bluuebunny/crossref_metadata_2025 huggingface dataset:
Immobilization of Cs-137, Co-60, Mn-54 And Sr-85 in Cement-Waste Composition
Authors: Plećaš I. , Drljača J. , Perić A. , Kostadinović A.
Published: March 2011

To assess the safety for disposal of radioactive waste cement composite, the leaching of Cs-137, Co-60, Mn-54 and Sr-85 from a waste composite into a surounding fluid has been studied [1, 2]. Leaching tests were carried out in accordance with a method recommended by IAEA |2, 3|. Determination of retardation factors, KF, and coefficients of distribution, kd, using a simplified mathematical model for analysing the migration of radionuclides, has been developed. |4, 7, 8|

Results presented in this paper are examples of results obtained in a 10 year mortar and concrete testing project, which will influence the design of the engineered trenche system for future central Yugoslavian radioactive waste storage center. |7, 8|.
The Effects of Radiation on Intermediate Level Waste Forms
Authors: Wilding C. R. , Phillips D. C. , Lyon CE.
Published: March 2011

The effects of accelerated gamma and alpha irradiation experiments on cement grouts alone and grouts containing simulated combustible plutonium contaminated material (PCM) at a number of dose rates and under various environmental and confinement conditions are considered. Cracking and spallation can occur over a wide range of water/cement ratios at a high dose rate of 2.8 Gys-1 for grouts based on blast furnace slag compositions. Grouts based on pulverised fuel ash do not show any signs of spallationand cracking. One possible reason for this is the accumulation of radiolytic gases to high pressures in pores in the cement. It has been demonstrated that under some circumstances, at the Laboratory scale, PCM waste form can swell sufficiently to rupture its container and may disintegrate.
The Swedish Repository for Low and Intermediate Reactor Waste- SFR. Radioactivity Release and Transport Calculations
Authors: Neretnieks Ivars
Published: March 2011

The Swedish repository for low and intermediate level waste- SFR was ready for operation in early 1988. The license to start operation for the low level waste part was given in the spring of the same year. A very detailed safety analysis of the repository has been made by the SWEDISH NUCLEAR FUEL AND WASTE MANAGEMENT CO.- SKB. The main issues of this work are presented in this paper.
Equilibrium Concept for the Assessment of the Actinide Release from Waste Forms into Salt Brines
Authors: Rudolph G. , Vejmelka P. , Köster R.
Published: March 2011

A novel approach for the assessment of the radionuclide release from a nuclear waste repository after an accidental water ingression is proposed: after a short time a stable final condition is assumed to be established in the near-field of the waste form in which each radionuclide is at equilibrium between the dissolved phase and the various solid phases. The total release may be assessed from the concentration in solution and the flow rate out of the near-field.

An experimental program stimulated by this concept includes studies on the solubility of actinide compounds in salt brines in equilibrium with cement. In Q-brine (a salt brine rich in magnesium chloride, pH = 6.5) the concentrations of U, Np, Pu and Am in solution are determined by a sorption equilibrium, in sodium chloride brine (pH = 12–13) by the solubility of the respective hydroxide.
Effect of Humic Substances on Americium (III) Retention onto Silica
Authors: Moulin Valerie , Stammose Denise
Published: March 2011

The migration/retention phenomena of radionuclides in geological systems are of great interest for the safety assessment of a nuclear disposal. Interactions at solid/liquid interfaces play a significant role in the speculation and transport of radionuclides in aquifer systems. Oxide surfaces and humic substances which occur in natural waters in large concentration ranges (from few mg/1 to several hundred mg/1) may have a major influence on radionuclides behaviour. For this purpose, studies have been carried out on a ternary system: oxide-humic substances-americium (III). The influence of pH, ionic strength and humic concentration on the adsorption of americium onto silica has been investigated. The ionic strength of the solution (0.1 and 0.01) has little effect on the americium adsorption. In the presence of humic materials, the fixation of americium is enhanced at low pH (pH<5) whereas, at higher pH (pH>5), the adsorption is lowered and dependent of humic concentration.
Theory and Calculation of Water Distribution in Bentonite in a Thermal Field
Authors: Carnahan C. L.
Published: March 2011

Analysis of observed distributions of water adsorbed by compacted MX-80 bentonite in the presence of temperature gradients according to methods of the thermodynamics of irreversible processes indicates the possibility of coupling among fluxes of heat and mass. Additional experiments are suggested to confirm the existence of coupling.
Channeling in Fractured Zones and its Potential Impact on the Transport of Radionuclides
Authors: Moreno Luis , Neretnieks Ivars
Published: March 2011

Recent observations in several tunnels and drifts in crystalline rocks in Sweden indicate that there are quite frequent fracture zones in the rock. In a 4500 m long tunnel in Kymmen which has been mapped, more than 60 fracture zones were identified. The water inflow in these zones was assessed and the locations and character of the inflow “points” were charted. It is evident that the water emerges in isolated spots often with quite limited dimensions. The frequency of wet spots is on the order of one or a few per several tens of square meters. Often the spots are seen to be connected to small holes. Similar observations have been made in the caverns and drifts of the Swedish low and intermediate waste repository- SFR.
Modeling Studies of Multiphase Fluid and Heat Flow Processes in Nuclear Waste Isolation
Authors: Pruess Karsten
Published: March 2011

Multiphase fluid and heat flow plays an important role in many problems relating to the disposal of nuclear wastes in geologic media. Examples include boiling and condensation processes near heat-generating wastes, flow of water and formation gas in partially saturated formations, evolution of a free gas phase from waste package corrosion in initially water-saturated environments, and redistribution (dissolution, transport, and precipitation) of rock minerals in non-isothermal flow fields. Such processes may strongly impact upon waste package and repository design considerations and performance.

