Positron annihilation spectroscopy of the interface between nanocrystalline Si and SiO2

Pi, Xiaodong; Coleman, P. G.; Harding, Ruth E.; Davies, Gordon; Gwilliam, R.; Sealy, B.J.

doi:10.1016/j.physb.2003.09.180

Cited by 3 publications

(3 citation statements)

References 22 publications

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“…Guessoum, Ramaty and Lingenfelter (1991) added spectral considerations to the positron-dust process but kept a simplified picture of the dust and showed that unless the abundance of dust in the annihilation regions is increased many times compared to "normal" quantities, grains change the spectrum of the line mostly in the hot phase. Astrophysical knowledge of grains has since increased considerably (see the reviews by Draine 2003, Li 2004, and Krugel 2003 and although a huge body of work exists on positron interactions with solids and solid surfaces (Nieminen & Oliva 1980;Huttunen et al 1990;Dannefaer et al 1996;Dupasquier & Mills 1995;Puska & Nieminen 1994;Weiss et al 1994;Suzuki et al 2003;Mills et al 1989;Mokrushin et al 2003;Pi et al 2003;Weber & Lynn 2000), experiments dealing with positrons and dust like materials remain scarce. We here summarize our best understanding of the relevant information we have collected on dust grains in our context.…”

Section: Grains and Positron Processesmentioning

confidence: 99%

The lives and deaths of positrons in the interstellar medium

Guessoum

Jean

Gillard

2005

A&A

101

178

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Abstract. We reexamine in detail the various processes undergone by positrons in the interstellar medium (ISM) from their birth to their annihilation using the most recent results of positron interaction cross sections with atomic and molecular hydrogen, as well as helium. The positrons' lives are divided into two phases: the "in-flight" phase (between ≈1 MeV and tens of eV) and the thermal phase. The first phase is treated with a Monte Carlo simulation that allows us to determine the fraction of positrons that form positronium and annihilate as well as the characteristics of the annihilation emission as a function of the medium conditions. The second phase is treated with a binary reaction rate approach, with cross sections adopted from experimental measurement or theoretical calculations. An extensive search and update of the knowledge of positron processes was thus undertaken. New reaction rates and line widths have been obtained. We investigate the treatment of the complicated interactions between positrons and interstellar dust grains. Fully relevant data were not always available, but we were nonetheless able to reach satisfactory understanding of positron annihilation on grains, both qualitatively and quantitatively. All factors of the problem have been considered, including the grain size distribution and composition, the electric charge of the grains, the backscattering, positronium formation and ejection from the grain, the pick-off annihilation inside them and the partial destruction of dust in the hot regions of the ISM. New reaction rates and widths of the line resulting from the annihilation inside and outside of the grain have been obtained. The final results of our calculations (reaction rates and spectra) showed that dust is only important in the hot phase of the ISM, where it dominates all other processes. Combining the new calculations, we have constructed annihilation spectra for each phase of the ISM, considering various grain contents, as well as an overall combined spectrum for the ISM as a whole.

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Section: Grains and Positron Processesmentioning

confidence: 99%

The lives and deaths of positrons in the interstellar medium

Guessoum

Jean

Gillard

2005

A&A

101

178

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“…2(a), so positronium exists in the porous SiO 2 . Hence the S-E curve is still higher than that of standard Si [11,12] .…”

Section: Doppler Broadening Of Gamma Linementioning

confidence: 83%

Identification of pore size in porous SiO ₂ thin film by positron annihilation

et al. 2009

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“…From '99, works have been carried out to deepen the knowledge on SiO 2 /Si interface [3][4][5][6][7][8] and to study positronium (Ps) formation in SiO 2 thin film on crystalline Si substrate [8,9]. The interface between Si nanocrystals embedded into thermally grown SiO 2 matrix has been also investigated [10,11]. Recently, a new approach based on the interaction of many positrons with the target has been used to study the dynamics of laser-induced paramagnetic centers in a-SiO 2 [12].…”

Section: Introductionmentioning

confidence: 99%