bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissolution Kinetics of Tuff Rock and Mechanism of Chemical Bond Formation at the Interface with Cement Grout
Authors: Malek R. I. A. , Roy D. M. 
Published: March 2011

AbstractThe interaction of tuff rock and cement was studied to evaluate the effectiveness of sealing of tuff boreholes with cementitious grouts. Previous studies indicated chemical bond formation between tuff and cement. Dissolution studies were carried out on Topopah Spring member tuff and on tuff with cement. The results indicate the formation of calcium silicate and calcium aluminosilicate hydrates; phase identification is confirmed by XRD studies. The significance of the results obtained and their implications on properties of the interfacial region are included.
Source Term Development For Tritium at the Sheffield Disposal Site
Authors: Mackenzie D. R. , Barletta R. E. , Smalley J. F. , Kempf C. R. , Davis R. E. 
Published: March 2011

AbstractThe Sheffield low-level radioactive waste disposal site, which ceased operation in 1978, has been the focus of modeling efforts by the NRC for the purpose of predicting long-term site behavior. To provide the NRC with information required for its modeling effort, a study to define the source term for tritium in eight trenches at the Sheffield site has been undertaken. Tritium is of special interest since significant concentrations of the isotope have been found in groundwater samples taken at the site and at locations outside the original site boundary. Previous estimates of tritium site inventory at Sheffield are in wide disagreement. In this study, the tritium inventory in the eight trenches was estimated by reviewing the radioactive shipping records (RSRs) for waste buried in these trenches. It has been found that the tritium shipped for burial at the site was probably higher than previously estimated. In the eight trenches surveyed, which amount to roughly one half the total volume and activity buried at Sheffield, approximately 2350 Ci of tritium from non-fuel cycle sources were identified.
Range Distributions of Boron In Silicon
Authors: Hautala Mikko 
Published: March 2011

ABSTRACTDepth profiles of 1-2000 keV boron in amorphous and crystalline silicon have been calculated using the computer simulation code COSIPO. Clear inconsistencies have been found in the experimentally measured range parameters. The optimum selection in channeling reduction is found to be a 9° tilt from the ˂001˃-axis combined with a 7° rotation from the ˂100˃- axis. A smaller offset angle yields noticeable channeling at low energies.
1-3 MeV B+and P+Implants for C-Mos Technology
Authors: Pontcharra J. De , Spinelli P. , Bruel M. 
Published: March 2011

ABSTRACTThe need for low temperature processes in VLSI CMOS technology has led to increasing interest in fully implanted wells. In comparison with diffused wells the advantages are good control of the doping profile, low lateral distribution and self-immunity to latch-up.The technique using a medium energy machine with multiple charged ions is not viable in a production context and only high energy machines can be improved to meet the high throughputs required.We have performed boron and phosphorus in the 1 to 3 MeV range on tandem and Van de Graaff machines to prove their effectiveness. Spreading resistance for boron and phosphorus and SIMS for boron are the characterizatton methods uped. The agreement with expected profiles for doses in the 1013to 1014/cm2range is good. We checked the compatibility with a N-well CMOS process: - low doping level at the surface to ensure low capitances and no disturbance of the channel region - high doping level at one micrometer under the surface to lower punchthrough and latch-up effects. The efficiency of masking materials such as Si02 and photoresists is experimentally measured detecting residual doping underneath various thicknesses of the masking pattern. The application to C-MOS technology is discussed.
Disptacement of Arsenic from Substitutional Sites in Silicon by MEV HE+ Irradiation
Authors: Maydell-Ondrusz E A , Wilson I H , Stephens K G 
Published: March 2011

ABSTRACTCross-sections were determined for displacement of arsenic from substitutional sites in silicon by 1.5MeV He+ ions. Results are presented for channelled and random incidence on (111) and (100) silicon, doped by arsenic implantation and annealed by scanning electron beam irradiation. Layers doped during MBE growth were also studied for comparison.Inner L-shell ionisation of host atoms is proposed to explain the observed displacement cross-section and its variation with arsenic concentration. The results are used to indicate the limits for using Rutherford backscattering and channelling techniques to measure the substitutionality of dopants in single crystals.
Thermodynamic Constraints on Ion Beam Mixing of Metals on Insulators
Authors: Farlow G. C. , Appleton B. R. , Boatner L. A. , Mchargue C. J. , White C. W. , Clark G. J. , Baglin J. E. E. 
Published: March 2011

