bluuebunny/crossref_metadata_2025 huggingface dataset:
Condiment: Source Code for Risk Assessment of French Nuclear Waste Repository
Authors: Mangin J. P. , Mouche E. , Lovera P. , Nguyen Ngoc H.
Published: March 2011

CONDIMENT is the source code used in MELODIE, the overall French computer code for risk assessment of nuclear waste repositories in geological formations. This code models the diffusion-convection of elements released by a waste package, up to a distance of a few meters from the package. Two versions have been developed simultaneously:

- CONDIMENT2 deals with the case of a single element. This version is more specifically designed for vitrified high-level wastes. The boundary conditions are furnished by studies on aqueous corrosion of French nuclear glass R7T7.

- CONDIMENT3, deals with two ions that are liable to precipitate. This version is more specifically designed for wastes immobilized in cement.

CONDIMENT3 is verified in a configuration for which an analytical solution exists.
Mechanism of Ionic Diffusion in Dense Bentonite
Authors: Cheung S.C.H. , Gray M. N.
Published: March 2011

A new model based on ionic diffusion in surface (bound) and interstitial (free) water in compacted bentonite systems has been developed. The model is supported by data obtained from flow-through diffusion experiments using Cs+, I- and Cl-. The results show that diffusion depends on the charge of the diffusing species: cations are attracted to the clay particle surface, but are not immobilized, whereas anions are repelled from the clay particle surface. Cations diffuse through both surface and interstitial water, and anions diffuse mainly through interstitial water. The clay structure has been found to affect the diffusion of cations and anions.
Equilibrium Leach Testing of Intermediate Level Waste
Authors: Heafield W , Barlow P , Hunt A
Published: March 2011

Experiments examining the leach characteristics of encapsulated Intermediate Level Wastes in repository near-field conditions have been undertaken in the UK since 1982. The Equilibrium Leach Test was developed in order to provide a realistic static leach test for the measurement of equilibrium concentrations and chemical states of individual nuclides within a particular waste, or combination of wastes, and the components of the near-field barriers of a repository, after water has ingressed into the system. The significant components of the near-field ie waste material, waste matrix and repository backfill are equilibrated with water under static conditions.

Results illustrate the high degree of protection afforded by the near-field, which under repository conditions will be complemented by the additional protection of the far-field and the biosphere. Analytical results show that a cement based matrix and cementitious backfill provide the lowest radionuclide concentrations, for long lived radionuclides.
Laboratory Experiments of Mass Transfer in the London Clay
Authors: Bourke P. J. , Gilling D. , Jefferies N. L. , Lever D. A. , Lineham T. R.
Published: March 2011

Aqueous phase mass transfer through the rocks surrounding a radioactive waste repository will take place by diffusion and convection. This paper presents a comprehensive set of measurements of the mass transfer characteristics for a single, naturally occurring, clay. These data have been compared with the results predicted by mathematical models of mass transport in porous media, in order to build confidence in these models.
Characterization of the Surface of the HLW Glass R7T7 Reacted in Salt Brines
Authors: Roggendorf H. , Conradt R. , Schmidt H.
Published: March 2011

Borosilicate glasses are proposed as waste form for the final disposal of High Level Waste (HLW) in salt formations by the Federal Republic of Germany. To check the safety of this waste form the corrosion of the non-radioactive borosilicate glass R7T7 in salt brines has been studied in collaboration with the Hahn-Meitner-Institut, Berlin. Temperatures up to 190°C and S/V ratios (surface area to solution volume ratio) between 3.3 and 1000 m were applied. S/V was varied by the addition of glass powder. The results presented here concern the characterization of the surface composition of the corroded glass (corroded at 190°C in a brine containing high amounts of MgCl-, called Q brine in this paper) after removing the reaction product layer. The corrosion conditions were chosen to obtain samples typical of long term (silica saturation) corrosion. The surface composition was analyzed quantitatively by X-ray photoelectron spectroscopy (XPS) by using external standard glasses with a composition similar to R7T7. Additionally scanning electron microscopy (SEM) was employed.
Determination of Technetium and Selenium Transport Properties in Laboratory Soil Columns
Authors: Del Debbio J. A. , Thomas T. R.
Published: March 2011

Laboratory studies are being conducted to measure the transport properties of various radionuclide species through soil columns. The studies are being conducted to support evaluations for potential near-surface disposal of high-level radioactive waste (HLW) calcine stored at the Idaho National Engineering Laboratory. The data will be used to model radionuclide transport through the vadose (unsaturated) zone of the site under various water-contact scenarios. Retardation factors and dispersion coefficients for technetium and selenium species have been measured in water-saturated soil columns made up of sediments taken from 12 and 35 meters below the surface. A one-dimensional, convective-dispersive, solute-transport equation was fitted to column effluent data by optimizing three parameters (retardation factor, dispersion coefficient and pulse time) using a non-linear, least-squares fitting routine. The data indicated no retardation of the pertechnetate ion (TcO4-)and selenate ion (SeO4-) and a large retardation of the selenite ion (SeO3-) relative to water transport through the soil column.
Atomic-Scale Modeling of Low-Energy Ion-Solid Processes
Authors: Dodson Brian W.
Published: March 2011

Various techniques which have been applied to modeling low-energy (<< 1 keV) ion-solid interactions on an atomistic scale are described. In addition to their individual strengths, all such methods also have a number of drawbacks, both fundamental and practical. The range of validity, and the problems encountered external to this range, will be outlined for the different approaches. Finally, examples of molecular dynamics simulations of low-energy ion-solid interactions will be presented.
Collision Cascade Densification of Materials
Authors: Bassel R. H. , Andreadis T. D. , Rosen M. , Mueller G. P. , Hubler G. K.
Published: March 2011