This paper summarizes important physical phenomena occurring in multiphase and nonisother-mal flows, as well as techniques for their mathematical modeling and numerical simulation. Illustrative applications are given for a number of specific fluid and heat flow problems, including: ther-mohydrologic conditions near heat-generating waste packages in the unsaturated zone; repository-wide convection effects in the unsaturated zone; effects of quartz dissolution and precipitation for disposal in the saturated zone; and gas pressurization and flow effects from corrosion of low-level waste packages.
Interactions and Transport of Plutonium-Humic Acid Particles in Groundwater Environments
Authors: Bidoglio G. , De Plano A. , Righetto L.
Published: March 2011

Pu adsorption on pure γ-alumina and heterogeneous mineral phases was investigated as a function of pH and humic acid (HA) concentration. Information on surface speciation was obtained by using various actinides as valence analogues for Pu. Surface redox transformations of Pu(V) appeared to control Pu uptake onto electron exchanging minerals. A one-dimensional transport experiment of high molecular weight HA in water saturated clayey sand column was performed under reducing conditions (Eh <-200 mV). This showed that HA particles larger than 600 nm were retained in the column. The HA breakthrough curve was characterized by extended tailing. Physico-chemical interactions at the mineral surface and particle straining in smaller pore spaces appeared to control HA transport through the soil. The chemical association of Pu with moving HA was investigated by leaching of 238-Pu-doped borosilicate glasses. Enhancement in Pu release rate was observed in HA solutions compared with organic-free groundwater.
The Solubility of Amorphous and Crystalline Schoepite in Neutral to Alkaline Aqueous Solutions
Authors: Bruno Jordi , Sandino Amaia
Published: March 2011

The solubility of schoepite, UO2(OH)2 H2O, has been investigated by potentiometric titration at 25 °C in 0.5 mol dm.−3 NaClO4 solution. The data indicates the predominance of the species (UO2)3(OH)5+ and either UO2(OH)3− or (UO2)3(OH)7− in the pH range studied. The formation constants of these species as well as the solubility product of the amorphous and microcrystalline schoepite have been determined. The consequences of these data on the hypothesis of schoepite as the solubility limiting phase in spent fuel dissolution studies is discussed.
Uranium Transport and the Partitioning of U, Th, and Ra Isotopes Between Solid and Aqueous Phases in the Krunkelbach Mine, Federal Republic of Germany
Authors: Dearlove Jeremy P.L. , Green D. C. , Ivanovich M.
Published: March 2011

This paper discusses some of the results from a natural geochemical analogue study on the Krunkelbach mine, F.R.G. These data, based largely on uranium series disequilibrium measurements, are used to compare the results of groundwater modelling programmes with observations made in the mine.
Sorption Properties of Natural Sulfides with Respect to Technetium
Authors: Bock W.-D. , Brühl H. , Trapp C. , Winkler A.
Published: March 2011

Technetium sorption properties of Fe2+-bearing minerals and different metal sulfides were studied by batch and column experiments. Pure stibnite (SbS3), pyrrhotite (FeS), pyrite (FeS2), galena (PbS) and loell ingite (FeAs2) fix Tc to a great extent (> 95 % of TcO4- starting inventory). They appear to be favourable backfill materials for redox-sensitive radionucli-des. Physico-chemical processes of fixation and possible fixation modes are discussed.
Aluminum Atom Surface Mobility on SiO2 During Ionized Cluster Beam Deposition
Authors: Levenson Leonard L. , Swartzlander Amy B. , Usui Hiroaki , Yamada Isao , Takagi Toshinori
Published: March 2011

An ionized cluster beam (ICB) source was used to deposit Al onto SiO2 substrates. A 60 gtm diameter wire held at the substrate served as a mask. After Al deposition, the wire was removed and the masked area was examined by scanning electron microscopy (SEM) and by scanning Auger microprobe (SAM). The ICB source was operated at 0, 3, and 6 kV acceleration voltages. The substrate was held at 80°, 200°, and 400°C during Al depositions. The Al deposition rate averaged 240 A per min. The chamber pressure during deposition was 2×10-6 Torr. The diffusion distance of Al under the mask edge was determined from the SEM micrographs and SAM line scans. The maximum diffusion distance for all acceleration voltages occured at a substate temperature of 200°C. The maximum diffusion distance at 200°C was 29 μm at 6 kV acceleration voltage. The minimum diffusion distance was 12 μm at 400°C for an acceleration voltage of 6 kV.
The Infidence of Defect Concentrations on Migration Energies in AgZn Alloys
Authors: Andreadis T. D. , Rosen M. , Eridon J. M. , Rosen D. J.
Published: March 2011

Migration energies in Ag of vacancies, interstitials, Zn impurity atoms, interstitial-iipurity cumplexes, and vacancy-impurity complexes were calculated using Embedded Atom. Method (EAM) potentials in Molecular Statics calculations. A new Zn EAM potential was determined and used in these calculations. The dependence of the migration energies on local defect concentrations was determined in a linear approximation. Binding and formation energies of defects are also presented. A new model for the migration energy appropriate for defect reactions is introduced.
Superadditivity in the Implantation of Molecular Ions
Authors: Cerofolini G. F. , Meda L. , Volpones C.
Published: March 2011