ABSTRACTSeveral different insulating substrates were coated with various metal films and ion beam irradiated using either Xe or Kr ions. These were then examined by Rutherford backscattering spectroscopy and scanning electron microscopy to determine if interfacial mixing had taken place. These results were compared with the sign of the reaction enthalpy of the metal and substrate to test the proposition that metals mix on insulators if the reaction enthalpy is negative and do not mix if it is positive. The enthalpy rule is in general valid. Two exceptions were found: Cr on Si02 and Zr on Al203; however, these exceptions contain ambiguous features.Irradiation with a light, reactive ion was found to produce no mixing.
Effects of Different Methods of Calculating Mixed Depth Upon The Mixing Rates During Ion Beam Mixing
Authors: Poker D. B. , Appleton B. R. 
Published: March 2011

ABSTRACTThe linearity of mixing rates of ion-beam mixing of metals on silicon has been found to depend critically upon the method by which the mixed depth is calculated. For nonstoichiometric mixing, several methods of calculating the mixed depth may be used, namely: integrated area, halfheight, moment, error function, and 10%-90%. When applied to the same data, these methods can yield divergent results, from linear to square-root dependences of the mixed depth upon the mixing dose. For stoichiometric mixing, the calculation of mixed depth is more straightforward, but different methods of calculation still yield widely differing results. Possible causes for these discrepancies are discussed.
Ion Implantation and Annealing in III-V Multilayer Heterojunctions
Authors: Farley C. W. , Streetman B. G. 
Published: March 2011

ABSTRACTThis paper reviews the status of implantation and annealing in III-V multilayer heterojunctions. The limitations on diffusion doping of multilayers are noted. Current heterojunction device applications for implantation are summarized. Issues relevant to the annealing of multilayers are discussed, including Si migration in modulation doped structures, the effectiveness of rapid annealing in reducing SI diffusion, and impurity enhanced diffusion in superlattices. The formation of damage in multilayers and the unique properties of strained multilayers are also discussed. Finally, implant activation studies are summarized.
Hydrogen Ion Beam Passivation of Electrically Active Defects in Crystalline Silicon Solar Cells
Authors: Tsuo Y.S. , Milstein J.B. , Matson R.J. 
Published: March 2011

ABSTRACTWe have observed significant improvements in the efficiencies of dendritic web and edge-supported-pulling silicon sheet solar cells after hydrogen ion beam passivation for a period of ten minutes or less. We have obtained electron-beam-induced current data that show the hydrogen passivation of dislocations as well as grain boundaries in edge-supportedpulling silicon sheet solar cells. We have studied the effects of the hydrogen ion beam treatment with respect to silicon material damage, silicon sputter rate, introduction of impurities, and changes in reflectance.
A Multilayer Resist for Direct Write Ion Beam Lithography
Authors: Milgram A. A. , Puretz J. 
Published: March 2011

ABSTRACTA focused ion beam of gallium was used to implant into the top layer of a bi-layer structure on a silicon wafer. The structures studied were spin-on glass/organic and electron beam deposited Si/organic. Plasma etch conditions were found which gave substantial etch rate differences between the implanted and non-implanted material. The material was then patterned by dry processing methods. The plasma etch produces a vertical wall 2.0 µm high with a rectangular profile free of debris. The variation in line width along the line is a small fraction of the line width. Or, the line width is constant along the line and is approximately equal to 0.4µm, the spot size of the focused ion beam on the wafer. The variation in line width as a function of implantation dose was determined and shown capable of yielding a reproducible line width. The results are shown to be superior to single resist exposure. Potential applications are presented.
Rapid Thermal Annealing in III-V Compounds
Authors: Davies D. Eirug 
Published: March 2011

ABSTRACTProgress in applying rapid thermal annealing for activating implants is surveyed. Advantages to be gained through curtailing substrate semiinsulating loss, enhancing heavy n-type activation, and in reducing the diffusive redistribution of p-type implants are discussed in detail. Consideration is given to encapsulation requirements and the role of stoichiometry in activation. While the emphasis is on GaAs, work on InP and InGaAs has also been included.
Diffusion of A Deposited GeSe Film in GaAs using Ion-Beam Mixing
Authors: Kepler N. J. , Cheung N. W. 
Published: March 2011