Computer simulations of the collision cascade process were used to investigate surface densification during ion beam assisted deposition (IBAD). The objective of the investigation was to see if densification resulted directly from the cascade, without any contribution from diffusion enhancement brought on by the bombardment. Calculations, using the computer code MARLOWE, were carried out for Ar bombardment of a crystalline Ge target, containing a void, using ion beam energies of 0.065, 0.5 and 1 keV. These results were used as data for a differential equation that describes the effect on void size of the simultaneous Ge atom deposition and Ar ion bombardment of a substrate containing voids. The present attempt examined the effects of irradiations on voids of 17 and 35 vacancies.
Molecular Dynamics Simulations of Low Energy Displacement Cascades in Silicon.
Authors: Mazzone A. M.
Published: March 2011

Displacement cascades formed in a silicon crystal by As+ and Si+ ions with energy in the range 50–500 eV are constructed with a molecular dynamics and a Monte Carlo simulation method. Conspicuous spike effects are observed with the molecular dynamics simulation.
Stress Modification in Tungsten Films Deposited by Ion-Assisted Evaporation
Authors: Roy R. A. , Petkie R. , Yee D. S. , Karasinski J. , Boulding A.
Published: March 2011

The modification of film stress in evaporated tungsten was studied as a function of deposition environment. Using concurrent ion bombardment of the growing film, the stress was seen to vary systematically with ion energy, ion flux, and substrate temperature. The qualitative behavior fits the model of stress modification developed for niobium films. X-ray diffraction was used to study the structure of the films, and a clear correlation between crystallographic texture and film stress is found. The original structure/impurity model for film stress modification due to ion bombardment has been modified to account for the relationship between film stress and texture.
Thermal Spike Related Nonlinear Effects in Ion Beam Mixing at Low Temperatures
Authors: Chen G-S. , Farkas D. , Rangaswamy M.
Published: March 2011

A semi-empirical model for ion mixing at low temperatures was developed taking into account collisional mixing and thermal spike effects, as well as the thermal spike shape. The collisional mixing part was accounted for by the Kinchin-Pease model, or, alternatively dynamic Monte Carlo simulation. For the thermal spike, the ion beam mixing parameter Dt/Φ is derived as being proportional to χ2+μ, where the damage parameter is defined as, χ = − F0/ΔHcoh, F0 is the damage energy deposited per unit path length, and μ is a constant dependent on the thermal spike shape and point defect density in the thermal spike regions. The shape of the thermal spike that best fit the experimental results depends on the magnitude of the cascade density. For relatively high density collisional cascades, where thermal spikes start to be important, it was found that a spherical thermal spike model was more consistent with experimental measurements at low temperatures. However, for extremely high density collisional cascade regions, a cylindrical thermal spike gave better results. Finally, three different regions of ion beam induced mixing were recognized according to different density levels of damage energy scaled by the damage parameter χ.
A Comparison of the Mixing Rates for Fe-Ti and Ni-Ti Bilayers
Authors: Børgesen P. , Lilienfeld D. A. , Wistrom R. E. , Johnson H. H.
Published: March 2011

Previous comparisons of the room temperature mixing of Ni-Ti and Fe-Ti multilayers have shown significant differences in the mixing rates in spite of closely similar heats of mixing as well as ballistic properties. This result suggests contributions from mechanisms other than ballistic and thermal spike effects, or a break-down of present thermal spike models for these materials. In order to identify the mixing mechanisms involved, quantitative measurements were made at various temperatures between 80K and 350K using bilayer samples. Surprisingly, the mixing rates were found to disagree significantly with those estimated for multilayer samples.
Ion-Beam Mixing in Amorphous and Crystalline Fe-Ti
Authors: Scheuer Udo , Rehn Lynn E. , Baldo Pete
Published: March 2011

Crystalline Fe and Fe-10at.%Ti and amorphous Fe-37at.%Ti films with Ag and Hf markers were produced by vapor deposition. Marker spreading during ion-beam mixing between 77 K and 580 K was measured using Rutherford Back-scattering (RBS). Marker spreading was also measured between temperatures of 300 K to 700 K after full crystallization of the Fe-37at.%Ti films. Microstructural changes during ion-beam mixing were studied in situ, in a High-Voltage Electron Microscope. Homogeneous nucleation of a metastable bcc phase, was observed at high temperatures. The results are discussed in terms of their relevance to “radiation-enhanced” diffusion in amorphous materials.
The Effect of Hydrogen Content on Ion Beam Mixing
Authors: Wistrom R. E. , Børgesen P. , Johnson H. H. , Lilienfeld D. A.
Published: March 2011

A qualitative study of ion beam mixing of multilayers has shown that the presence of hydrogen in the sample slows mixing considerably for Fe/Ti, and slightly for Ni/Ti. We have quantified this effect and extended the study to four more systems (Co/Ti, Pd/Ti, Ti/Cu, and Ti/Al) and to lower temperatures. The degree to which H charging reduced the mixing rate varied substantially with multilayer system. H was lost during mixing. H was lost fastest from those films for which the H effect was the smallest. Our data are consistent with a model that relates mixing inhibition to H-vacancy binding energy in the non-Ti component.
Ion Beam Induced Intermixing of Wsi0.45 on GaAs
Authors: Pearton S. J. , Short K. T. , Jones K. S. , Baca A. G. , Wu C. S.
Published: March 2011

