bluuebunny/crossref_metadata_2025 huggingface dataset:
A Kinetic Study of the C49 to C54 Conversion in TiSi2 Using Electrical Resistivity Measurements on Single Sub-Micron Lines
Authors: Saenger K. L. , Cabral C. , Clevenger L. A. , Roy R. A.
Published: April 2011

A simple, quasi-in situ resistivity technique was used to examine the C49 to C54 conversion kinetics of TiSi2 on sub-micron (0.2 to 1.1 μm) line structures formed in a self-aligned silicide (salicide) process. This technique was used to examine both aggregate conversion vs. time behavior and individual-line conversion vs. time behavior as a function of linewidth and polysilicon doping. As linewidth decreased, aggregate conversion vs. time at temperature behavior slowed, and the conversion behaviors shown by nominally identical lines became more variable. Four line behaviors were identified on the narrowest lines: short incubation/prompt conversion, gradual conversion, incomplete conversion, and no conversion. These behaviors are compared to those predicted by the Avrami equation, and to those predicted for a nucleation-site-density controlled reaction under conditions of low nucleation density. It is suggested that C49-C54 conversion in narrow lines may be primarily limited not by the number of C54 nucleation events, but by the presence of randomly occurring line-edge “defect” sites which slow and/or halt C54 grain growth.
Transport and Low Temperature Specific Heat Measurements of CrSi2 Single Crystals
Authors: Lasjaunias J. C. , Gottlieb U. , Laborde O. , Thomas O. , Madar R.
Published: April 2011

We have measured the Hall coefficient and the resistivity of single crystals of CrSi2. This compound crystallises in the hexagonal C40 structure and is generally reported as a semiconductor with a gap of around 0.35 eV. The resistivity is large, several hundreds of μΩ.cm and exhibits a metallic behaviour. RH leads to a hole concentration of 8.5×1026 m−3 at 300K.

The specific heat at low temperature (0.7 K < T < 8 K ) can be describe as the sum of an electronic (γΓ) and a phonon (βT3) contribution. The analysis of the data leads to θD = 556 K and to an electronic density of states which is only two times smaller than those obtained for the metallic parent compounds VSi2, NbSi2 and TaSi2. This result questions the semiconducting nature of the chromium disilicide.
Characterization of Zirconium Germanosilicide Formed by Solid State Reaction of ZR With Sil−xGex Alloys
Authors: Wang Z. , Aldrich D. B. , Goeller P. , Nemanich R. J. , Sayers D. E.
Published: April 2011

We have investigated the electrical and structural properties of zirconium germanosilicide (Zr-Si-Ge) films formed during the Zr-Sil−xGex solid state reaction. Thin films of C49 Zr(Si1−xGex)2 were formed from the solid phase reaction of Zr and Si1−xGex bilayer structures. It was observed that Zr reacts uniformly with the Sil−xGex alloy and that C49 Zr(Si1−x Gex)2 is the final phase of the Zr-Si1−xGex, solid phase reaction (such tht y = x) for all compositions examined (x = 0.20, 0.33, and 0.50). The sheet resistance of the Zr(Si1−xGex)2 thin films were higher than the sheet resistance measured for ZrSi2 films. The stability of Zr(Sil−x Gex)2 in contact with Si1−Gex was investigated and no germanium segregation was detected in the Zr(Si1−xGex)2/Si1−Gex structures.
Growth and Electrical Performance of Heterojunction P+ Si1−x−yGexCy/p+ Si Diodes
Authors: Chang C. L. , Amour A. St. , Lanzerotti L. D. , Sturm J. C.
Published: April 2011

We have fabricated heterojunction p+ Si1−x−yGexCy/ p+ Si diodes. The SiGeC layers were grown epitaxially on Si (100) substrates by the rapid thermal chemical vapor deposition (RTCVD) technique using methysilane gas as a carbon precursor. The germanium concentration is 20% in these SiGeC alloys and the carbon concentrations are in the range of 0% to 1%. By studying the current-voltage characteristics of these diodes as a function of temperature the valence band discontinuities between SiGeC and Si layers were obtained as a function of carbon concentrations. We have found that the valence band discontinuity of the SiGe/Si heterostructure decreases by II meV when 1% of carbon is incorporated. Photoluminescence (PL) results show that 1% carbon increases the bandgap of strained p+SiGe alloys by 25 meV. This would imply that the conduction band discontinuity of SiGe/Si will decrease by 14 meV when 1% carbon is incorporated.
Effect of Phonon Confinement on Intersubband Lasing Lifetimes of Si/SiGe Quantum Well Structures
Authors: Friedman L. , Sun G.
Published: April 2011

The feasibility of population inversion is studied for the Si/SiGe system. Because of the absence of polar optical phonon scattering, the lifetime difference of the upper and lower lasing levels, to which the population inversion and laser gain are proportional, are an order of magnitude larger than in the III-Vs; nor does this show the large decrease to negative values (loss of population inversion) when the intersuband energy difference exceeds the optical phonon energy. We have investigated the effect of phonon confinement of the Ge-Ge and Si-Ge vibrations on the intersubband scattering rates and find a furthur enhancement of the the intersubband lifetimes as compared to those due to unconfined phonons.
Diffusion of Arsenic in Single Crystalline CoSi2
Authors: Pisch A. , Cardenas J. , Svensson B. G. , Petersson C. S.
Published: April 2011