This paper deals with the implantation of molecular ions in silicon. The ‘molecular’ effect, i.e. the increase of the displacement yield compared with the sum of the atomic yields, is weak for light molecules (e.g., H2) and for heavy diatomic molecules (e.g., Sb2 and Bi2), but, for instance, it is strong for C6H6 at energy per atomic mass of the order of 1 keV/amu. Binary collision calculations are used to give a pictorial view of the phenomena occurring along the ion path, and to predict superadditivity and damage columnarity. The increase of pressure and temperature to extreme conditions by implantation of molecular ions is discussed.
Magnetic Anomaly and Icosahedral Phase Formation in Fe-Cu and Fe-Mo Systems
Authors: Huang L. J. , Chen Q. M. , Liu B. X. , Fan Y. D. , Li H-D.
Published: March 2011

The first observation of a new class of icosahedral phase associated with a magnetic transition in Fe-Cu and Fe-Mo systems are reported. It is found that the icosahedral order can be re-established when the destabilized Fe60Cu40 icosahedral phase subject to a magnetic transition at high annealing temperature. The Fe70Mo30 amorphous films obtained by sputtering exhibit a similar behavior at high magnetic transition temperature. A brief discussion of the observed phenomena is addressed.
Morphology of Amerphous Alloy Formed by Ion Beam Bombardment
Authors: Wei Tian , Ping Cai Wei , Jun Li , Run Wu
Published: March 2011

A study was performed to investigate the morphology of amorphous alloys which were formed on the surface of the samples by means of ion beam bombardment. The specimens of Fe deposited with Cr, Ti, Cr-Ni or Cr-Ni-Cr multilayers were bombarded by high doses of Ar+, N+ or Ti+ ion beams respectively. TEM and electron diffraction analysis were then used to study the kinetic transformation of amorphous to crystal during heating. The electro-chemical results hlvn showed after that the anodic current density Ic and Im were reduced remarkably.
Thermally and Ion-Induced Reactions of Metal with CuO Substrate
Authors: Li Jian , Wang S. Q. , Mayer J. W.
Published: March 2011

Thermally and ion-induced reactions of transition metals Zr, Ti, Cr and Ag with CuO substrates have been studied by Rutherford backscattering spectrometry and X-ray diffraction techniques. Reactions resulted in the configuration of ZrO2/Cu2O/CuO from Zr/CuO structure and TiOx/Cu2O from Ti/CuO structure after thermal annealing and ion irradiation. No significant reaction has been found in Cr/CuO after vacuum annealing at 410°C and 300 Key Xe ions irradiation at 240°C. Ag atoms balled up on CuO surface after annealing at 610°C. A comparison of the reaction layers has been made in both metal/SiO2 and metal/CuO systems after thermal annealing and ion irradiation. Both heats of reaction and bond strength in the substrates can influence the chemical reactivity between metal layer and substrate.
In Situ Hvem Study of Ion Irradiation-Induced Grain Growth in Au Thin Films
Authors: Liu Joyce C. , Li Jian , Mayer J. W. , Allen Charles W. , Rehn Lynn E.
Published: March 2011

In situ observations of 1.5 MeV Xe+ ion irradiated Au films at room temperature and at 150°C reveal the evolution of grain growth: the average grain size increases by the mechanisms of grain boundary migration and grain coalescence.
Radiation Induced Amorphization in YBa2 Cu3O7 and GdBa2 Cu3O7 Superconductors
Authors: Parkin Don M. , Nastasii Michael
Published: March 2011

The response of YBa2Cu3O7 and GdBa2Gu3O7 high temperature superconductors to particle irradiation is examined. Both ion and electron irradiations have been shown to first produce an orthorhombic-to-tetragonal transformation at relatively low doses followed by a tetragonal-to-amorphous transformation at doses roughly a factor of 10 higher. Analysis of the displacement stoichiometry that results from 120, 300, and 1000 keV electron irradiations, 400, and 500 keV O irradiations, and 300 keV helium irradiations indicate that the orthorhombic-to-tetragonal transformation is driven by O atom displacements either alone or in the presence of metal atom displacements and that the transformation to the amorphous phase is driven by displacements on the Y, Gd or other rare earth atom site.
0.5 MeV Submicron Ion Probe System for RBS/PIXE.
Authors: Inoue K. , Takai M. , IshibashI K. , Kawata Y. , Suzuki N. , Namba S.
Published: March 2011

A nuclear microprobe-forming system for the microscopic RBS/PIXE measurement of micro devices has been developed and installed at the Research Center for Extreme Materials, Osaka University. The use of precision quadrupole magnets and an objective collimator ensures a final spot size of less than 1μm.
Enhanced Wear Resistance by Compressive Strengthening a Novel Combination of Laser and Ion Implantation Technology
Authors: Beurs H. De , Hosson J. Th. M. De
Published: March 2011

Despite the advantages of laser processing for the production of wear resistant materials, laser surface melting results in tensile stresses because the melted layer shrinks during resolidification. These tensile stresses may lead to severe cracking of the material and to deleterious effects on the wear behaviour. Our basic idea presented in this paper is to convert the high tensile stresses in the laser melted surface into a compressive state after implantation. In general, neon implantation is not very effective in the reduction of wear rates. However, neon implantation into laser melted steel turns out to reduce the wear rate substantially.
Unlubricated Sliding Properties of Ion Beam and Excimer Laser Mixed Fe-Ti-C Multilayered Films
Authors: Hirvonen J-P. , Nastasi M. , Jervis T. R. , Tesmer J. R. , Zocco T.G.
Published: March 2011