The systematics of ion beam induced intermixing of WSi0.45 on GaAs have been studied after through-implantation of Si or O in the dose range 1013 − 5 × 1016 cm−2. SIMS profiling shows significant knock-on of Si and W into the GaAs at the high dose range in accordance with Monte Carlo simulations, but there is virtually no electrical activation (≤0.1%) of this Si after normal implant annealing (900°C, 10 sec). This appears to be a result of the high level of disorder near the metal-semiconductor interface, which is not repaired by annealing. This damage consists primarily of dislocation loops extending a few hundred angstroms below the end of range of the implanted ions. Extrapolation of the ion doses used in this work to the usual doses used in GaAs device fabrication would imply that ion-induced intermixing of WSix will not be significant in through-implantation processes.
Ion Beam Mixing of High-Tc Superconductor Components.
Authors: Borgesen P. , Lilienfeld D. A.
Published: March 2011

The design of the necessary multilayer structures for producing superconducting thin films by ion beam mixing methods requires, among others, the knowledge of the individual (binary) mixing rates. In order to measure these, various combinations of Y, Ba, Cu, and Bi were irradiated with 600 keV Xe-ions at 80K and 300K. The systems exhibited a wide range of mixing behaviors which are also of fundamental interest. Ba and Cu readily formed the BaCu phase, and further mixing with Cu progressed only via binary collision mechanisms. At 80K Cu and Y were rapidly mixed in any ratio by thermal spikes, whereas a Cu rich sample rapidly formed the Cu6Y phase at 300K. Ba could not be mixed into Y or a Y-Cu mixture. Finally, irradiation of polycrystalline layers of Cu and Bi apparently lead to rapid motion of Bi along grainboundaries at both temperatures.
Angle of Incidence Effects in Ion Beam Processing
Authors: Harper J. M. E. , Hörnström S. E. , Rudeck P. J. , Bradley R. M.
Published: March 2011

The angle of incidence of ion bombardment is an important processing parameter, which can strongly affect the shape, composition and microstructure of bombarded surfaces. We describe several phenomena directly related to the angle of ion incidence during ion beam etching and ion beam assisted deposition. First, the development of surface ripple topography during ion beam etching is modeled. Surface perturbations are shown to grow under ion bombardment, while surface selfdiffusion acts to select a characteristic wavelength. The orientation of these characteristic ripples changes by 90° as the angle of ion incidence is varied from near-normal to near-glancing angle. The second example is the effect of angle of incidence on the etching rate of Ta under mixed Ar-O2 ion bombardment. For pure Ar bombardment, the sputtering yield of Ta increases with angle of ion incidence slower than secθ, producing a maximum etch rate at normal incidence. Above a critical pressure of O2, however, the yield increases faster than secθ dependence, producing a maximum etch rate at a non-normal angle of incidence. The third example is the effect of angle of incidence on the preferential sputtering of Al relative to Cu in Al-5% Cu thin films. Films deposited by evaporation with simultaneous Ar ion bombardment at 500 eV show a depletion of Al relative to Cu. This composition change is enhanced by increasing the angle of incidence away from normal, resulting in a higher Cu concentration in a film deposited on a tilted surface. Finally, a mechanism is described for the generation of oriented microstructure in films deposited under simultaneous glancing-angle ion bombardment, demonstrated previously for Nb. Grain orientations are selected which allow channelling of the ion beam. These results show that the shape, composition and microstructure of films deposited under ion bombardment respond to changes in angle of incidence, and that these effects need further study and modeling.
Epitaxial Growth of Ni on Si by Ion Beam Assisted Deposition
Authors: Grabowski K. S. , Kant R. A. , Qadr S. B.
Published: March 2011

Epitaxial Ni films were grown on Si(111) substrates to a thickness of about 500 nm by ion beam assisted deposition at room temperature. The films were grown using 25-keV-Ni ions and electron-beam evaporation of Ni at a relative arrival ratio of one ion for every 100 Ni vapor atoms. The ion beam and evaporant flux were both incident at 45° to the sample surface. Standard θ-2θ X-ray diffraction scans revealed the extent of crystallographic texture, while Ni {220} pole figure measurements identified the azimuthal orientation of Ni in the plane of the film. Films grown without the ion beam consisted of nearly randomly oriented fine grains of Ni whereas with bombardment the Ni (111) plane was found parallel to the Si (111) plane. In all the epitaxial cases the Ni [110] direction was perpendicular to the axis of the ion beam, suggesting that the azimuthal orientation of the film was determined by channeling of the ion beam down {110} planar channels in the Ni film. Additional experiments with different ions, energies, and substrates revealed their influence on the degree of epitaxy obtained.
Soft Magnetism and Morphology of Fe Films by Dual Ion Beam Sputtering
Authors: Nagakubo M. , Yamamoto T. , Naoe M.
Published: March 2011

Fe films have been deposited by using dual ion beam sputtering apparatus under various conditions, and the dependence of their magnetic properties and morphology on preparation parameters such as film thickness, δt, and argon gas pressure, PAr, have been investigated in detail.
The saturation magnetiza ion 4πMs of the specimen films did not change remarkably with 6t in the range of 50 ∼1000nm. However, with decrease of 6t below 50 nm, 4πMs decreased to less than 20 kG and coercivity Hc increased to more than 16 Oe. As PAr increased from 0.5 to 1.6 mTorr without ion bombardment, 4πMs decreased to less than 20 kG and Hc increased to about 20 Oe. The SEM micrographs of these films deposited at higher PAr showed the columnar structure. On the other hand, the films deposited at Yower PAr and ones bombarded by argon ions with proper kinetic energy during deposition did not present any texture and exhibited better soft magnetism. Such a morphology may be attributed to the difference in arrival energy of sputtered Fe particles to film surface and related closely to soft magnetism. It has been found that the dual ion beam sputtering method can control 4πMs and Hc with changing PAr and so prepare Fe films with superior soft magnetism by adjusting the kinetic energy of bombarding argon ions at lower PAr.
The Effect of Simultaneous Electron and Kr+ Irradiation on Amorphization of CuTi
Authors: Koike J. , Okamoto P. R. , Rehn L. E. , Meshii M.
Published: March 2011

