bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain Rate Effects on Tensile Properties of Fiber Reinforced Concrete
Authors: Nammur George G. , Naaman Antoine E.
Published: March 2011

High strain rates lead to substantial modifications in the stress-strain (or stress-displacement) response of fiber reinforced concrete in tension. These modifications include higher strength and corresponding strain, as well as smaller displacement at failure.

The purpose of this paper is to investigate the behavior of fiber reinforced concrete under impact tensile loading, and to study the effect of strain rate on the post-cracking strength of the composite. The variation of the tensile strength of the matrix with the reinforcement parameters such as volume fraction Vfand aspect ratio |/φ of the fibers is also studied ip this paper. A special emphasis is placed on the stress-displacement relationship of steel fiber reinforced concrete in its post-cracking range. An empirical model of the stress- displacement relationship as a function of the strain rate is developed from experimental data from tensile tests on dogbone shape notched tensile prisms. The model highlights the effects of strain rate and fiber properties on the post-cracking strength of the composite, as well as the displacement at failure. The effect of strain rate on the post-cracking toughness of fiber reinforced concrete is also addressed. The literature on impact effects on concrete in tension (plain and fiber reinforced) is briefly reviewed in this paper, and so is the state of the art of testing techniques for strain rate effects.
Available Alkalis in Fly Ash
Authors: Lee Chau , Schlorholtz Scott , Demirel Turgut
Published: March 2011

The available alkalis of six Iowa fly ashes, four Class C and two Class F, have been studied as outlined by the procedures listed in ASTM C 311. The purposes of the study were to: (1) assess the significance of the test when it is used to analyze different fly ashes; (2) to investigate the possibility of decreasing the time required to complete the test (it currently requires 28 days for curing). When cured for 28 days at 38 C, the available alkalis were found to be about 60% and 30% of the total equivalent alkalis (equivalent alkalis = %Na20 + 0.658 × %K20) for Class C and Class F fly ashes, respectively. However, more than 85% and more than 40% of the total equivalent alkalis for the Class C and Class F fly ashes, respectively, were mobilized after 5 to 6 months of curing at 38 C. It was concluded that the available alkali test described in ASTM C 311 tends to underestimate the amount of equivalent alkalis present in Class C fly ash-calcium hydroxide mixtures after long periods of time.
A Simple Technique for Fly Ash Specimen Preparation for Scanning Electron Microscopy
Authors: Lovell Janet , Diamond Sidney
Published: March 2011

A method of mounting fly ash specimens for scanning electron microscopy is described that avoids almost all charging difficulties and permits imaging of close packed fields of representative particles. The procedure facilitates a true assessment of the kinds of particles present in that specific fly ash and their relative frequencies of occurrence.
3D Chemical Characterization of Micron-Sized Coal Fly Ash Particles
Authors: Linton Richard W. , Bryan Scott R. , Cox X. B. , Griffis Dieter P.
Published: March 2011

The surface layers on coal fly ash particles are of special environmental interest in that concentration enrichments of trace elements may occur [1], thereby enhancing the potential bioavailability of toxic species. Little research, however, has been devoted to the analytical characterization of intraparticle and interparticle distributions of trace elements. The high detection sensitivity, spatial resolution, and depth profiling capabilities of secondary ion mass spectrometry (SIMS), coupled to digital image acquisition and processing [2], permit three-dimensional (3D) compositional maps for collections of individual micron-sized particles. The 3D analysis of trace element distributions in coal fly ash particles is the subject of this SIMS investigation
Relationship Between Pozzolanic Activity and Chemical and Physical Characteristics of Selected Canadian Fly Ashes
Authors: Joshi R. C. , Malhotra V. M.
Published: March 2011

Raymond E. Davis and his associates appear to have coined the term “fly ash” in 1937. Following the pioneering studies by the U.S. Bureau of Reclamation for the Hungry Horse Dam, the use of fly ash for massive hydroelectric structures increased rapidly in the U.S., with ASTM issuing the first standard in 1954. In 1982, Canada issued a National Standard, CAN 3-A23.5-M82, entitled “Supplementary Cementing Materials and Their Use in Concrete Construction.” Because of the increasing interest in fly ash utilization, Canada Centre for Mineral and Energy Technology (CANMET) initiated research in the area of supplementary cementing materials in the early 1970's and has since published several comprehensive reports on the subject [1,2]. At the University of Calgary, we are studying Canadian fly ashes and their use in concrete, through an investigation of the physical, chemical, mineralogical and pozzolanic properties of fly ashes from fourteen sources across the country. We report here preliminary results from this study.
Fly Ash Cement: Production Methods, Materials Properties and Energy Savings
Authors: Stoltenberg-Hansson Erik
Published: March 2011

