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Surface modification of solids

Description: The use of ion beam and pulsed laser processing is reviewed for the near-surface modification of a wide range of materials. The techniques of ion implantation doping, ion beam and laser mixing, and pulsed-laser annealing are stressed with particular emphasis on the nonequilibrium aspects of these processing techniques and on new materials properties which can result. Examples are presented illustrating the utility of these techniques for fundamental materials research as well as practical surface modifications.
Date: May 1, 1984
Creator: Appleton, B.R.
Partner: UNT Libraries Government Documents Department

A National Spallation Neutron Source for neutron scattering

Description: The National Spallation Neutron Source is a collaborative project or perform the conceptual design for a next generation neutron source for the Department of Energy. This paper reviews the need and justification for a new neutron source, the origins and structure of the collaboration formed to address this need, and the community input leading up to the current design approach. A reference design is presented for an accelerator based spallation neutron source that would begin operation at about 1 megawatt of power but designed so that it could be upgraded to significantly higher powers in the future. The technology approach, status, and progress on the conceptual design to date are presented.
Date: October 1, 1996
Creator: Appleton, B.R.
Partner: UNT Libraries Government Documents Department

Laser annealing of ion implanted silicon

Description: Pulsed laser annealing of ion implanted silicon leads to the formation of supersaturated alloys by nonequilibrium crystal growth processes at the interface occurring during liquid phase epitaxial regrowth. The interfacial distribution coefficients from the melt (k') and the maximum substitutional solubilities (C/sub s//sup max/) are far greater than equilibrium values. Both K' and C/sub s//sup max/ are functions of growth velocity. Mechanisms limiting substitutional solubilities are discussed. 5 figures, 2 tables.
Date: January 1, 1980
Creator: White, C.W.; Appleton, B.R. & Wilson, S.R.
Partner: UNT Libraries Government Documents Department

Structural alterations in SiC as a result of Cr/sup +/ and N/sup +/ implantation

Description: Ion scattering and channeling techniques were used to study production of disorder and randomization of SiC by implantation of Cr/sup +/ and N/sup +/ at doses of up to 3 x 10/sup 16/ /cm/sup 2/ for Cr/sup +/ and 8 x 10/sup 16/ /cm/sup 2/ for N/sup +/. Experiments were designed so that the calculated damage energy profiles would be well matched for the two ion species. The results were compared for the degree of effectiveness of Cr/sup +/ and N/sup +/ in producing disorder. At higher doses, Cr/sup +/ was much more effective than N/sup +/ for a given damage energy using the same calculational method for Cr/sup +/ as for N/sup +/. In correlated studies of swelling, both species had about the same effectiveness in producing swelling.
Date: January 1, 1982
Creator: Williams, J.M.; McHargue, C.J. & Appleton, B.R.
Partner: UNT Libraries Government Documents Department

Reversibility effects in disordered and ordered solids leading to scattered-ion yield enhancements near 180/sup 0/

Description: A general review is given of the recently discovered phenomenon of enhanced ion backscattering near 180/sup 0/. Examples of experimental results are presented that illustrate the nature of the enhancement and its basic dependences on angle and depth. It is shown that the various aspects of the effect can be reproduced by computer simulations that include the effects of trajectory reversibility, nuclear recoils and detector depth resolution. Measured and calculated results are given that illustrate the dependences of the enhancement on ion and target parameters. Results are presented of the enhancement observed in amorphous Ge and in a single crystal of Ge rotated to create a reference spectrum. The enhancement is greater for the rotating crystal case demonstrating crystalline effects on the enhancement. Also presented are some results for the enhancement of the surface yield in a channeling direction of a crystal in the 180/sup 0/ geometry; possible application for surface studies is discussed.
Date: March 1, 1981
Creator: Appleton, B.R.; Holland, O.W. & Barrett, J.H.
Partner: UNT Libraries Government Documents Department

Evidence of surface migration and formation of catalytically inactive Pt in corrosion studies of Pt/sup +/ implanted Ti

