bluuebunny/crossref_metadata_2025 huggingface dataset:
The Thermodynamics and Geochemistry of Ca, Sr, Ba, and Ra Sulfates in Some Deep Brines From the Palo Duro Basin, Texas
Authors: Melchior Daniel , Langmuir Donald , Rogers Pamela S. Z. , Hubbard Norman
Published: March 2011

The work reported here involved application of the ion-interaction approach of Pitzer [1] [2] to model the activities of some major and minor cations and major anions in deep brine systems at elevated temperatures and pressures.

The solubilities of anhydrite (CaS04), gypsum (CaSO4·2H2O), celestite (SrS04), barite (BaS04), and radium sulfate (RaSO4) in brines from the Wolfcamp Formation and granite wash facies, Palo Duro Basin, Texas, were modeled using ion-interaction equations. Waters with ionic strengths ranging from 2.89 to 4.76 m, and temperatures and pressures up to 40°C and 130 bars were sampled from five horizons in three wells, at depths between 970 and 1,670 meters. Theoretical solubility products as a function of temperature and pressure were obtained for comparison with ion activity products computed using ion-interaction theory. The effect of temperature on model calculations was found to reside almost entirely in the Debye-Hückel AΦ parameter, which accordingly was corrected for brine temperatures [3].

Modeling results indicated that all five brines are saturated with respect to anhydrite and celestite, and three of the five with respect to barite. Saturation may result from hydrologic connection with adjacent overlying evaporite units, or increased Ca, Sr and Ba concentrations caused by their desorption from clays. Radium concentrations, which range from 10-11.3 to 10-12.7 m, are not controlled by RaSO4 solubility or adsorption, but probably by solid solution in other sulfate minerals in these low pH (4.4 – 6.3) high calcium (0.18 – 0.52 m) brines [4] [5].
Hydrothermal Interaction of Topopah Spring Tuff With J-13 Water as a Function of Temperature
Authors: Knauss Kevin G. , Delany J. M. , Beiriger W. J. , Peifer D. W.
Published: March 2011

In support of the Nevada Nuclear Waste Storage Investigations Project experiments were conducted to study the hydrothermal interaction of rock and water representative of a potential repository in tuff. These experiments provided data relevant to near-field repository conditions that can be used to: assess the ability to use “accelerated” tests based on the SA/V (surface area/volume) parameter and temperature; allow the measurement of chemical changes in phases present in the tuff before reaction as well as the identification and chemical analysis of secondary phases resulting from hydrothermal reactions; and demonstrate the usefulness of geochemical modeling in a repository environment using the EQ3/6 thermodynamic/kinetic geochemical modeling code. Crushed tuff and polished wafers of tuff were reacted with a natural ground water in Dickson-type gold-cell rocking autoclaves which were periodically sampled under insitu conditions. Results were compared with predictions based on the EQ3/6 geochemical modeling code. Eight short-term experiments (2 to 3 months) at 150°C and 250°C have been completed using tuff from both drillcore and outcrop. Long-term experiments at 90°C and 150°C using drillcore polished wafers are in progress. This paper will focus on the results of the 150°C and 250°C experiments using drillcore polished wafers.
Rubidium-Strontium Geochronologic Systematics in Igneous Contact Zones: Analog for 90-Sr and 137-Cs Behavior in the Near Field
Authors: Brookins D. G.
Published: March 2011

The behavior of 90-Sr and 137-Cs in the near field of a HLW package can be investigated by use of Rb-Sr geochronologic information from igneous contact zones. The chemical behavior of 90-Sr is identical to other Sr isotopes, and Cs behavior is very similar to that of Rb. During igneous intrusion, the effect of heat from the igneous rock, coupled with fluid action, is to perturb Rb-Sr systematics of minerals in the intruded rock. Rb-Sr redistribution diagrams are useful not only for indirectly dating the time of intrusion, but also for determining the extent of closed versus open system conditions in the contact zones. Once open or closed system behavior is determined, the Rb-Sr systematics can be evaluated in terms of diffusion, fluid-induced metasomatism, selective dissolution, other, and coupled processes. All these can be discussed in terms of time-temperaturefluid compositional parameters. Rb migration is controlled predominantly by fluid flow, while diffusion models better explain some Sr isotopic behavior Cs, from geochemical arguments, should be less mobile than Rb. In most cases, even when temperature of the intrusive is 800–1200°C the cooling period on the order of 104 – 105 years, and in a highly convective system, Sr and Rb mobility is on the order of only microns to meters.
Gamma and Alpha Radiolysis of Salt Brines
Authors: Gray W. J. , Simonson S. A.
Published: March 2011