A standard system for grinding of Portland clinker to cement and the different principles for producing fly ash cement is described. The quality is influenced by the grinding system selected. The preferred system for intergrinding of fly ash and clinker involves introduction of fly ash into the finishing compartment of the mill. Efforts made to relate cement quality to specifications are described. Much attention is put on the physical characteristics of the fly ash: bulk weight, specific weight, particle distribution, particle shape, degree of agglomeration and colour. Surface areas and pozzolanic activity matter, but the air void content, which is much affected by grinding, is more important. This observation is based on testing of fly ashes and fly ash cements from production and laboratory grindings. The testing includes compressive strength, specific gravity, laser granulometry and SEM. The results have led to the introduction of new analytical and control procedures. A review of fly ash quality factors of most importance for cement producers is given. The energy balance in the production of blended fly ash cement involves savings from reduced consumption of clinker, and expenditure on transport, handling of fly ash and extra grinding of clinker and fly ash; net savings may be considerable.
Trapping of Chloride Ions in Cement Pastes Containing Fly Ash
Authors: Roy D. M. , Malek R. I. A. , Rattanussorn M. , Grutzeck M. W.
Published: March 2011

Chloride ions, when present at sufficient concentration in the concrete pore fluid, may be associated with corrosion of the reinforcing steel even in normally passivative environments. The effectiveness of fly ash containing pastes in trapping chloride ions was studied. A paste was prepared containing 30% low-calcium fly ash and 70% type I cement, with mixing water (50% by weight) containing 0.4% C1− with respect to the solid. Samples were cured at 25°C and 38°lC at 95% R.H. At designated times extending over a six-month period, the pore fluids were expressed from the hardened pastes using a squeezing cell designed for this purpose. Special precautions were taken to avoid carbonation of the fluids; contact with the atmosphere was minimized. The expressed fluids were analyzed by DC plasma emission spectrometry for cations and by automated selective ion exchange chromatography for anions. Other studies (XRD, thermal analysis) were carried out to identify the compounds formed and determine their mechanisms of formation. Investigations indicated that the mechanism of trapping chloride ion is partly chemical and partly physical through adsorption on the surface of fly ash particles (initially physical and subsequently chemical).
Danish Fly Ash Utilization
Authors: Jensen Svend Aage
Published: March 2011

Since 1976 the rate of utilization of fly ash from Danish power stations has increased from about zero to more than 75% of production. The main reason for this growth is the co-operation between the utilities and the fly ash consumers, i.e. predominantly the Danish and the Norwegian cement producers. This paper deals mainly with the precautions against separation, with storage and shipment of quality ash, and with the main principles of the co-operation between the producer and the consumer.
The Research-Technology Interface in the Fly Ash-Concrete Regime
Authors: Idorn G. M.
Published: March 2011

Opportunities for development of the use of fly ash in blends with Portland cement by improvement of the relevant research are discussed in view of the currently modest growth of the fly ash utilization, despite copious research activity during the past decade. Refined characterization is suggested of the decisive parameters of the chemistry, mineralogy and granulometry of both the components of the reacting, blended system, and also of the effects induced by chemical admixtures. Effective dispersion of the finest particle fractions in the fresh paste, and monitored integral hydration are indispensable successive precursors for the creation of a blended, hardened cement paste which acts as a “microconcrete”, having dense matrix consisting of fully hydrated, finest fractions of both source materials and coarser unhydrated particles representing “microaggregates”. Surface chemistry and energetics are emphasized as essential scientific regimes to apply for the explanatory research having as their aim substantial increases of the replacement ratios of fly ash to cement in concrete.

The Materials Research Society (MRS) is a possible instrument for activity to encourage development of research planning and management methods, which are used in other fields of materials research, to strengthen research as an instrument for effective recovery of the chemical energy inherent in fly ash and for improvement of concrete durability.
Technical Basis for Codisposal of Gasification and Combustion Ash from the Plants at Beulah, North Dakota
Authors: McCarthy G. J. , Hassett D. J. , Manz O. E. , Groenewold G. H. , Stevenson R. J. , Henke K. R. , Kumarathasan P.
Published: March 2011

The technical hasis for codisposal of gasification ash from the Great Plains Gasification Associates plant, combined with cementitious “scrubber ash” and bottom ash from the adjoining Antelope Valley generating station, both located in Beulah, North Dakota, has been explored. Nine blends containing only the ashes and tap water were fabricated into cylinders and tested for compressive strength and other physical properties. A blend having the ash proportions of the two plants was tested for leachability with respect to several regulated and minor elements. Mineralogical characterization by XRD was performed on the individual waste solids and the cured mixes. Most of the blends had compressive strengths greater than 400 psi after 7-day/38 C and 28-day/21 C curing. The 7-day treatment led to better consolidated test cylinders. Leaching behavior, evaluated by the EPA-EP and ASTM tests, was determined for As, Se, B, V, Mo, Ba, Sr, and K. Average fixation factors (the ratio of leaching expected from a weighted average of its components to the actual leaching of the specimen) of 2 to 4 were observed for the 7-day cured specimens and 1 to 2 for the 28-day specimens. Not all elements had reduced leaching in the fabricated specimens; Se and V leaching increased in the fabricated specimens. In addition to ash proportions, curing conditions (T, pH2O, time) and water to solid ratio appear to key parameters in obtaining well-consolidated and lower leachability products. XRD indicated that ettringite and minor calcite were the only crystalline reaction products of the cementitious reactions in the cured codisposal mix.
Fly Ash in Shale Stabilization for Highway Construction
Authors: Saleh M. , Laguros Joakim G.
Published: March 2011