Description: This investigation is part of an ongoing research project directed at applying the techniques of ion implantation doping and ion scattering analysis to identify the mechanisms associated with the anodic dissolution of Ti-Pt alloys. The Ti-Pt alloys produced by ion implantation were electrochemically examined in hydrogen saturated 1 N H/sub 2/SO/sub 4/ by both potentiostatic polarization and open-circuit potential methods. In this study, Ti samples implanted to relatively high doses (5.4 x 10/sup 15/ to 2.9 x 10/sup 16/ atoms/cm/sup 2/) were examined by ion scattering analysis at various stages in the electrochemical measurements. Quantitative measurements showed that the majority of the implanted Pt accumulated on the surface during anodic dissolution and underwent large scale surface migration. Evidence is also presented for the transition of the Pt on the surface from a catalytically active to inactive state. Possible mechanisms for the observed catalytically inactive Pt are discussed.
Date: August 1, 1980
Creator: Appleton, B.R.; Kelly, E.J.; White, C.W.; Thompson, N.G. & Lichter, B.D.
Partner: UNT Libraries Government Documents Department

Comparison of effects of pulsed Ruby laser and pulsed electron beam annealing of /sup 75/AS/sup +/ implanted silicon

Description: Ion-backscattering, ion-channeling, and transmission electron microscopy (TEM) were used to study a series of ion implanted silicon samples that were annealed with either a pulsed laser or a pulsed electron beam. Single crystal ((001) orientation) silicon samples were implanted with either 35 or 100 keV /sup 75/As/sup +/ to a dose of approx. 1 x 10/sup 16/ As/cm/sup 2/ and subsequently annealed with either a Q-switched pulsed Ruby laser or the electron beam generator. A series of energy densities was used in both cases to optimize results. It was determined from backscattering that the as-implanted profiles were redistributed in essentially the same manner for both types of anneals, indicating that melting and rapid recrystallization has occurred. For the 35 keV /sup 75/As/sup +/ implanted samples the two techniques produced equivalent anneals with no remaining damage as indicated by channeling and TEM. However, for the 100 keV implants the anneal was not uniform across the sample in the electron beam case and the channeling minimum yields for the major axes ((110), (111), and (100)) were higher than the laser annealed results. In both cases, the As substitutionality (97 to 99%) and minimum yields are better than results obtained from conventional thermal annealing.
Date: December 1, 1978
Creator: Wilson, S.R.; Appleton, B.R.; White, C.W. & Narayan, J.
Partner: UNT Libraries Government Documents Department

Near surface yield enhancement in narrow acceptance 180/sup 0/ elastic scattering for He ions in non-crystalline and poly-crystalline solids. [0. 8 to 1. 6 MeV]

Description: Observations of an unusual near-surface (0 less than or equal to x less than or equal to 700A) yield enhancement in the energy distribution of elastically scattered He ions from amorphous and polycrystalline materials is reported. The integrated excess yield for small (theta/sub 1/2/ = 0.2/sup 0/) versus large (theta/sub 1/2/ = 4.5/sup 0/) acceptance angle at 180/sup 0/ scattering is typically 20% for He energies in the range 0.2 less than or equal to E less than or equal to 2.5 MeV. Maximum peak-to-normal yield ratios as high as 60 to 70% were observed. Materials in which the effect was observed include amorphous germanium, the glassy metal alloy Nb/sub 40/Ni/sub 60/, fine-grained polycrystalline Au, Pt, Mo, and Cu, and also single crystals of Si and Au continuously rotated during data collection to simulate a random lattice. The excess yields are largest for materials of atomic number above Z = 40, and decreases rapidly for elements below this value. The angular width and depth dependences of this effect suggest that it is sensitive to multiple scattering and also imply that the particle, upon scattering, must retrace its inward path within a cone of less than or equal to 0.2/sup 0/ from depths comparable to or less than a few hundred Angstroms. 5 figures.
Date: January 1, 1979
Creator: Pronko, P P; Appleton, B R; Holland, O W & Wilson, S R
Partner: UNT Libraries Government Documents Department

