Amorphous hydrogenated silicon studied by positron lifetime spectroscopy

Probing of microvoids in high-rate deposited a-Si: H thin films by variable energy positron annihilation spectroscopy

“…Positron lifetimes in a-Si : H films produced by evaporation and by sputtering were measured by Dannefaer et al 9 They found that both types of film contained void-like defects, with sizes estimated to be the equivalent of about five vacancies from comparison of the lifetime components to those for vacancy clusters in crystalline Si. Similar lifetime studies were conducted by Schäefer et al 12 However, the interpretation of the size of the vacancies remains in dispute. This, however, was assigned to a void size smaller than four missing atoms.…”

Defect generation and analysis in mechanically alloyed stoichiometric Fe–Ni alloys

“…PAS is a standard technique used to characterize open volume defects such as vacancies and dislocations in a variety of materials [18]. It also permits an estimate of the free volume fluctuations in condensed matter [19]. PAS has been used to qualitatively assess defect changes in bulk metallic glasses (BMGs) in relation to sub-Tg annealing [20,21], plastic deformation [22,23], cooling rate variations [24] and fatigue-induced cracks [25].…”

Photoinduced Dehydrogenation of Defects in Undopeda-Si:H Using Positron Annihilation Spectroscopy

“…Despite many PAS studies using both positron beams [21,22,25,26] and conventional sources [23,[27][28][29], there is as yet no general consensus on the positron trapping sites in a-Si:H. Much of the uncertainty apparently arises from the variations in film preparation techniques [21,25]. However, evidence exists for four possible positron trapping states, namely, (i) coordination defects ͑1n͒ (ii) divacancylike defects ͑2n͒ (iii) vacancylike agglomerates comprising of ϳ5 missing atoms ͑5n͒, and (iv) large 10-20 Å diameter microvoids in which some positrons exist as bound Ps (MV).…”