The lattice diffusion of arsenic in CoSi2 has been studied in the temperature range from 750°C to 950°C. Two types of bulk samples were used: single crystals prepared by a modified Czochralski pulling technique from a radio frequency levitated melt and polycrystals synthesised by quenching from the melt. The latter samples were subsequently annealed in vacuum at 900°C and displayed grain sizes in the millimetre range. Starting from an ion implanted arsenic profile with two different doses (5·1014 and 5·1015 cm−2) the concentration versus depth profiles after annealing at different temperatures and different times were measured using secondary ion mass spectrometry (SIMS). Contrary to previous studies by other authors substantial diffusion has been observed with an activation energy of 3.3 eV and a pre-exponential factor of 7.37 cm2/s for the diffusion coefficient. These values are very close to the self diffusion coefficient of Si in CoSi2 suggesting that the As atoms migrate via thermal vacancies on nearest neighbour lattice sites by a similar type of mechanism as the Si (and Co) atoms. In the high dose implanted polycrystalline samples arsenic precipitation occurred which gives an estimate for the solid solubility in the 1019 atoms/cm3 range at 800 °C.
Phase Transformation of Titanium Disilicide Induced by High-Temperature Sputtering
Authors: Fujii K. , Tung R. T. , Eaglesham D. J. , Kikuta K. , Kikkawa T.
Published: April 2011

The reaction between sputtered Ti thin films and heavily arsenic doped Si(100) is studied. The use of an arsenic implantation to pre-amorphize the Si substrate and the choice of the substrate temperature during Ti sputtering are both found to have a significant effect on subsequent TiSi2 reactions. Cross-sectional transmission electron microscopy reveals that an amorphous TiSix layer is formed at the interface between Si and as-sputtered Ti. The thickness of this interfacial layer increases with the sputtering temperature. After rapid thermal anneals in nitrogen, the sheet resistances of TiSi2 thin films grown with the pre-amorphization step and a high sputtering temperature (450°C) are generally lower than films processed under other conditions. This apparent reduction in the temperature for the polymorphic C49 to 54 phase transformation in TiSi2 is shown to originate from a higher nucleation density of the C54-TiSi2 phase. These dependencies of the silicide reaction are ascribed to the interfacial amorphous TiSix layer. In increasing the nucleation density of the C54-TiSi2 phase, the amorphous TiSix layer is speculated to either act as a direct nucleation source for the C54-TiSi2 phase, or lead to more defective C49-TiSi2 structures which facilitate the C54-TiSi2 nucleation.
Grain Orientation Mapping and Spatially Resolved Strain Measurements for Polycrystalline Films by X-Ray Microdiffraction
Authors: Wang P.-C. , Cargill G. S. , Noyan I. C. , Liniger E. G.
Published: April 2011

We describe spatially resolved grain orientation mapping of polycrystalline films using a synchrotron-based x-ray microdiffraction system. The system consists of a tapered glass capillary as a white x-ray concentrator, an energy-dispersive solid state detector and an x-y-z sample stage. Two mapping modes are discussed: reciprocal-space mapping and real-space mapping. Information about the orientations of grains within the irradiated volume is determined by reciprocal-space mapping. The locations of grains having a specified orientation are determined by real-space mapping. Examples are shown for blanket films of AI(4 wt.% Cu) 4μm-thick and 0.5μm thick. Results are also shown for 10μm-wide and μm-wide pure lines. X-ray beams of 10inm diameter were used for these measurements. Spatially resolved thermal strain measurements were made for a single 10μm-wide, 200μm-long passivated Al line, and they were found to be consistent with calculations based on equi-biaxial thermal stress within the line.
Effect of Substrate Heating During Excimer Laser Annealing on Poly-Si TFT
Authors: Noguchi T. , Tang A. J. , Tsai J. A. , Reif R.
Published: April 2011

Single-shot ELA was performed on 45nm-thick amorphous Si films. With an increase in pulse energy density, the cystallinity improved drastically for both samples without heating and with heating at 400°C. Correspondingly, the characteristics of TFT fabricated using a low temperature process improved distinctly. The threshold voltage decreased depending on the decrease in gate voltage swing due to the improvement in crystallinity of Si films. Efficient single-pulse ELA of less than 250MJ/cm2 as the optimum condition for poly Si TFT has been attained as a result of saving an energy amount of 100mJ/cm2 by heating the substrate. Moreover, a uniform distribution of TFT characteristics across the wafer was obtained.
Selective Deposition of Polycrystalline Silicon Thin Films by Hot-Wire CVD
Authors: Yu Shuangying , Gulari Erdogan , Kanicki Jerzy
Published: April 2011

Polycrystalline silicon thin films have been selectively deposited at a deposition rate of 60–100Å/min and a substrate temperature of 300°C on molybdenum or silicon over silicon dioxide, silicon nitride or Coming 7059 glass substrate in a continuous hot-wire CVD process involving hydrogen and disilane. Excellent selectivity is achieved on features as small as one micrometer spaced molybdenum lines. The crystallinity of the selectively deposited polysilicon films is thickness dependent. The substrate selectivity is sensitive to both silicon content in the gas phase and substrate temperature. Selective deposition shifts to lower Si content in the gas phase when substrate temperature increases. At a certain substrate temperature, for a silicon content above a certain value in the gas phase, films with similar crystallinity are non-selectively deposited on both molybdenum and silicon dioxide.
Significance of Microstructure for a MOCVD-Grown YSZ Thin Film Gas Sensor
Authors: Vetrone J. , Foster C. , Bai G.
Published: April 2011