The expansive shales used for roadbeds in Oklahoma are traditionally stabilized with lime. Stabilization with a Class C (high-calcium) fly ash was explored and compared to an optimum design utilizing the conjunctive use of fly ash, lime and cement, in the laboratory and in a field experimental project. Periodic visual observations indicated that the performance of test sections was excellent. Analyses of field samples showed that fly ash, either alone or mixed with lime and cement, was effective in ameliorating the texture and plasticity of the shale by reducing the amount of clay size particles and by imparting higher strength levels to the shale. Laboratory samples showed better stabilization than field samples, but the field samples performed at an acceptable level in measurements of compressive and beam strength, cohesion, angle of internal friction and resistance to deflection. The microstructure of stabilized shale was studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nonbasal (hkl) reflections in stabilized oriented specimens suggest that the clay particles acquire high resistance to dispersive forces. The reduction of the areas under the peaks help explain the strength gain observed. The SEM observations indicated newly formed hydration products, possibly calcium aluminum silicate hydrate crystals, and a rather dense degree of packing as manifested by the substantial reduction of void areas as a result of stabilization.
Using Rapid Thermal Annealing to Improve Epitaxial CaF2/CoSi2/Si(111) Structures
Authors: Phillips Julia M. , Augustyniak W. M.
Published: March 2011

We have extended our studies of epitaxial insulator-metal-semiconductor heterostructures composed of CaF2 and CoSi2 layers grown on Si(111) substrates to cover a broader range of growth conditions. We find that rapid thermal annealing plays a crucial role in optimizing the epitaxial quality of the CaF2 layer over the entire range of conditions studied. The chemical stability of the fluoride layer is also enhanced by the annealing process.
Heteroepitaxy of Gallium Arsenide on Germanium Coated Silicon Substrates
Authors: Chu Shirley S. , Chu T. L. , Firouzi H.
Published: March 2011

Single crystalline epitaxial GaAs layers have been grown on silicon substrates with a thin germanium interlayer. All semiconductor layers were deposited by the chemical vapor deposition technique. The surface condition of the silicon substrate is an important factor affecting the quality of GaAs/Ge films on silicon. P+/n homojunction solar cells of 0.25 cm2 area with an AM1 efficiency near 12% have been prepared.
A HgCdTe/CdTe/GaAs/Si Epitaxial Structure
Authors: Zanio K. , Bean R. , Hay K. , Fischer R. , Morkoc H.
Published: March 2011

Four layer HgCdTe/CdTe/GaAs/Si structures have been prepared by the sequential growth of (100) GaAs on (100) Si by MBE, (100) CdTe on GaAs/Si by congruent evaporation in UHV and (100) HgCdTe on CdTe/GaAs/Si by vapor transport. Infrared transmission, X-ray rocking curves, differential interference contrast microscopy and selected area electron channelling patterns characterize the structures.
High Speed GaAs Based Devices on Si Substrates
Authors: Morkoc Hadis
Published: March 2011

Remarkably good device performance at both dc and microwave frequencies has recently been obtained from GaAs based devices grown on Si substrates. In GaAs MESFETs on Si, current gain cutoff frequencies and maximum oscillation frequencies of fT = 13.3 GHz and fmax = 30 GHz have been obtained for 1.2μm devices, which is nearly identical to the performance achieved in GaAs on GaAs technology for both direct implant and epitaxial technology. For heterojunction bipolar transistors, current gain cutoff frequencies and maximum oscillation frequencies of fT = 30 GHz and fmax = 11.3 GHz have been obtained for emitter dimensions of 4×20μm2. In GaAs AlGaAs MODFETs. current gain cut-off frequencies of about 15 GHz with lμm gates were obtained on GaAs and Si substrates. The pseudomorphic InGaAs/GaAs MODFETs were also fabricated and found to be comparable to GaAs MODFETs although they should perform better. The structures were also shown to maintain their properties when put through ion implantation and annealing process. Given the performance already demonstrated in GaAs on Si devices and the advantages afforded by this technology, the growth of III-Vs on Si promises to play an important role in the future of heterojunction electronics.
High-Speed Photoconductive Detectors Fabricated in Heteroepitaxial GaAs Layers
Authors: Turner G. W. , Diadiuk V. , Le H. Q. , Choi H. K. , Metze G. M. , Tsaur B-Y.
Published: March 2011

Response times of ∼60 and 25 ps (FWHM), respectively, have been measured for photoconductive detectors fabricated in GaAs layers grown by molecular beam epitaxy on silicon substrates and silicon-on-sapphire substrates. Photoconductive detectors, which can be readily combined with GaAs logic devices such as MESFETs to provide high-speed optical to electrical conversion, could be used in optical interconnects that are integrated with Si circuits on monolithic GaAs/Si wafers. Transconductance values of 120 mS/mm have been obtained for MESFET's fabricated in GaAs layers grown on silicon-on-sapphire substrates.
Structure and Properties of Ultrathin Ge-Si Superlattices
Authors: Bevk J. , Mannaerts J. P. , Feldman L. C. , Davidson B. A. , Lowe W. P. , Glass A. M. , Pearsall T. P. , Menendez J. , Pinczuk A. , Ourmazd A.
Published: March 2011

