bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of the Fracture Toughness Parameters for an MDF Cement Composite
Authors: Arzamendi M. , Sierakowski R. L. , Wolfe W. E.
Published: March 2011

The experimental results of fracture toughness testing of a Macro Defect (MDF) Free cement are presented. The material, a hydraulic cement with hydrolyzed polyvinyl polymers, behaves much like a hardened ceramic with measured maximum compressive and tensile strengths of 380 MN/m2 and 69 MN/m2 respectively. Fracture toughness tests were performed on compact tension (CT) and single edge notched beam (SENB) specimens cut from test panels which were supplied in 3mm, 5mm and 10mm thicknesses. The results were evaluated with respect to the fracture toughness parameter Kic using a modification of standard test methods as determined by observed natural behavior. The MDF material exhibited an essentially linear elastic behavior with a fracture toughness slightly higher than typical values recorded for hardened cement paste.
Production and Characterization of Fly Ash from New South Wales Coals
Authors: Roper Harold , Baweja Daksh , Kirkby Graham A.
Published: March 2011

Factors affecting fly ash characteristics are examined by consideration of the various processes and constituents involved in its production. Coal conversion, boiler-furnace operations and collection procedures are discussed. Current classification schemes applied to fly ash, in particular to those for use as a pozzolanic mineral admixture in concrete are reviewed. The variability of the material is highlighted using physical and chemical data. Shape and size characteristics of selected fly ashes from sources within New South Wales, Australia are illustrated by electron micrographs. The influence of these properties on resultant concrete properties are briefly considered. The formation of nodules of fly ash material on the surface of fabric filters is chosen to illustrate the importance of physical and chemical conditions in the collection chamber, whereas pH changes with time of the water phase in contact with selected fly ashes demonstrate the importance of chemical characteristics of the collected materials. Such chemical characteristics may influence the path of pozzolanic reactions significantly.
Preparation and Characterization of Three New NBS Fly Ash Standard Reference Materials
Authors: Kanare Howard M.
Published: March 2011

Three new fly ash standard reference materials (SRM's) have been produced by CTL under contract with the U.S. National Bureau of Standards (NBS). Each unit of the SRM's consists of approximately ten grams of well-blended fly ash hermetically sealed in a glass vial. Twenty-thousand vials of each SRM were produced. The SRM's will be certified for major and minor chemical elements, loss on ignition, and for the percentage residue on the No. 325 standard sieve. The SRM's are suitable for use in developing new methods of chemical and physical analysis, for checking the performance of instruments and analysts, and for research into the composition and properties of fly ash.
Iowa Affiliate Research: Rapid Diagnostic Tests for Evaluating the Air Void System of Fly Ash Concrete
Authors: Zimmerman L. , Demirel T. , Bergeson K. , Schlorholtz S.
Published: March 2011

An on-going fly ash research program, funded by six Iowa power companies and their marketing representative has been established at Iowa State University. The broad objective of the affiliate program is to conduct basic research on Iowa fly ashes that can be directly applied to increasing their utilization in the construction industry. The first year goal is to evaluate the influence of various Iowa fly ashes on the air void system of concrete. Previous research at Iowa State University had indicated that fly ash may be influencing air void distribution in fly ash concrete, and hence durability. A variety of combinations of aggregates, fly ashes, cements and admixtures are being evaluated for compatibility in concrete. Rapid diagnostic tests are being developed, including (1) a modified Hallimond tube flotation test to evaluate physico-chemical compatibility of combinations, and (2) LeMont image analysis techniques to analyze the air void system. Procedures and preliminary results are presented and discussed.
Western Fly Ash Research, Development and Data Center
Authors: McCarthy G. J. , Manz O. E. , Stevenson R. J. , Hassett D. J. , Groenewold G. H.
Published: March 2011

With financial support from utilities and ash brokers*, the Western Fly Ash Research, Development and Data Center was established under the aegis of the North Dakota Mining and Mineral Resources Research Institute in August of 1985. Research will be performed by the two North Dakota universities in Grand Forks and Fargo. The fundamental objective of the Center is to enhance the knowledge base of the properties (chemical, mineralogical and physical) and reactions of the coal by-products (principally fly ash, but including bottom ash and FGD waste) produced in the Midwestern and Great Plains regions of the US. Most of the study specimens will be high-calcium (ASTM Class C) ash derived from low-rank lignite and subbituminous coals mined in North Dakota, Montana and Wyoming, although ash from other regions and coals is also being studied. The enhanced knowledge base should lead to more widespread utilization of these by-products [1,2] or, where this is necessary, to their safe and cost-effective disposal [3].
Chemical Changes Occurring During the Early Hydration of PFA-OPC Mixtures
Authors: Luke K. , Glasser F. P.
Published: March 2011

The course of the initial set reactions of Portland cement-PFA blends is markedly influenced by the presence of fly ash. Data are presented on the effect of two Class F PFA materials blended with cement in 30:70 ratio. Selected analyses of the aqueous phase compositions at lh to 336h are presented. During the first 6h a nearly steady state aqueous phase composition is achieved with respect to Na, K and Ca concentrations. Following a renewed burst of hydration activity, Ca decreases rapidly in the interval 6–24 h while Na and K contents rise more gradually.
Analysis of the Cementitious and Pozzolanic Properties of a Silico-Aluminous (Class F) Fly Ash
Authors: Carles-Gibergues Andre , Aitcin Pierre-Claude
Published: March 2011