Electrochemical behavior of titanium implanted with platinum

Description: The following conclusions apply to Ti(Pt) near-surface alloys studied. (1) Open-circuit corrosion measurements show that accumulation of platinum may occur at a surface concentration of 0.32 atomic percent Pt while no accumulation occurs at 0.16 atomic percent Pt. However, these results do not allow a distinction as to cause of accumulation to be made between concentration effects and effects due to the presence of an oxide film. (2) Potentiostatic corrosion at -0.450 V (active corrosion) establish that little or no accumulation of platinum occurs at an oxide-free surface for concentrations less than 0.086 atomic percent Pt; whereas, a large amount of accumulation occurs for a distribution with a peak concentration of 0.83 atomic percent Pt. (3) An initial distribution having a peak concentration of 0.32 atomic percent platinum is sufficient to induce natural passivity in titanium and bring a freely corroding sample to a potential of 0.269 V. This is nearly the applicable reversible potential (-0.260 V) for the hydrogen reaction in 1N H/sub 2/SO/sub 4/. (4) Of three samples which showed accumulation, platinum was eventually lost for two of these samples (0.32 atomic percent, open-circuit corrosion; 0.83 atomic percent, potentiostatic corrosion). The remaining sample (9.1 atomic percent, open-circuit corrosion) maintained the maximum possible potential of -0.260 V for the length of the experiment (approx. 30 days). (5) For samples which had been polarized at -0.300 to -0.340 V and which had eventually reverted to the behavior of pure Ti, post corrosion RBS measurements reveal that a substantial fraction of the Pt fluence is retained on the surface in an electrochemically inactive state.
Date: January 1, 1979
Creator: Thompson, N.G.; Lichter, B.D.; Appleton, B.R.; Kelly, E.J. & White, C.W.
Partner: UNT Libraries Government Documents Department

Pulsed laser and ion beam surface modification of sintered alpha-SiC. [Using Ni overlayers]

Description: Pulsed laser annealing and ion beam mixing have been used as surface modification techniques to enhance the physical properties of polycrystalline ..cap alpha..-SiC. Thin Ni overlayers (20 nm to 100 nm) were evaporated onto the SiC surface. The specimens were subsequently irradiated with pulses of a ruby or krypton fluoride (KrF) excimer laser or bombarded with high energy Xe/sup +/ or Si/sup +/ ions. Both processes are nonequilibrium methods and each has been shown to induce unique microstructural changes at the SiC surface which are not attainable by conventional thermal treatments. Under particular (and optimum) processing conditions, these changes considerably increased the mechanical properties of the SiC; following laser irradiation, the fracture strength of the SiC was increased by as much as 50%, but after ion beam mixing, no strength increase was observed. High resolution cross-section transmission electron microscopy (X-TEM), scanning electron microscopy (SEM), and Rutherford backscattering techniques were used to characterize the extent of mixing between the Ni and the SiC as a result of the surface modification.
Date: December 2, 1985
Creator: More, K.L.; Davis, R.F.; Appleton, B.R.; Lowndes, D. & Smith, P.
Partner: UNT Libraries Government Documents Department

Lattice location of As and Sb implanted in silicon after annealing with a pulsed ruby laser. [Implanted with 100 keV /sup 75/As and /sup 121/Sb]

Description: The lattice location of implanted arsenic and antimony in single crystal silicon ((100) orientation) after pulsed laser annealing was studied using positive ion channeling-backscattering. The samples were implanted with 100 keV /sup 75/As or /sup 121/Sb to doses in the range 1 x 10/sup 15/ to 3 x 10/sup 16//cm/sup 2/ and subsequently annealed using the Q-switched output of a pulsed ruby laser (1.5 to 1.7 J/cm/sup 2/, approx. 50 x 10/sup -9/ sec pulse duration). Channeling measurements (2.5 MeV He/sup +/ ions) along major axial directions ((100), (110), and (111)) and detailed scans across the axes were used to determine the lattice location of the implanted dopants after annealing. In the dose range investigated, 98 to 99% of the As occupy substitutional sites. Antimony doses less than 1.5 x 10/sup 16//cm/sup 2/ yield similar results. Electrical measurements of the number of electrically active dopants support the high substitutional fractions observed by the ion channeling-backscattering measurements. Also reported are channeling results for /sup 75/As implanted (approx. 1 x 10/sup 16/ As/cm/sup 2/) samples that were annealed with an electron beam generator. Substitutional fractions (97 to 99%) comparable to laser annealing were obtained, but some nonuniformities across the samples were observed that were not present in the laser annealed samples.
Date: December 1, 1978
Creator: Wilson, S.R.; White, C.W.; Pronko, P.P.; Young, R.T. & Appleton, B.R.
Partner: UNT Libraries Government Documents Department

