crack detection in metals and (5 ) stacking faults in semiconductors. Many other examples are mentioned. It needs to be emphasized that electrical measurements alone are not sufficient to identify the microstructural features of interest but must always be accompanied by complementary techniques. Proper data collection and data interpretation of properties of a specific set of materials can lead to in-line process monitoring, quality control monitoring, mechanical damage monitoring and environmental degradation monitoring of those materials.
Investigation of Quasi-Breakdown Mechanism in Ultrathin Gate Oxides
Authors: Guan Hao , He Y. D. , Li M. F. , Cho Byung Jin , Dong Zhong
Published: April 2011

The conduction mechanism of quasi-breakdown (QB) for ultra-thin gate oxide has been studied in dual-gate CMOSFET with a 3.7 nm thick gate oxide. Systematic carrier separation experiments were conducted to investigate the evolutions of gate, source/drain, and substrate currents before and after gate oxide QB. Our experimental results clearly show that QB is due to the formation of a local physically-damaged-region (LPDR) at Si/SiO2 interface. At this region, the effective oxide thickness is reduced to the direct tunneling (DT) regime. The observed high gate leakage current is due to DT electron or hole currents through the region where the LPDR is generated. Under substrate injection stress condition, there is several orders of magnitude increase of Isub(Is/d) at the onset point of QB for n(p) - MOSFET, which mainly corresponds to valence electrons DT from the substrate to the gate. Consequently, cold holes are left in the substrate and measured as substrate current. Under gate injection stress condition, there is sudden drop and even change of sign of Isub(Is/d) at the onset point of QB for n(p)-MOSFET, which corresponds to the disappearance of impact ionization and the appearance of hole DT current from the substrate to the gate. In the LPDR region, the damaged structure may have two or multi metastable states corresponding to different effective oxide thickness. The thermal transition between two or multi metastable states leads to random telegraph switching noise (RTSN) fluctuation between two or multi levels.
Correlation Between Gate Induced Drain Leakage and Plasma Induced Interface Traps
Authors: Ma Siguang , Zhang Yaohui , Li M. F. , Li Weidan , Wang J. L. F. , Yen Andrew C. , Sheng George T. T.
Published: April 2011

In this paper we carefully investigate the correlation between gate induced drain leakage current and plasma induced damages in the deep submicron p+ polysilicon gate pMOSFETs with gate oxide thickness of 50 Å. Low field enhancement of gate induced drain leakage current caused by plasma charging damage is a function of metal 1 antenna area/length ratio and cell location. Combined with the charge pumping measurements, it is found that gate induced drain leakage current enhancement is mainly due to the plasma induced interface traps. A linear relationship between the gate induced drain leakage and the plasma induced interface trap density is observed within the experimental error. On the other hand, the threshold voltage measurements show that oxide trapped charge has no major contribution to, and no correlation with, the gate induced drain leakage current for thin gate oxide MOSFET devices.
Characterization of Ta2O5 Thin Films With Small Current Leakage for High Density DRAMS
Authors: Kanda N. , Furukawa R. , Ishibashi M. , Kunitomo M. , Homma T. , Takahashi M. , Uemura T. , Kanai M. , Kubo M. , Ogata K. , Yoshida T. , Yamamoto H. , Ohji Y
Published: April 2011

We have confirmed that grain boundaries are related to leakage problems in Ta2O5/SiON capacitors for high dielectric DRAMs. XRD studies using an intensity ratio of (200) to (001) showed that the crystallographic structure of Ta2O5 film was strongly dependent on preparation conditions. As the (200) oriented grains grew faster than the other grains, it became important to control its grain growth in forming uniform grain boundaries. TEM observation has shown that Ta2O5 film with a high intensity ratio of (200) to (001) was made up of large size grains and had SION interface intruding into grain boundaries. By using the current-mode AFM, we could monitor leakage current directly through grain boundaries on Ta2O5 film.
Improved Performance and Reliability in Aggressively-Scaled NMOS and PMOS FETs: i) Monolayer Interface Nitridation, and ii) Replacement of Stacked Oxide/Nitride Dielectrics With Optimized Oxide/Oxynitride Stacks
Authors: Yang Hanyang , Niimi Hiro , Lucovsky Gerry
Published: April 2011