A silico-aluminous (Class F) French fly ash has been studied during the last ten years. While over this period the fly ash was produced from different bituminous coals, it has demonstrated high constancy in terms of its chemical and physical composition as well as cementitious properties. The first part of this paper gives a complete physico-chemical characterization of this fly ash, including chemical composition, mineralogical composition of its crystallized fraction, chemical composition of its glass, grain-size distribution, specific surface area, and bulk density. The second part deals with physico-chemical experiments performed to determine the cementitious components of this fly ash through its dissolution in pure water and in lime water. The lime water experiment was also carried out on a washed sample containing few residual sulfates. This series of experiments demonstrates the importance of sulfates in this particular fly ash, especially during the early stages of hydration. Their action results in the formation of ettringite. The cementitious role of these sulfates has been confirmed by comparing the compressive strength of mortar cubes containing washed and nonwashed fly ash. After 7 days, mortar cubes made with this fly ash showed a slight compressive strength increase when compared to a reference mix containing the same amount of quartz. This compressive strength increase can be related to the formation of C-S-H due to the pozzolanic reaction. After 8 months, the pozzolanic reaction had consumed most of the lime generated by the hydration of C2S and C3S, so that practically no portlandite remained in the mortar.
Evaluation of Fly Ash on the Basis of Mass Equivalent, Maturity Equivalent and Permeance
Authors: Mills R. H.
Published: March 2011

Combinations of two types of commercially available Fly Ash (FA) and Portland cement (PC) were tested for compressive strength and permeance to gas flow. The cementitious components were combined in the concrete mixture in proportions PC/FA = 100/0, 75/25, 60/40 and 45/55 for a range of water/cement ratio, and equal workability. Strength and maturity efficiency factors were satisfactory for 75/25 and 60/40 blends. Gas tightness was improved at all levels of Fly Ash substitution.
Engineering and Microstructural Studies of Western-Canadian Fly Ash Bricks
Authors: Day Robert L. , Joshi Ramesh C. , Slota Rudolf J. , Langan Brian W.
Published: March 2011

An experimental programme was undertaken to determine whether Canadian fly ash, and in particular Western-Canadian fly ash, can be used to replace clay as the main ingredient in brick-masonry units.

These preliminary examinations show that Western-Canadian fly ash as the solid material, combined with an adequate binder, can be used to produce a superior ceramic material. Strengths are very much higher than that revuired for load-bearing masonry elements, densities are approximately 800 kg/m3 less than a normal clay brick and the material is durable to freezing and thawing. X-ray analysis and scanning electron microscopy clearly show chemical and physical changes which occur to the material due to firing. These chemical changes appear to be closely related to the subsequent strength which is developed.

Bricks manufactured from Alberta fly ash appear to be a viable alternative to standard clay brick. A substantially stronger and more economical brick may be possible; fly-ash bricks can be manufactured with lower firing temperatures of shorter duration. This, in itself, could lead to the realization of significant energy savings. Also, if large quantities of fly ash can be used in the brick industry, then significant gains will be made toward the elimination of this waste product from the environment and conservation of natural resources.
Mineralogy of Fixed-Bed Gasification Ash Derived from North Dakota Lignite
Authors: Stevenson Robert J. , McCarthy Gregory J.
Published: March 2011

The mineralogy of nine ash samples derived from North Dakota lignite and gasified in three different fixed-bed producers was determined by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The gasifiers had maximum temperatures in the 1100–1250°C range, but included several differences in ash residence time, oxidizing gas and pressure, and ash handling conditions. The lignite gasified came from the same geologic formation, but the mines were separated by 20 km. Despite these differences, all of the ash specimens had the same basic mineralogy: glass at the 15–30 wt.% level; a crystalline phase assemblage of ortho- and pyro-silicates (merwinite, dicalcium silicate (C2S), C2S-like phases, and melilite), network aluminosilicates (nepheline, carnegieite, and a sodalite-structure phase), oxides (ferrite spinel, hematite, and periclase), and calcite along with residual lignite minerals (quartz and felspar). SEM morphologies and XRD comparisons of the amounts of crystalline phases in size fractions both indicated that some of the phases (particularly merwinite and carnegieite) crystallized during cooling of portions of the ash that had melted during gasification.
Speciation in Size and Density Fractionated Fly Ash
Authors: Hemmings Raymond T. , Berry Edwin E.
Published: March 2011

Morphological, chemical and mineralogical speciation of fly ash from a power plant burning sub-bituminous coal has been investigated by examination of size and density fractions. It was found that whereas, fractionation by size revealed little information as to speciation among particle types, separation of the ash into six density fractions showed major differences in properties associated with true particle density. In particular it was found that at least two types of glass co-exist in the ash: “Glass I” – a predominantly silico-aluminous glass associated with particles of low density (cenospheres); “Glass II” – a calcium alumino-silicate glass associated with high-density particles. These glasses were found to differ greatly in composition and to be characterized by shifts in the position of the 2-theta of the XRD-halo. In addition, it was shown that cryptocrystalline mullite is associated only with the low-density particles. It is proposed that particles comprising low-density fractions can be considered as glassceramics with low degrees of crystallization. Particles of high-density are better described as the products of internal lime-sinter reactions.
GaAs MESFET's on Silicon Substrates for Digital IC Applications
Authors: Shichijo Hisashi , Lee Jhang Woo
Published: March 2011

The characteristics of GaAs MESFETs in GaAs-on-Si have been studied in detail for digital IC applications. The device structure utilizes GaAs and AlGaAs undoped buffer layers grown on a 3 degrees off (100) silicon substrate by MBE. The threshold voltage of the MESFET is adjusted by recessing the gate.