Gamma radiolysis of Permian Basin brine leads to equilibrium gas pressure of about 100 atm. at 75°C and about 40 atm. at 150°C, providing the gas space is very small and/or the total dose is very high. Dose rate dependence is being investigated but is not yet established. Alpha radiolysis of Permian Basin brine is still being evaluated, but it is clear that equilibrium gas pressures will be much higher than with gamma radiolysis. In addition, alpha radiolysis of brine results in a very high solution redox potential. Gas compositions in all cases have been about two parts H2 to one part O2. Efforts to simulate these results with computer models have been quite successful.
Application of XPS and Nuclear Technique to the Study of the Gel Layers Formed Under Different Redox Conditions on Leached Glasses
Authors: Manara A. , Lanza F. , Ceccone G. , Mea G. Della , Salvagno G.
Published: March 2011

Surface analysis has been conducted on samples leached in a Soxhlet apparatus at 100°C in presence and in absence of air. The XPS and RBS techniques were applied to analyse the content of the silicon, iron and uranium while the nuclear reaction method was utilized to analyse the hydrogen content. The anoxic environment favours the release of iron while decreasing the dissolution of uranium. Hydrogen content is always higher in samples leached in presence of air.

Silicon depletion is evident in all cases. The diffusion process seems to regulate the growth of the layer on the glass surface. After long leaching time a detachment, at least partial, of this layer is observed.
Alpha-Recoil Damage in Thorianite and Uraninite: Effect on Dissolution and Time-Scale for Spontaneous Annealing of Damage
Authors: Eyal Yehuda , Fleischer Robert L.
Published: March 2011

Using natural ThO2 and UO2 in which radiation damage has accumulated over geologic periods, we have measured the relative in dissolution rates bicarbonate-carbonate solutions of the actinide isotopes 238U, 234U, 232Th, 230Th, and 228Th. An enhanced dissolution by a factor of 2 to 7 of the short lived (1.9 yr) 228Th relative to that of its structurally incorporated primary isotope 232Th indicates the presence of severe localized atomic displacement damage created by alpha-recoil atoms. In contrast, the relatively small (<20%) isotopic fractionation between the radiogenic 8.0 × 104 yr- 230Th isotope and 232Th, and between the radiogenic 2.5 × 105 yr- 234U isotope and its primary structurally incorporated isotope 238U, suggests the nearly complete annealing of the alpha-recoil damage during a period of less than 105 yr. An estimate of the mean fading time for the leachable damage is 15,000 yr.
The Purpose of the Materials Characterization Center
Authors: Mendel John E.
Published: March 2011

The Materials Characterization Center (MCC) at the Pacific Northwest Laboratory is the experimental arm of the Materials Characterization Organization (MCO), which was established by the U.S. Department of Energy (DOE) in FY 1980 to ensure high quality characterization and qualification of waste package materials essential to the reliable performance of DOE nuclear waste management programs. The MCC is responsible for publishing key test methods and data in the Nuclear Waste Materials Handbook (DOE/TIC-11400) after the methods and data have been reviewed and approved by the Materials Review Board (MRB), which is the other major operating arm of the MCO.

The MCC is carrying out its responsibilities in several ways. It sponsors a continuing series of workshops that address materials characterization test method issues. It supplies well-characterized reference and testing materials for use by the DOE nuclear waste management programs. It develops generic test methods and supports the repository waste package projects in developing selected site-specific test methods and performing confirmatory testing of these methods. When these test methods are approved by the MRB they constitute the formal tests to be used by laboratories to test and qualify materials, evaluate waste package components, and assure compliance with standards and/or specifications for the final product.
Materials Interactions Test Method to Measure Radionuclide Release from Waste Forms Under Repository-Relevant Conditions
Authors: Strickert Richard G. , Erikson Robert L. , Shade John W.
Published: March 2011

At the request of the Basalt Waste Isolation Project, the Materials Characterization Center has collected and developed a set of procedures for a waste form compliance test method (MCC-14.4). The purpose of the test is to measure the steady-state concentrations of specified radionuclides in solutions contacting a waste form material. The test method uses a crushed waste form and basalt material suspended in a synthetic basalt groundwater and agitated for up to three months at 150°C under anoxic conditions. Elemental and radioisotopic analyses are made on filtered and unfiltered aliquots of the solution. Replicate experiments are performed and simultaneous tests are conducted with an approved test material (ATM) to help ensure precise and reliable data for the actual waste form material. Various features of the test method, equipment, and test conditions are reviewed. Experimental testing using actinide-doped borosilicate glasses are also discussed.
Improved Uranium Recovery from the Process Streams in an Electroplating Facility
Authors: Pickett John B.
Published: March 2011