We report the fabrication and characterization of a low temperature (200°C-400°C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-sensing response is produced by applying a cyclic voltage which generates voltammograms with gas-specific current peaks and shapes. Growth conditions are optimized for preparing YSZ films having dense microstructures, low leakage currents, and maximum ion conductivities. In particular, the effect of growth temperature on film morphology and texture is discussed and related to the electrical and gas-sensing properties of the thin film sensor device.
Structural Processes in Gold-Based Metallization During the Formation of Ohmic Contacts to GaSb
Authors: Piotrowska A. , Kańifiska E. , Guziewicz M. , Mizera E. , Dynowska E. , Lin X. W. , Rouvimov S. , Weber Z. Liliental , Kwiatkowski S.
Published: April 2011

Annealing behavior of Au, AuZn, and AuSb metallization on GaSb have been investigated by the combined use of RBS, XRD, TEM, and I-V characterization. The results give evidence that the thermally activated contact reaction strongly depends on the particular elements incorporated in the Au layer. Pure Au reacts with GaSb at 100°C. The addition of Zn to Au metallization increases the thermal stability of the metallization/semiconductor system to 200°C. Antimony, forming with gold the AuSb2 phase in metallization, provides the most stable ohmic contact system.
Low Resistivity Mo-W Alloy for A-Si Tft Gate Electrode
Authors: Hara Y. , Atsuta M. , Oka T. , Tsuji Y. , Ogawa Y. , Takemura M. , Ikeda M. , Suzuki K.
Published: April 2011

Among various requirements for the a-Si TFT-LCD gate electrode, low resistivity is becoming more emphasized with the increase of display size and information content as well as process feasibility. We have developed a low resistivity Mo-W alloy as a material for gate buslines.

The Mo-W film was formed by DC magnetron sputtering using Ar or Kr as the working gas. The resistivity of the fabricated film was 16 μΩ-cm when deposited with Ar, and decreased to a value as low as 13 μΩ-cm with Kr, which was less than a half that of the conventional Mo-Ta film. Inverted staggered a-Si TFTs having Mo-W gate electrodes formed with Kr were fabricated, and good transfer performance with thermal- and electrical stability was obtained. The applicability of the new alloy to LCDs with large area and high resolution was shown.
Diffusion Barrier Property of Sputtered Molybdenum Nitride Films for Dram Copper Metallization
Authors: Park Jong-Wan , Lee Jeong-Youb
Published: April 2011

Diffusion barrier property of sputtered molybdenum nitride films for DRAM copper metallization was investigated as a function of annealing temperature. Molybdenum nitride thin films on silicon remained stable upon annealing 650°C-30min, but h-MoSi2 and t-MoSi2 were formed after the heat treatment at 700°C and Mo5Si3 phase was formed at 850°C. Increasing the annealing temperature decreased the stress of the γ-Mo2N/Si film down to about 0.8×1010dyne/cm2 at 800°C due to the reduction of the intrinsic stress component. Copper films on silicon substrates separated by thin layers of molybdenum nitride remained stable during the heat treatment at 600°C, but they began to fail as a diffusion barrier after the heat treatment at 650°C, when molybdenum silicides and copper silicide were thought to be formed. On heating, Cu/γ-Mo2N/Si films were affected by thermal stress as due to the thermal expansion coefficient between copper and molybdenum nitride thin films. Furthermore, interlayer interactions between copper and silicon increased with increasing the annealing temperature. The interlayer reactions were investigated by Rutherford backscattering spectrometry, X-ray photoelectron spectrscopy and Nomarski microscopy.
Energy-Filtered Tem of Ag-Co Thin Films
Authors: Scott John Henry J. , Majetich Sara. A.
Published: April 2011

TEM grids containing Ag65Co35 thin films were annealed under protocols corresponding to maximum giant magnetoresistance (GMR) response in thicker films. These films were examined using high resolution TEM, electron energy loss spectroscopy (EELS), and electron spectroscopic imaging (ESI), which revealed small (50 nm diameter) Ag particles and very small (approximately 2 nm diameter) clusters in a suspending matrix of Ag-Co alloy. Cobalt maps did not reveal individual cobalt clusters, indicating that if such clusters exist, they are smaller than the 1–2 nm resolution limit of the technique.
Embrittlement of Cracks at Interfaces
Authors: Thomson Robb , Emeritus  , Carlsson A. E.
Published: April 2011

This paper presents a synopsis of already published work for cracks on interfaces and new results on the effect of changing the chemistry of the atoms at the interface. Once the appropriate cut-off for the oscillatory singularity in the interface analysis is determined, the physics of the crack is determined in terms of an appropriate driving force for a particular event of interest, and a lattice resistance to the event. Analytic approximations are available for the driving forces, and the lattice resistance is determined on the basis of a block construction for the lattice. We show that for the case where the chemical bonding at the interface is different from that in the matrix, the same ideas are applicable, provided the different chemistry is incorporated correctly in the lattice resistance construction.
A Tight-Binding Model Beyond Two-Center Approximation
Authors: Wang C. Z. , Tang M. S. , Pan Bicai , Chan C. T. , Ho K. M.
Published: April 2011

We present a tight-binding model which goes beyond the traditional two-center approximation and allows the hopping parameters and the repulsive energy to be dependent on the bonding environment. We show that this model works well for metallic as well as covalent systems.
Formation Energy, Stress, and Relaxations of Low-Index Rhodium Surfaces
Authors: Filippetti Alessio , Fiorentini Vincenzo , Stokbro Kurt , Valente Riccardo , Baroni Stefano
Published: April 2011

Ab initio local-density- functional- theory calculations of formation energies, surface stress, and multilayer relaxations are reported for the (111), (100), and (110) surfaces of Rh. The study is performed using ultrasoft pseudopotentials and plane waves in a parallel implementation.
Valence-Band Offset at the Zn-P Interface Between ZnSe and III-V Wide Gap Semiconductor Alloys: A First-Principles Investigation
Authors: Bernardini F. , Nieminen R. M.
Published: April 2011