CuTi was irradiated with 1-MeV electrons and Kr+ ions simultaneously at temperatures from 10 to 423 K. Retardation of Kr+-induced amorphization was observed with simultaneous electron irradiation at 295 and 423 K. The retardation effect increased with increasing irradiation temperature and relative electron-to-Kr dose rate. In contrast, simultaneous irradiation below 100 K showed an additive effect of electron- and Kr+-induced amorphization. The results can be explained by the mobility point defects introduced by electron irradiation interacting with Kr+-induced displacement cascades.
Argon Ion Bombardment During Molecular Beam Epitaxy of Ge (001)
Authors: Chason Eric , Horn K. M. , Tsao J. Y. , Picraux S. T.
Published: March 2011

Using in situ, real-time reflection high energy electron diffraction (RHEED), we have measured the evolution of Ge (001) surface morphology during simultaneous molecular beam epitaxy and Ar ion beam bombardment. Surprisingly, low-energy Ar ions during growth tend to smoothen the surface. Bombardment by the ion beam without growth roughens the surface, but the surface can be reversibly smoothened by restoring the growth beam. We have measured the effect of such “ion beam growth smoothening” above and below the critical temperature for intrinsic growth roughening. At all measured growth temperatures the surface initially smoothens, but below the critical roughening temperature the final surface morphology is rough whereas above this temperature the final morphology is smooth.
Tribological and Mossbauer Studies of Ion-Implanted Iron
Authors: Williamson D. L. , Qu Yi , Wei Ronghua , Sampath W. S. , Wilbur P. J.
Published: March 2011

A modified pin-on-disc wear test technique and conversion electron Mössbauer spectroscopy (CEMS) have been used to characterize the tribological and microstructural properties, respectively, of pure Fe implanted with N and Ar ions at high current densities. CEMS measurements were made before and after wear testing. For the lubricated, mild adhesive wear conditions used here, no evidence was found for iron-nitride dissolution or N atom migration. Disordering of γ'-Fe4N did occur as a result of the wear process. All Nimplanted surfaces were tribologically superior to the Ar-implanted surface and an extremely wear-resistant surface layer about 30–50 nm thick was produced with a dose of 8×1016 N atoms/cm2, at a dose rate of 100 μA/cm2. However, once this layer was worn away the wear rate returned sharply to that of unimplanted pure Fe. A high retained N dose has been observed even for a dose rate of 750 μA/cm2 during which the sample reached 280°C.
Characterization of TiN Films Prepared by Ion Beam Assisted Deposition
Authors: Chang Albert L. , Kant R. A.
Published: March 2011

One of the advantages of the ion beam assisted deposition process is its controllability of the processing parameters such as: ion-to-atom arrival ratio and the ion energy. In this study, the effects of the nitrogen ion energy (from 1 KV to 30KV) on the TiN film morphology and microstructures were systematically investigated as a function of ion-to-atom arrival ratios, using TEM, XTEM, SEM, ESCA and other analytical techniques.
A Study of the Anodic Oxidation on Aluminium by Ion-Implanted Xe Ions Marker and RBS Analysis Techniques
Authors: Chen Hemting , Bai Xinde , Li Wangpei , Dai Mingjiang
Published: March 2011

This paper presents the results on the mechanism of the anodic oxidation on Al by means of ion–implanted marker Layer of xenon and RBS analysis techniques. ExperimentaLly, it has been shown that the mechanisms of anoulic oxidation on Al are different in the different elctrolytes. In the solution of 15%.wt sulphuric-acid, the anodic oxide film is formed by the react ion be tweeit metal rations at the metal/oxide interface and continuously migrated oxygen anions. While in the solution of 5%wt ammonium citrate, both tie migration of the metal cations and that of the oxygen anions contribute to the formation of the anodic flim, and the oxidization takes place in internal region of the oxide ftim or at lhe interface. The transport numbers for Al in 5%.wt ammonium citrate were found to vary with the voltage or current density front 44% to 64∼
High Dose Implantation of Nitrogen and Phosphor into Silica Glass
Authors: Tagami Takashi , Oyoshi Keiji , Tanaka Shuhei
Published: March 2011

The surface chemistry of silica glass implanted with N+ or P+ ions has been studied. The X-ray photoelectron spectroscopy (XPS) spectra of N(1s) for silica glass implanted with N+ shows the possibility of the formation of oxynitride glass. For the first time, the effect of the implantation of N+ and additional Si+ on the surface chemistry of silica glass has been studied and found to be significant in increasing the nitrogen concentration in the silica glass. The peak concentration of N increases several times, and does not change even if the sample is annealed at 900°C. The XPS spectra of P(2p) for silica glass implanted with P+ ions shows two interactions, both P-O and P-P. Therefore, the XPS spectra shows the possibility for the formation of phosphosilicate glass using P+ implantation into silica glass.
Damage Formation in Semiconductors During Mev Ion Implantation
Authors: Sjoreen T. P. , Holland O. W. , El-Ghor M. K. , White C. W.
Published: March 2011

