A positron study of plastic deformation of silicon

1983 ◽  
Vol 61 (3) ◽  
pp. 451-459 ◽  
Author(s):  
S. Dannefaer ◽  
N. Fruensgaard ◽  
S. Kupca ◽  
B. Hogg ◽  
D. Kerr
Keyword(s):  
Plastic Deformation ◽  
Room Temperature ◽  
Functional Form ◽  
Isothermal Annealing ◽  
Positron Lifetime ◽  
Activation Enthalpy ◽  
Isochronal Annealing ◽  
Doppler Broadening ◽  
Trapping Rate ◽  
Vacancy Clusters

Positron lifetime and Doppler broadening experiments have been conducted in silicon which was subjected to various degrees of plastic deformation. With increasing plastic deformation (from 2.5 to 38%) the trapping rate per unit dislocation concentration decreased from about 8 × 1015 to 4.5 × 1015 s−1 as measured at room temperature. Two annealing stages were identified by isochronal annealing, one of which had an activation enthalpy of 3.2 to 3.8 eV as determined by isothermal annealing. Measurements in the temperature range 15 to 673 K show that the positron annihiliation parameters (lifetimes, intensities, and S-parameters) depend strongly on temperature and that the functional form of these dependencies is related to the state of annealing of the deformed samples. These results are disscussed in terms of the presence of vacancy clusters and dislocations, and evidence is presented indicating the existence of the hexavacancy.

Microstructural Evolution of Radiation Induced Defects In ZnO During Isochronal Annealing

1998 ◽  
Vol 540 ◽  
Author(s):  
S. Brunner ◽  
W. Puff ◽  
P. Mascher ◽  
A.G. Balogh
Keyword(s):  
Room Temperature ◽  
Proton Irradiation ◽  
Positron Lifetime ◽  
Thermal Evolution ◽  
Isochronal Annealing ◽  
Doppler Broadening ◽  
Thermal Dependence ◽  
Radiation Induced ◽  
Induced Defects ◽  
Mev Protons

AbstractIn this study we discuss the microstructural changes after electron and proton irradiation and the thermal evolution of the radiation induced defects during isochronal annealing. The nominally undoped samples were irradiated either with 3 MeV protons to a fluence of 1.2× 1018 p/cm2 or with 1 MeV electrons to a fluence of 1×1018 e/cm2. The investigation was performed with positron lifetime and Doppler-broadening measurements. The measurements were done at room temperature and in some cases down to 10 K to investigate the thermal dependence of the trapping characteristics of the positrons.

Annealing Study of Al-Mg Wrought Alloys Using Two Different Techniques and Estimation of the Activation Enthalpy of Migrating Defects

2013 ◽  
Vol 337-338 ◽  
pp. 29-37
Author(s):  
Ahmed G. Attallah ◽  
M.A. Abdel-Rahman ◽  
M. El-Sayed ◽  
A.A. Ibhraim ◽  
S.A. Aly ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Electrical Resistivity ◽  
Annealing Time ◽  
Room Temperature ◽  
Isothermal Annealing ◽  
Activation Enthalpy ◽  
Full Recovery ◽  
Mg Alloy ◽  
Annealing Study

The electrical resistivity and the corresponding mechanical properties (hardness) of some 5xxx Al-Mg alloy processed by plastic deformation were investigated. Plastic deformation was performed at room temperature. Isothermal annealing produced a significant change in both the electrical and mechanical properties of the samples. As the annealing time was increased, the resistivity and hardness up to full recovery. The activation enthalpy of migration of defects was determined, was found to be 0.234±0.06 eV, 0.218±0.049 eV, 0.316±0.016 eV 0.232±0.012 eV for 5005, 5251, 5052 and 5754 alloys, respectively.

Dislocation Recovery in Casting Alloy by Positron Lifetime Technique

2008 ◽  
Vol 280-281 ◽  
pp. 113-119
Author(s):  
M.A. Abdel-Rahman ◽  
M.S. Abdallah ◽  
N.A. Kamel ◽  
Emad A. Badawi
Keyword(s):  
Annealing Temperature ◽  
Positron Lifetime ◽  
Activation Enthalpy ◽  
The Other ◽  
Isochronal Annealing ◽  
Casting Alloy ◽  
Perfect Lattice ◽  
Mean Lifetime ◽  
Recovery Behavior ◽  
Fast Cooling

Recovery behavior of 20% plastically deformation of casting AlSi11.35Mg0.23 in various stages of isochronal annealing has been investigated by positron Lifetime (LT). The experimental results show that the positron mean lifetime is a function of annealing temperature. Lifetime of the positron annihilating in perfect lattice is 187.3ps and in 20% deformed is 229.8 ps. There are two regions in the isochronal annealing, one of them relating to the point defect and the other to the dislocation. The activation enthalpy for the dislocation is calculated from the isothermal study in the dislocation region from (575-675) K by slow and fast cooling as 0.16±0.02 and 0.53±0.06 eV respectively.