We report the synthesis, structural characterization, and preliminary optical studies of ultrathin Ge-Si superlattices with individual sublayers smaller than the Si unit cell, grown by MBE on (001) silicon substrates. Structures are fabricated one monolayer at a time in a configuration GeGeSiSiGeGe..., resulting in either ordered alloys or complex cell superlattices. Rutherford backscattering and channeling experiments on these highly strained heterostructures indicate excellent crystallinity with tetragonal distortion as high as 3.5%. Electron diffraction patterns exhibit characteristic superlattice reflections indicative of one-dimensional layering with periodicity of four monolayers. X-ray scans along the growth direction at the (002) position in reciprocal space reveal a strong peak not observed in random GeSi alloys. This scattering is attributed indirectly to the GeSi ordered phase. The optical transition energies measured by Schottky barrier electroreflectance correspond to those expected from homogeneous alloys of the same composition; however, the width of optical transitions is less than 30 meV at room temperature, allowing a clear resolution of the splitting of the valence band by strain. Modification of the unit cell of the diamond lattice in this way should permit the design of materials with novel opto-electronic characteristics. Preliminary Raman and photoconductivity measurements are also reported.
MBE Growth of GaAs on Si: Problems and Progress
Authors: Kroemer Herbert
Published: March 2011

Several fundamental problems are reviewed that must be solved if GaAs on Si growth is to be achieved with device-quality already close to the GaAs/Si interface, rather than relying on thick buffer layers: (a) antiphase disorder, (b) interface charge and cross-doping, and (c) misfit dislocations. An extensive discussion is given of the mechanism by which antiphase disorder is suppressed on (100)-oriented substrates
The Growth of GaAs on Si by Molecular Beam Epitaxy
Authors: Koch S. M. , Rosner S. J. , Schlom Darrell , Harris J. S.
Published: March 2011

Successful growth of GaAs on Si has recently been demonstrated. This work is directed toward an understanding of the processes occurring during the growth and their effects on the quality of the GaAs epilayers. Reflection High Energy Electron Diffraction monitoring of the growth in situ shows that the islands that are initially formed coalesce into an epilayer with a 2×4 surface reconstruction. Ion channeling indicates that the crystallinity of the entire epilayer improves with coverage. Substantial reordering of the material occurs when buffer layers grown at low temperatures are annealed at 575°C before and during further growth at this temperature. Comparison of 300 nm layers differing in the growth temperature of the first 100 nm shows no variation in the crystallinity as determined by ion channeling. Surface morphology degrades, however, and 77K photoluminescence intensity rises with the initial growth temperature. The optical and structural properties of 2μm thick films are also discussed.
Dopant Incorporation of Boron Implanted Silicon During Rapid Thermal Annealing
Authors: Hung-Yu Liu Hung-Yu Liu , Peng-Heng Chang Peng-Heng Chang
Published: March 2011

Surface layer damage of boron implanted (100) silicon crystals were characterized by x-ray rocking curves using computer fitting procedures. The implantation was carried out at ion energy of 130 KeV with the dose of 1*1016 atoms/cm2. The in-depth strain distribution of the surface layer after rapid thermal annealing was discussed based on x-ray rocking curve observation. It is clearly revealed that the strain profile reverses completely from the positive (tensile) strain in the as-implanted condition to the negative (compressive) strain after annealing. This change is ascribed to the incorporation of boron atoms from interstitial sites to substitutional positions. The results were also compared with transmission electron microscopy (TEM) observations.
Effects of Tisix/Tinx/Al Contact Metallization Process on the Shallow Junction Related Properties
Authors: Sun S.W. , Pintchovski F. , Tobin P.J. , Hance R.L.
Published: March 2011

An extremely reliable TiSix/TiNx diffusion barrier was formed by the rapid thermal annealing of a thin Ti layer which was sputtered into the contacts before Al metallization. The effects of this barrier metal process on the material properties of heavily implanted n+ and p+ regions were studied. The TiNx-to-TiSix thickness ratio is determined by the dominant reaction at the sintering temperature. Arsenic implanted in the substrate tends to substantially retard the silicidation of Ti. Substantial redistribution of both B and As across the silicide layer was observed during rapid thermal annealing. Film stress was found to be greatly affected by the annealing temperature. Contact resistance, contact electromigration and thermal stability of the structure were also investigated.
An Electrical Characterization of Sol Films Using Devices Formed by Oxygen Implant and Rapid Thermal Processing
Authors: Whitfield Jim D. , Burnham Marie E. , Varker Charles J. , Wilson Syd.R.
Published: March 2011

The advantages of Silicon-on-Insulator (SO) devices over bulk Silicon devices are well known (speed, radiation hardened, packing density, latch up free CMOS,). In recent years, much effort has
been made to form a thin, buried insulating layer just below the active device region. Several approaches are being developed to fabricate such a buried insulating layer. One viable approach is by high dose, high energy oxygen implantation directly into the silicon wafer surface (1-3). With proper implant and annealing conditions, a thin stoichiometric buried oxide with a good crystalline quality silicon overlayer can be formed on which an epitaxial layer can be grown and functional devices and circuits built. As SO1 circuits become market viable, mass production tools and techniques are being developed and evaluated. Of particular interest here is the evaluation of high current oxygen implantation with rapid thermal processing on the electrical characteristics of the oxide-silicon interfaces, the silicon overlayer and the thermally grown oxide on the top surface using measurements on gated diodes and guarded capacitors.
Rapid Thermal Processing — A User'S Perspective
Authors: Fulks R. T.
Published: March 2011