Multilayered Fe-Ti-C films consisting of eleven sublayers were vacuum deposited onto an AISI 304 stainless steel substrate and subsequently mixed using either 400 key Xe ions or an excimer laser operating at a wavelength of 308 nm. Ion mixing was accomplished in a two step process: the multilayers were first irradiated with 1×1017 Xe/cm2 at 520°C, after which half of the sample was irradiated with 5×1015 Xe/cm2 at 0 °C. Laser mixing was carried out at both i.i and 1.7 J/cm2 with the number of pulses varied between 1 and 10. Pin-on-disc studies revealed only slight differences between the two kinds of ion beam mixed samples, whereas the dry sliding properties of laser mixed samples were strongly dependent on the total fluence used. In the optimum conditions, similar friction coefficients were obtained on both kinds of samples.
Growth of Stoichiometric bn Films by Pulsed Laser Evaporation
Authors: Murray P. T. , Donley M. S. , McDevitt N. T.
Published: March 2011

The feasibility of growing stoichiometric thin films of BN by pulsed laser evaporation has been investigated. Films grown under high vacuum conditions were N-deficient. This result is consistent with thermodynamic calculations, which indicate that B metal formation, with concomitant N2 desorption, is energetically favored over BN formation. Stoichiometric films were grown in NH3 with substrate temperatures of 400, 500, and 1000°C. Analysis of films grown under these conditions by grazing incidence x-ray diffraction indicates the films to be highly oriented, hexagonal BN.
Effects of Ion Bombardment on the Environmental Durability of Silver Coatings
Authors: Al-Jumaily G. A. , Mooney T. A. , Smajkiewicz A.
Published: March 2011

Effects of ion bombardment during deposition on the environmental durability of silver coatings have been examined. Films deposited under otherwise identical conditions were bombarded at different levels with 300 eV argon ions. Examination of the environmental durability of coatings revealed that films deposited with ion assisted deposition are more durable than evaporated coatings. Adhesion and scratch resistance of coatings were also improved as a result of ion bombardment.
Ion-Assisted Deposition of Protective Overlayers for Magneto-Optic Alloys
Authors: Cornett Kenneth D. , Gibson Ursula J. , Taylor Anthony
Published: March 2011

Rare-Earth Transition-Metal alloys such as Tb-Fe-Co are being studied and used as magneto-optic data storage materials. These materials are susceptible to oxidation by either oxygen or water vapor, particularly the rare earth component. Pitting corrosion is also a problem when protective overlayers have pinholes or a porous microstructure. Both degradation mechanisms are significant for application of this material to optical data storage. We have used ion assisted deposition (IAD) to produce protective overlayers of refractory oxides, such as Al2O2 and ZrO2. These layers were deposited both with and without IAD onto iron films and exposed to environments with controlled temperature and humidity. A scanning micro-reflectometer capable of detecting micrometer-sized pinholes was used to monitor the degradation of the iron layer with exposure time.
Segregation of Ag and Cu During Ion Beam and Thermally Induced Recrystallization of Amorphous Si
Authors: Custer J. S. , Thompson Michael O. , Poatet J. M.
Published: March 2011

The segregation of Ag and Cu impurities in amorphous Si during both thermal and ion beam induced epitaxial crystallization has been studied. During thermal regrowth at 550°C, both Ag and Cu are initially trapped at increasing concentration in the shrinking a-Si layer. At a critical concentration, though, regrowth becomes non-planar and the impurities are no longer entirely trapped in the a-Si. Above 0.08 at% and 0.15 at% respectively, the excess impurity is lost to the crystal region and diffuses rapidly away from the interface. Under low temperature (200 - 400°C) epitaxy induced by a 2.5 MeV Ar+ beam, segregation and trapping are initially observed. As regrowth proceeds, however, the segregation no longer follows the simple model
Electrical Activation of Heavily Doped Arsenic Implanted Silicon
Authors: Said J. , Jaouen H. , Ghibaudo G. , Stoemenos I. , Zaumseil P.
Published: March 2011

The combination of electrical, Transmission Electron Microscopy and Triple Crystal X-ray Diffraction measurements allow us to separate the existence of a local impurity activation process from the amorphous- crystal transformation. The local process occurs in the highly damaged surface layer induced by the arsenic implantation and is efficient well below the Solid Phase Epitaxy transition temperature. It is suggested that point defect migration should play an important role in the electrical impurity activation at low annealing temperatures.
Ion Bombardment Effects on GaAs Using 100eV Nitrogen Ions
Authors: Lau W. M.
Published: March 2011

The ion bombardment effects of low energy molecular nitrogen ions (100eV) on GaAs have been investigated using in-situ polar angle dependent X-ray photoelectron spectroscopy. It was found that arsenic and gallium nitrides were formed as a result of the nitrogen ion bombardment. The ion bombardment also caused a depletion of arsenic in the near surface region. For example, with a dose of 6×1015 cm-2 of nitrogen molecular ions at 100eV, the surface structure can be described approximately as 1.5nm of Ga0.67A0.33N on GaAs. The ion bombardment moves the Fermi levels of both n-type and p-type GaAs to mid-gap. Heating the ion bombarded samples in a vacuum chamber to 500°C desorbs all arsenic nitrides but most of the gallium nitrides remain on the surface. The Fermi levels of both n-type and p-type are then stablized at about 0.4eV from the valence band maximum. A surface type-inversion of the n-type substrate is therefore induced by the nitrogen-ionbombardment/annealing treatment.
Thin Films of p-Type CdTe Grown with Ion-Beam-Assisted Doping
Authors: Sharps Paul , Fahrenbruch Alan L. , Lopez-Otero Adolfo , Bube Richard H.
Published: March 2011