The maximum observed transconductance of 135 mS/mm is comparable to what is expected from the bulk GaAs device with the same parameters. The device also shows good pinch-off characteristics. Both enhancement and depletion mode MESFETs have been fabricated.
The Formation of Thin Layers and Double Heterostructures of Epitaxial Silicides
Authors: Tung R. T. , Gibson J. M.
Published: March 2011

This paper reviews the “template” growth technique in UHV and the novel structures and properties of single crystal silicide thin films and double heterostructures.
Tunneling Spectroscopy of Single-Crystal CoSi2 and NiSi2 Epilayers on n-type Si
Authors: Hauenstein R. J. , Schowalter L. J. , Hunt B. D. , Marsh O. J. , McGill T. C.
Published: March 2011

Electron tunneling spectroscopy experiments have been performed on single-crystal epitaxial silicide films grown on (111)-oriented (off 4 °) Si:As. 250 Å-thick films of CoSi2, and type-A and -B NiSi2 on degenerate substrates (Nd = 2 × 1019 cm−3) have been studied. All spectra show forward bias peaks at energies corresponding to k-conserving bulk Si phonons while in reverse bias only the Si TA phonon is observed for NiSi2 /Si structures. Plots of dV/dI vs. V for CoSi2 /Si structures yield maxima at a forward bias of 39meV, indicating an enhancement in n-type dopant concentration within ˜ 100 Å or more of the silicide-silicon interface.
Properties and Applications of Molecular Beam Epitaxial Silicides
Authors: Wang K. L. , Kao Y. C.
Published: March 2011

Transition metal silicides are now being used as essential and integral elements of microelectronics technology. Epitaxial growth and deposition provide additional flexibility for many device and circuit applications.

In this paper, various epitaxial growth techniques, namely solid phase epitaxy and molecular beam epitaxy are reviewed. The resulting morphology, crystallinity, and Schottky barrier heights as well as deep-level defects are contrasted. The parallel and perpendicular strains as a function of film thickness is reported.

Application of the epitaxial silicide in improving conventional integrated circuits as well as in fabricating new devices are discussed.
Growth of Group IV-IV Heterostructures: Initial Stages of Interface Formation
Authors: Gossmann H.-J. , Feldman L. C.
Published: March 2011

The two major issues in the growth of a heterostructure are (1) the degree of perfection of the overlayer and (2) the sharpness of the interface. The initial stages of interface formation play a crucial role in this respect. Relevant questions are addressed under atomically clean conditions in the Si/Ge Si/Si and Ge/Sn systems, using ion scattering surface analysis, low energy electron diffraction and Auger electron spectroscopy. Of particular interest with respect to (1) is the general role of reconstruction in epitaxial growth: A necessary condition for perfect growth is the reordering of the substrate surface reconstruction. We show that the deposition temperature necessary to achieve this reordering depends strongly on the topography of the substrate reconstruction. For example, Ge deposition at room-temperature reorders the Si(100)2×1 reconstruction but not the Si(111)7×7, implying different epitaxial temperatures for these two substrates. To illustrate (2) we discuss the complex growth and anomalous diffusion found in the Ge/Sn system. Below a certain critical coverage Θc (1.15·1015 cm−2) no indiffusion of the Sn overlayer takes place, even at 700 K, although above Θc severe indiffusion does occur at this temperature. This result is discussed in terms of theories of surface segregation.
Growth of GaAs on Si and its Application to FETs and LEDs
Authors: Akiyama Masahiro , Kawarada Yoshihiro , Nishi Seiji , Ueda Takashi , Kaminishi Katsuzo
Published: March 2011

In recent years, the heteroepitaxial growth of GaAs layers on Si substrates has been gained an increasing interest [1 - 14]. GaAs is one of the most important III-V materials and has been well studied and used for optical and electrical devices. On the other hand, with Si we have large size wafers of superior quality and sophisticated technologies and Si is a main material for semiconductor industries. Therefore, GaAs/Si system has possibilities for realizing new types of functional devices or ICs with GaAs and Si devices. This system, however, has two serious problems. One is the large lattice mismatch of about 4 % between these materials and the other is the polar on nonpolar problem i.e., the formation of an antiphase domain disorder. It was reported that when (211)-oriented Si substrates were used, there was no problem of the formation of an antiphase domain structure 5. For growing materials on lattice mismatched substrates, it was reported that the thin layers deposited at low temperatures were effective to relax the lattice mismatches for the systems such as SiC on Si[15] and Si on saphire [16]. In GaAs/Si system, the Ge buffer layer has been used to relax the lattice mismatch[17 - 22] It was also reported that the composite strained layer superlattice with GaP/GaAsP and GaAsP/GaAs was very effective as a buffer layer[23 - 25].
GaAs/Ge Crystal Growth on Si and SiO2/Si Substrates
Authors: Ohmachi Yoshiro , Shinoda Yukinobu , Oku Satoshi
Published: March 2011