Damage produced by 1.0-2.5 MeV self-ion and O-ion implantation into Si and Ge single crystals has been characterized by cross-sectional electron microscopy and ion channeling. In Si, it is observed that the damage morphology varies substantially along the ion's track. Near the end-of-range of the ion, damage accumulation is very similar to that which occurs during medium- to low-energy implantation (i.e., damage increases monotonically with dose until the lattice is made completely amorphous). In front of this end-of-range region, however, damage saturates at a very low level for moderate implantation fluences. A model based on homogeneous damage nucleation in Si is discussed. For Ge, damage accumulation is very different; a monotonic increase of damage with dose is observed over the entire range of the ion. Possible mechanisms responsible for the differences between Si and Ge are discussed.
Properties of Silicon Oxynitride and Aluminum Oxynitride Coatings Deposited Using Ion Assisted Deposition
Authors: Al-Jumaily G. A. , Mooney T. A. , Spurgeon W. A. , Dauplaise H. M.
Published: March 2011

Optical thin films of nitrides, oxynitrides and oxides of aluminum and silicon were deposited using ion assisted deposition. Coatings were deposited by thermal evaporation of AlN and e-beam evaporation of Si with simultaneous bombardment with 300 eV ions of nitrogen, a mixture of nitrogen and oxygen or oxygen. The chemical composition and the index of refraction of the coating was varied by varying the gas mixture in the ion beam. Optical properties of and environmental stability of coatings were examined. Results indicated that coatings are stable even under severe conditions of humidity and temperature.
A Comparison of Low Energy BF2 Implantation in Si and Ge Preamorphized Silicon
Authors: Ruggles Gary A. , Hong Shin-Nam , Wortman Jimmie J. , Ozturk Mehmet , Myers Edward R. , Hren John J. , Fair Richard B.
Published: March 2011

Low energy (6 keV) BF2 implantation was carried out using single crystal, Ge-preamorphized, and Si-preamorphized silicon substrates. Implanted substrates were rapid thermal annealed at temperatures from 600°C to 1050'C and boron channeling, diffusion, and activation were studied. Ge and Si preamorphization energies were chosen to produce nearly identical amorphous layer depths as determined by TEM micrographs (approximately 40 nm in both cases).
Boron segregation to the end-of-range damage region was observed for 6 keV BF2 implantation into crystalline silicon, although none was detected in preamorphized substrates. Junction depths as shallow as 50 nm were obtained. In this ultra-low energy regime for ion implantation, boron diffusion was found to be as important as boron channeling in determining the junction depth, and thus, preamorphization does not result in a significant reduction in junction depth. However, the formation of junctions shallower than 100 rmu appears to require RTA temperatures below 1000°C which can lead to incomplete activation unless the substrate has been preamorphized. In the case of preamorphized samples, Hall measurements revealed that nearly complete electrical activation can be obtained for preamorphized samples after a 10 second rapid thermal anneal at temperatures as low as 600°C.
Ion Impiantation Doping of Siox with 31P and 69Ga
Authors: Jones K. S. , Venables D. , Horne C. R.
Published: March 2011

Implantations of annealed SIMOX and Si wafers have been done using P and Ga to investigate the effect of excess oxygen and oxygen precipitates on amorphous layer regrowth and category II (end-of-range) dislocation loop elimination. Solid phase epitaxial regrowth of the amorphous silicon in both SIMOX and Si control wafers occurred at 550°C without the formation of category III defects and annealing at 900°C 16 hours resulted in complete removal of the category II defects. In an oxidizing ambient, the implanted SIMOX wafer again exhibited complete defect elimination whereas the Si control wafer showed growth and development of extrinsic stacking faults. It is speculated that the buried oxide may act as a sink for the Si. SIMS results indicate the dopant getters to the Si/SiO2 interfaces and that redistribution can be modelled reasonably well with SUPREME III.
Low-Defect, High-Quality Simox Produced By Multiple Oxygen Implantation with Substoichiometric Total Dose
Authors: Namavar F. , Cortesi E. , Sioshansi P.
Published: March 2011

This work addresses the formation of Separation by IMplantation of OXygen (SIMOX) structures by multiple oxygen implantation into silicon and high temperature annealing. We observed no threading dislocation defects in the several plane view TEM and XTEM micro graphs of each of the samples implanted with a single dose of up to 8 × 1017 0+/cm2. We also demonstrated that with a multiple low-dose (3 to 4 × 1017 0+/cm2) oxygen implantation and high temperature annealing process, we are able to produce continuous and uniform buried SiO2 layers with a total dose of 1.1 × 1018 0+/cm2 (about 60% of the total dose for standard SIMOX). The density of defects is about 105/cm2. There are no silicon islands in the buried layer, no SiO2 precipitates in the silicon top layer, and the Si-SiO2 interfaces are sharp and smooth. SIMOX material with a high-quality Si top layer and a continuous buried layer has been produced with a total dose of 7 × 1017 0+/cm2 (40% of the total dose for standard SIMOX) and a two-step process. However, in this case there are a few Si islands present in the buried SiO2 layer.
On the Structure, Composition, and I–V Characteristics of AL/Ti:W/a-Si Contacts.
Authors: Berger S. , Komem Y.
Published: March 2011

The effect of heat treatments on the microstructure, composition and I–V characteristics of Al/TiW/a-Si contacts was studied.

It was found that heat; treatments of the amorophized contacts at the temperature range of 450–520°C led to an interdiffusion of Si atoms into the Al film and of Al atoms into the a-Si region through the Ti:W layer and silicides formation.However, no such interdiffusion and silicides formation could be detected in the contacts made of the unamorphized Si substrate under identical heat treatments.

