bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulsed Electron Beam Annealing Induced Deep Level Defects in Virgin Silicon
Authors: Barbier D. , Kechouane M. , Chantre A. , Laugier A. 
Published: March 2011

ABSTRACTDLTS has been used to investigate deep level defects induced by Pulsed Electron Beam Annealing (PEBA) in virgin (100) boron doped silicon. Various PEBA conditions were selected resulting in different molten layer thicknesses, melt front velocities and thermal gradient distributions. Discrete hole traps distributed in the regrowth layer were observed in all the annealed samples. The activation energies and thermal signatures of these levels do not correspond to already known defects except for one level which has been assigned to the carbon interstitial substitutional pair. Carbon contamination during irradiation is the most probable explanation for the creation of this defect. Other discrete hole trap levels are likely to be generated by quenching of the molten layer as far as their profiles do not extend beyond the regrowth layer. Moreover, a broad band of levels, characteristic of extended defects, has been observed only on the samples which have suffererd the highest thermal stresses. This band of levels might be related to the generation of dislocation networks as recently observed by means of T.E.M. on the same PEBA processed samples.
Zone-Melting Recrystallization of Semiconductor Films
Authors: Geis M. W. , Smith Henry I. , Tsaur B-Y. , Fan John C. C. , Silversmith D. J. , Mountain R. W. , Chapman R. L. 
Published: March 2011

ABSTRACTThe use of zone melting recrystallization (ZMR) to prepare large-grain(and in some cases single-crystal) semiconductor films is reviewed, with emphasis on recent work on Si on SiO2. Encapsulants are generally required to minimize contamination and decomposition, induce a crystalline texture,improve surface morphology and prevent agglomeration. In the case of Si, the solid-liquid interface is faceted, which gives rise to subboundaries. These can be entrained by laterally modulating the temperature through the use of an optical absorber on top of the encapsulant. Control of thermal gradients and in-plane crystallographic orientation are important for reliable entrainment.
Beam Shaping for Cw Laser Recrystallization of Polysilicon Films
Authors: Zorabedian P. , Drowley C.I. , Kamins T.I. , Cass T.R. 
Published: March 2011

ABSTRACTA shaped laser beam has been used for laterally seeded recrystallization of polysilicon films over oxide. Direct maps of the shaped-beam intensity distribution in the wafer plane are correlated with the grain structure of the recrystallized polysilicon. Using 60% overlapping of shaped-beam scans along <100> directions, we have obtained seeded areas one mm wide and 50 to 500μm long. These consist of 40μm-wide adjacent single-crystal strips regularly separated by low-angle grain boundaries extending laterally away from the seed openings. The spacing between grain boundaries is equal to the scan spacing, providing a means for controlling the location of grain boundaries in otherwise defect-free, single-crystal films.
Transient Annealing of Ion Implanted Gallium Arsenide
Authors: Williams J.S. 
Published: March 2011

ABSTRACTThis paper provides a brief overview of the application of transient annealing to the removal of ion implantation damage and dopant activation in GaAs. It is shown that both the liquid phase and solid phase annealing processes are more complex in GaAs than those observed in Si. Particular attention is given to observations of damage removal, surface dissociation, dopant redistribution, solubility and the electrical properties of GaAs. The various annealing mechanisms are discussed and areas in need of further investigation are identified.
Rapid Isothermal Annealing of Si Implanted Semi-Insulating GaAs by Means of High Frequency Induction Heating.
Authors: Cetronio A. , Bujatti M. , D'eustacchio P. , Ciceroni S. 
Published: March 2011

ABSTRACTExperimental results obtained by rapid isothermal annealing of Si implanted semi-insulating GaAs are presented and compared with results obtained by electron-beam and conventional furnace annealing. We shall show that for high Cr-doped material the problem of redistribution cannot be avoided and that for undoped material, this technique yields very good activation (near 100%) and high mobility (approximately 4400 cm2 /V.sec).
Electron Beam Processing of Semiconductors
Authors: Ahmed B. , McMahon R.A. 
Published: March 2011

