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Defects of Non-Stoichiometry and Dynamic Stability of SnTe Crystal Lattice

100%

Rogacheva E., Sinelnik N., Nashchekina O., Popov V., Lobkovskaya T.

Acta Physica Polonica A

1993

vol. 84

issue 4

733-736

The temperature dependencies of coefficient of linear expansion α in the range of 4.2-300 K were obtained for SnTe samples with various degrees of deviation from stoichiometry. For the sample of stoichiometric composition in the α vs. temperature curves the anomalies connected with ferroelectric phase transition were detected. It was found that within cubic phase existence region α isotherms have a minimum at 50.4 at.% Te. Maximum dynamic stability at indicated composition is believed to be associated with the formation of vacancy superstructure.

Defect Recovery in α-Fe e^{-}-irradiated at 300 K

80%

Dai G., Li X., Moser P., Moya G., Van Duysen J.

Acta Physica Polonica A

1993

vol. 83

issue 3

277-286

Defect annealing recovery has been studied, by measuring positron lifetime spectra, in high-purity α-iron irradiated at 300 K with 3 MeV electrons to a fluency of 7 × 10^{19} cm^{-2}. Vacancy clusters containing 6-10 single vacancies were observed immediately after irradiation during which they were possibly forming (the so-called "irradiation annealing"). With increasing temperature, the agglomerates continually grow in size at the expense of their concentration, giving rise to the formation of microvoids (> 15 vacancies). Also present were other types of defects, probably immobile vacancies trapped by impurity (e.g. carbon) atoms and dislocation/loops generated presumably from collapse of voids during the relatively high dose irradiation and/or the annealing. The immobile vacancies eventually became movable at around 350 K, supplying the growing clusters and thus leading to a stabilization in their concentration till around 500 K. Between 500 and 700 K, microvoids gradually evaporated, but the dislocation-associated defects were able to survive annealing at temperatures as high as 700 K. The void size and concentration and their evolution have been evaluated on the basis of both the to date theoretical and experimental studies. The temperature dependence was also, observed of positron trapping into vacancy agglomerates of various sizes.

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2 Acta Physica Polonica A

2 1993

1 Dai G.

1 Li X.

1 Lobkovskaya T.

1 Moser P.

1 Moya G.

1 Nashchekina O.

1 Popov V.

1 Rogacheva E.

1 Sinelnik N.

1 Van Duysen J.

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Defects of Non-Stoichiometry and Dynamic Stability of SnTe Crystal Lattice

Defect Recovery in α-Fe e^{-}-irradiated at 300 K