ABSTRACTIon-beam mixing and rapid thermal annealing (RTA) techniques are used to form shallow and heavily-doped n+ layers in undoped GaAs. RTA reduces surface degradation and improves crystalline quality compared to lengthy thermal cycles, although furnace annealing producesidentical electrical characteristics. Ion-beam mixing has only a small effect on the diffusion of a deposited GeSe film, because the damage created by implantation is repaired during RTA before significant diffusion occurs. We define a threshold temperature representing the onset of significant electrical activation and/or diffusion, and propose a model relating the annealing, activation, and diffusion temperatures for the GeSe/GaAs system. RBS. SIMS, and electrical measurements show that extremely shallow layers with a sheet resistivity as low as 1480/El can be formed in GaAs by diffusion from a GeSe source. This technique has potential application to the formation of shallow ohmic contacts for GaAs integrated circuits.
Time Resolved Reflectivity Measurements Applied to Rapid Isothermal Annealing of Ion Implanted Silicon
Authors: Timans P. J. , McMahon R. A. , Ahmed H. 
Published: March 2011

ABSTRACTThe annealing of ion implantation damage in silicon by rapid isothermal heating has been monitored by the time resolved reflectivity (TRR) method. This technique was applied simultaneously at a wavelength of 632.8nm and also at 1152nm, where the optical absorption coefficient of silicon is less. The two wavelength method simplifies the interpretation of TRR results, extends the measurement depth and allows good resolution of the position of the interface between amorphous and crystalline silicon. The regrowth of amorphous layers in silicon, created by self implantation and implanted with electrically active impurities, was observed. Regrowth in rapid isothermal annealing occurs during the heating up stage of typical thermal cycles. Impurities such as B, P, and As increase the regrowth rate in a manner consistent with a vacancy model for regrowth. The maximum regrowth rate in boron implanted silicon is limited by the solid solubility.
Clustering Kinetics of Arsenic and Phosphorus in Laser Annealed Silicon
Authors: Goetzlich Josef 
Published: March 2011

ABSTRACTHigh-dose arsenic and phosphorus ion implanted silicon was annealed either by a CW CO2 or a pulsed Nd:YAG laser creating supersaturated dopant concentrations up to 3·1021 cm−3. The relaxation of these metastable electrically active atoms was investigated during thermal post-annealing at temperatures between 600 and 1000°C for times between 3 and 106 s. In heavily doped samples which contain residual damage after laser annealing, a very fast first relaxation phase is observed followed by a much slower second phase. In samples without residual damage only this second slower phase is seen. Carrier concentration profile measurements show that the saturation concentration after the relaxation depends only on temperature and corresponds to the concentration in thermal equilibrium. Using reaction kinetics a cluster model is proposed which demonstrates that in As doped layers the most probable number of As atoms in one cluster depends on temperature (4 As atoms at 700°C, 3 As atoms at 800 - 1000°C). In P doped layers the most probable clusters contain 3 P atoms at temperatures between 700 and 900°C.
Conventional and Rapid Thermal Annealing of Paramagnetic Oxygen Vacancy Defects (E'1 Centers) in Ion Implanted Amorphous SiO2: A Uni-Molcular Recombination Process
Authors: Golanski A. , Tung N. Chan , Pfister J.C. , Nicolle T. 
Published: March 2011

ABSTRACTThe irreversible thermal annealing behaviour of paramagnetic oxygen vacancy defects (E' centers) induced by 40 keV Ne+ and 140 keV Kr+ ion implantation in amorphous SiO2 has been studied by means of electron paramagnetic resonance. The reversible E'l⇆ B2 defect transformation occurring via a hole injection/trapping process under ionising radiation (190 keV H+) is used as a means of distinguishing a reversible modification of the defect charge state from irreversible annealing of oxygen vacancies. Irreversible thermal recovery is shown to occur between 500 and 900°C. Both conventional and tungsten lamp heater annealing results are compared to predictions based on Simpson and Sosin's model for diffusional recombination of spatially correlated Frenkel pairs and to a simple model for unimolecular recombination. The annealing behaviour observed is accounted for assuming a gaussian distribution in activation energy for diffusion.
Incoherent Light Annealing of Glow Discharge PF5 - Implanted Silicon: Analysis of Damage Recovery and Electrical Activation
Authors: Pedulli L. , Correra L. , Galloni R. , Adekoya O. , Barhdadi A. , Muller J. C. , Siffert P. 
Published: March 2011