ABSTRACTElectron beams can transfer energy very efficiently to semiconductors. Systems have been developed for rapid heating to temperature around 1000°C under a variety of conditions from adiabatic to isothermal. Pulsed, focused, line and synthesized shaped beams are used to obtain a wide range of thermal cycles. The following applications are described: the annealing of ion-implanted Si, particularly the activation of As implants and shallow implants (Rp<150Å), the annealing of Si and Se in GaAs, the e-beam processing of implanted silicon devices and the improvement of SOS substrate quality. Localized annealing by a computer controlled e-beam and the recrystallization of deposited films on insulators are also considered.
Optical and Electrical Properties of Cd Te Laser-Synthetized
Authors: Baufay L. , Pigeolet A. , Andrew R. , Laude L.D. 
Published: March 2011

ABSTRACTOptical and electrical characterization of CdTe synthetized by laser irradiationofamultilayer film of alternately Cd and Te is achieved. Optical absorption measurements evidence the good quality of these films and show that they have behaviour comparable to the single crystal. The influence of the irradiation conditions on the electrical properties of such CdTe films is discussed; they are compared to single crystal from the point of view of resistivity. It is shown that it is possible to prepare by this means samples devoid of impurity states in the middle of the forbidden gap. Finally, the ohmicity of Au, Al, Cr, ITO and non irradiated Cd/Te sandwich contacts is tested.
Impurity Redistribution Studies on Laser-Formed Silicides
Authors: Wakita A. S. , Sigmon T. W. , Gibbons J. F. 
Published: March 2011

ABSTRACT4He+ Backscattering and SIMS were used to study impurity redistribution during laser formation of refractory silicides. Thin films of Mo and W were evaporated on to <100> p-type silicon substrates, which were As or B implanted to doses of 1 ×1015 to 1 ×1016cm−2 . These samples were laser reacted with multiple or single laser scans at various powers. Analysis of these films indicate impurity movement into the forming silicide layer. Impurity concentrations in the films were observed to be as high as 7.8×1020 cm−3−> for As in WSi2 , however a reduction in this concentration occurred with subsequent thermal annealing.
Processing/Microstructure Relationships in Surface Melting
Authors: Schaefer R. J. , Mehrabian R. 
Published: March 2011

ABSTRACTThe development of predictive models for rapid surface melting and resolidification requires coupling of realistic heat flow models to emerging theories of rapid solidification processing. Attainment of unique microstructures and phases,for example through plane-front solidification and solute trapping, can be correlated to solid/liquid interface velocity,temperature and temperature gradients, and to theories of morphological stability. However, there are important limitations on achievable solid/liquid interface velocity depending upon the heating mode and heat flux distribution,melt thickness and location of the interface within the molten zone.An overview is given of the emerging guidelines for prediction and control of rapid solidification conditions and microstructures. Homogenization of the liquid by convection and diffusion is also discussed. Electron beam surface melting of alloy substrates is used as an example of these processes.
Metastable Fe(Pd) Alloys Formed By Pulsed Electron Beam Melting
Authors: Follstaedt D. M. , Knapp J. A. 
Published: March 2011

ABSTRACTFe(Pd) surface alloys formed by either ion implanting Pd into Fe or by vapor depositing Pd on Fe have been examined after pulsed (∼70 nsec) electron beam melting. TEM and ion backscattering/channeling showed that the implanted alloys with up to 9.6 at.% Pd were bcc and epitaxial with the substrate, inspite of predictions of initial solidification to the fcc phase by the Fe-Pd phase diagram. The resolidified Pd films, however, were fcc as predicted by the diagram. The defect structures observed in these alloys are discussed.
Amorphous Al(Ni) Alloy Formation by Pulsed Electron Beam Quenching
Authors: Picraux S. T. , Follstaedt D. M. 
Published: March 2011

ABSTRACTThe Microstructural Transition From The Epitaxial Crystalline To Amorphous State As A Function Of Ni Concentration Is Examined In Al(Ni) Alloys Formed By Ion Implantation And E-Beam Melt Quenching. The Evolution From Epitaxial Crystalline Al At ≲ 3.5 At.% Ni To Amorphous Phase Formation At 15–30 At.%Ni Is Characterized In Detail For 8, 10 And 12% Ni Uniform Concentration Samples By Ion Channeling And Transmission Electron Microscopy. The Transition Occurs Via Complete Loss Of Epitaxial Regrowth At 9 At.% And The Formation Of A Finegrained Polycrystalline Al, With Grain Size Decreasing With Increasing Ni From 20–100 Å At 10% Ni Concentration To ≲ 10–50 Å At 12% Ni.
Mineralogy of the Residues from an Underground Coal Gasification Test
Authors: McCarthy Gregory J. , Stevenson Robert J. , Oliver Robert L. 
Published: March 2011