The technique of rapid thermal processing (RTP) has evolved from research laboratory efforts to quickly heat small pieces of semiconductor material using pulsed or scanned lasers to high throughput, production RTP equipment capable of rapidly heating eight-inch silicon wafers to greater than 1000 deg C in 10 seconds. Furthermore, the initial application of annealing ion implantation damage has expanded to include silicide formation, oxide reflow, contact formation, hillock control and more recently oxidation and nitridation. Nearly a dozen vendors now produce RTP equipment and the potential user must answer the question — “Which equipment is best for me?” The researcher's principal concerns for RTP equipment are flexibility and control while the production engineer wants unifomity, reproducibility, and a reasonable throughput. Meanwhile, the device designer wants a “safe” process with no contamination or other adverse device degradation effects. This paper will focus on these and other issues associated with the use of rapid thermal processing from a user' perspective including some thoughts on where RTP may be headed in the future.
A Study of Diffusion, Clustering and Defects in As+ And Bf2+ Implanted Silicon During Scanning Electron Beam Annealing.
Authors: Hart Michael J. , Evans Alan G.R. , Amaratunga Gehan A.J. , Altrip John L.
Published: March 2011

Scanning electron beam annealing techniques have been applied to the study of diffusion of implanted arsenic and boron difluoride. Electron beam anneals over the time range 0-180s (at Tmax), with peak temperatures in the range 1100-1200°C have been performed on uniformly implanted samples. Controlled slow cooling has been performed for some samples. Direct sample temperature measurements were made using a dual-colour pyrometer under control of a microcomputer, which provided data-logging and feedback control of temperature. The accurate temperature control achieved using this system is important for realistic diffusion modelling.

Measurement of the resulting chemical and electrical dopant profiles, using SIMS, RBS and spreading resistance methodshas shown the presence of non-equilibrium diffusion at short times [6]. Channelling RBS studies used to investigate the activation and clustering behaviour of arsenic during the first stages of these very rapid anneals is reported.

Modelling of the arsenic diffusion occuring for a range of implant doses subjected to these anneals has been performed,applying avariety of models, including a dynamic clustering model. This dynamic clustering model, based upon an equilibrium cluster model and a measured de-clustering rate, has been shown previously to give good agreementwith experiment. Forthese experiments, a modified de-clustering coefficient was needed to model the diffusion occuring for a wider range of arsenic implants. A solution of the Poisson equation for the internal electric field has also been incorporated.

DLTS techniques have been used to study the defects remaining in diodes fabricated using these implagts andanneals. Trap densities of <5×1010cm−3 and leakages of <2×10−9 A.cm2 at −5V have been measured for the best devices, similar tothose observed for control furnace anneals.
Microwave Plasma LPCVD of Tungsten in a Cold-Wall Lamp-Heated Rapid Thermal Processor
Authors: Moslehi Mehrdad M. , Saraswat Krishna C. , Shatas Steven C.
Published: March 2011

A novel cold-wall single-wafer lamp-heated Rapid Thermal/Microwave Remote Plasma Multiprocessing (RTMRPM) reactor has been developed for multilayer in-situ growth and deposition of dielectrics, silicon, and metals. This equipment is the result of an attempt to enhance semiconductor processing equipment versatility, to improve process reproducibility and uniformity, to increase growth and deposition rates at reduced processing temperatures, and to achieve in-situ multiprocessing in conjunction with real-time process monitoring and automation. For high-performance MOS VLSI applications, a variety of selective and nonselective tungsten deposition processes were investigated in this work. The tungsten gate MOS devices fabricated using the remote plasma multiprocessing techniques exhibited negligible plasma damage and near-ideal electrical characteristics. The flexibility of the reactor allows optimization of each process step yet allows multiprocessing.
Defect Structures and Electrical Behavior of Rapid Thermally Annealed Ion Implanted Silicon
Authors: Sadana D. K.
Published: March 2011

The importance of the knowledge of implantation induced damage structures in annealing studies is emphasized. The existence of various observed microstructures is reviewed and their distributions are presented schematically. It was found that although the usefulness of RTA in controlling dopant profiles is indisputable, the control of microstructure by RTA especially in “non-amorphized” or incompletely amorphized Si samples is questionable. Significance of complete surface amorphization to achieve better structural perfection on subsequent RTA or FA is discussed. An attempt was made to explain the published electrical data on rapid thermally annealed B+ and As+ implanted Si based on expected location and annealing behavior of defects for such implants. Recent structural and electrical results from B implanted pre-amorphized Si are presented.
Enhanced Diffusion During Rapid Thermal Annealing Of Indium And Boron In Double Implanted Silicon
Authors: Ganin E. , Sai-Halasz G. A. , Sedgwick T. O.
Published: March 2011

Experimental results on the diffusion and precipitation of In and B doubly implanted into Si, followed by rapid thermal treatment are reported. It was observed that In redistributes itself and accumulates in defected regions. The amount of motion of each species is enhanced by the presence of the other. While the B influences In diffusion probably through the same mechanism that leads to concentration enhancement, the effect of In on B is not clear. There is no correlation with strain and no apparent chemical effects. Also the presence of B facilitates the sweeping out of In during low temperature solid phase regrowth.
Rapid Thermal Annealing of Oxygen-Vacancy Centers In O-Implanted Silicon
Authors: Stein H. J.
Published: March 2011