Kinetic effects and mechanisms limiting substitutional solubility in the formation of supersaturated alloys by pulsed laser annealing

Description: Pulsed laser annealing of silicon implanted by Group (III,V) dopants leads to the formation of supersaturated alloys by nonequilibrium processes occurring in the interfacial region during liquid phase epitaxial regrowth. The distribution coefficient from the melt (k') and the maximum dopant substitutional solubility (C/sub s//sup max/) are far greater than equilibrium values and both are functions of growth velocity. Substitutional solubility is limited by lattice strain and by constitutional supercooling at the interface during regrowth. Values for C/sub s//sup max/ obtained at different velocities are compared with predictions of thermodynamic limits for solute trapping.
Date: November 1, 1980
Creator: White, C.W.; Appleton, B.R.; Stritzker, B.; Zehner, D.M. & Wilson, S.R.
Partner: UNT Libraries Government Documents Department

Lattice location of implanted As and Sb in silicon after pulsed laser annealing

Description: The substitutional fractions for As and Sb implanted into silicon and subjected to pulsed laser annealing have been determined using ion channeling techniques. Substitutional fractions of 98 to 99% are achieved by laser annealing for both of these dopants at doses up to approximately 1.4 x 10/sup 16//cm/sup 2/. Channeling results are also presented showing the effect of different laser energy densities on the removal of lattice damage and the incorporation of As into substitutional lattice sites.
Date: August 1, 1978
Creator: White, C.W.; Pronko, P.P.; Appleton, B.R. & Wilson, S.R.
Partner: UNT Libraries Government Documents Department

Coherent-precipitate formation in Tl-implanted Si

Description: Ion scattering, ion channeling, and cross-section electron microscopy were used to investigate Si single crystals implanted with /sup 205/Tl/sup +/ (0.29 - 1 x 10/sup 16/ Tl/cm/sup 2/, 90 keV) and annealed with pulses (1.6 J/cm/sup 2/, 15 ns) from a ruby laser. Coherent precipitates of Tl were found to form as a result of laser processing. The systematics of the effect are presented and a formation mechanism proposed.
Date: September 1, 1982
Creator: Appleton, B. R.; Narayan, J.; White, C. W.; Williams, J. S. & Short, K. T.
Partner: UNT Libraries Government Documents Department

Comparison of pulsed electron beam-annealed and pulsed ruby laser-annealed ion-implanted silicon. [100keV As/sup +/]

Description: Recently two new techniques, pulsed electron beam annealing and pulsed laser annealing, have been developed for processing ion-implanted silicon. These two types of anneals have been compared using ion-channeling, ion back-scattering, and transmission electron microscopy (TEM). Single crystal samples were implanted with 100 keV As/sup +/ ions to a dose of approx. 1 x 10/sup 16/ ions/cm/sup 2/ and subsequently annealed by either a pulsed Ruby laser or a pulsed electron beam. Our results show in both cases that the near-surface region has melted and regrown epitaxially with nearly all of the implanted As (97 to 99%) incroporated onto lattice sites. The analysis indicates that the samples are essentially defect free and have complete electrical recovery.
Date: November 1, 1978
Creator: Wilson, S.R. (Oak Ridge National Lab., TN); Appleton, B.R.; White, C.W.; Narayan, J. & Greenwald, A.C.
Partner: UNT Libraries Government Documents Department

Ion implantation and laser annealing of high T/sub c/ superconducting materials

Description: The materials investigated consisted of thin films of Nb-Ge, V-Si, Nb-N, Nb-C-N and Nb-Ir prepared by evaporation, sputtering or CVD onto substrates of alumina, sapphire or polycrystalline Hastelloy B. Single crystals of Nb/sub 3/Ir, NbN, V/sub 3/Si and V/sub 3/Ge were also studied and some laser annealing results will be presented. Laser annealing was performed in air using a Q-switched, (15 x 10/sup -9/ sec duration), Ruby laser with energy densities ranging from 0.1 to 10 J/cm/sup 2/. Single, sometimes overlapping, pulses were used. The texture, microstructure and phase composition of the films were examined by x-ray diffraction. Ion scattering and nuclear reaction analysis were used to determine stoichiometries versus depth in the films. Near-surface melting was monitored from ion scattering measurements of the depth profiles of an ion implanted marker species before and after laser annealing. Surface topography was monitored with optical microscopy and SEM. Ion channeling analysis was utilized to determine lattice defect configurations and damage effects to the single crystal samples. These various analyses were correlated to measurements of superconducting transition temperatures, T/sub c/, before and after laser annealing.
Date: December 1, 1979
Creator: Appleton, B.R.; White, C.W.; Stritzker, B.; Meyer, O.; Gavaler, J.R.; Braginski, A.I. et al.
Partner: UNT Libraries Government Documents Department