This paper demonstrates optimized performance and reliability in ‘second generation’ gate dielectrics which include monolayer nitrided Si-SiO2 interfaces, and deposited silicon oxynitride alloy gate dielectrics. Devices with oxynitride alloy gate dielectrics with an approximate 2:1 ratio of N:O display reduced tunneling current, improved hole mobilities and improved reliability compared to devices with Si-nitride gate dielectrics and the same nitrided interface.
Controlling the Concentration and Position of Nitrogen in Ultrathin Oxynitride Films Formed by Using Oxygen and Nitrogen Radicals
Authors: Watanabe K. , Togo M. , Tatsumi T.
Published: April 2011

The formation of oxynitride films less than 2.0 nm by using oxygen and nitrogen radicals produced by an electron cyclotron resonance plasma in an ultrahigh-vacuum system has been studied. The nitrogen concentration of the films was evaluated by x-ray photoelectron spectroscopy, and the position of the N in the films was evaluated by secondary ion mass spectroscopy. The interface roughness was also investigated by using atomic force microscopy. We found that the N concentration can be controlled at values up to 22.5%, and that although the interface roughness tends to increase with increasing N concentration, supplying oxygen and nitrogen radicals simultaneously decreases the roughness of the film and increases its nitrogen concentration (N: 18.2%, RMS: 0.12 nm). We also found that the nitrogen profile can be controlled by using different processing sequences. Radical oxynitridation should thus be very useful for making ultrathin gate-insulator films.
Process Improvements for Reductions in Total Charge and Interface Trap Densities of Thermally-Grown Sub-3.5nm-Thick Silicon Nitrides
Authors: Dang Sanjit Singh , Takoudis Christos G.
Published: April 2011

Ultra-thin silicon nitride films are being studied for use as high-dielectric constant (highk) materials in future gate dielectric applications, as Complementary Metal-Oxide-Semiconductor (CMOS) transistors are scaled down to the sub-100nm regime. In this study, process modifications are proposed to reduce the total charge and interface trap densities in sub-3.5 nm-thick silicon nitride films, grown in NH3, in a conventional furnace at 900°C and 1 atm. It is shown that by employing a short (<1 min) oxynitridation step in NO, before nitridation, and oxynitridation/Ar-annealing steps, after nitridation, silicon nitride films can be thermally grown with a total charge density as low as about 2.5E10 q/cm2 and an interface trap density of about 2.1E11/(eV-cm2). Besides, the effect of using NO as opposed to N2O for oxynitridation steps is also discussed.
Low-Temperature Oxidation of Silicon(100) Substrates Using Atomic Oxygen
Authors: Ueno T. , Chikamura S. , Sakuraba F. , Iwasaki Y
Published: April 2011

Low temperature oxidation process of Si(100) substrates using atomic oxygen has been proposed. For the generation of atomic oxygen, microwave plasma remotely attached on the oxidation chamber was used. In the microwave plasma, the large amount of rare gas and a small amount of 02 gas mixture was supplied. The existence of the large amount of rare gas controls the plasma energy to some restricted values associated with the metastable states of the rare gas. Consequently, using Kr as mixed rare gas, atomic oxygen were efficiently generated instead of excited 02 molecules with any vibrational or ionized states. The oxidation kinetics of crystalline Si using this process was shown to be diffusion limiting, even if the oxide thickness was less than several nm. The activation energy of B, which is referred to as the parabolic rate constant, was found to be as low as 0.14eV In addition, lower interface trap density of 2.6 × 1011/cm2/eV at the mid gap could be achieved for the as-grown SiO2/Si(100) interface at the processing temperature of 500C.
Theoretical and Experimental Investigation of Ultrathin Oxynitrides
Authors: Demkov A.A. , Liu R.
Published: April 2011