ABSTRACTDetailed mineralogical characterization by X-ray diffraction, scanning electron microscopy and electron microprobe analysis has been performed on a suite of residues and on three samples of unaltered overburden excavated from a 1983 underground coal gasification (UCG) test conducted at a mine site near Centralia, Washington. The residues were classified into nine zones based on their appearance and location in the burn cavity. Because they were isochemical with the overburden, six of these zones could be identified as altered overburden and proved to be particularly useful for correlations of mineralogy with the temperature and redox atmosphere prevailing in these materials during the UCG process. A previously unrecognized, moderate temperature, reaction between reduced iron phases and clay minerals to form an Al-rich hercynite-spinel solid solution (Al-spinel), (Fe,Mg)Al2O4, was identified. This reaction is a precursor to the well-known formation of Fe-cordierite, (Mg,Fe)2 Al4Si5O18 from SiO2 and the Al-spinel at higher temperatures. The mineralogies of altered overburden were analogous to high-temperature, low pressure, metamorphic rocks of the sanidinite facies, and to thermally altered rocks from natural coal combustion. Modeling of the mineral phase assemblages was successfully performed using a phase diagram for the system (FeO+MgO)-Al2O3-SiO2 constructed from literature diagrams. Melting relations were also modeled with this diagram. Deviations from the assemblages predicted by this diagram were attributed to oxidizing conditions.
Evaluation of Acid-Leached Fly Ash as a Pozzolan
Authors: Hemmings R. T. , Berry E. E. , Cornelius B. J. , Golden D. M. 
Published: March 2011

ABSTRACTDirect acid leaching (DAL) with HCl to recover Al and other metal values from fly ash has been examined extensively by the Electric Power Research Institute (EPRI) under RP2422. Large scale utilization of the solid residues from the DAL-process (DAL-residues) could significantly influence the economics of resource recovery. This paper describes a study of the potential use of DAL-residue as a pozzolan in the concrete industry.Samples of six ashes from a range of coal types were beneficiated to remove magnetic particles and particles larger than 45 gim. The beneficiated fractions were leached with 6M HCl at 105°C to determine metals recovery for Al, Fe, Ca, Mg, Na, K, and Ti. The corresponding DALresidues were characterized by chemical composition, morphology and mineralogical content, and examined as potential concrete pozzolans by standard ASTM tests. One DAL-residue from a highrank coal was examined more extensively in Portland cement mortars.The greatest yields of Al were from low-rank coal ashes, but were obtained at the ‘cost’ of substantial salt-cake production and high acid consumption. The DAL-residues from all ash types showed high-Si content: those from high-rank coals being spherical pseudomorphs of the original ash particles, and those from low-rank coals containing substantial quantities of gel-like materials.All of the residues were pozzolanic, but those from low-rank coals caused an unfavorable increase in water demand in mortars. DAL-residues from beneficiated high-rank coal ashes are enhanced pozzolans conforming to standard specification requirements with pozzolanic indices in excess of 100%.
Fly Ashes Used For Blended Portland Cement: Effect Of Grinding on Cement Quality
Authors: Stoltenberg-Hansson Erik 
Published: March 2011

ABSTRACTTests have been performed with Class F fly ashes used for the production of interground 20% fly ash cement. Unground and ground fly ashes were mixed with a reference high fineness Portland cement and tested for strength in mortar (ISO/CEN method). The fly ashes were also tested for chemical composition, bulk density and specific gravity, fineness (Blaine) and particle size distribution (laser method). There are considerable variations in the specific weights of the asdelivered fly ashes. It is shown that even a small amount of grinding increases the specific gravity significantly, and improves and homogenizes the particle size distributions, resulting in higher strength. The strength increase corresponds to the decrease in air void content.Intergrinding of fly ash and clinker in large scale mills reduces the power consumption, giving the same 28-day strength as mixed fly ash cement with higher fineness.
Similarities and Differences in Shale, Aggregate Mixes and Concrete Containing Fly Ash
Authors: Zenieris Petros E. , Laguros Joakim G. 
Published: March 2011