We present a first-principles calculation of the valence-band offset at the (001) interface between ZnSe and III-V lattice-matched alloys based on Al, Ca, In, P elements, namely Al0.5In0. 5P and Ga0.1n0.5P. Among the different possible interface geometries we have focused on the P-terminated alloy in contact with the Zn-terminated ZnSe crystal. The results of this study show the existence of a very low band offset at the abrupt interface, both for the ideal geometry and for the relaxed atomic positions. The investigation of the electronic interface band structure reveals the presence of a low-lying half-filled interface band related to the Zn-P bond.
Atomic Force And Scanning Electron Microscopy Of Corrosion And Fatigue Of An Aluminum-Copper Alloy
Authors: Kowal K. , DeLuccia J. , Josefowicz J.Y. , Laird C. , Farrington G.C.
Published: April 2011

The morphological features of 2024-T3 aluminum alloy were delineated using atomic force microscopy (AFM) during separate and combined actions of corrosion and fatigue.

In-situ AFM corrosion studies in hydrochloric acid environments without mechanical deformation showed accelerated dissolution in the vicinity of second phase precipitates leading to intergranular corrosion. During fatigue in air, AFM images revealed steps along grain boundaries, as well as parallel extrusions and intrusions during the early stages of fatigue life. At later stages of mechanical deformation persistent slip bands (PSBs) were observed on the sample's surface. Cracks were observed to nucleate and propagate along PSBs. For experiments where samples were subjected to the simultaneous action of a corrosive environment and mechanical deformation, intergranular cracking was observed during the early stages of fatigue life. The corrosive environment was observed to accelerate the crack nucleation process.
The Roles Of Atomic-Scale Dynamics And Structure In The Brittle Fracture Of Silica
Authors: Swiler Thomas P. , Varghese Tansen , Simmons Joseph H.
Published: April 2011

We modeled the initiation of fracture in vitreous silica at various strain rates using molecular dynamics simulations. We avoided biasing the location for fracture initiation within the sample so that we could study the effects of dynamics and structure on determining the path to fracture, defined as the particular bonds that break during the course of fracture. We sought to show that the path to fracture would be primarily determined by the local variations in the structure of the vitreous phase at low strain rates, with diminished sensitivity on structural variations at higher strain rates. However, the results of our model indicate that the path to fracture is dependent not only on the initial structure of the system and the applied strain rate, but also on the initial phase of the thermal vibrations. This underscores the importance of atomic dynamics in determining the path to fracture in brittle materials and provides a justification for extending the analysis of fracture surfaces to the near-atomic scale.
Fracture Process Control For A Peel-Apart Imaging Film
Authors: Choi H.-C. , Kniazzeh A. , Habbal F.
Published: April 2011

Peeling delamination and image-layer fracture of a multilayer imaging film is analyzed by a simple beam approximation. Criteria for propagation of the delamination cracks and tensile failure of the imaging layer are established. The critical role of substrate strain in controlling tensile strain in the imaging layer is explored. For the case of a thin imaging layer with a fracture strain below a critical level, image layer fracture occurs while the leading-edge delaminations length is comparable to the layer thickness. Experimental Helios film image quality is optimized at a small level of substrate tensile strain where delamination length at leading and trailing edges of small holes is balanced and small and where hole size is minimized.
Cooperative Dislocation Generation And The Brittle-To-Ductile Transition
Authors: Khantha M. , Pope D. P. , Vitek V.
Published: April 2011

The characteristic features of the brittle-to-ductile transition are explained using a model of cooperative dislocation generation. In two dimensions, the onset of the ductile behavior corresponds to a thermally-driven, stress-assisted dissociation of many atomic-size dislocation dipoles in the vicinity of the crack tip above a critical temperature Tc. The instability is caused by thermally induced screening of dislocation interactions as in the Kosterlitz-Thouless phase transition. However, the critical temperature is well below the melting temperature in the presence of a stress. The nature of dislocation dynamics in the vicinity of the crack tip is also described and its role in the onset of the cooperative instability is examined. The origin of the correlation between the strain-rate dependence of the transition temperature and the temperature dependence of dislocation mobility is explained.
Structures of New Nitrides Prepared using Solid Oxide Precursors
Authors: Houmes Joel D. , Bem David S. , Loye Hans-Conrad Zur
Published: April 2011

Several novel transition metal nitrides and oxynitrides were synthesized via ammonolysis of solid state oxide precursors at temperatures ranging from 700°C-900°C and reaction times ranging from 12 hours to 4 days. The products were characterized by powder X-ray diffraction and their structures were determined by powder X-ray Rietveld refinement. The relationships between the structures of these nitrides and oxynitrides, and their similarity to the structures of the transition metal dichalcogenides, is discussed.
Spins, Phonons, and Hardness
Authors: Gilman John J.
Published: April 2011

In crystals (and/or glasses) with localized sp3 or spd-bonding orbitals, dislocations have very low mobilities, making the crystals very hard. Classical Peierls-Nabarro theory does not account for the low mobility. The breaking of spin-pair bonds which creates internal free-radicals must be considered. Therefore, a theory based on quantum mechanics has been proposed (Science, 261, 1436 (1993)). It has been applied successfully to diamond, Si, Ge, SiC, and with a modification to TiC and WC. It has recently been extended to account for the temperature independence of the hardness of silicon at low temperatures together with strong softening at temperatures above the Debye temperature. It is quantitatively consistent with the behaviors of the Group IV elements (C, Si, Ge, Sn) when their Debye temperatures are used as normalizing factors; and appears to be consistent with data for TiC if an Einstein temperature for carbon is used. Since the Debye temperature marks the approximate point at which phonons of atomic wavelengths become excited (as contrasted with collective acoustic waves), this confirms the idea that the process which limits dislocation mobility is localized to atomic dimensions (sharp kinks).
Effect of Boron on Polytype Phase Transformation Occurring During Sintering of Si-C-B Powders Obtained By Combustion (SHS)
Authors: Gierlotka S. , Stel'makh S. , Palosz B.
Published: April 2011