ABSTRACTSilicon wafers (100) orientation, were implanted with 3 × 1015 and 1 × 1016 PF5 at 30 keV by glow discharge and subsequently annealed by a commercially available lamp set-up. The annealing temperatures were in the range 620–980°C with irradiation times of 4–7 sec.Sheet resistivity and Hall measurements together with anodic oxidation stripping have been used to determine the mobility and the carrier concentration profiles; the residual damage and the presence of precipitates were investigated by Rutherford Backscattering (RBS) and Transmission Electron Microscopy (TEM).Comparison between the as-implanted dopant depth distribution and the carrier concentration profiles of the annealed samples shows the evolution of the electrically active, substitutional dopant fraction, at increasing annealing temperatures. It is found that the maximum electrical activity is obtained at 720°C; between 720°C and 820°C a process of reverse annealing takes place and the sheet resistivity increases by a factor of about 3. By annealing at temperatures higher than 820°C the substitutional dopant fraction increases again to its maximum value and it is possible to observe the presence of diffusion tails.Finally, RBS, TEM, and Deep Level Transient Spectroscopy (DLTS) were used to investigate the depth location and the evolution of the damage after annealing.
Metallic Impurities and Dopant Cross-Contamination Effects in Ion Implanted Surfaces
Authors: Larson L. A. , Current M. I. 
Published: March 2011

ABSTRACTContamination of implanted surfaces by metals and dopants is a significant limitation to the use of high-dose implantation for semiconductor IC fabrication. RBS, SIMS, SRP, chemical etching and IC device parameter measurements have been used to characterize contaminated surfaces implanted with modern, production-type implanters. Levels of dopant cross -contamination of the order of 10% of the primary dose have been observed. A systematic study of the effects of As, P, B and Sb implanted Si has shown measurable effects on diffusion profiles and junction depths at contamination levels as low as 0.01% of the primary dose. These effects are particularly serious for fast-diffusing contaminants in slow-diffusing primary dopants (such as P contamination in As implants). Evidence has been found for both sputtering and ‘vaporization’ mechanisms for transfer of contaminants from implanter surfaces to the wafer target. The effectiveness of machine design choices and process procedures (such as wafer clamp design, post-implant chemical cleans, and the use of screen oxides) in minimizing the effects of contamination are discussed.
Defect Structure and Properties by Junction Spectroscopy
Authors: Kimerling L. C. , Benton J. L. , Lee K. M. , Stavola M. 
Published: March 2011

AbstractThe application of transient junction current and capacitance techniques to the study of imperfection in semiconductor materials is reviewed. An array of perturbation techniques are described which allow direct determination of electronic and atomic structure, as well as electrical and physical properties. The methods are illustrated with silicon materials studies of the divacancy using Polarized Excitation Photocapacitance, the oxygen donor using Stress and Electric Field Modulated DLTS, dislocations using spatially resolved DLTS, and iron impurities employing Charge State Control of Structure.
Theoretical Study of Native Defect Coiplexes in GaAs
Authors: Lin-Chng P.J. , Li Yuan 
Published: March 2011

AbstractA theoretical study of native defect complexes in GaAs is reported here. These calculations are based on tight-binding Hamiltonians and employ a large cluster recursion method to obtain the changes of local densities of states. A new description of the tight-binding matrix elements developed by us is used to take into account the lattice relaxation and to provide the interaction matrix elements between the antisite defect and its neigiitors. We have examined the complexes GaAsVGa, (VGa)2, VGaAsGaVGa, VGaAsGaVGa, AsGaVAs and VAsAsGaVAs. The results indicate that the use of realistic interaction between the antisite atom and its neighloors is essential to obtain an accurate result for the midgap state of the isolated antisite and that the GaAsVGa,AsGaVAs, (VGa)2 may be responsible for the A,D hole traps and the electron trap C as proposed recently by Zou et al. using a thermochemical model. Both VGaAsGaVGa and VGaAsGaVAs are found to produce states in the gap. It is not possible to exclude either of them as a candidate for the EL2 state. A detailed analysis of the states induced by the defect complexes is made.
EL2 and Related Defects in GaAs--Challenges and Pitfalls
Authors: Gatos H. C. , Lagowski J. 
Published: March 2011