The purpose of the present work is to investigate p-CdTe thin films grown by ionassisted doping (IAD). Controlled doping in homo-epitaxial films resulting in carder densities up to 2×1017 cm-3 was obtained using P ions as the dopant. About 1.5% of the impinging P ions became electrically active in the films. Solar cells of n-CdS/p-CdTe were prepared and used as a diagnostic tool in understanding the p-CdTe films.
Effect of Microstructure on the Sheet Resistance of Ion-Beam Deposited ZnO Thin Film
Authors: Isa Saliman A. , Ghosh P. K. , Kornreich P. G.
Published: March 2011

ZnO thin films were deposited by ion-beam sputtering technique. Preliminary results show that the films are stoichiometric and crystalline in nature. The microstructure of ZnO films obtained depends very much on the process parameters. Among these parameters is the substrate temperature whose effect has been carefully examined.

ZnO films were deposited with substrate temperatures ranging from 200°C to 350°C. We observed that the sheet resistance of the films varies with their microstructure. In this investigation, a sheet resistance of 6.6 Mega-ohms per square is measured on a dense film deposited at a substrate temperature of 325°C.

We present in this paper a correlation between the film's microstructure and stoichiometry with some of it's electrical properties.
Investigation of Titanium Nitride Synthesized by Ion Beam Enhanced Deposition
Authors: Jiankun Zhou , Xianghuai Liu , Youshan Chen , Zhihong Zheng , Wei Huang , Zuyao Zhou , Shichang Zou
Published: March 2011

Titanium nitride films have been synthesized at room temperature by alternate deposition of titanium and bombardment by nitrogen ions with an energy of 40KeV. The component depth profiles and the structure of titanium nitride films were investigated by means of RBS, AES, TEM, XPS and X-ray diffraction. The results showed that titanium nitride films formed by ion beam enhanced deposition (IBED) had columnar structure and were mainly composed of TiN crystallites with random orientation. The oxygen contamination in titanium nitride films prepared by IBED was less than that of the deposited film without nitrogen ion bombardment. It was confirmed that a significant intermixed layer exists at the interface. The thickness of this layer was about 40 nm for the film prepared on iron plate. The mechanical properties of the film have been investigated. The films formed by IBED exhibited high hardness, improved wear resistance and low friction.
Electrically Conducting Thin Films by Ion Implantation of Pyrolyzed Polyacrylonitrile
Authors: Basheer R. A.
Published: March 2011

Heat treatment of polyacrylonitrile leads to products with semiconductor to metal like conductivities. The electrical properties of these materials are further modified by ion implantation. It is noted that the conductivity (∼10-7 (Ω cm)-1) of heat treated Polyacrylonitrile at 435°C (PAN435) increases upon ion implantation with As+, Kr+, Cl+ of F+ reaching a maximum value of 8.9 × 10-1 (Ω cm)-1 at as does of 5 × 1016 ion/cm2 and an energy of 200 KeV for the case of F+ implantation. On the other hand, ion implantation of the more conducting heat treated PAN at 750°C (PAN750) leads to a decrease in the electrical conductivity of the material. It is proposed that the conductivity modifications are primarily due to structural rearrangements induced by the energetic ions. Specific chemical doping contribution to conductivity is noted for halogen implantation in PAN435. The temperature dependence of conductivity of PAN heat treated at 750°C suggests a two path conduction, namely, a three dimensional variable range hopping conduction and a metallic conduction. After ion implantation, the conductivity-temperature dependence is interpreted in terms of a variable range hopping conduction mechanism.
Depth Profiling of Ion Beam Induced Damage in Semiconductor Heterostructures
Authors: Germann R. , Forchel A. , Hörcher G. , Weimann G.
Published: March 2011

We have produced beveled cross-sections of GaAs/GaAlAs multiple quantum well structures with inclination angles of 0.55 minutes of arc with a special ion beam etching technique. The extension of the damage which is induced during the dry etching process can be evaluated directly by a comparison of spatially resolved secondary ion mass spectroscopy and photoluminescence measurements. We observe a thickness of the damaged surface layer between 36 nm for 250 eV Argon ions and 160 nm for 1000 eV Argon ions in a GaAs/GaAlAs multiple quantum well structure.
Studies of Laser-Induced Surface Reactions by Surface Temperature Modulation Techniques
Authors: Comita Paul B. , Strongin Daniel R. , Kodas Toivo T.
Published: March 2011

Two relaxation techniques are described, both of which use surface temperature modulation as their basis. In these techniques, modulation of laser light intensity results in a modulation of surface reaction rates. The first technique, a diffusive transport relaxation technique, has been developed to study the chemical reactions occurring under the high pressure conditions used in laser-induced chemical vapor deposition. Perturbation of the reaction rate in a high pressure reactor produces transients in the gas phase reactant and product concentrations for the case of gas phase transport-limited deposition. The product species are differentiated from species formed from the reactant during ionization and fragmentation due to the phase-sensitive nature of the detection scheme. The system response is examined theoretically by examining the response of the gas phase reactant and product concentrations to the modulated surface reaction. The second technique is a new technique which has been developed for obtaining detailed information concerning reaction energetics and pathways of elementary surface reactions. This technique also employs a laser to generate a surface temperature modulation. The laser light is incident on a pure metal film which is mounted within an ultra high vacuum chamber. By modulating the laser intensity, the surface chemical reaction rates are modulated. The combined use of surface temperature modulation and appropriate linearization methods allows a quantitative analysis of the overall reaction energetics to be made. and is used here to investigate the surface processes in a thermal laser-induced reaction.
Laser Deposition of Gold
Authors: Sell Jeffrey A. , Meyer Martin S. , Meisner Gregory P.
Published: March 2011