Application of nuclear reactions for quantitative hydrogen analysis in a variety of different materials problems

Description: The application of nuclear reaction techniques to hydrogen analysis problems in metallurgical, mineralogical and semi-conductor areas are described. Hydrogen analyses and profiles obtained with both the /sup 1/H(/sup 19/F,..cap alpha gamma..)/sup 16/O and /sup 1/H(/sup 15/N,..cap alpha gamma..)/sup 12/C reactions are presented. The advantages and disadvantages of the two techniques are discussed. Both crystalline and amorphous materials are examined. Particular emphasis will be given to interpretative problems associated with analyzing the data. Various corrections to the data will be discussed, including off-resonance cross-section corrections and lower energy resonance corrections. The hydrogen content of electrodeposited hard gold films has been determined as a function of plating conditions. Hydrogen contents as high as 9 atom percent have been measured. The hydrogen profile of natural and synthetic SiO/sub 2/ samples was determined. Hydrogen was found to be quite stable in amorphous silica samples but highly mobile in crystalline quartz samples under the analysis conditions. A hydrogen depth profile for a film of glow and discharge deposited amorphous silicon (approximately 4500 A thick) has been obtained and will be compared with a profile measured by secondary ion mass spectrometry (SIMS) on the same sample.
Date: January 1, 1977
Creator: Clark, G. J.; White, C. W.; Allred, D. D.; Appleton, B. R.; Koch, F. B. & Magee, C. W.
Partner: UNT Libraries Government Documents Department

Structure of ceramic surfaces modified by ion-beam techniques

Description: A wide variety of structures are produced by ion implantation in ceramics. Random (substitutional and interstitial site occupancy) solid solutions with concentrations of solute that exceed the solubility limit can be produced in Al/sub 2/O/sub 3/. The changes that occur during annealing are complex and sometimes unpredictable. Silicon carbide becomes amorphous in a manner analogous to Si for ion fluences that produce more than 0.2 dpa damage. Light (N) and heavy (Cr) ions produce similar results if the fluence is scaled to damage energy deposited. Because of mass differences in the ions, two damage regions are developed in TiB/sub 2/. The structure remains crystalline to very high damage levels. These structural alterations cause changes in the surface mechanical properties. Since virtually any chemical species can be implanted, one can independently control structural damage and chemical effects. When coupled with selective annealing, this technique has the potential for producing a wide range of surface structures and properties. 8 figures.
Date: January 1, 1982
Creator: McHargue, C.J.; Naramoto, H.; White, C.W.; Williams, J.M.; Appleton, B.R.; Sklad, P.S. et al.
Partner: UNT Libraries Government Documents Department

New materials properties achievable by ion implantation doping and laser processing

Description: It is well established that ion implantation techniques can be used to introduce selected impurities into solids in a controlled, accurate and often unique manner. Recent experiments have shown that pulsed laser processing of materials can lead to surface melting, dopant redistribution and crystal regrowth, all on extremely short time scales (approx. < 1 ..mu.. sec.). These two processes can be combined to achieve properties not possible with normal materials preparation techniques, or to alter materials properties in a more efficient manner. Investigations are presented utilizing the combined techniques of positive ion scattering-channeling, x-ray scattering and transmission electron microscopy which show that supersaturated alloys can be formed in the surface regions (approx. 1 ..mu..m) of ion implanted, laser annealed silicon single crystals, and that these surfaces undergo a unique one dimensional lattice contraction or expansion depending on the dopant species. The resultant surface has a lattice parameter significantly different from the bulk, is free from any damage defects, has essentially all the dopant atoms in substitutional sites and the impurity concentrations can exceed solid solubility limits by more than an order of magnitude.
Date: December 1, 1978
Creator: Appleton, B.R.; Larson, B.C.; White, C.W.; Narayan, J.; Wilson, S.R. & Pronko, P.P.
Partner: UNT Libraries Government Documents Department