Microscopic properties of thin oxynitrides are investigated using a combination of the infrared ATR and ab-initio electronic structure methods. We use a theoretical structural model based on the Si-SiO2 interface with the oxide thickness of 0.8 nm. The interfacial region amounts to about 0.4 nm (the total thickness of the oxygen containing layer is 1.2 nm). The Quantum Molecular Dynamics simulations suggest that N accumulates at the interface. We have generated samples with the nitrogen concentrations from 1.69 × 1014 cm−2 to 6.78 × 1014 cm−2. The structural analysis of nitrogen containing cells indicates a significant improvement of the oxide layer and the strain reduction at the interface. We have performed a calculation of the vibrational density of states. A N-localized mode at 809 cm-1 has been identified. The experimental ifnrared ATR data is in qualitative agreement with the calculation. The valence band offset calculations reveal a 0.3 eV increase of the offset due to nitrogen at the highest nitrogen concentration considered. The valence band offset increase comes mainly from the structural change in the oxide layer. The interfacial dipole contributes 0.12 eV to the increase, while the structural change in the oxide layer gives additional 0.2 eV.
Furnace Oxynitridation in Nitric Oxide of Thin Silicon Oxide: Atomic Transport Mechanisms and Interfacial Microstructure
Authors: Trimaille I. , Ganem J.-J. , Gosset L. G. , Bailly O. , Rigo S. , Cantin J.-L. , Bardeleben H. J. Von
Published: April 2011

Oxynitridation in nitric oxide of commercial 5 nm and 13 nm oxides is investigated, as well as reoxidation steps. The results are discussed in terms of atomic transport mechanisms and modification of interfacial microstructure. Atomic transport is studied through the use of isotopic tracing and nuclear reactions analyses (NRA): we measured the atomic areal densities (14N, 15N, 16O, 18O) in the films and the concentration depth profiles of the heavy and stable isotopes (15N, 18O) with near surface subnanometric resolution. To scan the evolution of the interfacial microstructure, Pb0 centers concentrations were measured by electron paramagnetic resonance spectroscopy (EPR), after each treatment step. The previously proposed mechanisms for NO oxynitridation of silica are confirmed: i) the NO molecules diffuse via interstitial sites, without reaction with the lattice, before reacting with the dielectric/Si interface; ii) at the external surface region, oxygen exchange is observed due to a step-by-step motion of network oxygen atoms induced by the presence of network defects. During reoxidation in O2 neither loss or observable redistribution of nitrogen is evidenced. For the 13-nm thick film, in the external surface region, the oxygen exchange is seen to be more effective than in the case of silica (or silicon) oxidation: that is O2 is more reactive on NO-nitrided silica than on pure silica. The concentration of Pbo centers decreases after the NO thermal step and increases again after the further reoxidation step.
Impact of temperature and breakdown statistics on reliability predictions for ultrathin oxides
Authors: Groeseneken G. , Degraeve R. , Kaczer B. , Maes H.E.
Published: April 2011

This paper discusses the evolution in the degradation and breakdown behaviour of ultra-thin oxides when scaling the oxide thickness into the sub-4 nm range for future CMOS technology generations. It will be shown that changes in the breakdown statistics, which can be explained by a percolation model for breakdown, lead to an increased area dependence of the time-tobreakdown. This has to be taken into account when predicting the oxide reliability. Also the impact of the test methodology, the relevance of a so-called polarity gap in the charge-tobreakdown and its consequences for reliability testing, are highlighted. Moreover, a strong increase in the temperature dependence of breakdown, especially for sub-3 nm oxides, is demonstrated and the impact of temperature on trap generation and critical trap density at breakdown is discussed. Finally it is shown that the combined effects of all these phenomena might lead to oxide reliability becoming a potential showstopper for further technology scaling.