Silicon carbide powders were synthesized by SHS method with boron added in various quantities as either amorphous elemental or boric acid additive. The powder samples were then heat treated at a selected temperature (up to 22000°C). Crystallographic structure of the powders were analyzed by means of X-ray powder diffraction technique. It was found that boron added in the form of H3BO3 tends to precipitate in the form of small clusters and does not dissolve evenly in the SiC lattice. Upon annealing the boron clusters dissociate. The boron atoms diffusing across the SiC lattice generate a large number of stacking faults with simultaneous transformation of hexagonal polytype 6H (α-phase) present in as-synthesized powders into the cubic 3C (βphase) modification.
Phase and Disorder Investigations in Boron Nitride Thin Films Grown by Pecvd
Authors: Depero L. E. , Sangaletti L. , Schaffnit C. , Rossi F. , Gibson P. N.
Published: April 2011

Based on X-ray diffraction and infrared spectroscopy measurements, BN thin films grown by PECVD on silicon substrates have been studied with the aim of identifying the thin film phase. In a set of samples, while the infrared spectra showed characteristic bands of the hexagonal phase, X - ray diffraction patterns only displayed reflections belonging to the cubic BN phase. Therefore, structural models have been developed to explain the apparent inconsistency between the two sets of experimental data. In particular, static disorder effects - which have been introduced in the model starting from the sp2 hybridization of the ordered hexagonal phase, as suggested by the infra-red spectroscopy results - allowed a consistent interpretation of the X-ray diffraction patterns. For another set of samples, which also showed a characteristic hexagonal signal in the IR data, the XRD pattern could not be indexed with any of the BN phases. In this case, the presence of molecular and ionic phases, associated with impurities, was considered in structural modeling studies.
Microstructural Development to Toughen Sic
Authors: Moberlychan W. J. , Cannon R. M. , Chan L. H. , Cao J. J. , Gilbert C. J. , Ritchie R. O. , De Jonghe L. C.
Published: April 2011

SiC offers a promise for high strength applications at high temperature; however, poor fracture resistance has inhibited its utility. Recent developments to control microstructure during hot pressing have improved fracture toughness >3 fold, while also improving strength 50% above that of a commercial SiC, Hexoloy. This ABC-SiC (designated for the Al, B, and C additives) utilizes liquid phase sintering to obtain full densification at 1650°C, and to induce the β-3C to α-4H phase transformation below 1900°C. Interlocking, plate-like, α grains, coupled with a thin (˜1 nm) amorphous layer, provide for tortuous intergranular fracture and high toughness.

This study focuses on the developing microstructure; how the α-4H polytype grows as a stacking modification of the β-3C grains, and how amorphous grain boundaries and crystalline triple point phases develop and interact with the crack geometry. HR-TEM and Image-Filtered EELS characterize the amorphous grain boundaries. Field Emission - SEM, EDS and Auger Electron Spectroscopy characterize the fracture morphology and the chemistry of grain boundaries and triple points. Electron Diffraction and HR-TEM depict an epitaxial relationship between triple point phases (Al8B4C7 and A14O4C) and matrix α-SiC grains, the development of which affects the mechanical toughening. The transformation to toughen SiC is compared to the well-studied transformation processing in Si3N4. A distinct advantage is the interlocked nature of the plate-like grains which causes strong elastic bridging behind the crack tip.
Preparation of Polycrystalline Cds Thin Films by Chemical Bath Deposition
Authors: Lee Eun A , Kim Bum-Soo , Shin Sung Ho , Park Jung Il , Park Kwang Ja
Published: April 2011

We prepared CdS thin films from a solution containing cadmium acetate, thiourea, ammonia, and ammonium acetate. We varied fabrication conditions such as the concentrations of reactants, reaction temperature, and heat treatment, to investigate the changes in structural and optical properties of the film. Effects of substrate on the properties were also investigated.
Atmospheric Pressure Chemical Vapor Deposition of Titanium Nitride from Titanium Bromide And Ammonia
Authors: Gordon Roy G. , Frisbie Ross W. , Musher Joshua , Thornton John
Published: April 2011

Titanium nitride films were formed by chemical vapor deposition from titanium tetrabromide and ammonia at atmospheric pressure and substrate temperatures from about 400 to 600 °C. Although titanium tetrabromide is a highly hygroscopic solid at room temperature, it can be handled conveniently as a very concentrated liquid solution (85 weight percent) in bromine as a solvent. This solution can be vaporized by a direct liquid injection system. Alternatively, the solution can be pumped into a bubbler, from which the bromine solvent is then removed by fractional distillation. Rutherford Backscattering Spectroscopy was used to determine that the bromine content of TiN deposited at 500°C was about one atomic per cent. Growth rates were about 17 nm/min, and electrical resistivity was found to be about 200 μΩ-cm.
Deposition And Characterization Of Silicon And Carbon Nitride
Authors: Myers A. F. , Tucker D. A. , Bozeman S. P. , Camphausen S. M. , Powers M. J. , Bruley J. , Hren J. J. , Cuomo J. J.
Published: April 2011