Infrared absorption by localized vibrational modes has been used to investigate rapid thermal annealing (RTA) of oxygen-vacancy (O-V) defects in O-implanted Si. At least three processes are involved in the annealing of O-V defects. An activation energy of 1.0 ± 0.2 eV for a process leading to O-V formation is attributed to O-V diffusion. The final O-V annealing stage is attributed to oxygen clustering around O2-V centers. Processes observed here in RTA are expected to be operative during implantation at the temperatures (400 to 600°C) used for production of silicon-on-insulator structures.
The Effect of Rapid Thermal Treatment on the Structural and Optoelectronic Properties of Epitaxial Gaas on Si Grown With or Without Ge Intermediate Layers
Authors: Lee El-Hang , Awal M.Abdul , Chan E. Y. , Opila R. L. , Jacobson D. C. , Pearton S. J.
Published: March 2011

Characteristics of MOCVD GaAs grown on Si are compared before and after a rapid thermal treatment. The GaAs-on-Si samples were prepared both with and without a Ge intermediate layer, which is used to accomodate mismatches of lattice, thermal and chemical origin between GaAs and Si. Structural, interfacial, chemical, and electrical changes have been examined. RBS and Raman characterization showed improvement of GaAs crystallinity after RTA. In most cases, the interfaces were found to become sharper after RTA, but chemical interdiffusion was observed to cause some effect on the structural and electrical properties. For gold-contacted GaAs, RTA seems to degrade the electrical and optoelectronic properties via gold interdiffusion into GaAs. Comparative studies of the GaAs/Si and GaAs/Ge/Si samples suggests that the two respond somewhat differently to RTA.
Rapid Thermal Processing of Silicon Ion Implanted Channel Layers in GaAs
Authors: Hara Tohru , Gelpey Jeffrey C.
Published: March 2011

The use of Rapid Thermal Processing (RTP) for the activation of silicon ion implanted channel layers in GaAs MESFET devices has been studied. Tungsten-halogen lamp and Water-wall DC arc lamp RTP have been compared. The arc lamp gave superior abruptness of the carrier concentration profile (78% at 850°C for 15 seconds or 1000°C for 2 seconds) and dopant activation greater than 60%. These parameters are important to achieve good MESFETs fabricated using arc lamp RTP was also studied. The transconductance (gm) of the devices usinq RTP was 78mS/mm which is much higher than achieved with similar samples using furnace annealing. Both capped and capless RTP was examined. Although capped annealing generally yields superior surface quality, the capless annealing provided good electrical properties in a process window which also yielded adequate surface quality and good devices.
Formation of Device Quality p-Type Layers in GaAs using Co-Implantation of Mg+ and As+ and Capless Rapid Thermal Annealing
Authors: Masum Choudhury A.N.M. , Armiento C.A.
Published: March 2011

Low (1 × 1014 cm-2) and high (1 × 1015 cm-2) dose implants of Mg+ in undoped GaAs have been activated using the enhanced overpressure proximity (EOP) rapid thermal annealing (RTA) technique. Hall measurements have yielded electrical activation efficiencies as high as 86% and 38% for low and high dose implants, respectively. For high dose implants, the outdiffusion of Mg+ from the wafer surface reduces the activation efficiency. A dramatic improvement in the activation for high dose Mg+ (1×1015 cm−-2, 100 keV) implants has been obtained by the co-implantation of As+. Compared with an activation of 18% for an implant of Mg+ only, the co-implantation of As has increased the activation to as much as 61% with a concomitant sheet resistance of 136 Ω/□. The placement of the As+ implant with respect to the position of the Mg+ profile has been found to play a significant role in the activation efficiency. This co-implantation technique in conjunction with the EOP-RTA method has been applied to the formation of thick p+ regions with high surface carrier concentrations, which has important applications in device fabrication for reducing contact resistance.
Rapid Thermal Annealing of Se-Implanted Gallium Arsenide
Authors: Inada T. , Miyamoto K. , Nishida A.
Published: March 2011

Rapid thermal annealing by using a graphite strip heater has been employed to activate Se atoms implanted in either In-doped or undoped LEC GaAs. Doping profile measurements have shown that highly doped n-type layers with the maximum carrier concentration of 1.2E19/cm3 are formed in the In-doped GaAs implanted with 100keV Se ions at room temperature after rapid thermal annealing at 1000°C for 10 sec. Residual defects existing in Se-implanted layers have been examined. The results show that the introduction of dislocations into Se-implanted layers during post-implant annealing is minimized in the In-doped GaAs samples treated by rapid thermal annealing.
Rapid Thermal Annealing of High Energy Si Implants Into GaAs
Authors: Legge Ronald N. , Paulson Wayne M.
Published: March 2011

Rapid thermal annealing (RTA) technology offers potential advantages for the processing of ion implanted GaAs. High energy implants of 300 keV or above are used for power MESFETs as well as in the ohmic contacts for low noise devices. The purpose of this paper is to investigate and characterize the RTA of Si implants into LEC GaAs using implant energies of 300keV and above, and a range of doses from 2.3 ×1012 to 3×1014 /cm2. The wafers were analyzed using capacitance-voltage and Hall measurements. Factors which cause variability in pinchoff voltage are identified and an RTA process comparable to conventional furnace annealing is presented for low dose implants. Superior implant activation is observed for higher dose implants through the use of higher annealing temperature.
Anneal Behavior of Zn Implanted InP : Furnace and Rapid Thermal Anneals
Authors: Djamei M. , Rao E.V.K. , Krauz P.
Published: March 2011

It is shown here that high-dose Zn implants in semi-insulating InP substrates, after conventional furnace anneals lead to the following anomalies : step-like atomic Zn and carrier distributions and the presence of electrically inactive Zn at all depths of the profiles.