An approach to the composite layer growth of GaAs/Ge on Si(100) and insulator–coated Si(100) has been investigated. To overcome a problem of antiphase disorder of GaAs occurring along with epitaxial growth on Ge, thermal etching on Ge surfaces in hydrogen was introduced just prior to the growth. Antiphase–domain–free GaAs grown on a Ge(100) wafer exhibited mirror surfaces, photoluminescence characteristics comparable to those of homoepitaxial layers, and low etch–pit densities. The autodoping of Ge into GaAs induced a highly doped interfacial layer several thousand angstroms thick. The present study also involves heteroepitaxial growth of Ge on Si by vacuum deposition and Ge crystal growth on insulating layers over Si by LESS method.
Material Characterization of Epitaxial GaAs and Ge Films on (100) Si Substrates
Authors: Awal M. Abdul , Lee El Hang , Koos G. L. , Chan E. Y. , Celler G. K. , Sheng T. T.
Published: March 2011

We report some results on the chemical, structural and electrical characterization of Ge and GaAs films, grown on Si (100) substrates by electron-beam evaporation and MOCVD, respectively. Good quality Ge films have been obtained at 700°C substrate temperature at a growth rate of 5 nm/sec in 5 × 10−7 torr. Similarly, good GaAs films were obtained at 650°C and at 0.3 nm/sec. RBS data for GaAs films (1.1 μm) show Xmin approaching 3.5%, and Ge films (1.5 μm) around 3.6%. Photoluminescence of the same films show peaks around 852 nm with FWHM of 14 meV. Cross-sectional TEM and etching show a near-exponential decrease in defect density away from the Ge/Si interface. Detailed characterization results of the S-R, I-V, C-V, and X-ray studies are also described.
Kinetics of Rapid Thermal Oxidation of Silicon
Authors: Lassig Stephan E. , Debolske Thomas J. , Crowley John L.
Published: March 2011

This paper presents kinetic data for the rapid thermal oxidation (RTO) of <100 silicon using a wall stabilized low pressure arc lamp as the heating source. The data shows a single activation energy of 1.31 eV over the temperature range of 900°C to 1200°C and times of 60 seconds to 240 seconds. Comparisons are made with published kinetic data of RTO using tungsten-halogen lamp source [1] and with furnace oxidation kinetics for short times (<240 sec.) [2]. “Wet” oxidation results using O2:H2 as the oxidizing ambient reveal a lower activation energy and preexponential coefficient than the dry oxidation. Also presented are results using an experimental set-up which exhibits ultraviolet enhanced oxidation.
Rapid Thermal Processing of Gate Dielectric Films and their Characterization
Authors: Flowers D. L. , Nulman J. , Krusius J. P.
Published: March 2011

Rapid thermal processing has been used to grow high quality, low defect density, low mobile charge, dielectric films of oxide and nitrided oxide. Suitable annealing can lower the fixed charge and interfacial trap density present in these filmsto acceptably low levels. Both RTA and RTN were shown to improve the dielectric properties of the grown oxides. These filmsshould be strong candidates for use in high density, shallow junction, integrated circuits where a minimal time/temperature constraint is imposed on further processing after diffusion.
Oxidation of Silicon and Nitridaticn of SiO2 by Rapid Thermal Processes
Authors: Chan Tung N. , Caratini Y. , Buevoz J.L.
Published: March 2011

Thin gate oxides of 30 to 150 Å have been grown in a rapid thermal annealing machine. Experiments were performed in the temperature range of 1000 to 1250°C for an oxidation time of 5 to 60 s. The fairly extensive kinetics data show that linear growth occurs with an activation energy Ea of 1.4 eV for the 5-60 s period. The oxide homogeneity was evaluated and gave a value of 1.9 A for a mean oxide thickness of 102 A. The electrical characteristics of Al-gate capacitors were assessed by C-V and I-V measurements. Rapid thermal nitridation of a 96 A SiO2 has been performed at a temperature of 1150°C for a nitridaticn time up to 150 s. An average breakdown field of 14.6 MV/cm has been obtained for MIS capacitors. High resolution TEM show a good interface SioXNY-Si.
Rapid Thermal Processing for Self-Aligned Silicide Technology
Authors: Ku Y. H. , Lee S. K. , Louis E. , Shih D. K. , Kwong D. L.
Published: March 2011

A self-aligned titanium silicide process which combines the use of ion-beam mixing and rapid thermal processing (RTP) has been developed for CMOS VLSI applications. Shallow silicided junctions are formed by implanting dopants into silicide layers previously formed by ion-beam mixing with Si ions and low temperature annealing, and the subsequent drive-in of the implanted ions into the Si substrate during high temperature RTP. In addition, the formation of TiN on TiSi2 is achieved simultaneously during this process as a diffusion barrier for Al metallization. Short-channel MOS transistors with SALICIDE structure have been successfully fabricated and tested. Results of the impurity diffusion in silicide layer, the impurity segregation at both silicide/Si and oxide/silicide interfaces, contact stabilit of Al/TiN/TiSi2 structure, and device characteristics will be reported. Issues related to this process and its application to submicron device fabrication are discussed and foreseeable problem areas identified.
Low Temperature Rapid Thermal Formation of Tin Barrier Layers
Authors: Barney Cohen Barney Cohen , Jaim Nulman Jaim Nulman
Published: March 2011

TiN and TiN/TiSi2 films, formed by reacting titanium sputtered onto source-drain and field areas, may be used as local interconnects, low resistance plated junctions, and diffusion barriers. This paper discusses the application of RTP to the low temperature reaction of titanium on silicon and oxide substrates. By adjusting temperature and ambient the nitridation and silicidation reactions may be controlled to provide the desired TiN-TiSix thickness ratio. The advantages of ammonia ambient are discussed.
Characterization of Process Uniformity and Control of Titanium Silicide Formed by Rapid Thermal Processing (RTP)
Authors: David Hodul David Hodul , Sandeep Mehta Sandeep Mehta
Published: March 2011

