Calculation of positron annihilation characteristics of six main defects in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>6</mml:mn><mml:mi>H</mml:mi></mml:mrow></mml:math>-SiC and the possibility to distinguish them experimentally

Linez, Florence; Makkonen, Ilja; Tuomisto, Filip

doi:10.1103/physrevb.94.014103

Cited by 13 publications

(9 citation statements)

References 56 publications

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“…7, and the S parameter for saturation trapping in Zn monovacancies is expectedly to be located roughly around S(V Zn )/S c−ZnO ∼ 1.03-1.04 in this S-W diagram. Also, it should be noted that even normalized values of S and W are affected by the energy resolution of the HPGe detector and the energy windows for S and W [49]. The detector resolution and energy windows employed in this study are close to the corresponding settings of Refs.…”

Section: Evolution Of the S-w Points Of The Top And Bottom Zno:al Laysupporting

confidence: 56%

Evolution and role of vacancy clusters at grain boundaries of ZnO:Al during accelerated degradation of Cu(In,Ga)Se2 solar cells revealed by positron annihilation

Shi

Theelen

Illiberi

et al. 2018

Phys. Rev. Materials

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Positron annihilation lifetime spectroscopy (PALS) and Doppler broadening positron annihilation spectroscopy (DB-PAS) depth profiling demonstrate pronounced growth of vacancy clusters at the grain boundaries of as-deposited Al-doped ZnO films deposited as transparent conductive oxide (TCO) on Cu(In, Ga)Se 2 (CIGS) solar cells upon accelerated degradation at 85 • C/85% relative humidity. Quantitative fractions of positrons trapped either in the vacancy clusters at the grain boundaries or in Zn monovacancies inside the grains of ZnO:Al were obtained by detailed analysis of the PALS data using a positron trapping model. The time and depth dependence of the positron Doppler depth profiles can be accurately described using a planar diffusion model, with an extracted diffusion coefficient of 35 nm 2 /hour characteristic for in-diffusion of molecules such as H 2 O and CO 2 into ZnO:Al TCO films via the grain boundaries, where they react with the ZnO:Al. This leads to increased open volume at the grain boundaries that imposes additional transport barriers and may lead to charge carrier trapping and nonradiative recombination. Simultaneously, a pronounced increase in series resistance and a strong reduction in efficiency of the ZnO:Al capped CIGS solar cells is observed on a remarkably similar timescale. This strongly indicates that these atomic-scale processes of molecular in-diffusion and creation of open volume at the grain boundaries play a key role in the degradation of the solar cells.

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Section: Evolution Of the S-w Points Of The Top And Bottom Zno:al Laysupporting

confidence: 56%

Evolution and role of vacancy clusters at grain boundaries of ZnO:Al during accelerated degradation of Cu(In,Ga)Se2 solar cells revealed by positron annihilation

Shi

Theelen

Illiberi

et al. 2018

Phys. Rev. Materials

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“…4(b) represent narrower (S, W ) windows, discussed in the Appendix. We wish to stress that while the (S, W ) windows should be optimized for each material [45], in practice they often are not and "standard" windows are used instead, and the (S, W ) windows used in this work are similar to the "standard" windows. At this point we also wish to point out the fact that the (S, W ) parameters only describe the shape of the Doppler spectrum, without any direct physical interpretation.…”

Section: Positrons In the β-Ga 2 O 3 Latticementioning

confidence: 99%

Split Ga vacancies and the unusually strong anisotropy of positron annihilation spectra in β−Ga2O3

et al. 2020

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We report a systematic first-principles study on positron annihilation parameters in the β-Ga 2 O 3 lattice and Ga monovacancy defects complemented with orientation-dependent experiments of the Doppler broadening of the positron-electron annihilation. We find that both the β-Ga 2 O 3 lattice and the considered defects exhibit unusually strong anisotropy in their Doppler broadening signals. This anisotropy is associated with low symmetry of the β-Ga 2 O 3 crystal structure that leads to unusual kind of one-dimensional confinement of positrons even in the delocalized state in the lattice. In particular, the split Ga vacancies recently observed by scanning transmission electron microscopy produce unusually anisotropic positron annihilation signals. We show that in experiments, the positron annihilation signals in β-Ga 2 O 3 samples seem to be often dominated by split Ga vacancies.

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“…The experimentally determined ðS; WÞ point characteristic of the isolated V Ga is denoted by "V Ga exp." This point and its error bars have been determined by remeasuring and combining [23] the data from electron-irradiated samples [24], He þ ion-irradiated samples [25], and H þ ion-implanted samples [26]. In addition to the experimental data, the figure shows theoretically calculated ðS; WÞ points and positron lifetimes for defects related to V Ga and Be Ga .…”

mentioning

confidence: 99%

Amphoteric Be in GaN: Experimental Evidence for Switching between Substitutional and Interstitial Lattice Sites

et al. 2017

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We show that Be exhibits amphoteric behavior in GaN, involving switching between substitutional and interstitial positions in the lattice. This behavior is observed through the dominance of Be_{Ga} in the positron annihilation signals in Be-doped GaN, while the emergence of V_{Ga} at high temperatures is a consequence of the Be impurities being driven to interstitial positions. The similarity of this behavior to that found for Na and Li in ZnO suggests that this could be a universal property of light dopants substituting for heavy cations in compound semiconductors.

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Calculation of positron annihilation characteristics of six main defects in6H-SiC and the possibility to distinguish them experimentally

Cited by 13 publications

References 56 publications

Evolution and role of vacancy clusters at grain boundaries of ZnO:Al during accelerated degradation of Cu(In,Ga)Se2 solar cells revealed by positron annihilation

Evolution and role of vacancy clusters at grain boundaries of ZnO:Al during accelerated degradation of Cu(In,Ga)Se2 solar cells revealed by positron annihilation

Split Ga vacancies and the unusually strong anisotropy of positron annihilation spectra in β−Ga2O3

Amphoteric Be in GaN: Experimental Evidence for Switching between Substitutional and Interstitial Lattice Sites

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