Role of open volume defects in Mg-doped GaN films studied by positron annihilation spectroscopy

2005 ◽  
Vol 72 (16) ◽  
Author(s):  
S. Hautakangas ◽  
K. Saarinen ◽  
L. Liszkay ◽  
J. A. Freitas ◽  
R. L. Henry
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Open Volume ◽  
Mg Doped

High-density magnetic-vacancy inclusion in Co2MnGa single crystal probed by spin-polarized positron annihilation spectroscopy

2021 ◽  
Author(s):  
Atsumi Miyashita ◽  
M. Maekawa ◽  
Y. Shimoyama ◽  
N. Seko ◽  
Atsuo Kawasuso ◽  
...  
Keyword(s):  
Single Crystal ◽  
Positron Annihilation ◽  
Electrical Transport ◽  
Positron Annihilation Spectroscopy ◽  
Ordered Structure ◽  
Electrical Transport Properties ◽  
Weyl Semimetal ◽  
Spin Polarized ◽  
B2 Structure

Abstract Co2MnGa is a Weyl semimetal exhibiting giant anomalous Hall and Nernst effects. Using spin-polarized positron annihilation spectroscopy, we examined a Bridgman-grown Co2MnGa single crystal with a nearly perfect L21-ordered structure and a reference Co2MnAl polycrystal with a Mn-Al-disordered B2 structure. We found that a large amount of magnetic vacancies (more than 100 ppm) were included in the Co2MnGa crystal but not the Co2MnAl crystal. We discuss possible reasons for the inclusion of vacancies, the role of vacancies in the development of the ordered structure, and the electronic states associated with the vacancies. Towards the development of Co2MnGa-based devices, the manners for reducing vacancies as well as the influence of vacancies on the electrical transport properties should be considered.

scholarly journals Spectroscopy of defects in neutron irradiated ammono-thermal GaN by combining photoionization, photoluminescence and positron annihilation techniques

2020 ◽  
Vol 59 (4) ◽  
Author(s):  
Jevgenij Pavlov ◽  
Tomas Čeponis ◽  
Laimonas Deveikis ◽  
Tanja Heikkinen ◽  
Jyrki Raisanen ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Thermal Method ◽  
Radiation Defects

In this work, pulsed photoionization as well as photoluminescence and positron annihilation spectroscopy were combined to detect different species of defects. The GaN crystals, grown by the ammono-thermal method, doped with Mn as well as Mg impurities and irradiated with different fluences of reactor neutrons, were examined to clarify the role of the technological and radiation defects. The evolution of the prevailing photoactive centres was examined by pulsed photoionization spectroscopy. Positron annihilation spectroscopy was applied to reveal vacancy-type defects.

Investigation of Dual-Beam-Implanted Oxide-Dispersed-Strengthened FeCrAl Alloy by Positron Annihilation Spectroscopy

2012 ◽  
Vol 331 ◽  
pp. 149-163 ◽  
Author(s):  
Reinhard Kögler ◽  
Wolfgang Anwand ◽  
Asta Richter ◽  
Maik Butterling ◽  
A. Mücklich ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Positron Annihilation ◽  
Defect Formation ◽  
Positron Annihilation Spectroscopy ◽  
Vacancy Clusters ◽  
Open Volume ◽  
Dual Beam ◽  
Hardness Increase ◽  
Ods Alloy ◽  
Nuclear Applications

Oxide-dispersion-strengthened (ODS) FeCrAl steel is a class with promising materials to be applied for future nuclear applications. However, radiation damage, especially the formation of vacancy clusters or gas-filled bubbles, may result in hardness increase and the loss of ductility. Positron annihilation spectroscopy (PAS) is demonstrated to be a very useful and non-destructive analysis method to detect and to determine open volume defects of sub-nm size in ODS alloy. Synchronized dual beam implantation of Fe and He ions is performed to simulate the radiation damage caused by (n, α) reactions and to avoid induced activation. For room temperature implantation, i.e. without significant point defect recombination, the differences in the defect formation are shown by comparison between irradiation of ODS alloy and pure Fe bulk. The open volume defects created in ODS alloy are vacancy clusters closely connected with dispersed Y oxide nanoparticles. Their profiles are in reasonable qualitative agreement with the hardness profiles, indicating a relationship between sub-nm vacancy clusters or He bubbles and the hardness of the material. In heat-treated ODS alloy, containing larger vacancy clusters, the radiation induced hardness increase is more distinctive than for as-received ODS alloy. For irradiation at a moderately enhanced temperature of 300°C open volume defects are drastically reduced. The few remaining defects are vacancy clusters of the same type as in as-received ODS alloy. Close to the surface the open volume defects completely disappear. These results are in agreement with the hardness measurements showing little hardness increase in this case. The suitability of ODS-based materials for nuclear applications was verified.