Sputtered titanium films with thicknesses in the range of 300 to 1200Å were processed in a commercial rapid annealing system to form TiSi2 films. The films were first reacted at low temperatures (500-700°C), etched in ammonia/peroxide solution, and then reacted at 850-900°C to simulate a typical self-alignedsilicide (salicide) process. A method to correctfor dynamic temperature nonuniformities and the resulting etch nonuniformities will be discussed. Sheet resistance maps of the resulting films will be presented. In addition, film properties were measured as a function of annealing ambient in particular, the effects of oxygen contamination were studied.
Properties Of High Dose Low Temperature Rapid Thermally Annealed Gallium Implanted Silicon
Authors: Lee Y.H. , Harrison H.B. , Pogany A.P. , Olson G.L.
Published: March 2011

High doses: 1, 3 and 6×1015/cm2 of Ga71+ ions were implanted into <100> silicon at 100keV and annealed in the temperature regime of 550-675° C for seconds to tens of seconds. Two different annealing rigs were used; however the physical and electrical results obtained from each provided remarkably similar results.

We have observed a regrowth rate/dose dependency through both our physical and electrical measurements that provide surprisingly good correlation. We also note that for the highest dose complete solid phase epitaxial regrowth is inhibited, and for temperatures as low as 640°C and times as short as 9sec. onset of movement of the gallium toward the surface is observed. We also show that extremely high free carrier concentrations of gallium can be obtained under the correct anneal conditions.
Raman Scattering from Rapid Thermally Annealed Tungsten Silicide
Authors: Samhita Dasgupta Samhita Dasgupta , Kumar Sandeep , Jackson Howard E. , Boyd Joseph T.
Published: March 2011

Raman Scattering as a technique for studying the formation of tungsten silicide is presented. The tungsten silicide films were formed by rapid thermally annealing tungsten films that were sputter deposited on silicon substrates. The Raman scattering data is correlated with data from resistivity measurements, Auger and Rutherford Backscattering measurements, and scanning electron microscopy.
Slip Free Rapid Thermal Processing
Authors: Blake Julian , Gelpey Jeffrey C. , Moquin John F. , Schlueter James , Capodilupo Ron
Published: March 2011

Slip is a primary concern in Rapid Thermal Processing (RTP). Diagnostics for slip are compared, including: visual inspection, differential interference contrast microscopy (Nomarski), X-ray topography, decorative etching and optical surface scanning. Data from each technique are presented. RTP control parameters (temperature uniformity, heat up and cool down rates, edge cooling) and substrate parameters (wafer size, oxygen content, edge damage) which may have an effect on slip are discussed. Typical results for implant annealing sequences on a water-wall DC arc lamp RTP system are presented and used to suggest techniques for process optimization.
Limited Reaction Processing: Growth of III-V Epitaxial Layers by Rapid Thermal Metalorganic Chemical Vapor Deposition
Authors: Reynolds S. , Vook D.W. , Gibbons J.F.
Published: March 2011

Rapid thermal processing (RTP) has been applied to improve the versatility of metalorganic chemical vapor deposition (MOCVD). We have demonstrated a new pulsed growth method which yields enhanced layer thickness control and abrupt interfaces (2–4 atomic layers) while maintaining a high growth rate (10Å/sec). In this technique, substrate temperature is used as a switch to control the growth of epitaxial layers.
The unfocused tungsten halogen lamps used in RTP have also facilitated a novel thermal precracking technique, producing the best GaAs ever grown using trimethylarsenic (TMAs). Background doping is reduced by a factor of 5, and carbon incorporation is reduced by a factor of 10 or more. Net background doping below 1016 cm−3 and room temperature electron mobilities of 4000 to 4500 cm2/V. sec have been obtained.
Point Defect Evolution During Rapid Thermal Annealing of Si+-Implanted GaAs.
Authors: Levinson M. , Armiento C. A. , Shah S. S. P.
Published: March 2011

The point defect reactions in GaAs by which ion implant damage is removed and implanted dopants are activated remain poorly understood. Deep level capacitance transient spectroscopy (DLTS) has been used to study the effects of rapid thermal annealing (RTA) on Si-implant damage generated defects. In low implant dose samples, the results of RTA are similar to those of furnace anneals and also agree well with previous reports of boron-implanted and neutron-irradiated material. In contrast to this, higher dose samples showed much smaller than expected apparent defect concentrations. After RTA, very broad DLTS spectra and relatively little EL2 or EL3 defect formation was observed. The significance of these results with regard to the mechanisms of dopant activation and damage removal are discussed.
Rapid-Thermal-Processing Induced Deep Level Traps and their Spatial Distribution in MBE GaAs
Authors: Kitagawa Akio , Tokuda Yutaka , Usami Akira , Wada Takao , kano Hiroyuki
Published: March 2011

Rapid thermal processing (RTP) using halogen lamps for a Si-doped molecular beam epitaxial (MBE) n-GaAs layers was investigated by deep level transient spectroscopy. RTP was performed at 700°C, 800°C and 900°C for 6 s. Two electron traps NI ( Ec-0.5-0.7eV) and EL2 (Ec - 0.82 eV) are produced by RTP at 800 and 900°C.The peculiar spatial variations of the Nl and EL2 concentration across the MBE GaAs films are observed. The larger concentrations of the trap N1 and EL2 are observed near the edge of the samples, and the minima of N1 and EL2 concentration lie between the center and the edge of the sample. It seems that these spatial variations of N1 and EL2 concentration are consistent with that of the thermal stress induced by RTP. Furthermore, the EL2 concentration near the edge of the sample is suppressed by the contact with the GaAs pieces on the edge around the sample during RTP.
Formation of p+ and High Resistivity Regions in GaAs-AIGaAs Heterojunctions
Authors: Pearton S. J. , Brown J. M. , Short K. T.
Published: March 2011

