Rapid three-dimensional imaging of defect distributions using a high-intensity positron microbeam

Oshima, Nobuyuki; Suzuki, Ryoichi; Ohdaira, Toshiyuki; Kinomura, A.; Narumi, T.; Uedono, Akira; Fujinami, Masanori

doi:10.1063/1.3137188

Cited by 44 publications

(27 citation statements)

References 14 publications

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“…Details of the positron focusing system are described elsewhere. 28 The incident energy of positrons was fixed at 25 keV, and approximately 4 Â 10 6 counts were accumulated. The beam position was set to the center of the sample (see the inset of Fig.…”

Section: Methodsmentioning

confidence: 99%

Vacancy-type defects introduced by plastic deformation of GaN studied using monoenergetic positron beams

Uedono

Yonenaga

Watanabe

et al. 2013

Journal of Applied Physics

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Vacancy-type defects in plastically deformed GaN were studied using monoenergetic positron beams. Dislocations with a Burgers vector of (1/3)[1 210] were introduced by applying compressive stress at 950 C. Measurements of Doppler broadening spectra of the annihilation radiation and positron lifetime spectra showed that both microvoids and Ga-vacancy-type defects were introduced into the deformed sample. The former defects are considered to be introduced through an agglomeration of vacancies introduced by dislocation motions. We observed a distribution of the mean positron lifetime along a long side of the deformed sample, which corresponds to the stress distribution during the deformation. In photoluminescence studies, yellow-band luminescence (2.2 eV) decreased due to the deformation. The suppression of this band was attributed to the vacancy-type defects and/or dislocations introduced by the deformation. V C 2013 AIP Publishing LLC. [http://dx.

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Section: Methodsmentioning

confidence: 99%

Vacancy-type defects introduced by plastic deformation of GaN studied using monoenergetic positron beams

Uedono

Yonenaga

Watanabe

et al. 2013

Journal of Applied Physics

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“…To overcome the problem of the requirement of the large sample size, we developed a positron probe microanalyzer using an electron linear accelerator at the National Institute of Advanced Industrial Science and Technology (AIST). [18][19][20][21] The positron probe microanalyzer is a positron lifetime measurement system, in which a pulsed, brightness enhanced positron beam 22 with a diameter much less than 1 mm is incident on the sample. With positron probe microanalysis (PPMA) it has become possible to perform PALS not only on samples of smaller size but also on a specified region or a point of particular interest on the sample of relatively large size.…”

mentioning

confidence: 99%

Free volume change of elongated polyethylene films studied using a positron probe microanalyzer

Oka

Oshima

Suzuki

et al. 2012

Applied Physics Letters

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Free volume change of low density polyethylene (LDPE) and high density polyethylene (HDPE) films upon mechanical deformation was microscopically investigated by positron probe microanalysis (PPMA). The ortho-positronium (o-Ps) lifetimes were gradually shortened by uniaxial deformation, indicative of shrinkage of the free volume. The o-Ps intensity for HDPE increased by deformation, whereas that for LDPE varied little. It suggests that destruction of crystallites plays an important role in the deformation of HDPE. PPMA is demonstrated to be a promising, powerful probe investigating free volume changes, at different local points subjected to different degrees of deformation, in elongated polymers.

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“…The PPMA is a positron annihilation lifetime measurement system using an intense positron microbeam with a typical beam diameter of about 30-100 μm. 15) A one-dimensional scanning measurement was carried out using the positron probe microanalyzer at beam energy of 30 keV that provides information at depths to 1 μm, a step scan of 0.2 mm and a beam diameter of 100 μm.…”

Section: Time Dependence Of Enhanced Lattice Defectsmentioning

confidence: 99%

Enhanced Lattice Defect Formation Associated with Hydrogen and Hydrogen Embrittlement under Elastic Stress of a Tempered Martensitic Steel

et al. 2012

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Hydrogen behavior and hydrogen-enhanced lattice defect formation under elastic stress of tempered martensitic steel were clarified with respect to dislocations and vacancies by thermal desorption analysis (TDA) using hydrogen as a probe of defects and a positron probe microanalyzer (PPMA). The relationship between hydrogen embrittlement and lattice defects associated with hydrogen was also investigated. The amount of lattice defects increased gradually with increasing time of applied stress during hydrogen charging. The specimen fractured under elastic stress in the presence of hydrogen macroscopically showed brittle fracture without necking. Whereas fracture surface was attributed to localized plastic deformation, since the morphology of the microscopic fracture surface was mostly quasi-cleavage fracture. The increased lattice defects in the near-fracture area were subsequently removed by annealing at 200°C. The mean positron annihilation lifetime measured with the PPMA for a fractured specimen was longer in the near-fracture area than in other areas. Thus, the most probable reason for the increase in the amount of lattice defects can be ascribed to an increase in the amount of vacancies or vacancy clusters. Regarding hydrogen embrittlement involving microscopic plastic deformation, the localized enhanced vacancies due to interactions between dislocations and hydrogen under elastic stress directly caused ductility loss, because ductility loss occurred even though hydrogen was completely removed by degassing before the tensile test. Besides hydrogen content and applied stress, the time of formation and accumulation of vacancies are also concluded to be important factors causing hydrogen embrittlement.

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Rapid three-dimensional imaging of defect distributions using a high-intensity positron microbeam

Cited by 44 publications

References 14 publications

Vacancy-type defects introduced by plastic deformation of GaN studied using monoenergetic positron beams

Vacancy-type defects introduced by plastic deformation of GaN studied using monoenergetic positron beams

Free volume change of elongated polyethylene films studied using a positron probe microanalyzer

Enhanced Lattice Defect Formation Associated with Hydrogen and Hydrogen Embrittlement under Elastic Stress of a Tempered Martensitic Steel

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