(Invited) Positron Annihilation Spectroscopy on Open-Volume Defects in Group IV Semiconductors

2014 ◽  
Vol 64 (11) ◽  
pp. 241-253 ◽  
Author(s):  
J. Slotte ◽  
F. Tuomisto ◽  
J. Kujala ◽  
A. M. Holm ◽  
N. Segercrantz ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Group Iv ◽  
Group Iv Semiconductors ◽  
Open Volume

Doppler broadening positron annihilation spectroscopy: A technique for measuring open-volume defects in silsesquioxane spin-on glass films

1999 ◽  
Vol 74 (15) ◽  
pp. 2146-2148 ◽  
Author(s):  
Mihail P. Petkov ◽  
Marc H. Weber ◽  
Kelvin G. Lynn ◽  
Kenneth P. Rodbell ◽  
Stephan A. Cohen
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Open Volume ◽  
Glass Films

scholarly journals Short Range Chemical Ordering in Bulk Metallic Glasses

2000 ◽  
Vol 644 ◽  
Author(s):  
P. A. Sterne ◽  
P. Asoka-Kumar ◽  
J. H. Hartley ◽  
R. H. Howell ◽  
T.G. Nieh ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Metallic Glasses ◽  
Bulk Metallic Glasses ◽  
Critical Density ◽  
Positron Annihilation Spectroscopy ◽  
Atomic Scale ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Chemical Ordering ◽  
Open Volume

AbstractWe provide direct experimental evidence for a non-random distribution of atomic constituents in Zr-based multi-component bulk metallic glasses using positron annihilation spectroscopy. The Ti content around the open-volume regions is significantly enhanced at the expense of Cu and Ni, indicating that Cu and Ni occupy most of the volume bounded by their neighboring atoms while Ti and Zr are less closely packed and more likely to be associated with open-volume regions. Temperature-dependent measurements indicate the presence of at least two different characteristic sizes for the open volume regions. Measurements on hydrogen- charged samples show that the larger open-volume regions can be filled by hydrogen up to a critical density. Beyond this critical density, local atomic-scale open-volume damage is created in the sample to accommodate additional hydrogen. The onset of this local damage in positron annihilation data coincides with the onset of volume expansion in X-ray diffraction data.

Characterization of Mg doped GaN by positron annihilation spectroscopy

2002 ◽  
Vol 92 (4) ◽  
pp. 1898-1901 ◽  
Author(s):  
Jeremy Moxom ◽  
Jun Xu ◽  
R. Suzuki ◽  
T. Ohdaira ◽  
George Brandes ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Annihilation Spectroscopy ◽  
Mg Doped

scholarly journals Positron Annihilation Spectroscopy in Material studies

2019 ◽  
Vol 29 (4) ◽  
pp. 501 ◽  
Author(s):  
P. Horodek ◽  
L. H. Khiem ◽  
K. Siemek ◽  
L. A. Tuyen ◽  
A. G. Kobets
Keyword(s):  
Positron Annihilation ◽  
Science And Technology ◽  
Nuclear Research ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Atomic Energy ◽  
Joint Institute ◽  
Experimental Techniques ◽  
Open Volume ◽  
Material Studies

Positron annihilation spectroscopy (PAS) is a method dedicated to detection of open-volume type of defects in materials. Nowadays, this technique is of a great interest due to the practical character of obtained results. New devices using monoenergetic positron beams are built. The paper presents the basics of PAS, a description of popular experimental techniques and their application on the basis of results obtained in the frame of collaboration between Joint Institute for Nuclear Research (JINR), Institute of Physics - Vietnamese Academy of Science and Technology (VAST) and Vietnam Atomic Energy Institute (Vinatom).. The positron beam with energy up to 35 keV and other apparatus for PAS studies are under operation in Dubna.

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