Electron Irradiation Induced Vacancy Defects Detected by Positron Annihilation in 6H-SiC

2005 ◽  
Vol 483-485 ◽  
pp. 473-476 ◽  
Author(s):  
Marie France Barthe ◽  
L. Henry ◽  
S. Arpiainen ◽  
G. Blondiaux
Keyword(s):  
Temperature Dependence ◽  
Positron Annihilation ◽  
Electron Energy ◽  
Electron Irradiation ◽  
Positron Lifetime ◽  
Resolution Function ◽  
Vacancy Defects ◽  
Nitrogen Doped

This paper presents positron lifetime results which give information on the nature of vacancy defects induced by electron irradiation in bulk nitrogen doped (nD-nA= 2.3x1017 cm-3) Cree 6H-SiC. The electron irradiations have been performed at different energies and with different fluences from 5􀂗1017 e-cm-2 to 3􀂗1018 e-cm-2. Positron lifetime have been measured with a 22NaCl source as a function of temperature between 15 and 300 K. The lifetime spectra were analyzed as sums of two exponential lifetime components 􀁗i weighted by the intensities Ii, convoluted with the resolution function. From the temperature dependence of the lifetime spectra we can infer that several vacancy defects exist in the electron irradiated n-type 6H-SiC. The nature of detected vacancy defects depends on the electron energy.

scholarly journals Positron annihilation characteristics in UO2: for lattice and vacancy defects induced by electron irradiation

2007 ◽  
Vol 4 (10) ◽  
pp. 3627-3632 ◽  
Author(s):  
M.-F. Barthe ◽  
H. Labrim ◽  
A. Gentils ◽  
P. Desgardin ◽  
C. Corbel ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Electron Irradiation ◽  
Vacancy Defects

scholarly journals A positron annihilation study of defect accumulation in phosphorus- and titanium-alloyed austenitic stainless steels under electron irradiation at room temperature

2020 ◽  
pp. 27-34
Author(s):  
D. A. Perminov ◽  
Keyword(s):  
Positron Annihilation ◽  
Electron Irradiation ◽  
Stainless Steels ◽  
Room Temperature ◽  
Austenitic Stainless Steels ◽  
Positron Annihilation Spectroscopy ◽  
High Concentration ◽  
Noticeable Effect ◽  
Vacancy Defects ◽  
Positron Annihilation Study

The effect of phosphorus and titanium additions on the accumulation of vacancy defects in Cr16Ni15Mo3 austenitic stainless steels under electron irradiation at room temperature is studied by positron annihilation spectroscopy. It is shown that, at this temperature, phosphorus has no noticeable effect on the accumulation of vacancy defects. This is due to the low mobility of vacancies and the low concentration of impurities. Titanium, due to its high concentration, enhances the accumulation of vacancy defects during irradiation, but this effect is weak.

scholarly journals Vacancies in electron irradiated 6H silicon carbide studied by positron annihilation spectroscopy

2003 ◽  
Vol 792 ◽  
Author(s):  
C. H. Lam ◽  
C. C. Ling ◽  
C. D. Beling ◽  
S. Fung ◽  
H. M. Weng ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Positron Annihilation ◽  
Electron Irradiation ◽  
Room Temperature ◽  
Positron Lifetime ◽  
Positron Annihilation Spectroscopy ◽  
Isochronal Annealing ◽  
Positron Lifetime Spectroscopy ◽  
Irradiation Process ◽  
Positron Lifetime Measurement

ABSTRACTPositron lifetime spectroscopy was employed to study the as-electron-irradiated (10 MeV, 1×1018 cm-2) n-type 6H silicon carbide sample in the measuring temperature range of 15 K to 294 K. Isochronal annealing studies were also performed up to the temperature of 1373 K by carrying out the room temperature positron lifetime measurement. Negatively charged carbon vacancies and VCVSi divacancy were identified as the major vacancy type defects induced by the electron irradiation process. The concentration of the VCVSi divacancy was found to decrease dramatically after the 1973 K annealing.

Positron Lifetime Studies of Irradiated Ultra-High Molecular Weight Polyethylene and Composites Made of Martian Regolith

2014 ◽  
Vol 783-786 ◽  
pp. 1585-1590 ◽  
Author(s):  
Naidu V. Seetala ◽  
Naeem Tull-Walker ◽  
Abhijit Baburaj ◽  
Jian Ren Zhou ◽  
Richard Wilkins ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Positron Annihilation ◽  
High Molecular Weight ◽  
Free Volume ◽  
Irradiation Dose ◽  
Positron Lifetime ◽  
Positron Source ◽  
Vacancy Defects ◽  
Martian Regolith ◽  
Ultra High Molecular Weight