Zn anneal behavior is compared using conventional furnace anneals, and two different types of short-time anneals ; rapid furnace anneals(RFA)at ∼750°C with a rise-time of ∼ 50 s, and halogen lamp rapid thermal anneals (RTA)also at ∼ 750°C with a rise-time of ∼ 4 s. We have established that the Zn anomalous diffusion is an instantaneous phexomenon occuring during annealing transients. Also, we have further shown that RTA would help to smooth carrier profiles by removing the step in carrier (but not in atomic Zn) distribution.

The properties of differently Zn co-implanted layers (Zn plus P, Zn plus In and Zn plus As) after RTA, and of P or In implanted Zn doped InP substrates after different anneals,have been studied. We have shown that the presence of electrically inactive Zn in the depth of the layers is a consequence of interaction between Zn atoms and defects. A simple model based on the density of damage deposited in the layer during implant, has been proposed and discussed.
Tungsten Silicide Zinc as a High Temperature Zinc Diffusion Source
Authors: Plumton D.L.
Published: March 2011

A process for Zn diffusion into GaAs during rapid thermal processing has been developed using Zn doped tungsten silicide as the diffusion source. The WSi:Zn is a sputter deposited, solid source layer that undergoes capless annealing in a quartz-halogen lamp system. For a given time and temperature the diffusion of Zn into GaAs is controlled by both the Zn concentration and the W/Si ratio in the film. Tungsten-rich films are Zn concentration “independent” while Si-rich films are Zn concentration “dependent.” Changing the film composition allows shallow Zn diffusions at either a low or a high temperature. Deep Zn diffusions are possible through higher temperatures or longer anneal times for any given WSi:Zn composition.
Drift of Arsenic in SiO2 in a Lamp Furnace With a Built-In Temperature Gradient
Authors: Celler G. K. , Trimble L. E. , West K. W. , Pfeiffer L. , Sheng T. T.
Published: March 2011

We have found that arsenic implanted into SiO2 segregates at high temperatures in an oxygen-free ambient into spherical, As-rich inclusions of 50 to 500A in diameter. The phase separation prevents diffusion of arsenic, even at temperatures as high as 1400 °C. However, the As-rich inclusions or droplets can be easily moved in a temperature gradient. They migrate towards the heat source at a rate of 2300A /hour in a gradient of 0.14 °C/μm, at 1405 °C, permitting their efficient removal from the oxide and into silicon. We propose a model to explain the dependence of droplet velocity on their size.
Applications of Pulsed Co2 Laser Processing of Silicon
Authors: James B.
Published: March 2011

The absorption of CO2 laser radiation in doped silicon is dominated by free-carrier transitions, which is an extrinsic absorption property. For applications where one would like to preferentially deposit the pulse energy in heavilydoped layers, the CO2 laser is found to be preferable to other laser systems that oscillate at a photon energyexceeding the bandgap.The advantages of laser processing with below-bandgap radiation are illustrated by three different applications that areeither impossible or much more difficult to achieve with a visible or ultraviolet laser: (1) the melting of buried layerswithout melting the material that encapsulates the molten layer, (2) the melting of shallow layers at the surface, and(3)the annealing of lattice imperfections caused by high-temperature diffusion of phosphorus dopants into small diffusion wells.
Characterization of Shallow Junctions Fabricated by Gas Immersion Laser Doping (Gild)
Authors: Carey P.G. , Turner J. E. , Nauka K. , Reid G. A. , Sigmon T. W.
Published: March 2011

The viability of Gas Immersion Laser Doping (GILD) for VLSI processing of ultra shallow junctions is assessed using chemical, electrical and structural characterization of boron doped diodes. Diodes with good ideality factors (1.1) overarange of junction depths (50nm Xj 200 nm) have been fabricated by GILD. This process uses a pulsed XeCI excimer laserincident on a silicon surface saturated with B2H6.

Dopant profiles as a function of laser energy and number of pulses aredetermined using Secondary Ion Mass Spectrometry(SIMS). For low energy or a large number of pulses, comparison with computer modelling suggests the junction is determined by melt depth. For higher laser energy and few pulses, liquid phase diffusion limits the depth of dopant incorporation.