Cylindrical uranium slugs are used as irradiation targets in the production reactors at the Savannah River Plant. These slugs are first chemically etched, nickel plated, encased in aluminum, inspected, and individually pressure tested. An improved process was developed to recover the uranium from the acidic etching streams by controlling pH and the PO4 to U ratio so that the precipitation of the uranium as hydrogen uranyl phosphate was maximized. Bench scale tests demonstrated that the recovery of uranium could be increased to greater than 99.9% (vs. the current level of about 95% recovery). The recommended changes involved the addition of process effluent “hold” tanks. The addition of the various process streams to the neutralization/precipitation tank could therefore be controlled to maintain a consistent ratio of uranyl nitrate and phosphoric acid. Also, it was determined that a strong caustic solution (resulting from the dissolution of rejected aluminum slugs) could be utilized to neutralize the nitric and phosphoric acid solutions. The buffering action of the aluminum in the “caustic recovery solution” would reduce the sensitivity of the hydrogen uranyl phosphate precipitation to the phosphate ion concentration.
Evaluation of Materials Performance in a Large-Scale Glass Melter after two Years of Vitrifying Simulated SRP Defense Waste
Authors: Iverson Daniel C. , Bickford Dennis F.
Published: March 2011

The Large Slurry Fed Melter (LSFM) at the Department of Energy's Savannah River Plant recently completed two years of service and was shut down for evaluation. The melter operating history is reviewed and the condition of the refractories and metal components is described. The excellent condition of the LSFM verifies the expected performance of the materials of construction, and indicates that a two year melter life is achievable in the Defense Waste Processing Facility (DWPF).
Diffusivities of Cesium and Strontium in Concretes and in Mixtures of Sodium Bentonite and Crushed Rock
Authors: Muurinen Arto , Rantanen Juha , Ovaskainen Raisa
Published: March 2011

Diffusivities of Cs and Sr in concretes and in mixtures of sodium bentonite and crushed rock were measured. The order of magnitude of the apparent diffusivities (Da) for Cs and Sr in concretes was −14−10−13 m2/s and in the mixtures of bentonite and crushed rock 10−13− 10−11 m2/s. The calculated effective diffusivities (De) in the mixtures of bentonite and crushed rock seemed in some cases to exceed the corresponding values in water, which suggests that the pore diffusion/sorption model cannot explain the transport phenomena in all cases.

The experiments where the sorption factors were varied in the diffusion samples suggest that the nuclides diffuse also while being sorbed. A combined pore diffusion-surface diffusion model has been used to explain the transport and the corresponding diffusivities have been evaluated. This paper will give the measured diffusion and sorption data and discuss the models used to describe diffusion in porous sorbing agents.
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

The 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

The 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.
Long-Term Release from High Level Waste Glass - Part IV: The Effect of Leaching Mechanism
Authors: Freude Eberhard , Grambow Bernd , Lutze Werner , Rabe Harald , Ewing Rodney C.
Published: March 2011

During the past ten years extensive data have been determined for the corrosion of nuclear waste forms in short-term laboratory experiments (usually less than one year). The long-term behavior of glass has been inferred by: (1) the acceleration of corrosion rates at high temperatures [1]; (2) the use of high surface areas of the glass to small volumes of solution [1]; and the analysis of natural glasses altered over long periods of geologic time [2, 3]. The most recent efforts have concentrated on understanding the mechanisms of corrosion [1, 4, 5]. The corrosion mechanism may be used to make long-term extrapolations of the “stability” of the waste form. In this paper, we consider a linear time dependence for the corrosion under near saturation conditions and use a rate equation in the QTERM code [6, 7, 8] to model the long-term behavior of the German glass, C-31−3EC [9], JSS A [10, 11] and SRL TDS 131 [1]. The data base for C-31−3EC has been published elsewhere [9, 12, 13, 14], and we include experimental work completed by Rabe for boron and silica, at 200°C.
Range Distributions of Boron In Silicon
Authors: Hautala Mikko
Published: March 2011

Depth 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

The 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

Cross-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

Several 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

The 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

This 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

We 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

A 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

Progress 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

Ion-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

The 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

High-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

The 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

Silicon 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

Contamination 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

The 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

A 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

The 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

2" 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

The 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

Annealing 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

We 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.
A Tentative Identification of Certain Deep Levels in GaAs and Related Compounds
Authors: Yuanxi Zou , Yuanhsi Chou , Peigen Mo , Qianzhi Yang , Huifang Min , Guicheng Zhang
Published: March 2011