We attempted to deposit carbon nitride films on flat Si (111) substrates and on sharp <111>-oriented silicon needles in a radio frequency (rf) inductively coupled plasma system utilizing a graphite source and a nitrogen plasma. The resultant polycrystalline films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Auger electron spectroscopy (AES), and electron energy loss spectroscopy (EELS). Both selected area electron diffraction (SAED) and lattice imaging were used to identify and characterize the particles, which grew as faceted crystals up to 1 Rm in size. From SAED, high resolution TEM, and EELS, it was found that the particles on the Si needles were α-Si3N4 and that those on the Si wafer were mostly β-Si3N4 and β-C3N4, with some β-C3N4 possible. Auger quantitative analysis suggests that β-C3N4 could be stabilized by the presence of silicon, resulting in a material with compositions CxSiyNz.
CVD Growth of SiC on Ultrathin SOi2: A Step Towards Development of a Compliant Substrate for SiC and III-V Compounds
Authors: Namavar Freydoon , Colter P. , Cremins-Costa A. , Gagnon E. , Perry D.
Published: April 2011

This paper addresses the initial stage of epitaxial growth of SiC on thin (about 300A) and thick (2000Å) Si films. Our results as obtained by Rutherford backscattering spectroscopy (RBS), Auger spectroscopy, and plan-view/cross-sectional TEM, demonstrate epitaxial growth of 3C-SiC structures on ultrathin Si films (even under non-optimized growth conditions). These preliminary results indicate that the crystalline quality of SiC on thin SIMOX is better than that grown on thick SIMOX or bulk Si substrates. Growth of SiC epi on thin Si will pave the way for growth of SiC directly on SiO2 (a compliant substrate) by carbonization of the entire thin Si top layer of SIMOX.
Oxidation Studies of Silicon Oxynitride Using X-Ray Photoelectron Spectroscopy and Transmission Electron Microscopy
Authors: Manessis D. , Du H. , Singer I. L. , Larker R.
Published: April 2011

Silicon oxynitride (Si2N2O) ceramics were oxidized in 1 atm dry oxygen at 11 00IC and 13000C. The oxidized samples were studied using x-ray photoelectron spectroscopy and crosssectional transmission electron microscopy in conjunction with energy dispersive x-ray analysis. TEM characterization revealed the chemical abruptness of the SiO2 and Si2N2O interface. Further investigation indicated the inclusions of residual SiO2 in Si2N2O, which contributed to the broad XPS elemental distribution in the oxide-substrate interface region.
Unimolecular Precursors to Binary Metal Sulfides: Mechanistic and Structural Correlations
Authors: Schluter Rodney D. , Kräuter Gertrude , Rees William S.
Published: April 2011

The roles which ligand size and stability play in influencing solid-state thermolyses products and phases are developed for a group of metal thiolate compounds. The exploration includes Pb(SR)2 [R = t-Bu, i-Bu, s-Bu], Cd(SR*)2 [ R* = i-Pr, I-Bu, Bz], ClHgSR** [ R** = i- Pr, neo-Pent, Bz] and In(SR***)3 [R*** = 2,4,6-(i-Pr)3C6H2, 2-CH3O-5-CH3C6H3, o- C6H4CH2N(CH3)2]. In several examples, the precursors have been characterized by single crystal X-ray diffraction. In most cases, solid-state decomposition products have been identified by XRPD, and volatile decomposition products have been identified by GC/MS. All precursors have been studied by TGA.
A Novel Self-Assembled Collagenous Matrix which Serves as a Template for Oriented Growth of Hydroxyapatite Crystal
Authors: Christiansen D. L. , Pins G. D. , Huang E. K. , Silver F. H.
Published: April 2011

Collagen fibers self-assembled from solutions of molecular type I collagen were mineralized at pH 9.5, by exposure to super-saturated solutions of calcium and phosphate for a one week period in a double diffusion chamber. Uniaxial tensile mechanical properties increased with mineralization and electron microscopy of the mineral formed within the fiber was morphologically similar to the mineral phase of calcified tissues. Selected area electron diffraction confirms the presence of hydroxyapatite crystal. Further, the aligned fibrillar substructure serves as a template for the orientation of the c-axis diffraction maxima of the hydroxyapatite. These results indicate that an aligned system composed exclusively of selfassembled type I collagen fibrils serves as a scaffold for oriented growth of mineral analogous to calcification in vertebrate bone.
Polystyrene Surfaces Terminated with a Single Functionality of Alcohol
Authors: Sun J.Q. , Bello I. , Lau W.M. , Lipson R.H. , Lin Z.D.
Published: April 2011

Polymer surfaces terminated with a specific chemical functionality are attractive for biomaterial applications because of the predictability and selectivity of surface reactions towards the anchoring of a biochemical agent to the polymer. In the present work, engineering of surface functionality was performed using OH radicals generated in gas phase by the reaction between a hot filament and water molecules in vacuum. The generation of OH was confirmed by laser induced fluorescence spectroscopy. The incorporation of oxygen and formation of alcohol groups on polystyrene were confirmed by x-ray photoelectron spectroscopy. High resolution electron energy loss spectroscopic data also showed that for polystyrene with an uptake of less than a monolayer equivalent of oxygen, C-OH was the only detectable surface functionality containing oxygen.
Photomodulation spectroscopy of thin Ge films formed by molecular beam epitaxy on Si (111)
Authors: Stoke K. L. , Deelman P. , Kang H. S. , Schowalter L. J. , Persans P. D.
Published: April 2011