Determination of the activation enthalpy for migration of dislocations in plastically deformed 8006 Al-alloy by positron annihilation lifetime technique

2016 ◽  
Vol 30 (18) ◽  
pp. 1650110 ◽  
Author(s):  
Mohammed Salah ◽  
M. Abdel-Rahman ◽  
Emad A. Badawi ◽  
M. A. Abdel-Rahman
Keyword(s):  
Plastic Deformation ◽  
Positron Annihilation ◽  
Point Defects ◽  
Isothermal Annealing ◽  
Activation Enthalpy ◽  
Hydraulic Press ◽  
Al Alloy ◽  
Slow Cooling ◽  
Positron Annihilation Lifetime

The activation enthalpy for migration of dislocations of plastically deformed 8006 Al-alloy was investigated by positron annihilation lifetime technique. Plastic deformation using a hydraulic press produces mainly dislocations and may produce point defects. The type of defect was studied by isochronal annealing which determines the temperature range of recovery of each type. Only one type of defect (dislocations) was observed for the investigated sample and was found to be recovered within the range 455–700 K. Isothermal annealing by slow cooling was performed through this range and used in determination of the activation enthalpy of migration of dislocations which was found to be 0.26 ± 0.01 eV.

Radiation-Induced Defects in Electron and Proton Irradiated ZnS

1998 ◽  
Vol 540 ◽  
Author(s):  
S. Brunner ◽  
W. Puff ◽  
P. Mascher ◽  
A.G. Balogh
Keyword(s):  
Vapour Deposition ◽  
Proton Irradiation ◽  
Positron Lifetime ◽  
Chemical Vapour ◽  
Isochronal Annealing ◽  
Doppler Broadening ◽  
Defect Complexes ◽  
Radiation Induced ◽  
The Stability ◽  
Induced Defects

AbstractIn this contribution, we present a study aimed at investigating the microstructural changes of ZnS single crystals and CVD (chemical vapour deposition) grown crystals after electron and proton irradiation. Positron lifetime and Doppler-broadening measurements were performed to investigate the stability of the radiation induced defects and possible clustering mechanisms during isochronal annealing. After electron as well as proton irradiation the significant changes in the annihilation characteristics are indications of radiation induced open-volume-type defects. It is found that electron and proton irradiation causes different changes in the positron annihilation characteristics. After electron irradiation a significant defect component is observed which can be attributed to the annihilation in monovacancies. During isochronal annealing agglomerations to divacancy-type defects take place. Proton irradiation reveals a significantly different defect structure. Isochronal annealing causes agglomerations to larger defect complexes. The observed annealing stages are indications of the annealing of variously sized vacancy complexes.

A STUDY OF RECOVERY STAGES IN SOME PLASTICALLY DEFORMED ALUMINUM ALLOYS BY POSITRON LIFETIME SPECTROSCOPY

2005 ◽  
Vol 12 (02) ◽  
pp. 203-207 ◽  
Author(s):  
M. A. ABDEL-RAHMAN ◽  
M. S. ABDALLAH ◽  
EMAD A. BADAWI
Keyword(s):  
Aluminum Alloys ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Positron Lifetime ◽  
Isochronal Annealing ◽  
Temperature Range ◽  
Positron Lifetime Spectroscopy

Positron annihilation was performed to study the isochronal annealing of wrought (2024, 7075) and casting ( AlSi 11.35 Mg 0.23, AlSi 10.9 Mg 0.17 Sr 0.06) aluminum alloys in the temperature range from room temperature to 773 K after they had been deformed at room temperature with 25% deformation. Two annealing stages of microstructures were distinguished which were attributed to recovery in 2024, and AlSi 11.35 Mg 0.23, AlSi 10.9 Mg 0.17 Sr 0.06 due to point and dislocations respectively, and only one due to dislocations in 7075.