Metallic gold was deposited on several different substrates by laser pyrolysis of a goldcontaining ink. The gold was deposited in the form of lines by translating the substrate during laser pyrolysis; linewidths ranged from 10 Am to 1.5 mm. This process was performed in open air. Prior to annealing, the films contain 40 to 50 % carbon impurity and the resistivity is extremely high. After a 1 hour anneal in air, the carbon content is reduced to < 5 %, and the resistivity is reduced to roughly 13 times bulk gold. Further improvement may be possible with a different annealing schedule.
Laser Induced Decomposition of Triethylgallium and Trimethylgallium Adsorbed on GaAs(100)
Authors: Mccaulley J. A. , Mccrary V. R. , Donnelly V. M.
Published: March 2011

We report X-ray photoelectron spectroscopy (XPS) studies of excimer laser stimulated decomposition of triethylgallium (TEGa) and trimethylgallium (TMGa) adsorbed on Gastabilized GaAs(100) surfaces in ultrahigh vacuum. TEGa and TMGa dissociatively chemisorb on GaAs at room temperature, whereupon irradiation by an excimer laser (at 193 or 351 nm) leads to further dissociation and desorption of carbon-containing species. The carbon removal rate (per laser pulse) decreases as carbon is removed suggesting multiple reaction sites, coverage dependent Arrhenius parameters, or second-order reactions. Based on the dependence of the rate on laser wavelength and fluence, we conclude that at low fluence, a two-photon electronic excitation of the adsorbate occurs, while at high fluence, laser induced pyrolysis dominates.
Low Temperature Epitaxy of Hg1−xCdxTe
Authors: Cody N. W. , Sudarsan U. , Solanki R.
Published: March 2011

Mercury cadmium telluride epitaxial layers have been grown using methylallyltelluride (MATe), dimethylcadmium (DMCd), and elemental Hg. Using these precursors high quality films have been achieved over the temperature range of 200-300°C. Comparisons are made between UV photon-assisted and thermally deposited films. Composition, growth rate, and electrical properties are compared for the two processes under various parameter conditions. Properties of films deposited on various substrates including CdTe, GaAs, and GaAs/Si are also described.
Low Temperature OMVPE of ZnSe from Alkyl Sources Using a Plasma Disk Lamp
Authors: Tokuda K. L. , Pihlstrom B. , Kisker D. W. , Schnoes M. Lamont , Collins G. J.
Published: March 2011

The growth of high quality ZnSe by organometallic vapor phase epitaxy (OMVPE) has generally been hindered because of parasitic source pre-reactions or relatively high source decomposition temperatures. In this work, we have used vacuum ultraviolet photons generated by a disk-plasma lamp to assist the ZnSe growth process using diethylselenium and diethylzinc as source materials. This approach has resulted in satisfactory growth rates and high material quality at temperatures as low as 250°C, without the limitations of prereaction typically observed when H2Se is used for the selenium source material. In addition, the alkyl selenium compound offers advantages due to reduced toxicity compared to H2Se. This new, low-growth-temperature process thus offers the possibility of improved stoichiometry and impurity incorporation control as well as a reduced thermal effect on the underlying substrate during growth. At the same time, the advantages of excellent morphology and uniformity typically exhibited by the alkylbased growth processes are retained.
Photoreactions of Mo(CO)6 on Potassium Precovered Silicon Surface with UV to IR Radiation
Authors: Ying Z. C. , Ho W.
Published: March 2011

The adsorption and photoreactions of Mo(CO)6 coadsorbed with K on Si(111)7×7 at 90 K have been studied under ultra-high vacuum conditions. It is found that dissociative adsorption of Mo(CO)6 on the K preadsorbed surface occurs for coverages below a monolayer. A multilayer of physisorbed Mo(CO)6 molecules is formed on top of the monolayer. Under photon irradiation physisorbed Mo(CO)6 molecules are dissociated and CO desorption is observed. The photoreactions of Mo(CO)6 occur over a wide wavelength range from the UV to IR. In contrast, only UV radiation induces photoreactions of Mo(CO)6 on the K-free Si(111)7×7 surface. Evidently K opens a new channel for the photoreactions of Mo(CO)6 on the surface. A mechanism involving interactions between photogenerated charge carriers and the substrate-adsorbate complex is proposed.
Al Photodeposition and Light-Induced Nucleation on p-Type Si from TMA
Authors: Bouree J.E. , Flicstein J. , Bresse J.F. , Rokmeluere J.F. , Pougnet A.M.
Published: March 2011

Photodecomposition of trimethylaluminum (TMA) flowing with H2 on p-type Si under UV irradiation is shown to be exclusively a reaction confined to surface species. Thus photonucleation and photodeposition of Al on Si is controlled either by Si-H or Si-O and Si-OH bonds. In the regions where Si-O and Si-OH are present, Al-O forms, which inhibits Al deposition either directly or via the adsorption of C containing photoproducts. In the other regions where Si is H terminated, it is assumed that H2 adsorbs dissociatively on Al clusters, thus leading to the formation followed by the desorption of methane from the adsorbed phase. For this reason, Al thin films are C contamination free.
High Resolution Direct - Write Photochemical Etching of InP Using Methyl Iodide
Authors: Durose K. , Summersgill J.P.L. , Aylett M.R. , Haigh J.
Published: March 2011