The photomodulated transmission spectrum of a single Ge layer grown at 500°C on the Si(1 11) surface by molecular beam epitaxy is reported. The nominal Ge layer thickness was 50 nm. The modulation spectrum of thicker layers is dominated by a threelobed structure centered 70–80 meV above the bulk direct band edge. This structure is ascribed to excitation-induced broadening of the lowest direct exciton.
Sensitivity of Nanocrystalline Copper Sulfide/Cadmium Sulfide Heterojunction in Near-Ir Region
Authors: Artemyev M. V. , Sviridov D. V. , Gaponik N. P. , Maljarevich A. M.
Published: April 2011

The photovoltaic p-n heterojunction based on thin layer of 10 nim size copper sulfide nanocrystals and evaporated cadmium sulfide film was prepared. The partial oxidation of copper sulfide nanocrystals prior the fabrication of the heterostructure results in the formation of additional absorption band in near-IR region beyond the fundamental absorption of bulk copper sulfide and cadmium sulfide. This band can be attributed to the intervalence charge transfer between copper ions in the core and in the oxidized shell. The photovoltaic effect observed in the near-IR region at ITO/nano-CuS/CdS/Au heterojunction is due to the generation of the electron-hole pairs in the CuS nanocrystalline film followed by the separation of charge carriers at the CuS/CdS junction.
The Optical Properties of InGaAs(P)/InP Under Group V Sublattice Two-phase Interdiffusion
Authors: Li E. Herbert , Micallef Joseph , Shui W. C.
Published: April 2011

Using the fundamental transition state, we will investigate the two phase interdiffusion of group V sublattice in a strained lattice matched InGaAs/InP quantum well (QW) structures. The model employs three parameters namely the diffusion coefficients in the barrier (Db)and in the well (Dw)and the concentration ratio (k) of the diffused species at the heterstructure. The QW model includes the effects of strain and the exciton. A pseudo time dependent calculation is also considered and results are fitted to the reported experimental data. These parameters which characterize the diffusion mechanism can be measure to form a better understanding of the interdiffsion process for group V sublattice.
Selective Growth of GaP on Si by Metal Organic Vapor Phase Epitaxy
Authors: Lee J. S. , Salzman J. , Emerson D. , Shealy J. R. , Ballantyne J. M.
Published: April 2011

Extremely flat layers of GaP were grown on 4° miscut (100) Si substrates by selective Metal- Organic Vapor Phase Epitaxy. An enhancement of Re@3 was measured at the growth edges, which corresponds to a Sherwood number of 12.5. Defect-free growth is obtained at the edge of the silicon nitride mask. A gradual transition to growth with a large defect density is observed with increasing distance from the mask edges. In the defect free areas, a recovery of the (100) crystal plane is consistently measured on top of the grown mesas. This seems to indicate a pure layer-bylayer homoepitaxial mode (Frank-van der Merve mode) after the island mode nucleation (Volmer- Weber mode) on Silicon is completed, forming a thin smooth seed layer. High Resolution TEM shows a uniform Si-GaP transition. Micro-Raman Spectroscopy with spatial resolution of ˜1 micrometer was performed to assess the crystal quality as a function of the distance from the growth edge.
Determination of the Order Parameter by Quantitative Tem Techniques
Authors: Bode Michael H. , Ahrenkiel S. P. , Kurtz S. R. , Bertness K. A. , Arent D. J. , Olson J.
Published: April 2011

To quantitatively measure the order parameter in ordered III-V materials we have developed two techniques based on electron microscopy. The first technique calculates the diffraction pattern of ordered material quantitatively and fits the calculated data to experimentally obtained data. A test sample, specifically grown for this technique, shows that the method can determine the average order parameter with high accuracy. We found an order parameter of 0.34, which coincides with the value found by piezo-reflectance measurements. To measure the order parameter on a smaller length scale, we use a technique based on image processing of high-resolution TEM images. By comparing ordered and disordered parts of the image, we calculate the relative order parameter on an atomic length scale. Analyzing the data provides information about the development of the ordering in the crystal.
Activation Energy of Electromigration in Copper Thin Film Conductor Lines
Authors: Gladkikh A. , Lereah Y. , Karpovski M. , Palevski A. , Kaganovskii Yu. S.
Published: April 2011

Activation energy of electromigration damage was determined as 1.2 eV for Cu lines, indicating grain boundary paths for electromigration. The surface diffusion was found to play a role during electromigration in Cu and impeded the failure process.
Chemical-Mechanical Polishing of Copper in Glycerol Based Slurries
Authors: Kumar K. S. , Murarka S. P.
Published: April 2011

The development of a reliable/reproducible chemical-mechanical polishing (CMP) process to planarize and define copper using a dual damascene approach is essential for introducing copper as the interconnection metal. In this paper we present results of a new polishing slurry containing glycerol and Al2O3 abrasive. The slurry is a near-neutral medium and does not have the effect of acidic or basic slurries on copper. The effect of glycerol concentration and the abrasive size on the CMP behavior is investigated. The changes in the slurry temperature, pH, viscosity, dielectric constant and surface tension were examined as a function of the glycerol concentration. The results, indicating a strong dependence on both the glycerol concentration and the abrasive size, are explained on the basis of viscosity and dielectric constant of the solution and the van der waal forces and the electrostatic repulsion between the particles.
Phase and Mechanical Stress in and Surrounding Tisi2 and Cosi2 Lines Studied by Micro-Raman Spectroscopy
Authors: Wolf I. De , Howard D. J. , Maex K. , Maes H. E.
Published: April 2011