Some recent data on minority carrier diffusion length MCDL in GaAs and certain optoelectric parameters of LEDs obtained by the authors as well as reported in the literature have been analysed to shed light on the probable configuration of certain deep levels in GaAs and related compounds. The practical implications of the results obtained are discussed from the view point of the mechanism of slow degradation of the related optoelectronic devices.
Excitation Spectroscopy on Silicon Using Color Center Lasers Study of the Thermally Induced P Line (0.767eV) Defect
Authors: Wagner J. , Dörnen A. , Sauer R.
Published: March 2011

Recently developed tunable color center lasers allow to extend the experimental technique of excitation spectroscopy to the 1–2 μm region. This spectral range is of special interest for the study of luminescent defects in silicon. We discuss the color center laser systems available at present and their application to defect spectroscopy. As an example, results on the 0.767 eV (P line) defect in silicon are presented. Excitation spectroscopy reveals several high lying excited electronic states. They are interpreted as effective—mass—like states of a pseudo-donor with an ionization energy of 34.3 meV.
Electronic Structure of Deep-Lying Sulfur Centers in Si
Authors: Zeiger H. J. , Kleiner W. H.
Published: March 2011

A theoretical analysis has been made of infrared absorption spectra measured earlier for four deep-lying sulfur centers in Si. The data consist of absorption frequencies and polarization selection rules determined for uniaxial stress applied along [001], [111], and [110] axes. Both ls + np transitions and ls → ls transitions are observed. The A and B centers (binding energies 0.1090 eV and 0.1872 eV, respectively) are found to be He-like, while the C and D centers (binding energies 0.3683 eV and 0.6116 eV, respectively) are found to be He+-like. The D center spectra are consistent with Td symmetry, while the A, B and C spectra are consistent in most respects with C3v or D3d symmetry. One noteworthy result is the finding that the ls + np spectral frequencies observed under stress for the A center are consistent with a ls(E) ground state.
Structural and Electrical Characterization of Polycrystalline Semiconductor Materials
Authors: Matson Richard J. , Tsuo Y. Simon
Published: March 2011

Secondary electron imaging, electron channeling and electron-beaminduced current (EBIC) are used alternately in a scanning electron microscope to characterize and correlate the morphology, crystallographic orientation, and electronic quality (types and spatial distribution of defects) of individual grains in polycrystalline semiconductor samples. The technique is discussed in some detail, and a number of applications and results in the study of edge-supported-pulling (ESP) silicon sheet and low-angle silicon sheet (LASS) materials are reported.
The Role of Theory in Defect Physics
Authors: Schluter M.
Published: March 2011

This paper addresses the contributions modern theoretical developments have made to the understanding of the physics of deep defects in semiconductors. The nature of theoretical results will be discussed and underlying approximations and limitations will be examined.
Crystallization of Ge-Rich Amorphous Mo-Ge Alloys
Authors: Marshall Ann F. , Yoshizumi S.
Published: March 2011

The crystallization behavior of amorphous Mo-Ge alloys in the Ge-rich region have been characterized by resistivity measurements and transmission electron microscopy (TEM). Alloys with compositions in the metalsemiconductor transition region, where two distinct types of SRO occur, show compositional segregation on a fine scale during the first transformation step. Alloys in the adjacent composition region, where SRO is similar to the intermetallic compounds, crystallize polymorphically into metastable structures based on the equilibrium intermetallic structures. The resistivity characteristics and the relationship between the amorphous and partially transformed structures are discussed.
The Relationship of Structure to Properties in Electrodeposited Films
Authors: Sheppard Keith , Weil Rolf
Published: March 2011

The recent development of a more systematic, scientific basis for knowledge in electrodeposition technology is discussed, focussing on the influence of microstructure on deposit properties. Internal stresses, tensile strength, ductility, preferred orientation and the ability to electrodeposit amorphous materials are considered. In particular the unique influence on these properties of small quantities of chemical additives is discussed. The application of current modulation techniques during electrodeposition is described as an alternative means of controlling structure and properties.
Characterization of W-N Alloys Formed By Sputter Deposition
Authors: Affolter K. , Kattelus H. , Nicolet M-A.
Published: March 2011

Thin films of W-N alloys have been prepared by reactive rf sputtering from a W target. Alloy compositions up to about 65at.%N, amorphous phases are formed with crystallization temperatures up to above 600°C. All the films gradually release N upon vacuum annealing and decompose into αW between 700 and 800°C in vacuo. Application of W-N alloys as diffusion barriers in a Si metallization scheme is discussed.
Chemical Composition and Electrical Behavior of Contacts on Highly and Moderately Silicon-Doped (100) GaAs
Authors: Holloway P. H. , Wang Y. -X. , Xie Y. -J. , Bussing T. D.
Published: March 2011

