Positron trapping at vacancies in electron-irradiated Si at low temperatures

Mäkinen, J.; Corbel, C.; Hautojärvi, P.; Moser, P.; Pierre, F.

doi:10.1103/physrevb.39.10162

Cited by 118 publications

(44 citation statements)

References 41 publications

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“…This can be interpreted as decreasing of the vacancy formation volume in transition from PV 0 to PV − , which agrees with DLTS (Ref. 9) and positron lifetime 10,11 experiments. The magnitude of inward relax- Normally, a substitutional P atom, having before ionization five electrons ͑s 2 p 3 ͒ in its outer electronic shell, is in the state P + , which means that one valence electron is donated to the conduction band, while the remaining four electrons provide bonding to the surrounding Si atoms.…”

Section: Discussionsupporting

confidence: 89%

“…These DLTS results indicate the shrinkage of the E-center in the transition from neutral to negative charge state. Later positron life time experiments by Mäkinen et al 10,11 confirmed the inward relaxation associated with this kind of charge transition. These findings are in agreement with molecular dynamics simulation, 12 based on the CarParrinello approach, 13 which also shows the inward relaxation of the first neighbor shell of a vacancy.…”

Section: Introductionmentioning

confidence: 91%

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Electronic structure of the phosphorus-vacancy complex in silicon: A resonant-bond model

2004

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All material supplied via Aaltodoc is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user.Powered by TCPDF (www.tcpdf.org) Using first-principles calculations, the electronic structure of the phosphorus-vacancy pair in silicon has been studied. Detailed analysis of the atomic displacement fields associated with the atomic structure optimization after the defect formation indicates a strong dependence of the character and magnitude of relaxation both on the supercell size and the E-center charge state. Our simulation results strongly suggest that the E-center structure is of the resonant-bond type with a strong localization of an electron pair at the phosphorus atom. The energy level splitting for shared electrons in a vacancy due to the appearance of the resonance distortion is discussed, as well as the nature of and the reasons for the level occupation.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 91%

Electronic structure of the phosphorus-vacancy complex in silicon: A resonant-bond model

2004

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“…3.5 x 1 0' ' cm-'ns while fkom [74] 1 -5 x 10" cm -'ns . Using the average value and the average of trapping rate per unit dose (Table 8) the new value is 0.5 cm-', and from the reirradiated sarnple (Table 6) we find 0.7 f 0.2 cm-' (at 3.3 MeV).…”

Section: Chapter Fivementioning

confidence: 95%

Positron annihilation investigation of vacancies in as-grown and electron-irradiated diamonds

Bretagnon

Kerr

et al. 2000

Diamond and Related Materials

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Permission has been granted to the Libnry of The University of Manitoba to lend or sen copies of this thesislpracticum, to the National Library of Canada to microfilm this thesis/practicum and to lend or seil copies of the film, and to Dissertations Abstracts international to pubiisb an abstract of this thesis/prrcticum.The author reserves other publication rights, and neither this thesis/prrcticum nor extensive extracts from it m a y be printed or otherwisc reproduccd without the author's written permission. Abstract ABSTRACTVacancy-type defects in the four main types of diamond (Ia, Ib, IIa and IIb) were investigated using positron lifetime, Doppler broadening and optical absorption spectroscopies. In unirradiated sarnples vacancy clusters were found in al1 types, synthetic as well as natural. These clusters are situated in highly defected regions, rather than homogeneously distributed, and their concentration varies significantly from sample to sample. For synthetic Tt, diamonds vacancy clusters were investigated as a function of nitrogen content. The bulk positron lifetime for diamond is calculated to be 98 + 2 ps and the bulk Doppler S parameter is estimated to be 25% lower than that for silicon. Electron irradiation (2.3 MeV) produced neutral monovacancies in IIa diamond and the positron data correlated well, as a function of dose, with the GR1 optical zero-phonon line (the optical absorption at 740nm arise fiom neutral monovacancies in diarnond); the introduction rate was estimated to be 0.5 k 0.2 cm-'. In Ib diamond monovacancies were found to be negatively charged whereas they were neutral in IIa diamonds. The positron lifetime for monovacancies was (40 t 6)% larger than the bulk lifetime and the Doppler S parameter increased by (8 + 1)%. At-temperature Doppler measurements between 30 and 770 K indicated that irradiation-produced neutral monovacancies can convert to the negatively charged state above 400 K but this was dependent on diamond type.Isochronal annealing of irradiated Ib diarnonds showed that the complex of a substitutional nitrogen and a vacancy, formed upon annealing close to 6 0 0°c , undergoes two detectable modifications between 600 and 870 OC reaching a configuration stable to 1 170 OC . Key conclusions based on positron and optical data are in mutual accord.

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“…No experimental Doppler broadening data exists for the monovacancy in Si. Mäkinen et al 46 and Polity et al 47 obtained the positron lifetimes of 273 and 282 ps, respectively, for the monovacancy in Si created by electron irradiation. Taking into account that the calculated bulk lifetime with the LDA lattice constant used ͑208 ps͒ is lower than the experimental ones by Mäkinen et al and Polity et al ͑221 and 218 ps, respectively͒ we conclude that our result for the lifetime is in a good agreement with experiment.…”

Section: Neutral Monovacancy In Simentioning

confidence: 99%

Modeling the momentum distributions of annihilating electron-positron pairs in solids

2006

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Measuring the Doppler broadening of the positron annihilation radiation or the angular correlation between the two annihilation gamma quanta reflects the momentum distribution of electrons seen by positrons in the material. Vacancy-type defects in solids localize positrons and the measured spectra are sensitive to the detailed chemical and geometric environments of the defects. However, the measured information is indirect and when using it in defect identification comparisons with theoretically predicted spectra is indispensable. In this article we present a computational scheme for calculating momentum distributions of electron-positron pairs annihilating in solids. Valence electron states and their interaction with ion cores are described using the all-electron projector augmented-wave method, and atomic orbitals are used to describe the core states. We apply our numerical scheme to selected systems and compare three different enhancement ͑electron-positron correlation͒ schemes previously used in the calculation of momentum distributions of annihilating electron-positron pairs within the density-functional theory. We show that the use of a state-dependent enhancement scheme leads to better results than a position-dependent enhancement factor in the case of ratios of Doppler spectra between different systems. Further, we demonstrate the applicability of our scheme for studying vacancy-type defects in metals and semiconductors. Especially we study the effect of forces due to a positron localized at a vacancytype defect on the ionic relaxations.

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Positron trapping at vacancies in electron-irradiated Si at low temperatures

Cited by 118 publications

References 41 publications

Electronic structure of the phosphorus-vacancy complex in silicon: A resonant-bond model

Electronic structure of the phosphorus-vacancy complex in silicon: A resonant-bond model

Positron annihilation investigation of vacancies in as-grown and electron-irradiated diamonds

Modeling the momentum distributions of annihilating electron-positron pairs in solids

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