Damage rates of MeV Al ions in aluminum

Description: Damage rates of 5 MeV /sup 27/Al ions in Al have been measured as a function of the ion path length in Al. The technique developed for this study employed evaporated Al thin film (approximately 0.4 - 0.5 ..mu..m thick), electrical resistivity specimens, as a damage sensor and variation in ion path lengths were obtained by insertion of thin foils of Al immediately in front of the resistivity specimen. Irradiations and electrical resistance measurements were carried out below 10/sup 0/K to ''freeze in'' the displacement damage and to provide suitable conditions for precision electrical measurements. The resistance increase due to irradiation is a measure of the displacement damage resulting from ion-atom collisions in the specimen. The damage rates vary about an order of magnitude over the range of the ions and are in general agreement with calculated damage rates obtained from theory. 9 fig.
Date: November 1, 1976
Creator: Noggle, T. S.; Appleton, B. R.; Williams, J. M.; Oen, O. S.; Biggerstaff, J. A. & Iwata, T.
Partner: UNT Libraries Government Documents Department

Investigations of radiative electron capture by ion channeling techniques

Description: The unique constraints imposed on the interactions of energetic heavy ions as a result of the channeling effect are utilized to investigate the phenomenon of radiative electron capture (REC) for 17 to 40 MeV oxygen ions. Measured cross-sections and widths of the REC radiation are compared with calculations made specifically for the channeling situation.
Date: February 1, 1976
Creator: Appleton, B.R.; Ritchie, R.H.; Biggerstaff, J.A.; Noggle, T.S.; Datz, S.; Moak, C.D. et al.
Partner: UNT Libraries Government Documents Department

Amorphization of Ceramics by Ion Beams

Description: The influence of the implantation parameters fluence, substrate temperature, and chemical species on the formation of amorphous phases in Al/sub 2/O/sub 3/ and ..cap alpha..-SiC was studied. At 300/sup 0/K, fluences in excess of 10/sup 17/ ions.cm/sup -2/ were generally required to amorphize Al/sub 2/O/sub 3/; however, implantation of zirconium formed the amorphous phase at a fluence of 4 x 10/sup 16/ Zr.cm/sup -2/. At 77/sup 0/K, the threshold fluence was lowered to about 2 x 10/sup 15/ Cr.cm/sup -2/. Single crystals of ..cap alpha..-SiC were amorphized at 300/sup 0/K by a fluence of 2 x 10/sup 14/ Cr.cm/sup -2/ or 1 x 10/sup 15/ N.cm/sup -2/. Implantation at 1023/sup 0/K did not produce the amorphous phase in SiC. The micro-indentation hardness of the amorphous material was about 60% of that of the crystalline counterpart.
Date: January 1, 1984
Creator: McHargue, C. J.; Farlow, G. C.; White, C. W.; Williams, J. M.; Appleton, B. R. & Naramoto, H.
Partner: UNT Libraries Government Documents Department

Laser induced defects and materials interactions in the V-Si system

Description: Pulsed laser annealing has been evaluated as a technique for fabricating superconducting V/sub 3/Si from multilayer V-Si samples, and the nature of laser-induced defects in V/sub 3/Si single crystals has been examined. Correlated analyses by ion scattering, ion channeling, T/sub c/ measurements and TEM were used to examine the composition and structure of samples subjected to single and multiple laser pulses. It was observed that although the superconducting A15 phase could be formed by pulsed laser mixing, the associated rapid quenching effects introduced defects which were not completely removed by thermal annealing to 925 K for 1 hour. Ion channeling and TEM studies of V/sub 3/Si single crystals showed that pulsed laser irradiation caused microcracks to develop in the surface, probably from mechanical stresses induced by thermal gradients.
Date: January 1, 1980
Creator: Appleton, B.R.; Stritzkner, B.; White, C.W.; Narayan, J.; Fletcher, J.; Meyer, O. et al.
Partner: UNT Libraries Government Documents Department