The I–V characteristics of the amorphized contacts are explained by a model of electrical conductivity in amorphous solids.
Atomic Profiles and Electrical Characteristics of Very High Energy (8–20 MeV) Si Implants in GaAs
Authors: Thompson Phillip E. , Dietrich Harry B. , Eridon James M. , Gresko Thomas
Published: March 2011

High energy Si implantation into GaAs is of interest for the fabrication of fully implanted, monolithic microwave integrated circuits. Atomic concentration profiles of 8, 12, 16, and 20 MeV Si have been measured using SIMS. The range and shape parameters have been determined for each energy. The theoretical atomic concentration profile for 12 MeV Si calculated using TRIM-88 corresponded to the SIMS experimental profile. No redistribution of the Si was observed for either furnace anneal, 825° C, 15 min, or rapid thermal anneal, 1000°C, 10 s. The activation of the Si improved when co-implanted with S. The co-implanted carrier concentration profiles did not show dopant diffusion. Peak carrier concentration of 2×1018/cm3 was obtained with a Si and S dose of 1.5×104/cm2, each.
Self Annealing Implantation of As+ IN SILICON
Authors: Berti M. , Drigo A. V. , Lotti R. , Lulli G. , Merli P. G.
Published: March 2011

The structure of silicon layers implanted with high current As’ beams at different power densities under self-annealing conditions (i.e. with simultaneous damage recovery activated by beam heating) has been investigated with Rutherford Backscattering and Transmission Electron Microscopy techniques. The results have been compared with previous ones obtained with P÷ implantation. They show that, in both cases, an ion-induced mechanism of recrystallization, characterized by an activation energy of the order of 0.3 eV, is operative at temperatures below the values necessary to activate thermal epitaxy. Chemical impurity profiles in samples self-annealed with As+ ions at high beam power density, show the occurrence of two relevant radiation-induced effects: i) diffusion enhancement in the tail region; ii) formation of two impurity peaks, separated by a depletion region centred at the ion projected range. While the deeper peak disappears with increasing irradiation time, the one located at the maximum of nuclear energy loss grows, apparently as a consequence of segregation of As atoms at large clusters of vacancy-type defects.
Analysis of Nitrogen, Boron, and Hydrogen of i-BN Films Fabricated by the Ion Beam Assisted Deposition
Authors: Hirvonen J-P. , Hirvonen J. K.
Published: March 2011

The concentrations of the main constituents of hard i-BN films produced by the ion beam assisted deposition were measured using the nuclear resonance reactions 11B(p,γ) 12C at Ep = 163 keV, and 15N(p,αγ) 12C at Ep = 429 key, respectively. The hydrogen contamination of the samples was investigated using the forward recoil spectroscopy (FRES) technique with a 2 MeV He+ beam. Some complementary analyses of carbon and oxygen were performed using (d,p) and (d,α) -reactions.

Hyperstoichiometric boron concentration were found in almost all films. The relative concentrations of nitrogen and boron were also slightly dependent on the deposition conditions as well as the deposition temperature. Contrary to this, hydrogen contamination, that was generally at a low level with few exceptions, was more independent of these parameters.
Lattice Distortion Induced by Laser Assisted MOCVD of GaAs
Authors: Hussien S. A. , Karam N. H. , Bedair S. M. , Fahmy A.A. , El-Masry N. A.
Published: March 2011

Laser induced chemical vapor deposition (LCVD) of GaAs has been achieved at low temperature using trimethylgallium and arsine precursors. The deposited film traces the path of the Ar+ laser, thus making it attractive for several applications. The localized thermal expansion resulting from the laser induced temperature rise has to be elastically accomodated in order to prevent lattice distortion during the LCVD process. We report on the growth conditions that can be used without the occurence of plastic deformation in the epitaxial films. A model is presented to explain the thermal expansion induced distortion during the deposition process and will be compared with experimental results.
Argon Ion and Excimer Laser Induced Epitaxy of GaP
Authors: Sudarsan U. , Cody N. W. , Dosluoglu T. , Solanki R.
Published: March 2011

Laser-induced epitaxial growth of GaP has been achieved using both pyrolytic and photolytic reactions. A focused beam from an argon ion laser operating at 514.5 nm was used to ‘direct-write’ epitaxial microstructures of GaP on silicon using a pyrolytic process. An ArF excimer laser has also been used to demonstrate homoepitaxy utilizing the photolytic process.
Laser-Induced Chemical Vapor Deposition of Ge-Se Thin Films
Authors: Xiao Tongsan D. , Strutt Peter R.
Published: March 2011

The synthesis of Ge-Se deposits has been demonstrated by using continuous wave CO2laser excited reactions of GeC14and Se2Cl2precursors, each transported in an argon carrier gas. The deposited Ge-Se layers are rich in Ge with a composition of 70% of Ge and 30% of Se. Microstructural examinations reveal that the microstructure consists of amorphous Ge-Se particles ranging in diameter from 2000 Å to 7000 Å. Suggestions are made for the possible mechanisms that might occur during film deposition including, pyrolytic reactions, multiphoton dissociations, and Volmer-Weker film growth.
Synthesis of Diamond Films by Laser-Induced Chemical Vapor Deposition
Authors: Goto Yoshiyuki , Yag Toshinori , Nagai Haruhiko
Published: March 2011