AbstractThe incorporation process of nonequilibrium vacancies in melt-grown GaAs is strongly complicated by deviations from stoichiometry, and the presence of two sublattices. Many of the microdetects originating in these vacancies and their interactions introduce energy levels (shallow and deep) within the energy gap. The direct identification of the chemical or structural signature of these defects and its direct correlation to their electronic behavior is not generally possible. We must, therefore, rely on indirect methods and phenomenological models and be confronted with the associated pitfalls. EL2, a microdefect introducing a deep donor level, has been in the limelight in recent years because it is believed to be responsible for the semi-insulating behavior of undoped GaAs. Although much progress has been made towards understanding its origin and nature, some relevant questions remain unanswered. We will attempt to assess the present status of understanding of EL2 in the light of the most recent results.
Microscopic Examination of EL2 Associated with Single Dislocations in GaAs
Authors: Stirland D.J. , Brozel M.R. 
Published: March 2011

Abstract2" diameter wafers cut from indium doped, liquid encapsulated Czochralski (LEC) grown GaAs ingots have been examined by two different methods. Dislocations were revealed by etching, and isolated regions of enhanced [EL2], the concentration of the deep donor level EL2, weredetected by infrared transmission microscopy. In regions of low dislocation density (∼5 × 102 cm−2) single isolated dislocations were identified and at the identical sites infra-red micrographs showed increased absorption. The results demonstrate that enhancement of [EL2]occurs at single dislocations, and that the enhancement can be detected by suitable etching techniques.
Identity of the Nl8 Epr Spectrum with Thermal Donors in Silicon+
Authors: Lee Keon M. , Trombetta J. M. , Watkins G. D. 
Published: March 2011

AbstractThe effect of uniaxial stress on the NL8 EPR spectrum in 450°C heattreated silicon containing thermal donors (TD's) is described. Changes in the relative amplitudes of the NL8 spectral components are interpreted as arising from electronic redistribution between the differently oriented defects. These changes are consistent in sign and magnitude with those predicted for TD+ from observed stress effects on the TD IR and DLTS spectra.
Scattering of Free Carriers by Oxide Precipitates in Czochralski-Grown Silicon
Authors: Nauka K. , Walukiewicz W. , Lagowski J. , Gatos H.C. 
Published: March 2011

AbstractAnnealing of oxygen-rich Czochralski silicon at temperatures between 700°C and 1000°C introduces a new scattering mechanism which correlates very well with the presence of oxide precipitates. In lightly doped crystals (n,p ∼1015cm−3) this mechanism becomes dominant at T<170°C, and it determines to a large extent the value of the electron (hole) mobilities. The effect vanishes upon annealing at 1300°C; such heat treatment causes the dissolution of oxide precipitates. The new component mobility related to precipitates was found to exhibit a characteristic temperature dependence μ ∝ T0.5. This dependence was explained in terms of scattering of free carriers by spacially slowly varying potential associated with oxide precipitates of varying size.
A Photoluminescence Study of Cd Related Centers in InP
Authors: Swaminathan V. , Donnelly V. M. , Long J. 
Published: March 2011

AbstractWe report the results of a low temperature photoluminescence study of Cd related centers in InP. Besides the previously identified 1.365 eV band a new Cd related band is reported. The peak position of this band lies in the energy ranqe 1.2-1.3 eV at 5.5K dependinq upon the excitation intensity. The peak position of the bands shifts to higher energy with increasing excitation intensity but the change in the peak energy per decade chanqe in excitation intensity is much larger (50 meV) for the lower energy band compared to the 1-2 meV shift for the 1.365 eV band. Both bands exhibit thermal quenching of luminescence above lOOK with an activation energy of 54±4 meV which is comparable to the ionization energy for the substitutional Cd acceptor, CdIn. From this we infer that both bands involve the CdIn acceptor in the recombination process. While the excitation dependence of the bands suggests a donor-to-acceptor pair recombinaton for their origin, we present arguments to show that the larger shift of the peak energy of the 1.2-1.3 eV band with excitation intensity is perhaps a consequence of the involvement of a deep donor in its origin as opposed to a shallow donor in the 1.365 eV band. It is suggested that the deep donor is related to Cd and possible centers are discussed.