Using positron 2D-ACAR as a probe of point defects in GaAs: The As vacancy as a case study

Ambigapathy, R.; Corbel, C.; Hautojärvi, P.; Manuel, Α. A.; Saarinen, K.

doi:10.1007/bf01571688

Cited by 6 publications

(6 citation statements)

References 8 publications

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“…The comparison of figures 1a and 1b shows the following features of similarity in the  curves: a) a broad maximum centered at p x =0; b) a well-defined peak near p x =810 -3 m 0 c; c) a negative tail in the high momentum region. The same features can be found in previous CDB measurements for defected Al [29,30]. On the other hand, it may be noted that the curves in figures 1a and 1b cannot be scaled to a common master curve, as it would be predicted by equation (3) if the morphology of the traps were the same in quenched and in deformed Al.…”

Section: Electron-positron Momentum Spectra In Alsupporting

confidence: 82%

“… The broad maximum at p x =0 comes from the narrowing of the valence electron momentum distribution associated with the reduction of electron density at the defect. This effect is well known since the early studies of positron trapping at defects in metals [44], but is clearly visible also in semiconductors [29,30,42,43].  The negative value taken by Δ at high momentum is simply due to the reduction of the core electron contribution to annihilation, which always occurs when the positron wavefunction becomes localized in an open-volume defect.…”

Section: Electron-positron Momentum Spectra In Almentioning

confidence: 95%

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Nano-structures in Al-based alloys

Folegati

Puska

Staab

2011

J. Phys.: Conf. Ser.

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Simulation of properties of positrons trapped at Cu nanoparticles in Fe matrix J Kuriplach and O Melikhova Investigation of hydrogen interaction with defects in zirconia O Melikhova, J Kuriplach, J ížek et al. Current positron studies of structural modifications in age-hardenable metallic systems A Dupasquier, P Folegati, N de Diego et al.Abstract. The usefulness of first-principles calculations for studying solute-atom clustering in metal alloys is discussed. This usefulness stems directly from the properties predicted by the calculations or via a related interpretation of experimental results. In this paper we review the results of our computational studies on small solute clusters in Al-based alloys. The predicted coincidence Doppler broadening spectra of the positron annihilation method are used to analyse experimental results. The calculated binding energies of small solute atom clusters explain why Cu atoms form two-dimensional platelets on the (100) planes in Al whereas Zn forms three-dimensional clusters. Why is solute-atom clustering in Al-alloys interesting?Aluminium alloys are extensively employed in vehicle industry. The process of ageing, discovered by Alfred Wilm [1] already at the beginning of the 20th century, has been recognized as a tool for strengthening these alloys.Age hardening can be ascribed as precipitation of small particles blocking the crystallographic slip, increasing the resistance to deformation, and hindering the motion of dislocations. It has been recognized that to maximize the hardening one should optimize the size and the distance of the precipitation particles.

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Section: Electron-positron Momentum Spectra In Alsupporting

confidence: 82%

Section: Electron-positron Momentum Spectra In Almentioning

confidence: 95%

Nano-structures in Al-based alloys

Folegati

Puska

Staab

2011

J. Phys.: Conf. Ser.

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“…This effect is well known since the early studies of positron trapping at defects in metals, 7 but is clearly visible also in semiconductors. [8][9][10][11] The sensitivity of the effect to the size of the positron trap can be judged from Fig. 4, which shows the e + -e − momentum one-dimensional ͑1D͒ distribution including only the valence electron contribution; the curve for bulk Al is reported for comparison.…”

Section: Theorymentioning

confidence: 99%

Positron localization effects on the Doppler broadening of the annihilation line: Aluminum as a case study

et al. 2005

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The coincidence Doppler broadening ͑CDB͒ technique is widely used to measure one-dimensional momentum distributions of annihilation photons, with the aim of obtaining information on the chemical environment of open-volume defects. However, the quantitative analysis of CDB spectra needs to include also purely geometrical effects. A demonstration is given here, on the basis of CDB spectra measured in quenched and in deformed pure aluminum. The comparison of the experimental results with ab initio computations shows that the observed differences come from the difference in free volume seen by positrons trapped in quenched-in vacancies or in vacancylike defects associated to dislocations. The computation reproduces accurately all details of CDB spectra, including the peak near the Fermi break, which is due to the zero-point motion of the confined positron.

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“…These techniques are capable of characterizing defects in semiconductors. [17][18][19][20] The CDB method is able to demonstrate electron momentum distributions spectroscopically in a wide range. 21,22 In some cases, the examination of high-momentum region revealed the chemical environments of positron annihilation sites.…”

Section: Introductionmentioning

confidence: 99%

Electron-positron momentum distributions associated with isolated silicon vacancies in3C−SiC

et al. 2005

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Two-dimensional angular correlation of annihilation radiation ͑2D-ACAR͒ and coincidence Doppler broadening ͑CDB͒ of annihilation radiation measurements have been performed on electron-irradiated n-type 3C -SiC in which isolated silicon vacancies are responsible for positron trapping. After irradiation, the intensity of the CDB spectrum increased and decreased in low-and high-momentum regions, respectively. These features were explained by a theoretical calculation considering silicon vacancies. The central region of the 2D-ACAR spectra became isotropic after iradiation, while the overall anisotropies extending within the Jones zone were conserved suggesting that isolated silicon vacancies have tetrahedral symmetry, as expected from a previous electron spin resonance study.

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Using positron 2D-ACAR as a probe of point defects in GaAs: The As vacancy as a case study

Cited by 6 publications

References 8 publications

Nano-structures in Al-based alloys

Nano-structures in Al-based alloys

Positron localization effects on the Doppler broadening of the annihilation line: Aluminum as a case study

Electron-positron momentum distributions associated with isolated silicon vacancies in3C−SiC

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