The formation of p+ and high resistivity layers in GaAs-AIGaAs heterostructures is useful in a number of applications, including the fabrication of heterojunction bipolar transistors (HBTs). Control of the implanted dopant profile during annealing is paramount for rapidly diffusing acceptor species such as Be and Mg, and we show SIMS data of the dopant profile in implanted heterojunctions as a function of annealing temperature in the range 700–900°C for 1–5 sec. Annealing of implanted Be at ≥800°C even at a dose of 2×10l5cm−2 results in complete activation whereas Mg shows only 30% activation under these conditions. There is no significant interface disordering visible by TEM or RBS for either case. Multiple energy O implants (up to and including 1 MeV) were used to render the entire heterostructure resistive; for doses of ∼1013cm−2, the O bombarded layers showed resistivities of 108 Ω/□ after 525°C annealing.
Raman Scattering Study of the Au-Ge-Gaas Ohmic Contact Structure Formed by Rapid Thermal Processing
Authors: Kirillov D. , Chung Y.
Published: March 2011

Raman Scattering Was Used To Obtain New Information on the formation of Au-Ge-GaAs alloyed ohmic contacts. During alloying, we observe that amorphous Ge is transfoplmed into polycrystalline material. When Ge diffuses into the GaAs, no n+-GaAs layer is formed. Due to the intermixing of layers, both GaAs and Ge had a large number of impurities which formed deep electronic states in the forbidden gap. Electronic light scattering involving these states was observed. While several models for the Au-Ge-GaAs ohmic contact have been proposed, the model consistent with our Raman data includes resonant tunneling assisted by impurity levels in the graded Au-Ge-GaAs heterojunction structure as a basic conduction mechanism.
Rapid Thermal Diffusion of Zinc In GaAs
Authors: Kalkur T.S. , Lu Y.C. , Paz de Araujo C.A.
Published: March 2011

Rapid thermal diffusion of zinc into semi-insulating GaAs from spin-on zinc silica film is investigated. The rapid thermal diffusion is performed for various diffusion times (5 to 25 sec) and temperatures (800° to 950° C) with tungstenhalogen lamps as the heat source. The sheet resistivity, surface hole concentration and mobility of these zinc diffused layers as measured by Van der Pauw technique shows the formation of shallow p+ layer. The surface morphology of these diffused layers are observed in a low voltage Scanning Electron Microscope (SEM) and the depth profile of diffused impurities are determined by Secondary Ion Mass Spectroscopy (SIMS). Nonalloyed ohmic contacts are formed on these zinc diffused layers and the contact resistivity is determined by the Transmission Line Method (TLM).
Rapid Thermal/Plasma Processing for In-Situ Dielectric Engineering (Invited)
Authors: Moslehi Mehrdad M.
Published: March 2011

Rapid thermal processing of silicon in oxygen and ammonia ambients is an attractive technique for the growth of thin dielectrics such as silicon nitride, silicon dioxide, nitrided oxides, oxidized nitrides, and application-specific (composition-tailored) insulators. Multicycle rapid thermal growth processes are suitable for dielectric engineering and in-situformation of thin layered insulators with a variety of controllable oxygen and nitrogen compositional depth profiles by appropriate design of the temperature and ambient gas cycles. The growth and electrical properties of various dielectrics rapidly grown by the state-of-the-art techniques and their corresponding device performance are examined. Rapid thermal processing and microwave plasma generation have been combined in a novel custom-made multipurpose reactor for rapid plasma-enhanced multiprocessing of Si, Ge, and GaAs. Thin germanium nitride dielectrics can be formed by rapid thermal or plasma nitridation for germanium CMOS applications. Combination of in-situ rapid plasma nitridation followed by silicon nitride deposition may prove to be effective for MIS structures and surface passivation on GaAs. These new applications of rapid thermal/plasma processing are additional steps towards realization of fully RTP-based Si VLSI fabrication processes and development of new devices and technologies on other semiconductor materials.
Process and Equipment Issues in Rapid Thermal Oxidation (RTO)
Authors: Sandeep Mehta Sandeep Mehta , David Hodul David Hodul
Published: March 2011

Thin oxides with thicknesses in the range of 150 to 300Å were grown on lOO-mm <100> Si wafers in a commercial RTP reactor. Growth temperatures and times were llO0-1200°C for 60-180 seconds in 100% 02 at 1 atmosphere. Oxide thickness uniformity was measured using ellipsometry; contour maps of thickness uniformity will be presented. The standard deviation wascalculated to be 2-2.5% within 5 mm of the edge using a method which weights the area represented by each of 45 data points per wafer. In order to correct for dynamic changes in temperature uniformity, a new annealing method was developed.Results on wafer-to-wafer uniformity will be presented. Improvements achieved by post-oxidation annealing in N2 and electrical uniformity of films will be discussed.
Characterization of Buried-Nitride Silicon for Integrated Circuit Applications
Authors: Myers D. R. , Stein H. J. , Tsao S. S. , Arnold G. W. , Hughes R. C. , Miller W. M. , Jones R. V. , Datye A. K.
Published: March 2011

