Positron diffusion in solids and the reconstruction of inhomogeneous defect distributions from lifetime measurements

Kögel, G.

doi:10.1007/bf01567874

Cited by 30 publications

(16 citation statements)

References 24 publications

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“…This problem was attacked theoretically and experimentally by many authors; some of them are listed in Refs. [4][5][6][7][8]. The size of the scanned volume depends on the positron diffusion length which is equal about 0.1 µm.…”

Section: Introductionmentioning

confidence: 99%

Positron annihilation studies of recrystallization in the subsurface zone induced by friction in magnesium—effect of the inhomogeneity on measured positron annihilation characteristics

Dryzek

2013

Appl. Phys. A

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The discussion of the positron annihilation studies of crystal structure defects, like vacancies, dislocations, grain boundaries and the defect depth profile, is presented. The role of the positron implantation depth and positron diffusion in such studies has been considered in detail. For description of the measured annihilation characteristics the proposed theoretical models take into account both effects. The annealing studies of defects created in pure magnesium by compression or dry sliding-wear were used for demonstration of the discussed thesis. The positron lifetime measurements were applied for monitoring open volume defects behavior. It was demonstrated that annealing at the temperature of about 300°C removes the defects created by compression. Application of the proposed model to description of the data obtained allows to determine the activation energy of the grain boundary mobility in pure magnesium equal to Q = 0.56 ± 0.18 eV. However, defects created by the dry sliding are not completely annealed up to the temperature of 500°C. The defect depth profile induced by dry sliding evolves with the annealing temperature in such a way that at the worn surface concentration of defects gradually decreases but at the depth between 60 and 100 µm the generation of new defects takes place at temperature of 150 and 225°C. Above 300°C the defects still are extended up to the depth of about 80 µm.

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Section: Introductionmentioning

confidence: 99%

Positron annihilation studies of recrystallization in the subsurface zone induced by friction in magnesium—effect of the inhomogeneity on measured positron annihilation characteristics

Dryzek

2013

Appl. Phys. A

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“…The quoted specific function in dependence of γR [eq. (75) in [8]], which determines the mean e + lifetime and the intensity of the trap component, however, is not readily applicable. The appearance of a second-order pole in Eq.…”

Section: Discussionmentioning

confidence: 99%

“…The outer boundary condition ∂ρ l ∂r r=R = 0 (8) reflects the vanishing e + flux through the outer border (r = R) of the diffusion sphere.…”

Section: The Modelmentioning

confidence: 99%

“…(23) are taken into consideration. 8 Given the above initial condition ρ l (0) = ρ p (0) and ρ t (0) = 0.…”

Section: General Case With Voids and Lattice Vacanciesmentioning

confidence: 99%

“…Whereas the kinetics of e + trapping at vacancy-type point defects can be well described by rate theory (so-called simple trapping model), it is well known that for trapping at extended defects like grain boundaries, interfaces, voids, clusters, or precipitates, diffusion limitation of the trapping process may be an issue. Diffusion-limited positron trapping at interfaces and grain boundaries has been quantatively modeled by several groups, ranging from entirely diffusion-controlled trapping [5], diffusion-reaction controlled trapping including detrapping [6][7][8][9], up to diffusion-reaction controlled trapping at grain boundaries and competetive transition-limited trapping at point defects in crystals [8,[10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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Diffusion-reaction model for positron trapping and annihilation at spherical extended defects and in precipitate-matrix composites

2018

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The exact solution of a diffusion−reaction model for the trapping and annihilation of positrons in small extended spherical defects (clusters, voids, small precipitates) with competitive rate-limited trapping in vacancy-type point defects is presented. Closed-form expressions are obtained for the mean positron lifetime and for the intensities of the two positron lifetime components associated with trapping at defects. The exact solutions can be conveniently applied for the analysis of experimental data and allow an assessment in how far the usual approach, which takes diffusion limitation into account by means of effective diffusion-trapping rates, is appropriate. The model is further extended for application to larger precipitates where diffusion-and reaction limited trapping is not only considered for the trapping from the matrix into the precipitate−matrix interface but also for the trapping from inside the precipitates into the interfaces. This makes the model applicable to all type of composite structures where spherical objects are embedded in a matrix irrespective of their size and their number density.

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Decorated vacancy clusters in Si and thin C films grown on Si studied by depth profiling positron annihilation spectroscopies

Brusa

2007

Phys. Status Solidi (c)

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The combined use of different depth profiling positron annihilation spectroscopies give insight on distribution, type and decoration of open‐volume defects. Applications regarding defects produced in modified silicon and at the interface between deposited thin films and the silicon substrate are presented. The attention is focused on selected systems and situations potentially related to technological developments: a) identification of decorated vacancy clusters in silicon implanted by light‐ion (He, He+H) and evolution of the clusters with the thermal treatments; b) release of compressive stress through vacancy‐like defects formation at the interface during the growth of thin (10‐200 nm thick) carbon films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Positron diffusion in solids and the reconstruction of inhomogeneous defect distributions from lifetime measurements

Cited by 30 publications

References 24 publications

Positron annihilation studies of recrystallization in the subsurface zone induced by friction in magnesium—effect of the inhomogeneity on measured positron annihilation characteristics

Positron annihilation studies of recrystallization in the subsurface zone induced by friction in magnesium—effect of the inhomogeneity on measured positron annihilation characteristics

Diffusion-reaction model for positron trapping and annihilation at spherical extended defects and in precipitate-matrix composites

Decorated vacancy clusters in Si and thin C films grown on Si studied by depth profiling positron annihilation spectroscopies

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