Positron Annihilation Lifetime Spectroscopy (PALS) is used to study the nanoporosity and fractional free volume in Ultra High Molecular Weight Polyethylene (UHMWPE) and composites with the addition of Martian Regolith (UHMWPE-MR) as-made and irradiated with56Fe heavy ions at an energy of 600 MeV/u to three different doses (10, 32, 64 Gy). The positron lifetime spectra were obtained using22Na positron source and the spectra were analyzed to two lifetime components using POSFIT program. First short lifetime component around 0.28 ns is related to positron annihilation in material including vacancy defects and the second long lived component around 1.7 ns is due to Positronium formation in free volume pores. UHMWPE-MR composites were shown to be less porous with much lower nanopores concentration compared to the UHMWPE polymer. The average size of the nanopores is around 0.5 nm (obtained from a simple model). Larger variations in positron lifetime parameters are observed with increasing irradiation dose for UHMWPE polymer compared to UHMWPE+MR composites. The 3-point bend test results also showed larger variations with increasing irradiation dose for the UHMWPE polymer. The variations in PALS parameters may indicate an increasing competition between two processes at higher irradiation doses: 1) vacancy defects aggregation and 2) escape of vacancy defects as the local temperature increases at higher doses resulting in increased vacancy defects mobility. Present results clearly indicate a qualitative inverse relationship between nanoscale porosity measured by positron life time and mechanical properties of UHMWPE and its composite with MR.

Vacancy Defects Induced by Low Energy Electron Irradiation in 6H and 3C-SiC Monocrystals Characterized by Positron Annihilation Spectroscopy and Electron Paramagnetic Resonance

2006 ◽  
Vol 527-529 ◽  
pp. 571-574 ◽  
Author(s):  
X. Kerbiriou ◽  
Marie France Barthe ◽  
S. Esnouf ◽  
P. Desgardin ◽  
G. Blondiaux ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Positron Annihilation ◽  
Electron Irradiation ◽  
Positron Annihilation Spectroscopy ◽  
Low Energy ◽  
Energy Electron ◽  
Paramagnetic Resonance ◽  
Vacancy Defects ◽  
Low Energy Electron ◽  
Electron Paramagnetic

In this work we used Positron Annihilation Spectroscopy (PAS) and Electron Paramagnetic Resonance (EPR) to investigate the properties of vacancy defects produced by low energy electron irradiation. N-doped 3C-SiC and 6H-SiC monocrystals have been irradiated with electrons at different energies from 240keV to 900keV. EPR measurements show that Frenkel pairs VSi 3-/Si are created in 6H-SiC when electron irradiation is performed at low energy (240-360 keV). EPR also indicates that the silicon displacement threshold energy is higher in 3C-SiC than in 6HSiC. Moreover, PAS results show that the size and concentration of the vacancy defects decrease when the electron energy decreases for both polytypes. PAS detects vacancy defects in 240keV electron irradiated 3C-SiC, and the detection of the carbon vacancy is proposed.

scholarly journals Positron Annihilation Lifetime Spectroscopy in the study of defects in materials

2019 ◽  
Vol 24 ◽  
pp. 235
Author(s):  
K. Triantou ◽  
K. Mergia ◽  
I. E. Stamatelatos
Keyword(s):  
Positron Annihilation ◽  
Electron Density ◽  
Positron Lifetime ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Vacancy Defects ◽  
Positron Annihilation Lifetime ◽  
Defect Site ◽  
Experimental Apparatus ◽  
Valuable Method ◽  
Positron Lifetimes

The Positron Annihilation Lifetime Spectroscopy (PALS) is a valuable method for the study of the open volume defects in materials. The reduced electron density at the vacant/defect site increases the positron lifetime, and positron lifetime increases as the size of defect increases. In the current paper the experimental apparatus for the measurement of the positron lifetime in materials is described and the spectra from W and Cd specimens are analyzed. The presence of dislocations and vacancy defects is found, since the positron lifetimes of specimens are higher than the defect-free (bulk) values.

Electron Irradiated InP: A Positron Annihilation Study

1992 ◽  
Vol 262 ◽  
Author(s):  
T. Bretagnon ◽  
S. Dannefaer ◽  
D. Kerr
Keyword(s):  
Positron Annihilation ◽  
Charge State ◽  
Electron Irradiation ◽  
Positron Lifetime ◽  
Lifetime Measurements ◽  
Positron Annihilation Study

ABSTRACTPositron lifetime measurements show that electron irradiation produces indium vacancy related defects in InP. Divacancies are also found in semi-insulating and lightly doped p and n-type materials. Temperature investigations show a change in the divacancy charge state.

Temperature Dependence of Double Shockley Stacking Fault Behavior in Nitrogen-Doped 4h-Sic Studied by In-Situ Synchrotron X-Ray Topography

2020 ◽  
Author(s):  
Fumihiro Fujie ◽  
Shunta Harada ◽  
Kenji Hanada ◽  
Hiromasa Suo ◽  
Haruhiko Koizumi ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Stacking Fault ◽  
X Ray ◽  
Nitrogen Doped ◽  
Fault Behavior
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