Leakage current measurements as a function of diode perimeter to area (P/A) ratio and Deep Level Transient Spectroscopy (DLTS) suggest that leakage occurs along the diode perimeter, and is dueto point defects generated from thermal stresses during melt regrowth. Diodes show good I-V characteristics after GILD alone, yet subsequent rapid thermal annealingisfound to further reduce leakage currents, probably due to relief of thermal stresses. Sheet carrier densities from Halleffect measurements show that 5 - 10% of the boron is activated, with doping levels exceeding 1020 cm−3 in some samples. Transmission Electron Microscopy (TEM) demonstrates that reasonable crystalline quality is maintained for moderate GILD conditions with a defect density at the surface of approximately 108 cm−2 .For higher laser energy with boron incorporation exceeding solid solubility, TEM shows stacking faults along <110>directions. Electron diffraction on highly doped samples shows extra spots indicating a high degree of strain in the doped layer.
High-Quality SOI by Oxygen Implantation into Silicon
Authors: Ommen A. H. van , Ligthart H. J. , Politiek J. , Viegers M. P. A.
Published: March 2011

High quality Silicon-On-Insulator, with a dislocation density lower than 105cm−2, has been formed by high temperature annealing of high-dose oxygen implanted silicon. In the as-implanted state, oxygen was found to form precipitates in the top silicon film. In the upper region these precipitates were found to order into a superlattice of simple cubic symmetry. Near the interface with the buried oxide film the precipitates are larger and no ordering occurs in that region. Contrary to implants without precipitate ordering where dislocations are observed across the entire layer thickness of the top silicon film, dislocations are now only found near the buried oxide. The precipitate ordering appears to prevent the dislocations to climb to the surface. High temperature annealing results in precipitate growth in this region whereas they dissolve elsewhere. These growing precipitates pin the dislocations and elimination of precipitates and dislocations occurs simultaneously, resulting in good quality SOI material.
Mechanisms of Formation of Thin Buried Oxide Layers by Ion Implantation
Authors: White Alice E. , Short K. T. , Pfeiffer L. N. , West K. W.
Published: March 2011

We have studied buried oxide formation as a function of implantation and annealing conditions. The layers appear to form via a nucleation and growth process, so the quality of the oxide and the perfection of the overlying crystalline Si layer depend more strongly on the substrate temperature during implantation than on the annealing temperature. Since it is easier to observe the layer formation process in a thin (<1000Å) layer, we concentrated on sub-stoichiometric doses and chose substrate temperatures below 400°C to stay in a homogeneous nucleation regime. Then we varied the annealing temperature from 1150°C to 1407°C. Modeling the coalescence of the oxide layer as a thermally-activated process yields activation energies of approximately 6 eV, suggesting that crystalline damage removal may be the bottleneck for this substrate temperature regime.
Comparison of the Electrical Properties of Thermal and Ion Beam Oxides
Authors: Dumin David J. , Fossum E. R. , Todorov S. S.
Published: March 2011

A comparison of the current-voltage (I-V) and the capacitance-voltage (C-V) characteristics of thermal and low temperature ion beam grown films of silicon oxide was made. The oxides were in the thickness range between 5 nm and 10 nm. The ion beam oxides were grown at room temperature. The bulk resistivities of the thermal oxides were about 1017 ohm cm and were about 5 orders of magnitude lower for the ion beam oxides. The interface charge densities at the Si-SiO2 interface were about an order of magnitude higher in the case of the ion beam oxides. The oxide properties were also measured after current stressing at constant voltages. The thermal oxides showed an increase in the interface trap density at the Si-SiO2 interface after stressing with a distinct trap appearing above mid-gap. The ion beam oxides showed very little increase in the interface trap density after stressing. The higher conductivity of the ion beam oxides may have lead to discharging of the interface traps generated during stressing.
Semiconductor Superlattices: Order and Disorder
Authors: Hull R. , Turner J. E. , Fischer-Colbrie A. , Whitea Alice E. , Short K. T. , Pearton S. J. , Tu C. W.
Published: March 2011

We review and discuss the main structural phenomena inherent in epitaxial multilayer semiconductor growth: lattice mismatch, misfit dislocation generation, two-dimensional vs. threedimensional growth, interface abruptness and planarity and the local atomic structure of semiconductor alloys. The prevalence of metastable structures, often a function of crystal growth temperature, is discussed. We also investigate the effect of Si ion implantation and subsequent rapid thermal annealing of AlGaAs/GaAs and InGaAs/GaAs multilayer structures, with reference to strain relaxation, layer planarity and enhanced Al, In and Si diffusion.
Ion Beam Mixing of Au-Ti
Authors: Fleischer E. L. , Mayer J. W. , Hirvonen J-P.
Published: March 2011

Multi-layered films of Ti-Au of linearly varying composition were produced by ion irradiation using 600 KeV Ar++ ions. Rutherford Backscattering Spectrometry showed that mixing was complete. The microstructure observed by transmission electron microscopy consisted of a combination of crystalline and amorphous phases at the Ti-rich end and of a crystalline fcc Au solid solution at the Au-rich end. Corrosion testing in a simple immersion cell revealed remarkable corrosion resistance of the ion beam mixed sample compared to that of pure titanium or as-deposited Ti-Au samples (from 100%Au to 60%Ti-40%Au). Wear and friction testing was performed using a reciprocal sliding apparatus with a polytetrafluoroethylene (PTFE) pin. A composition of 60%Ti-40%Au was chosen as optimal for improved corrosion resistance without appreciable degradation in wear and friction properties.