Radiation-induced defect buildup and radiation-enhanced diffusion in a foil under energetic bombardment

ABSTRACTRoot-mean-square diffusion distances for both vacancy and interstitial defects in metals can be very large at elevated temperatures, e.g. several μm's in one second at 500°C. Consequently, defects that escape the implanted region at elevated temperature can produce compositional and microstructural changes to depths which are much larger than the ion range. Because of the high defect mobilities, and of the fact that diffusion processes must compete with the rate of surface recession, the effects of defect production (ballistic mixing), radiation-enhanced diffusion and radiation- induced segregation become spatially separated during ion bombardment at elevated temperature. Results of such experimental studies in a Cu-Ni alloy are presented, discussed and compared with predictions of a phenomenological model. Contributions to the subsurface compositional changes from radiation-enhanced diffusion and radiation- induced segregation are clearly identified.

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Enhancement of the Order/Disorder Reaction in Fe-Ni

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118564 ◽

1985 ◽

Vol 43 ◽

pp. 338-339

Author(s):

Kathleen B. Reuter

Keyword(s):

Phase Diagram ◽

Order Reaction ◽

Enhanced Diffusion ◽

Resistivity Measurements ◽

Voltage Electron ◽

High Voltage Electron Microscope ◽

Radiation Enhanced Diffusion ◽

Radiation Induced ◽

Kinetics Of ◽

Fcc Structure

The Fe-Ni phase diagram is not well understood below 400°C. Of particular interest in this region is a disorder to order reaction whereby Fe-50 wt% Ni transforms from an FCC structure to an L1o superstructure. The kinetics of this transformation, however, are extremely slow (Table I). Therefore, to observe low-temperature transformations in the Fe-Ni system, extremely slow-cooled alloys must be studied (e.g., meteorites) or diffusion must be enhanced. One method to speed diffusion is irradiation. In 1962 Fe-50 wt% Ni was neutron irradiated; electrical resistivity measurements revealed a critical temperature (Tc)of 320°C. In 1977 Fe-50 wt% Ni was irradiated on a high voltage electron microscope (HVEM) and a T of 320°C was again found. A question arises, however, whether radiation enhanced diffusion or whether the radiation induced the transformation, causing a non-equilibrium ordered phase to form.

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Prediction of High Dose Ion Implantation Profiles as Influenced by Radiation Induced Transport and Sputtering

MRS Proceedings ◽

10.1557/proc-45-91 ◽

1985 ◽

Vol 45 ◽

Cited By ~ 1

Author(s):

M. Rangaswamy ◽

D. Farkas

Keyword(s):

Probability Distributions ◽

Practical Interest ◽

High Dose ◽

High Fluence ◽

Enhanced Diffusion ◽

Preferential Sputtering ◽

Radiation Enhanced Diffusion ◽

Defect Probability ◽

Radiation Induced ◽

Effects Of Radiation

ABSTRACTVarious models for predicting high fluence ion collection profiles are reviewed. Recent calculations based on the diffusion approximation are described. The solute and defect probability distributions are calculated by a MONTECARLO code, TRIM. The method takes into account the effects of sputtering, including preferential sputtering of one of the components, and lattice dilation. In addition, the effects of radiation enhanced diffusion and radiation induced segregation are also considered. The calculations include the coupling of solute and defect fluxes. The described formalism can account for observed maximum attainable concentrations and distributions in high fluence implantation conditions of practical interest.

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Atomic Transport in Irradiated Solids

MRS Proceedings ◽

10.1557/proc-311-209 ◽

1993 ◽

Vol 311 ◽

Author(s):

R.R. Averback ◽

Mai Ghaly ◽

Y.Y. Lee ◽

H. Zhu

Keyword(s):

Ion Beam ◽

Rapid Quenching ◽

Primary Role ◽

Melting Points ◽

Crystalline Materials ◽

Enhanced Diffusion ◽

Atomic Transport ◽

Radiation Enhanced Diffusion ◽

Radiation Induced ◽

Kinetics Of

ABSTRACTAtomic transport in irradiated solids has been investigated in both the prompt and delayed regimes. Prompt effects are revealed on an atomic level through molecular dynamics computer simulations. It is demonstrated that for metals like gold, which have high atomic numbers and low melting points, thermal spikes play a primary role in the cascade dynamics and that concepts like melting and rapid quenching are useful descriptions. Surface effects in these metals are also discussed. For metals with higher melting points and lower atomic numbers, the cascade dynamics are determined almost exclusively by energetic collisions far above thermal energies. This is illustrated by simulations of cascades in NiAl. The effect of the high ordering energy in this intermetallic compound on the radiation-induced defect structure has also been studied.Atomic transport in the delayed regime is illustrated by two examples: an order-disorder alloy, Cu3Au, and an amorphous alloy, NiZr. The first example is used to illustrate various aspects of radiation enhanced diffusion (RED): ion beam mixing, diffusion kinetics, the effects of primary recoil spectrum, and the importance of chemical order. The second example illustrates that the basic theory of RED, which was developed to describe crystalline materials, appears to work adequately for amorphous metal alloys, suggesting that similar mechanisms may be operating. It is shown, however, that the kinetics of RED observed in amorphous alloys are not unique to point defect models.

