Positron Annihilation Techniques as Nondestructive Tool for Probing Nanosized Open-Volume Defects in Materials (abstract)

2009 ◽  
Author(s):  
Mona Mohsen ◽  
Beverly Karplus Hartline ◽  
Renee K. Horton ◽  
Catherine M. Kaicher
Keyword(s):  
Positron Annihilation ◽  
Open Volume

The SiO2/Si Interface Probed With Positrons

1987 ◽  
Vol 105 ◽  
Author(s):  
Bent Nielsen ◽  
K. G. Lynn ◽  
T. C. Leung ◽  
D. O. Welch ◽  
G. Rubloff
Keyword(s):  
Heat Treatment ◽  
Elevated Temperature ◽  
Positron Annihilation ◽  
Positron Beam ◽  
The State ◽  
Open Volume ◽  
Variable Energy ◽  
Thermally Grown

AbstractThe effects of the heat treatment of Si covered with a thermally-grown ˜50 nm overlayer of SiO2 were probed by means of measurements of positron annihilation characteristics obtained with a variable-energy positron beam. From measurements at elevated temperature (˜500°C) it was observed that positrons implanted overlapping the SiO2/Si interface decay from a state with properties distinctively different from the state in Si and in SiO2. The nature of the annihilation characteristics indicates the presence of open volume defects.

Identification of open-volume defects in disordered and amorphized Si: A depth-resolved positron annihilation study

2001 ◽  
Vol 63 (22) ◽  
Author(s):  
G. Amarendra ◽  
R. Rajaraman ◽  
G. Venugopal Rao ◽  
K. G. M. Nair ◽  
B. Viswanathan ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Open Volume ◽  
Positron Annihilation Study

Annealing Properties of Defects in BF2+ Implanted Silicon

1996 ◽  
Vol 438 ◽  
Author(s):  
T. Kitano ◽  
M. Watanabe ◽  
A. Yaoita ◽  
S. Oguro ◽  
A. Uedono ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Thermal Annealing ◽  
Depth Profile ◽  
Annealing Temperature ◽  
Projected Range ◽  
Large Size ◽  
Open Volume ◽  
Major Species

AbstractThe annealing properties of defects in BF2+ implanted silicon were investigated using positron annihilation, TEM and SIMS techniques. For the as-implanted specimens, the major species of defects was identified to be divacancies. After thermal annealing, vacancy-fluorine complexes were formed. The size of open volume in the vacancy-fluorine complexes became larger with increasing annealing temperature. Even after 1100 °C , the vacancy-fluorine complexes were still stable with the size of open volume close to V5. The depth profile of vacancy-fluorine complexes was not largely changed after re-crystallization. In this way, the fluorine atoms played an important role in forming the defects with a large size of open volume. After 1100°C annealing, the fluorine atoms piled up at two regions; the projected range of fluorine and the original amorphous/crystalline interface, where bubbles were observed by TEM. The vacancy-fluorine complexes detected by positron annihilation might be precursors of the bubbles observed by TEM.

The 3d Electrons and Microdefects in Binary Ti-Al Alloys Studied by Positron Annihilation

2011 ◽  
Vol 399-401 ◽  
pp. 99-102
Author(s):  
Wen Deng ◽  
Xiao Lei Guo ◽  
Bing Xie ◽  
Ding Kang Xiong ◽  
Yu Yang Huang
Keyword(s):  
Grain Boundary ◽  
Positron Annihilation ◽  
Free Electron ◽  
Positron Lifetime ◽  
Al Alloys ◽  
Doppler Broadening ◽  
Al Content ◽  
Open Volume ◽  
Ti Content ◽  
Coincidence Doppler Broadening

The behavior of 3d electrons and microdefects in binary Ti-Al alloys with Al contents from 47at.% to 53at.% have been studied by coincidence Doppler broadening and positron lifetime techniques. It has been found that the 3d electron signals in the spectra of binary Ti-Al alloys increase with Ti content. In Al-rich Ti-Al alloys, on increasing Al content, the open volume of defect on grain boundary increases while the density of free electron decreases. On the contrary, in Ti-rich Ti-Al alloys, on increasing Ti content, the open volume of defect on grain boundary decreases, and the electron density of the grain boundary increases.

Defect Detection in Fe-Cr Alloys with Positron Annihilation Doppler Broadening Spectroscopy

2012 ◽  
Vol 733 ◽  
pp. 270-273 ◽  
Author(s):  
Veronika Sabelová ◽  
Martin Petriska ◽  
Jana Veterníková ◽  
Vladimir Slugeň ◽  
Jarmila Degmová ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Positron Beam ◽  
Quantitative Information ◽  
Structural Defects ◽  
Doppler Broadening ◽  
Positron Energy ◽  
Open Volume ◽  
Order Of Magnitude ◽  
Radiation Induced ◽  
Induced Defects

Positron annihilation Doppler broadening spectroscopy (DBS) has been used for the detection of structural defects in Fe-9wt%Cr (Fe-9Cr) alloy in the as-prepared and implanted states. Defects were created by He and H ion implantation with a kinetic energy of 250 keV. DBS is a non-destructive method and is a unique tool for the observation of open volume defects like vacancies and vacancy clusters in solids. A positron beam with variable positron energy was used for the measurement of defect depth profiles up to 1.5 µm. The obtained results provide qualitative and semi-quantitative information about radiation induced defects and their chemical environment. Although the collision damage from helium implantation was one order of magnitude higher than for the case of hydrogen, the changes in S and W parameters are much less significant, probably due to considerably lower mobility of helium in the implanted materials, which results in helium capture by the created open volume defects.

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

Annealing Properties of Defects in Bf2+ Implanted Silicon

1996 ◽  
Vol 439 ◽  
Author(s):  
T. Kitano ◽  
M. Watanabe ◽  
A. Yaoita ◽  
S. Oguro ◽  
A. Uedono ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Thermal Annealing ◽  
Depth Profile ◽  
Annealing Temperature ◽  
Projected Range ◽  
Large Size ◽  
Open Volume ◽  
Major Species

AbstractThe annealing properties of defects in BF2+ implanted silicon were investigated using positron annihilation, TEM and SIMS techniques. For the as-implanted specimens, the major species of defects was identified to be divacancies. After thermal annealing, vacancy-fluorine complexes were formed. The size of open volume in the vacancy-fluorine complexes became larger with increasing annealing temperature. Even after 1100 °C, the vacancy-fluorine complexes were still stable with the size of open volume close to V5. The depth profile of vacancy-fluorine complexes was not largely changed after re-crystallization. In this way, the fluorine atoms played an important role in forming the defects with a large size of open volume. After 1100°C annealing, the fluorine atoms piled up at two regions; the projected range of fluorine and the original amorphous/crystalline interface, where bubbles were observed by TEM. The vacancy-fluorine complexes detected by positron annihilation might be precursors of the bubbles observed by TEM.

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.

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