We have examined the microstructure and the transport properties of nitrogen-implanted silicon-on-insulator wafers, as well as the performance of integrated-circuit transistors fabricated in this material. The insulating regions were fabricated in silicon by the unpatterned implantation of 4×1017/cm2, 300 keV nitrogen dimers followed by annealing at 1473 K for 5 hours. For these parameters, the buried nitrogen-implanted layer crystallized into α-silicon nitride, and contains ≈20% excess silicon in the form of silicon inclusions of 5–15 nm diameter. The surface silicon layers are characterized by low-mobility, p-type conduction. The buried dielectric has a resistivity of approximately 108Ωcm. Functional p-channel, integrated circuit transistors have been fabricated in n-type epitaxial silicon grown over the buried-nitride wafers. These transistors devices are similar in performance to those fabricated in bulk silicon,(hole mobilities in inversion layers of 140 cm2/V-s), and demonstrate the suitability of the buried nitride process for integrated circuit applications.
Formation of Silicon-On-Insulator Structures by Multiple Oxygen Implantations
Authors: Bunker S. N. , Sioshansi P. , Tobin S. P.
Published: March 2011

High dose oxygen ion implantation into silicon is an established method to form buried insulating layers. The material produced by standard processing techniques typically exhibits buried layers which are a few hundred nanome ers thick with a threading dislocation defect density on the order of 108/cm2. Unusual structures can be obtained by using repetitive cycles of partial doses of ions followed by annealing and possibly epitaxial growth. Both low and high doses may be used, the former intended to provide decreased defect density and the latter to increase the thickness of the buried layer above the theoretical maximum for higher voltage isolation. The material properties resulting from several variations of this technique are described and characterized.
Temperature Dependence of Implantation Damage in Strained-Layer Superlattices
Authors: Myers D. R. , Arnold G. W. , Dawson L. R. , Biefeld R. M. , Hills C. R. , Doyle B. L.
Published: March 2011

We have characterized damage production in both (InGa)As/GaAs and Ga(AsP)/GaP strained-layer superlattices for silicon implants at 80 K, 300 K or 673 K at fluences sufficient to induce compositional disordering of the superlattice layers. Implants at low temperatures (80 K for the (InGa)As/GaAs system, 300 K and below in the Ca(AsP)/GaP system) are characterized by well-defined amorphous layers at depths consistent with the predictions of ion range codes. Implants at higher temperatures are characterized by greatly reduced damage levels with substantial densities of extended defects located near the mean ion range. Point defect clusters are preferentially located in the ternary layers in the (InGa)As/GaAs SLS at the deepest part of the implanted zone. Despite the absence of amorphous layer formation, precipitous stress relief still occurs for the Si-implanted (InGa)As/GaAs SLS.
Ion Mixing of Ti/C and Fe/C Bilayers
Authors: Nastasi M. , Tesmer J. R. , Hirvonen J.-P.
Published: March 2011

Bilayer samples of Ti/C and Fe/C have been ion beam mixed with 400 keV Xe ions to a dose of 1 × 1016 ions/cm2. Mixing experiments were performed at 77, 300, 573, and 723 K. The transition between the temperature independent and temperature dependent mixing occurred between 300 and 573 K in Fe/C samples and between 573 and 723 in Ti/C sample. In the temperature independent mixing regime mixing is reasonably well explained by a thermodynamic model of ion mixing while at higher temperatures a radiation enhanced diffusion mechanism is evident.
Direct Formation of Thin Films and Epitaxial Overlayers at low Temperatures Using a Low-Energy (10–;500 ev) Ion Beam Deposition System
Authors: Zuhr R. A. , Alton G. D. , Appleton B. R. , Herbot N. , Noggle T. S. , Pennycook S. J.
Published: March 2011

A low-energy ion beam deposition system has been developed at Oak Ridge National Laboratory and has been applied successfully to the growth of epitaxial films at low temperatures for a number of different elements. The deposition system utilizes the ion source and optics of a commercial ion implantation accelerator. The 35 keV mass- and energy-analyzed ion beam from the accelerator is decelerated in a four-element electrostatic lens assembly to energies between 10 and 500 eV for direct deposition onto a target under UHV conditions. Current densities on the order of 10 A/cm are achieved with good uniformity over a 1.4 cm diameter spot. The completed films are characterized by Rutherford backscattering, ion channeling, cross-section transmission electron microscopy, and x-ray diffraction. The effects of substrate temperature, ion energy, and substrate cleaning have been studied. Epitaxial overlayers which show good minimum yields by ion channeling (3–4%) have been produced at temperatures as low as 375°C for Si on Si(100) and 250°C for Ge on Ge(100) at growth rates that exceed the solid-phase epitaxy rates at these temperatures by more than an order of magnitude.
Ionized Cluster Beam Epitaxy of Single Crystal Metal Films on Semiconductors and Insulators
Authors: Yamada I. , Levenson L. L. , Usui H. , Takagi T.
Published: March 2011