Photochemical etching of InP using a cw frequency doubled Ar+ laser is evaluated with a view to the production of optoelectronic device features. The diffusion-limited resolution of the unmodified etching process is discussed and a new method of etching high resolution grooves which utilises a native oxide coating is described. Grooves produced in this way have widths comparable to that of the laser beam.
Excimer Laser Induced Etching of Silicon-Carbide
Authors: Murahara M. , Arai H. , Matsumura T.
Published: March 2011

Resistless photoetching of SiC was performed by using XeF and KrF excimer laser beams. In this method, ClF3 gas was used for etchant. C1F3 gas has a unique absorption band in the range of 300- 430 nm. The strongest absorption band corresponds to the wavelength of the XeF laser (350 nm). So C1F3 gas is decomposed effectively. On the other hand, the absorption factor of SiC is about 30% in the range of 200-400 nm, and the bonding energy of SiC is lower than the photon energy of the KrF laser beam. For these reasons, it is possible to cut the bond of SiC directly. Thus, two laser beams were used. Fluence of the KrF laser beam was 200 mJ/cm2, of the XeF, 50 mJ/cm2. Total flow rates through the cell were 0.05 1/min. We can fabricated the etched feature of reticle pattern by reductive projection. Line and space was 10 μm and etching rate was 50Å/pulse.
Laser Induced Chemical Etching of Composite Structure of Ferrite and Sendust
Authors: Nagatomo S. , Takai M. , Lu Y. F. , Namba S.
Published: March 2011

Maskless etching of the composite structure of Mn-Zn ferrite and sendust (Fe-Si-Al alloy) was performed by focused argon-ion-laser irradiation in a CCl4 atmosphere and aqueous solutions. Only a mixture of KOH and NaOH aqueous solutions was found to smoothly etch the composite structure by thermochemical reaction using laser irradiation. A maximum etching rate of 14 μm/sec was obtained for sendust-on-ferrite substrates.
Patterning of High Tc Superconductor Films with a Focussed Excimer Laser
Authors: Hagerhorst J.M. , Mannhart J.D. , Oprysko M.M. , Scheuermann M.R. , Tsuei C.C.
Published: March 2011

Laser ablation using focussed excimner light has been found to be an effective technique for the direct, maskless patterning of High Tc superconductor films. The apparatus used in the work consists of an adjustable aperture which is illuminated by a 193 nm excimer laser beam. The aperture is imaged by a microscope onto the substrate into an area as large as 200 × 200 to an area as small as 2 × 2 square microns. The superconductor films are placed on a 0.5 micron resolution, computer controlled x-y stage. Laser fluences up to 5 J/cm2 and repetition rates of 10 Hz were found to be sufficient to ablate (pattern) the High Tc films with no apparent effect on their superconducting properties as evidenced by the films′ resistance as a function of temperature (R vs T) before and after patterning.

The technique and apparatus are flexible enough to allow patterning across entire substrates and/or the definition of isolated features as small as one micron. To date, the technique has been successfully used to pattern a wide variety of films (based on material and thickness), to fabricate transmission lines several millimeters long, to pattern superconducting quantum interference devices (SQUIDs) which operate at liquid nitrogen temperatures, and to study the behavior of individual grain boundaries within films.
Epitaxial Relationships in Esd Processes on Oxide Surfaces
Authors: Mccartney M.R. , Smith David J.
Published: March 2011

During intense electron irradiation inside the electron microscope, the electron—stimulated desorption of oxygen from the surfaces of several maximally—valent transition—metal oxides (TiO2, V2O5, Nb2 O5 and WO3) has been observed [1]. The irradiatedsurfaces become covered with a crystalline layer of the corresponding monoxide phase. These reduced phases, which are all based on cubic structures and have metallic conductivity, grow with a well— defined epitaxial relationship with the bulk oxide. Computer—drawn models of the crystal structures have been used to study the atomic arrangements implied by the epitaxial relationship, and certain structural features were found to be common to the oxides studied.
Process Margins for Laser Planarization of 1 to 5 µm Gold Films
Authors: Bernhardt A. F. , Contolini R. J. , Tuckerman D. B. , Weisberg A. H.
Published: March 2011

A pulsed excimer laser or flashlamp-pumped dye laser is used to melt 1 to 5 µm Au layers. The size of feature which can be filled by laser planarization is limited because of the finite melt duration, but the basic goal of levelling local surface topography is accomplished.

Laser reflow of thicker films reveals fundamental differences between the excimer laser and the flashlamp-pumped dye laser, resulting from the order-of-magnitude difference in pulse duration. The excimer pulse is short compared to the thermal diffusion time of the metal layer and this can create voids and craters in the metal above discontinuities in the underlying structure. For Au thicknesses greater than about 3 µm, void formation occurs at fluences at or below that necessary to planarize the film. The dye laser has a planarization threshold similar to that of the excimer but it takes over 60% greater energy to create voids than to planarize a 5 µm film.