The effects of 1 to 5 keV Ar+ sputtering of (100) GaAs doped with >3 × 1018 cm−3 or <2 × 1017 cm−3 Si and contacted with 1000 Å of Au have been studied. Sputtering caused the contacts on highly doped GaAs to change from ohmic to rectifying, while it caused the Schottky barrier height on moderately doped GaAs to decrease. For both doping densities, barrier heights of ∼0.6 eV were measured. Inverse Laplace transform analysis of angle-resolved X-ray photoelectron spectroscopy data showed that As was preferentially sputtered, probably by a damage-assisted Gibbsian surface segregation mechanism. Modifications of the electrical contacts were explained by sputter-induced self-compensation by Si rearrangement and by damage-created shallow donors with a density of >2 × 1017 cm−3.
Structural Studies of an InAs-GaAs Superlattice Alloy
Authors: Tamargo M. C. , Hull R. , Greene L. H. , Hayes J. R. , Tabatabaie N. , Cho A. Y.
Published: March 2011

Thin alternating layers of InAs and GaAs have been grown by MBE on buffer layers lattice matched to InP. The layer structure was evaluated by transmission electron microscopy (TEM) and low angle X-ray scattering. Commensurate epitaxial layers approximately 15Å thick were obtained in spite of the large lattice mismatch (7%). These results and their implication for growth conditions of strained-layer superlattices will be discussed.
Ion-Beam Deposition of Thin Films:Influence on Surface and Volume Microstructure
Authors: Al-Jumaily G. A. , Mcnally J. J. , Mcneil J. R.
Published: March 2011

The effects of ion bombardment during film deposition on surface and volume microstructure were studied. Both metal and dielectric films were investigated. Scattered light and optical constants were examined for evaporated, sputtered and ion assisted films.
Piiotoelectronic Proiioerties Of Amorpiious Silicon/Silicon Oxide Heterostructures
Authors: Carasco F. , Mort J. , Jansen F. , Grammatica S.
Published: March 2011

A glow-discharge deposited a-Si:H/insulator heterostructu re has been characterized by a range of measurements including optical absorption, internal photoemission, xerographic discharge and spectral dependence of photoconductivity. Efficient injection of photocarriers from a-Si:H into, and transport through, films of SiOx:N:H up to 10 μm thick has been achieved. Unlike the conventional thermal oxide on Si, no significant energy barrier to injection is fotInd in the plasma deposited heterostructure. The use of the structure as a potential xerographic device is demonstrated. A mobility lifetime product as high as 6 x 10-10 cm2/volt is found for electronsin the SiOx:N:H.
Local Bonding in A—Sige Alloy Films
Authors: Lucovsky G. , Rudder R.A. , Cook J.W. , Lin S.Y.
Published: March 2011

This paper discusses the bonding of hydrogen in a—Si,Ge:H alloy films prepared byreactive magnetron sputtering (RMS). We compare our results for H atom bonding with films produced by: (a) the glow discharge decomposition (GDD) of silane and germane mixtures, and (b) reactive diode sputtering (RDS). We discuss the energy states associated with Si and Ge atom nfeutrat angling bonds in the context of an empirical tight—binding modeL The model places the Ge atom dangling bond state deeper in the gap than the corresponding Si atom defect state. The differences between the electronic properties of GDDand RDS films, and R4S films are explained in terms of the degree of H compensation of Si and Ge atom dangling bonds.
Properties of Intrinsic a-Si Films Deposited From Higher Order Silanes by Chemical Vapor Deposition
Authors: Rocheleau Richard E. , Hegedus Steven S. , Baron Bill N.
Published: March 2011

Amorphous silicon films have been deposited by chemical vapor deposition using disilane at temperatures between 360 and 525°C at growth rates up to 50 A/s. Intrinsic films have the following properties: σp less than 5 × 10−6 (Ω-cm)−l; σd less than 5 × 10−11 (Ω-cm)−1 with Ea = 0.7 to 0.8 eV; diffusion length around 0.1 μm; Urbach energy 48 to 55 meV; and mid-gap density of states greater than 5 × 1016 cm−3 eV−1. Boron compensation improved collection efficiency by lowering the mid-gap density of states, not by improving the μτ product. Pin cells with effíciencies of 4% and Jsc = 10.9 mA/cm2 (87.5 mW ELH) were fabricated.