An experimental study of diamond formation by laser-induced chemical vapor deposition (CVD) technique using a gaseous mixture of H2 and CCl4 is reported. The laser used in this work is an ArF excimer laser which emits 80 - 200 mJ pulses with 20 ns duration. We have succeeded in obtaining thin films of diamond by the activation of hydrogen to enhance the removal of graphite and the production of CH radicals. Films obtained without the activation were composed of amorphous carbon and graphite. Hydrogen was activated by a microwave discharge tube or a hot tungsten filament. Films were characterized by Raman scattering and reflection electron diffraction. The diagnostic study using a visible optical emission spectroscope shows that the emission intensity ratio of CH to C2 radicals increases in the system with the activation.
Windowless Wide Area Vuv Lamp for Energy Assisted CVD
Authors: Yu Z. , Sheng T. Y. , Zarnani H. , Collins G. J.
Published: March 2011

A ring shaped cold cathode electron gun provides a large area disc shaped vacuum ultraviolet (VUV) light source up to 20 cm in diameter. The windowless disc plasma is also a source of radical and excited atomic gas species. VUV photons, excited species, and radicals can all assist dissociation of CVD feedstock reactants via volume photo-absorption and sensitized atom-molecule collisions, respectively. In addition, the excited radical flux and VUV impingement on the film may also assist heterogeneous surface reactions and increase surface mobility of absorbed species. Thin films of aluminum nitride, Si3N4, and hydrogenated amorphous silicon have been deposited at temperatures between 100°C - 400°C. The deposited films show significant improvement over other photoassisted CVD processes in the film quality achieved, the substrate temperature required and the maximum deposition rates.
Photogenerated Carrier Confinement During the Laser-Controlled Aqueous Etching of GaAs/AlGaAs Nultilayers
Authors: Ruberto M.N. , Willner A.E. , Podlesnik D.V. , Osgood R.M.
Published: March 2011

The sensitivity of the laser-controlled aqueous etching to the optical and electrical properties of semiconductors was utilized during the etching of n-GaAs/n-AlGaAs multilayers to produce novel microstructures. Since this process is controlled by the transport of photogenerated holes to the semiconductor/solution interface, we found that the morphology of etched features is dependent on the bandgap and hole diffusion length of each layer within the heterostructure.
Laser-Induced Atomic Chlorine Etching of Silicon
Authors: Treyz G.V. , Scarmozzino R. , Burke H.H. , Osgood R.M.
Published: March 2011

UV laser photolysis of chlorine (λ = 350-360 nm) has been used to produce a microscopic atomic chlorine source. Crystalline silicon has been etched and deep, through-wafer vias have been fabricated. The etching process has been modeled and both theoretical and experimental results are given.
Comparison of CW and Pulsed UV Laser Etching of LiNbO3
Authors: Beeson K.W. , Clements N.S.
Published: March 2011

The results of CW frequency-doubled argon-ion laser etching and pulsed excimer laser etching of lithium niobate (LiNbO3) are compared. Argon-ion laser etching occurs in the presence of Cl2 at laser intensities of 1.1 MW/cm2 or higher. The 257 nm laser beam with up to 25 mW power is focused to a 1.5 μm diameter spot and scanned at speeds of 10 μm/s or less. Excimer laser etching is done at 248 nm (KrF) with the laser beam focused onto the sample with cylindrical optics. Trenches <20 μm wide and several millimeters long are produced by ablating the target and without scanning the beam. Excimer laser etching of lithium niobate has been attempted in the presence of C12, O2, N2, H2 or air. Excellent results are obtained with air as the etching medium.
KrF Laser-Induced Chemical Etching of Nickel with Br2
Authors: Tyndall George W. , Moylan Christopher R.
Published: March 2011

A quartz crystal microbalance (QCM) has been used to study the 248 nm laser-induced etching of nickel by Br2. The experiment consists of focusing a pulsed UV laser beam at normal incidence onto the surface of a quartz crystal coated with 1μm of polycrystalline nickel. Absolute etch rates of nickel, in terms of mass removed per unit time, are determined from the integrated sensitivity function of the 6Mhz crystals used in this work. The dependence of the etch rate on Br2 pressure and laser fluence was measured. The kinetic data obtained from these measurements show that the mechanism of the etching process is dominated by the formation and the subsequent removal of a NixBry monolayer.
Ablation of UV-Transparent Materials with Femtosecond UV Excimer Laser Pulses
Authors: Küper S. , Stuke M.
Published: March 2011

Experiments on the ablation of undoped polytetrafluoroethylene (teflon), monocrystalline sodium chloride (NaCl) and polymethyl-methacrylate (PMMA) with 300 fs uv excimer laser pulses at 248 nm are reported. In contrast to standard 16 ns excimer laser pulses, these ultrashort pulses ablate essentially uv-transparent materials, heretofore not accessible to clean ablation, with good edge quality and no signs of thermal damage, with removal rates are on the order of one micrometer per pulse.
Excimer Laser Ablation of Sodium Trisilicate Glass
Authors: Eschbach P. A. , Dickinson J. T. , Pederson L. R.
Published: March 2011

We examine effects resulting from the irradiation of glassy sodium trisilicate (Na2O 3SiO2) with 248 nm excimer laser light at fluences from 1–5 J/cm2. We observe a threshold for the onset of etching of the surface at 3 J/cm2. We present SEM images of the resulting surface topography under etching conditions as well as recent measurements of the particle emission and photon emission from atoms leaving the surface region. A clear correlation is observed between this etching threshold and a) onset of emission of fast excited neutrals, as well as b) the appearance of atomic Na D resonance radiation emitted from particles up to several cm from the surface. We also present identifiction of the emitted positive ions.
Laser Physical and Laser Chemical Vapor Deposition of TiN and TiNxOy Films
Authors: Narayan J. , Biunno N. , Srivatsa A.R. , Singh R. , Chen B.
Published: March 2011