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Ion Implantation At Elevated Temperatures

MRS Proceedings ◽

10.1557/proc-51-467 ◽

1985 ◽

Vol 51 ◽

Cited By ~ 1

Author(s):

Nghi Q. Lam ◽

Gary K. Leaf

Keyword(s):

Present Model ◽

Elevated Temperatures ◽

Synergistic Effects ◽

Concentration Profiles ◽

Enhanced Diffusion ◽

Preferential Sputtering ◽

Radiation Enhanced Diffusion ◽

Spatial Redistribution ◽

Radiation Induced ◽

Effects Of Radiation

ABSTRACTA kinetic model has been developed to investigate the synergistic effects of radiation-enhanced diffusion, radiation-induced segregation and preferential sputtering on the spatial redistribution of implanted solutes during implantation at elevated temperatures. Sample calculations were performed for Al+ and Si+ ions implanted into Ni. With the present model, the influence of various implantation parameters on the evolution of implant concentration profiles could be examined in detail.

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Mechanisms and kinetics of ion implantation

Journal of Materials Research ◽

10.1557/jmr.1986.0251 ◽

1986 ◽

Vol 1 (2) ◽

pp. 251-267 ◽

Cited By ~ 24

Author(s):

Nghi Q. Lam ◽

Gary K. Leaf

Keyword(s):

Ion Implantation ◽

Elevated Temperatures ◽

Synergistic Effects ◽

Implantation Rate ◽

Host Lattice ◽

Ion Energy ◽

Enhanced Diffusion ◽

Preferential Sputtering ◽

Radiation Enhanced Diffusion ◽

Radiation Induced

The evolution of the implant distribution during ion implantation at elevated temperatures has been theoretically studied using a comprehensive kinetic model. In the model foreign atoms, implanted into both interstitial and substitutional sites of the host lattice, could interact with implantation-induced point defects and with extended sinks such as the bombarded surface. The synergistic effects of preferential sputtering, radiation-enhanced diffusion, and radiation-induced segregation, as well as the influence of nonuniform defect production, were taken into account. The bombarded surface was allowed to move in either direction, − x or + x, depending on ion energy, i.e., on the competition between the rates of ion deposition and sputtering. The moving surface was accounted for by means of a mathematical technique of immobilizing the boundary. The ion implantation process was cast into a system of five coupled partial differential equations, which could be solved numerically using a suitable technique. Sample calculations were performed for two systems: Si+ and Al+ implantations into Ni. It has been known from previous studies that in irradiated Ni, Si atoms segregate in the same direction as the defect fluxes, whereas Al solutes migrate in the opposite direction. Thus the effects of different segregation mechanisms, as well as the influence of target temperature, ion energy, and implantation rate on the evolution of implant concentrations in time and space, could be examined with the present model.

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Reduction of Defect Fluxes Using Dual-Ion-Beam Processing

MRS Proceedings ◽

10.1557/proc-316-57 ◽

1993 ◽

Vol 316 ◽

Cited By ~ 1

Author(s):

A. Iwase ◽

L. E. Rehn ◽

P. M. Baldo ◽

P. R. Okamoto ◽

H. Wiedersich ◽

...

Keyword(s):

Elevated Temperatures ◽

Ion Beam ◽

Beam Irradiation ◽

Near Surface ◽

Enhanced Diffusion ◽

Dual Beam ◽

Radiation Enhanced Diffusion ◽

Simultaneous Irradiation ◽

Radiation Induced ◽

Red Radiation

ABSTRACTRadiation-induced segregation (RIS) in Ni-12.7% Si and Cu-1% Au alloys was studied using Rutherford backscattering spectroscopy during He and Ne irradiation at elevated temperatures. During single ion-beam irradiation with 1.5 MeV He, strong RIS of Si toward the surface was observed in Ni-12.7% Si. Simultaneous irradiation with 400 keV Ne and 1.5 MeV He almost completely suppressed the Si segregation, even when the calculated damage production rate by Ne was only a few percent of that by He ions. A similar effect of dual-beam irradiation was observed in the Cu-1% Au alloy, i.e., the rate of near surface Au depletion was strongly reduced under simultaneous irradiation. The present result shows that dual-beam irradiation can be applied to control RIS and RED (Radiation Enhanced Diffusion) during ion beam processing.

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RADIATION-ENHANCED DIFFUSION AND RADIATION-INDUCED SEGREGATION

Radiation Effects in Solids - NATO Science Series ◽

10.1007/978-1-4020-5295-8_6 ◽

2007 ◽

pp. 123-151 ◽

Cited By ~ 6

Author(s):

Todd R. Allen ◽

Gary S. Was

Keyword(s):

Enhanced Diffusion ◽

Radiation Enhanced Diffusion ◽

Radiation Induced

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Mechanisms and Kinetics of Iion Beam-Induced Compositional Modifications

MRS Proceedings ◽

10.1557/proc-100-29 ◽

1988 ◽

Vol 100 ◽

Cited By ~ 4

Author(s):

N. Q. Lam

Keyword(s):

Synergistic Effects ◽

Relative Significance ◽

Near Surface ◽

Enhanced Diffusion ◽

Thermally Activated ◽

Target Composition ◽

Radiation Enhanced Diffusion ◽

Radiation Induced ◽

The Individual ◽

Kinetics Of

ABSTRACTNear-surface compositional modification of ion-bombarded alloys results from the dynamic interplay of several atomistic processes. In addition to displacement mixing leading to t randomization of atomic locations, which is dominant at relatively low temperatures, and preferential loss of alloying elements by sputtering, many thermally-activated processes, including radiation-enhanced diffusion, radiation-induced segregation and Gibbsian adsorption, also play important roles. The relative contributions of these processes to the evolution of the target composition profile depends on the target materials and irradiation variables. Although a good understanding of the individual processes has been achieved, information regarding their synergistic effects on alloy surface modification is still limited. In the present article, these processes will be characterized in simple physical terms, and the present understanding of their relative significance and contributions in changing the target composition during ion bombardment will be discussed in view of recent progress in theoretical modeling and experimental study.

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