A second damage mode, common to both laser sources, occurs where adjacent planarization zones overlap in a patterned area: thin spots can be created by the first planarization pulse which are vaporized by the second pulse.
Laser Surface Modification for Copper Deposition on Polyimide
Authors: Liu Y.S. , Cole H.S.
Published: March 2011

Selective modification of surface reactivities with lasers, using either direct writing or projection method, is intrinsically a sensitive method to prepare a surface for highresolution and high-speed area selective thin film deposition. In this paper, we demonstrated the use of laser direct-writing and projection patterning techniques for selective modification of the electrochemical property of a polyimide surface. High quality and highresolution copper patterns on polyimide surfaces are produced when the surface-modified sample is subsequently placed in an electroless plating solution. These results demonstrated that the use of laser-selective-modification of surface properties in conjunction with other batch thin film deposition processes provides an attractive approach for area-selective metallization for a variety of applications in which high writing speed and high sensitivity are required.
Patterned Excimer Laser Etching of GaAs Within a Molecular Beam Epitaxy System
Authors: Maki P. A. , Ehrlich D. J.
Published: March 2011

We have utilized an ArF excimer laser in a projection imaging geometry to etch GaAs layers grown in situ within a molecular beam epitaxy (MBE) system. Clean epitaxial surfaces were prepared using standard MBE growth procedures, then etched in a second chamber isolated by a gate valve. We report studies of the etching dependence on pulse rate (0.2 Hz to 150 Hz) and chlorine pressure (10−6, 10−4, and 5×10−3 Torr). We discuss the etching mechanism in terms of previous studies of the reaction between GaAs surfaces and molecular chlorine under high vacuum conditions. We show that the pulse rate and Cl2 pressure dependencies of the etching can be explained by the progress of the reaction at the instant of pulse exposure. Etch morphology is found to vary with the repetition rate, with the smoothest surfaces obtained at low repetition rates. We discuss the implications of the results in the context of in situ thin layer processing and epitaxial overgrowth.
Tunable Uv Laser Photolysis of Organometallic Compounds with Product Detection by Laser Mass Spectroscopy
Authors: Beuermann Th. , Stuke M.
Published: March 2011

We use tunable UV laser light in the region 200-320 nm, produced by frequency doubling the output of a dye laser for the decomposition of organometallic compounds. This method has been applied to TMA, trimethylaluminum AI(CH3)3. Only theTMA monomer absorbs UV light for λ>220nm. TMA decomposes by one-photon absorption mainly into two channels: aluminum plus organic fragments and aluminummonomethyl plus organic fragments. The ratio [A1]/[AICH3] is wavelength dependent. Finally, we present a mechanism to explain the photolysis of trimethyl compounds of group III elements (Al,Ga,In).
Fine Metal Particle Formation from Organometallic Compounds by Laser Ignited Mild Explosive Reaction
Authors: Shimo Nobuo , Yoshihara Keitaro
Published: March 2011

Fine metal particles are deposited on a surface by explosive decomposition of organometallic compounds with single pulse laser irradiation. This new technique has the following characteristics:

(1) High quantum efficiency of ca. 105, that depends on the size of the reaction chamber used and the concentration of organometallic compounds.

(2) Formation of uniform spherical particles of ca. 0.3 µm size under some reaction conditions.

(3) Rapid formation of metal particles. Most of the starting materials are decomposed within a few miliseconds.

The key points of this decomposition reaction are:

(1) Formation of high density active species in the gas phase by the irradiation with high power lasers.

(2) Propagation of a thermal chain reaction.
Indentation Technique to Investigate Elastic Moduli of Thin Films on Substrates
Authors: Stone D. S. , Wu T. W. , Alexopoulos P.-S. , Lafontaine W. R.
Published: March 2011

Closed-form elasticity solutions are introduced, that predict the average displacement beneath square and triangular, uniformly loaded areas at the surface of a bilayer. The solutions aid in the application of depth-sensing indentation techniques for measuring thin film elastic moduli. The elasticity solutions agree closely with experimental data of Al, Si, 1 μm Al on Si, and 2 μm Cr on Si. The case of poor adhesion between the film and substrate is briefly examined.
Substrate Step Induced Strain in Heteroepitaxial Growth
Authors: Lambrecht W. R. L. , Segall B. , Pirouz P.
Published: March 2011

During epitaxial growth of lattice-mismatched materials, substrate surface steps induce vertical misfit between substrate and epilayer. It is shown that the resulting strain is accomodated by an interface dislocation, which is of the Read-Shockley type for a complete step and supplemetary displacement type for a demistep, using R.C. Pond's classification. Alternative models for the strain accomodation are considered. A localized “displacement boundary” is shown to be unfavorable irrespective of the film-thickness. Residual shear strain in the film requires debonding from the substrate, which is shown to be unfavorable with respect to the dislocation model. The distribution of strain between film and substrate is shown to depend weakly on film-thickness but strongly on the material's elastic constants.
Delamination of LPD Tungsten Films by Residual Stress
Authors: Borer A. , Derby B. , May I.
Published: March 2011

Thin tungsten films have been deposited on sapphire and glass substrates using laser photolytic deposition from a tungsten hexa-fluoride precursor. Failure of the films is caused by the presence of large residual stresses (1–5 GPa). Compressive and tensile stresses are found at different stages of film growth and either may be responsible for delamination. Early compression is caused by oxidation and impurity influenced intrinsic stress. Tensile stress occurs with microstructural changes but is not maintained with film growth. Large stress gradients, indicative of up to 0.75–1.2% lattice strain difference across the film, are found through both compressive and tensile films and are not explained.
Ion Channeling Studies of CdTe Films on GaAs
Authors: Wilkens Barry
Published: March 2011

Thin films of [111] oriented CdTe have been MOCVD grown onto [111] GaAs substrates. When thicknesses exceed 1000Å the epitaxy is quite good (backscattering minimum yield of approximately 15%) in spite of a 14% lattice mismatch. A narrowing of the Cd angular scan suggests a displacement of some of the Cd atoms in the lattice. A model based on a Te vacancy is presented to describe the data.