ABSTRACTFly ash technology has been very effective in providing stability in roadway base courses composed either of shale or aggregate materials, and also in partly replacing Portland cement in concrete. X-ray diffractometry and scanning electron microscopy observations indicate that there are certain similarities among these three types of mixes concerning the hydration process; on the other hand, there is evidence of distinct differences in the hydration products which are found to act either as a filler, a chemical agent, or both. Fly ash suppresses the intensity of the clay minerals in shale, speeds up the hydration process in concrete and acts partly as a filler in aggregate mixes. The net practical result is strength development which varies not only in terms of the maximum level attained, but also in regard to its rate. The conversion of ettringite to monosulfoaluminate proceeds at a rate which is considered high in concrete, moderate in aggregate mixes, and moderate to low in shale. X-ray diffraction analyses help to identify other dissimilarities in the minerals produced. The modification which takes place in the fabric and the matrix of the mixes is morphologically the same; in contrast, the growth of crystallites at the “particle”/fly ash interface is explicitly different. Preliminary quantification of matrix changes resulting from new hydration products is also explored.
Performance Characteristics of Concrete Produced with Fluidized Bed Combustion Ash Residue
Authors: Bland A. E. , Jones C. E. , Rose J. G. , Harness J. L. 
Published: March 2011

ABSTRACTOver the last five years, the Kentucky Energy Cabinet (KEC) and the Tennessee Valley Authority (TVA) have developed and demonstrated the production of concrete from atmospheric fluidized bed combustion (AFBC) spent bed (SB) ash, and pulverized fuel ash (PFA). This AFBC concrete contains no cement and relies on the reaction of residual lime in the SB ash to react with the pozzolan PFA to form cementitious products. The SB ash is prehydrated in order to reduce exothermic lime hydration reactions and minimize molar volume expansion. Laboratory tests were conducted to establish the performance characteristics of AFBC concretes relative to conventional concrete. AFBC concretes exhibit slower strength gain characteristics, but long term (60 day), unconfined compressive strengths of 5,000 psi have been documented. This slow strength development is typical of pozzolanic concretes. AFBC concrete is more flexible and less brittle than conventional Portland cement concrete, as evidenced by its much lower modulus of elasticity. Setting times for AFBC concretes are extended, requiring the use of accelerators under certain applications. Field demonstrations of the AFBC concretes in ready mix concrete, masonry units, and road base applications have indicated excellent workability and finishing characteristics and confirm the laboratory performance characteristics.The paper describes the results of the testing program with emphasis on the ash chemistry/conditioning, the performance characteristics and field demonstrations.
Pore Structure, Permeability, and Chloride Diffusion in Fly Ash-and Slag-Containing Pastes and Mortars
Authors: Malek R. I. A. , Roy D. M. , Fang Y. 
Published: March 2011

ABSTRACTThe transport of ions through cement pastes and mortars with variable contents of fly ashes and granulated blast-furnace slag from different sources and with variable composition has been investigated. The research included the determination of chloride diffusion rate and chloride permeability in relation to microstructure development. The median pore size generally was much diminished in mature blended material compared with Portland cement (PC) pastes and mortars. It appears that, at the same age, a finer microstructure is generally developed in blended specimens compared to PC specimens. Also, it was found that the microstructure approaches a limiting value at longer ages of hydration. That limiting value may be reached at earlier ages with the blends. The chloride diffusion rates and permeabilities in the blends were significantly lower than PC mixes. A comparison between the blends containing fly ashes and those containing slag was made.
Densification and Migration of Ions in Blast Furnace Slag-Portland Cement Pastes
Authors: Feng Q. L. , Lachowski E. E. , Glasser F. P. 
Published: March 2011

ABSTRACTWell-cured slag cement blends are known to give rise to paste matrices of low permeability. Electron microscopy has been used to follow microstructural development in slag cement pastes. An initially dense layer of hydrated product develops around the slag grains. Its chemistry and microstructure are not constant but evolve with time. These variations have been explored by analytical electron microscopy, X-ray diffraction, etc. Mg is concentrated in this zone and serves as a useful chemical marker. However an outer matrix of mixed hydration products also develops, to which slag and cement both contribute. The additional contribution of Ca, Al and Si derived from slag to this matrix is considered to explain its gradual densification and resultant low permeability.
Microstructure and Porosity of Metakaolin Blended Cements
Authors: Bredy P. , Chabannet M. , Pera J. 
Published: March 2011