The local mechanical stress induced in a silicon substrate by silicide lines (CoSi2, CoSi, C49 and C54 TiSi2) with different thicknesses, widths and spacings is studied using micro-Raman spectroscopy. The results show that the stress becomes larger with increasing line thickness and decreasing line spacing. For the different silicides, the stress increases according to: CoSi < CoSi2 < C49 TiSi2 < C54 TiSi2. By fitting a simple stress model to the Raman data, quantitative values for the stress components can be determined. The dependence of the TiSi2 phase on thickness and line width is studied for the same samples. These studies show that micro-Raman spectroscopy can provide local information (μm resolution) on the TiSi2 phase.
Effects of Size and Shape of Lateral Confinement on the Formation of NiSi2, CoSi2 and TiSi2 on Silicon Inside Miniature Size Oxide Openings
Authors: Chen L. J. , Yew J. Y. , Cheng S. L. , Chen K. M. , Nakamura K. , Tsui B. Y.
Published: April 2011

The effects of size and shape of lateral confinement on the formation of NiSi2, CoSi2 and TiSi2 on silicon inside miniature size oxide openings have been investigated. Epitaxial growth of NiSi2 of single orientation on (111)Si was found to occur at a temperature as low as 400 °C inside both contact holes and linear openings of 0.3 μm or smaller in size. Contact holes were found to be more effective in inducing the epitaxial growth of NiSi2 of single orientation than that of linear openings of the same size. The effects of size and shape of lateral confinement on the epitaxial growth of NiSi2 on (111)Si are correlated with the stress level inside oxide openings. The faceting of CoSi2 was found to occur at a lower temperature inside oxide openings of smaller size. C49-C54 TiSi2 transformation was observed to be more difficult on both blank and BF2+ implanted (001)Si inside smaller size oxide openings.
Structural Characteristics of CoGe2 Alloy Films Grown Heteroepitaxially on GaAs(100) Substrates Using the Partially Ionized Beam Deposition Technique
Authors: Mello K. E. , Murarkak S. P. , Lee S. L. , Lu T.-M.
Published: April 2011

The Partially ionized beam (PIB) deposition technique was used to deposit CoGe2 thin films heteroepitaxially on GaAs(100) substrates in a conventional vacuum. For the CoGe2(001)/GaAs(100) system, which leads to an Ohmic contact, a substrate temperature of 280°C and ∼1200 eV Ge+ ions are required. Reducing the ion energy or lowering the substrate temperature both produce a different orientation in the films. Films deposited at 280°C with a zero accelerating potential for the ions, and those deposited at 200°C with -1200 eV Ge+ ions result in a CoGe2(100)//GaAs(100) type orientation domination, leading to rectifying behavior.
A microstructural and electrical investigation of Pd/Ge/Ti/Au ohmic contact to n-type GaAs
Authors: Kwak J. S. , Baik H. K. , Kim H. , Lee J. -L. , Shin D. W. , Park C. G.
Published: April 2011

Interfacial microstructure and elemental diffusion of Pd/Ge/Ti/Au ohmic contact to n-type GaAs have been investigated using x-ray diffraction(XRD), Auger electron spectroscopy(AES), and cross-sectional transmission electron microscopy(XTEM), and their results are used to interpret the electrical properties. The lowest contact resistance of 0.43 Ωmm is obtained after annealing at 380°C. The contact is thermally stable even after isothermal annealing for 5h at 400°C. The good Pd/Ge/Ti/Au ohmic contact is due to the formation of both AuGa and TiO compounds. The AuGa compound enhances the creation of more Ga vacancies, followed by incorporation of Ge into Ga vacancies and TiO compound suppresses As outdiffusion from GaAs substrate, respectively.
Comparison of pd/sn and pd/sn/au thin-film Systems for Device Metallization
Authors: Islam M. S. , Mcnally Patrick J. , Cameron D. C. , Herbert P. A. F.
Published: April 2011

An Ohmic contact system comprising of Pd/Sn metallization has been developed for n-GaAs and compared with Pd/Sn/Au metallization. Surface morphology of the contacts is investigated using surface profilometry measurements and Scanning Electron Microscopy (SEM). The contact depth profiles are analyzed by Secondary Ion Mass Spectrometry (SIMS). Contact resistivities, Pc, of the proposed metallizations are measured using a conventional Transmission Line Model (TLM) method. A lowest ρc, of ∼2.07×10−5 Ω-cm2 was obtained with a Pd(50 nm)/Sn(125 nm) contact on 2×1018 cm−3 n-GaAs after annealing at 400 °C for 30 min. A Au overlayer improves the characteristics of the Pd/Sn contacts. The Pd(50 nm)/Sn(125 nm)/Au(100 nm) contact shows a lowest ρc of ∼1.29×10−6 Ω-cm2 after annealing at 330 °C for 30 min. The Pd/Sn/Au contacts exhibit superior properties compared to those of alloyed five-layer Au/Ge/Au/Ni/Au contacts.
In-Situ UHV Electromigration In Cu Films
Authors: Vook R. W. , Jo B. H.
Published: April 2011

Copper stripes, current stressed under UHV, clean surface conditions, have an activation energy Q for electromigration (EM) of 0.5 eV, significantly lower than the 0.8 eV reported when the surface has been exposed to air. Application of positive or negative potentials to the stripes during EM testing raises or lowers the clean surface Q in a linear relationship in the range of 0.2 to 1.0 eV. These results were obtained from in-situ electrical resistance measurements during which potentials up to +/− 800 volts were applied to the stripe. Thus the rate at which surface EM takes place is influenced by the sign and magnitude of the applied potential. The low Q for the in-situ clean surface studies also implies that surface diffusion is the dominant physical mechanism whereby EM damage occurs. Ex-situ SEM studies support this conclusion. This work has important implications for ULSI since numerous recent studies have indicated that surface and/or interface diffusion are present during current stressing of passivated and unpassivated fine line stripes.