Our experiments show that ionized cluster beams (ICB) can form epitaxial Al films on Si(111) and Si(100) substrates. This is unique because the lattice misfit of this material combination is more than 25%. Al can also be epitaxially grown on CaF2 films deposited on Si substrates. The initial stage of the film formation is measured by in-situ electron diffraction. In the case of Al(111) growth on Si(111) and CaF2, growth of mixed layers of different epitaxial islands of approximately 20–50 Angstrom thickness on the substrate surface is observed. With increase of thickness, the film shows the single crystal state with a flat surface, which indicates the epitaxial single crystal film formation on CaF2 or on Si substrates. It should be noted that in the Al/CaF2/Si (MIS) structure, the epitaxial CaF2 is a good insulating layer, which can be used to prepare three dimensional devices. These results show that the kinetic energy and the ionic charge of cluster ions have much influence on surface and interface modification, and that ICB is capable of producing films of good quality at low substrate temperatures.
Ion-Beam-Induced Modifications of Thin Films: Growth Simulations
Authors: Müller Karl-Heinz
Published: March 2011

If the thermal adatom mobility is limited during film growth, the kinetic energy delivered to the film surface by arriving species is the key parameter which determines the resulting film microstructure and properties. Kinetic models and growth simulations of nonequilibrium film growth have been used to study the influence of incident kinetic energy of adatoms and energetic ions on the film microstructure, microporosity, density, stoichiometry and epitaxy. Deposition processes like vapor, sputter, ion-assisted and ionized cluster beam deposition, could be examined in detail with particular emphasis on optical coatings. The theoretical descriptions used are based on the solid-gas, thermal spike, collision cascade and molecular dynamics model.
Plasma-Activated CVD for the Production of Protective Layers in Optics, Electronics and Mechanical Engineering
Authors: Enke Knut , Geisler Michael , Kieser Jörg , Münz Wolf-Dieter
Published: March 2011

Conventional chemical vapor deposition (CVD) has historically utilized high melting temperature substrates. Recently there has been an increased desire to coat temperaturesensitive materials such as aluminum, glass, steel, and even plastic. Thus “cold” CVDprocesses, most using plasma excitation, have been developed. In these processes gas molecules or atoms are excited by dc or ac glow discharge, thereby allowing the possibility of keeping substrates at room temperature.

This paper describes plasma CVD reactors using capacitive coupling of r.f. voltage to an asymmetrical arrangement of electrodes. Using organic or metal-organic process gases and mixtures of them with inorganic gases, deposition takes place on the reactor walls, the anode, and the cathode. In this paper the emphasis is on deposition on negatively selfbiased substrate holders. Physical and chemical properties of plasma-CVD grown layers depend on about six process parameters, the most important of which are cathode voltage, gas pressure, choice of gases, and mixing ratio of gases. Map-like representations show the dependence of coating properties on deposition parameters. Layer materials discussed include amorphous hydrogenated carbon (a-C:H). WCx, SiOx:H, SiCxOy:H. and SnOx:H.
Wear of Ion Implanted Glassy Carbon
Authors: Pollock John T. A. , Farrelly Matthew , Wielunski Leszek S.
Published: March 2011

Significantly improved wear properties are described for glassy carbon following implantation with 2 MeV helium and 50 keV nitrogen to doses in the range 1015–1017 ions cm−2. Implanted material is up to 100 times more wear resistant to diamond abrasion than unimplanted material. Enhanced wear resistance is available at the surface with nitrogen but lies below the surface with helium, reflecting the difference in modified depth associated with implant energy and ion mass. Unusually for ion implantation, dose related surface compaction is observed for both nitrogen and helium. Changes in microstructure during implantation with particular regard to collision processes and amorphisation of the graphitic fraction of glassy carbon are discussed.
Boron Nitride: Composition, Optical Properties, and Mechanical Behavior
Authors: Pouch John J. , Alterovitz Samuel A. , Miyoshi Kazuhisa , Warner Joseph O.
Published: March 2011

A low energy ion beam deposition technique was used to grow boron nitride films on quartz, germanium, silicon, gallium arsenide, and indium phosphide. The film structure was amorphous with evidence of a hexagonal phase. The peak boron concentration was 82 at %. The carbon and oxygen Impurities were in the 5 to 8 at % range. Boron-nitrogen and boron-boron bonds were revealed by x-ray photoelectron spectroscopy. The index of refraction varied from 1.65 to 1.67 for films deposited on the III–V compound semiconductors. The coefficient of friction for boron nitride in sliding contact with diamond was less than 0.1. The substrate was silicon.
Compared Nitrogen Implantations of Various Alloyed Steels
Authors: Moncoffre N. , Jaffrezic H. , Marest G. , Tousset J. , Zawislak F. C. , Faveulle S. , Brissot J.
Published: March 2011

Nitrogen implantations in pure iron and various stE-els are investigated using nuclear reaction analysis, Conversion Electron M6ssbauer Spectroscopy and Grazing angle X-ray Diffraction. The present work sums up all the significant results although it does not constitue a systematic study. It describes the influence of the chemical composition and the structure effect of the matrix as well as those of the implantation time. The N-martensite, ε-nitride and ε-carbonitride phases are principally identified. The fraction of iron bound with nitrogen is evaluated in the different steels. The strong influence of the small chromium amounts inside the matrix upon the nitride formation is underlined. A preferential orientation of these phases is shown. SIMS experiments are presented in particular to determine the carbon distribution in the first surface layers.
Biological Tissue Adhesion to Ion Implanted Surfaces
Authors: Kelly J. C. , Evans M. D. M. , Wildish K. L. , Keirnan E. C. , Fisher L. R. , Howlett C. R.
Published: March 2011

Results of preliminary investigations on varying the adhesion and growth behaviour of osteoblast-like cells on silicon are presented. Significant changes in growth behaviour are obtained by implanting oxygen or by growing a thermal oxide on the surface. The objective of the work is to modify tissue adhesion to materials used as prosthetic devices.