We have investigated the formation of polycrystalline TiN and amorphous TiNxOy films using laser physical (LPVD) and laser chemical (LCVD) vapor deposition techniques. The LPVD method involved the ablation of a TiN hot pressed pellet and Ti in the presence of nitrogen plasma using nanosecond XeCl excimer laser pulses (wavelength 308nm, pulse duration 45×10−9 seconds, and energy density ∼4-5 Jcm−2). The films were polycrystalline (average grain size ∼100Å) with face-centered-cubic structure and lattice constant of 4.25Å. The average grain size remained constant as the substrate temperature ranged from 25 to 550°C. In the LCVD method, a pulsed CO2 laser beam was used to crack TiCl4 and NH3 and form TiN films. Amorphous TiNxOy films were formed under poor vacuum conditions in the LPVD techniques. These amorphous TiNxOy films often exhibited explosive recrystallization with characteristic star patterns. Resistivity and microhardness measurements were made on these films and these results have been correlated with microstructure and chemical composition.
Selective—Area Laser Photodeposition of Transparent Conductive SnO2 Films
Authors: Kunz R.R. , Rothschild M. , Ehrlich D. J.
Published: March 2011

The deposition of SnO2 films has been demonstrated using an ArF (193-nm) excimer laser to drive the photochemical reactions of mixed SnCI4 and N2O vapors. Without any annealing, films 100 nm thick grown on room—temperature substrates have resistivities as low as 0.04 Ω—cm. The optical bandgap of 3.20 ev and transmission cutoff wavelength of 330 nm compare favorably with films obtained using alternate higher temperature techniques. The maximum temperature excursion during the 20—ns laser pulse is estimated to be 300 to 400 ºC.
Laser-Induced Multi-Crystallization of Thin Germanium Films
Authors: Ortiz C. , Rubin K.A. , Iuria S. A.
Published: March 2011

We report here the crystallization kinetics of thin (35nm and 60nm) amorphous as-deposited Ge filins using diffraction limited laser beam irradiation and laser pulses between 30ns and IreS. The recrystallization of crystalline as-deposited films was also studied for similar laser conditions. Crystallization was observed for pulses as short as 50ns. We conclude that the use of small beam spots (-1μm) gives a very different crystallization morphology from that observed previously for larger beam diameter and same laser pulse length. In our case for short irradiation times, the nucleation process dominates over crystal growth. Laser irradiation of as-deposited crystalline films produced grains with significantly less defects than grains crystallized from as-deposited amorphous films. Temperature calculations allow us to understand these results by showing that only the small spot irradiation sustains the material at high temperature for times comparable to the pulse width.
The Microstructure of Gold Films Written by Focused Ion Beam Induced Deposition
Authors: Blauner Patricia G. , Ro Jae Sang , Butt Yousaf , Thompson Carl V. , Melngailis John
Published: March 2011

Focused ion beam induced deposition of gold microfeatures is accomplished by 40 keV Ga+ bombardment of a substrate on which dimethyl gold hexafluoro acetylacetonate is continuously adsorbed. Under optimum conditions, deposition rates exceeding 11 Å/s have been achieved as well as high aspect ratio features, linewidths of approximately 0.1.μm, and resistivities of 500—1500 μΩcm. The microstructure, composition, and yield of the deposits have been examined as a function of various process parameters. Improved film growth and purity are observed in deposits made with lower organometallic pressures or higher current densities.
Temperature Dependence of Etch Rate and Residual Damage in Reactively Ion Etched GaAs and AlGaAs
Authors: Pearton S. J. , Jones K. S. , Chakabarti U. K. , Emerson B. , Lane E. , Vasile M. J. , Fullowan T. R. , Hobson W. S. , Short K. T. , Haegel N. M.
Published: March 2011

The etch rate of GaAs and AIGaAs during CC12F2:O2 reactive ion etching was measured over the temperature range 50–400ºC. For GaAs, the etch rate increases super-linearly from ∼400Å.min−1 to ∼3000Åmin−1 over this temperature range for a 0.56 W.cm−2, 4 mTorr discharge with a 19:1 CC12F2:O2 mixture. The surface morphology of GaAs undergoes a smooth-to-rough transition near 150ºC, and theresidual damage in the near-surface region appears to decrease with increasing etch temperature. The I-V characteristics of Schottky diodes fabricated on the etched surfaces show ideality factors of 1.001 for 150ºC RIE, although these worsen because of thermal degradation of higher etching temperatures. From AES and XPS data the etched GaAs shows little contamination after etching. In contrast, little temperature dependence of the etch rate of AIGaAs is observed using CC12F2:O2, although once again there is surface degradation for etching temperatures above 150ºC.
Surface Morphological Changes of Polyimide with Oxygen Reactive Ion Beam Etching (RIBE)
Authors: Paik Kyung W. , Ruoff Arthur L.
Published: March 2011

At the beginning of etching, surface asperities appeared on the top plane of the polyimide (PI) film. The formation of surface asperities is due to the ordered phase in PI film. The known dimension of the ordered phase measured by X-ray diffraction is consistant with the size of surface asperities, 100 Å, observed by TEM. Further ion doses made these asperties evolve into smooth bumps which then eroded into cones as a result of etch yield difference as a function of the angle of beam incidence Y(θ)/Y(0) which has a maximum at θ=70. Finally cones led to the development of grass-likestructure on the top plane of the PI film. The formation of platelike structure on the cross-sectional plane of PI indicates that the structural inhomogeniety of the PI film(the ordered and disordered phase) is the main cause for the surface morphological changes of PI.