ABSTRACTFive compositions with 10% to 50% metakaolin for cement substitution were studied. The rate of hydration was studied from the compressive strength after up to 6 months of curing and from the hydrates formed (DTA-XRD). The metakaolin addition considerably reduced portlandite content in the hydrated cement and contributed to the formation of hydrated gehlenite which is not present in OPC paste. The microstructure study (SEM) shows that pozzolanic cement pastes were less crystallized than plain pastes. Mercury intrusion was used to measure porosity of hydrated cement pastes. The porosity with blended cements was higher than that with OPC, except for 10 and 20% metakaolin substitution. Evolution of the pore size distribution was studied: the pozzolanic pastes enhance small diameters.
Evidence for Minimal Pozzolanic Reaction in a Fly Ash Cement During the Period of Major Strength Development
Authors: Diamond Sidney , Sheng Qizhong , Olek Jan 
Published: March 2011

ABSTRACTStrengths developed in fly ash concretes usually equal or exceed that of similar plain concrete after a few months, with much of the response usually attributed to “pozzolanic” reaction between ash and secondary calcium hydroxide (CH). The CH contents of pastes made with five different fly ashes were determined by DTA for periods up to six months. The CH contents found did not decrease notably over the period, and were substantially identical to that expected for plain cement pastes diluted with the same amount of inert material as the amount of fly ash used. Scanning electron microscope examination of the pastes showed only minimal evidence of reaction even up to 1 year of age, although many fly ash grains were in intimate contact with CH. Non-evaporable water contents of the fly ash pastes were substantially higher than expected at each age, suggesting that the fly ash promoted more complete cement hydration or that the hydration products formed bound substantially greater amounts of water than plain cement paste ordinarily does.
Ontario Hydro's R&D on Sorbent Injection Waste Part I. Characterization and Conditioning
Authors: Mozes M. S. , Mangal R. , Thampi R. 
Published: March 2011

ABSTRACTThe effects of furnace sorbent injection on waste characteristics and the performance of electrostatic precipitators (ESPs) have been studied under conditions simulating full scale operation at Ontario Hydro's 640 MJ/h Combustion Research Facility. Twice as much waste was produced as with coal ash; the waste was found to contain high levels of calcium compounds (CaO, CaSO4, etc.). In situ resistivity and impactor data were obtained using various sorbents injected either as a dry powder or in the form of a slurry while burning coals with sulphur content ranging between 1.4 to 2.8%. Resistivities were found to increase 2- to 3-orders of magnitude from a baseline level of 108 ohm.cm, and the size distribution of particles suspended in the flue was slightly finer than the baseline ash. Experiments with flue gas conditioning showed that the resistivity of the ash/sorbent mixture produced from limestone injection could be reduced by 1- to 2.5-orders of magnitude during SO3 conditioning and 3-orders of magnitude during water conditioning. Both agents improved the performance of the ESP and reduced particulate emissions by a factor of 1.2 to 4.
By-Product Sulfur from the Stabilization of Coal Solid Wastes
Authors: Gokhalea A. J. , Burnet G. 
Published: March 2011

ABSTRACTA stabilization process for coal cleaning and coal combustion-related wastes has been developed that uses the energy derived from the fuel contained in the coal cleaning wastes. The wastes are pulverized, when necessary, formed into granules in a rotary pan agglomerator, and then fired to a sintering temperature. The result is a readily disposable product that is highly resistant to environmental degradation. Granules of refuse only, and of refuse/fly ash and refuse/FGD sludge mixtures have been investigated. About 90 wt% of the sulfur in the refuse/sludge mixtures is evolved as SO2 during the combustion/sintering portion of the process. Studies using a microreactor system have shown the generation of SO2 to be a function of temperature and to parallel the decomposition of the sulfur-containing compounds present. Based on laboratory tests, SO2 concentrations of 4–8 vol% are predicted in the SO2-rich off-gases. By-product sulfur recovery from the off-gases appears practical and attractive using current technology that is proven and well established.