Deformation-induced vacancy-type defects in GaAs

1991 ◽  
Vol 69 (3-4) ◽  
pp. 298-306 ◽  
Author(s):  
P. Mascher ◽  
S. Dannefaer ◽  
D. Kerr
Keyword(s):  
Isothermal Annealing ◽  
Positron Lifetime ◽  
Total Concentration ◽  
Vacancy Cluster ◽  
Void Size ◽  
Shallow Trap ◽  
Vacancy Clusters ◽  
Positron Lifetime Spectroscopy ◽  
Average Size ◽  
Shallow Traps

Semi-insulating undoped GaAs was plastically deformed and then investigated by positron-lifetime spectroscopy. Strains between 0 and 40% and temperatures of deformation of 450, 500, and 600 °C were investigated, with detailed investigations carried out for the lowest temperature of deformation. Between 0 and 4% strain, a reduction of the grown-in vacancy response takes place simultaneously with a slight increase in vacancy cluster size to two or three vacancies. Between 4 and 6% strain a very substantial increase in vacancy production occurs but nearly all of these vacancies are clustered into voids with a radius of about 50 Å (1 Å = 10−10 m) and density in the order of 1013–1014 cm−3. The total concentration of vacancies necessary to produce these voids is 1017–1018 cm−3. This clearly shows that vacancies are formed upon deformation and that they are mobile at 450 °C. Upon further deformation to 20% strain, the overall defect concentration becomes so high that all positrons become trapped for which reason no absolute defect concentrations can be deduced. The dominant defect types can nevertheless be identified as voids (of average size of 20 Å), two- or three-vacancy clusters, and shallow traps. Isothermal annealing of 40% strained samples shows that heat treatment reduces the void concentration but increases the average void size, and results only in a small decrease in shallow-trap concentration. The shallow traps are likely the dislocation lines themselves and the small vacancy clusters appear to be associated with the dislocation lines.

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.

An Investigation of Point Defects in NiAl Using Positron Annihilation Techniques

1998 ◽  
Vol 552 ◽  
Author(s):  
Werner Puff ◽  
Bernd Logar ◽  
Adam G. Balogh
Keyword(s):  
Positron Annihilation ◽  
Point Defects ◽  
Proton Irradiation ◽  
Positron Lifetime ◽  
Composition Range ◽  
Isochronal Annealing ◽  
Doppler Broadening ◽  
Positron Lifetime Spectroscopy ◽  
Induced Defects

ABSTRACTVacancy-like defects in NiAl in the composition range 47 at.-% < CNi < 53 at.-% are investigated by means of positron lifetime spectroscopy and Doppler-broadening measurements. The observed lifetimes in the annealed samples confirm that defects are quenched-in during the production of the samples. Isochronal annealing of samples quenched at 1600°C and after proton irradiation show that the induced defects are quite different.

Positron annihilation measurements in high energy alpha irradiated undoped indium antimonide

2014 ◽  
Vol 28 (30) ◽  
pp. 1450210 ◽  
Author(s):  
Sandip Pan ◽  
Arunava Mandal ◽  
Subrata Mukherjee ◽  
Achintya Kumar Saha ◽  
Anirban Roychowdhury ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Temperature Region ◽  
Indium Antimonide ◽  
Line Shape ◽  
Room Temperature ◽  
Positron Lifetime ◽  
High Energy ◽  
Isochronal Annealing ◽  
Positron Annihilation Lifetime ◽  
Lifetime Analysis

Positron annihilation lifetime spectroscopy and Doppler broadening annihilation line-shape measurements were carried out in 40 MeV alpha-irradiated undoped InSb. After irradiation the sample was subjected to an isochronal annealing over temperature region of 25°C–400°C with annealing time of 30 min at each set temperature. After each annealing the positron measurements were carried out at room temperature. Formation of radiation induced defects and their recovery with annealing temperature were investigated. A three component positron lifetime analysis was undertaken to observe the trapping of positrons in the sample after irradiation and during annealing. The average positron lifetime value τ avg = 313 ps at room temperature after irradiation indicated the presence of defects and the high value of τ2 at room temperature suggested that the probable defects were divacancies. A two stage recovery of defects was observed during post irradiation isochronal annealing over the temperature region 25°C–400°C. The variations in line-shape parameter (S) and defect specific parameter (R) during annealing in the temperature region 25°C–400°C resembled the behavior of τ avg indicating the migration of vacancies, formation of vacancy clusters and the disappearance of defects between 300°C to 400°C.

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