scholarly journals Positron lifetime spectroscopy applied to pure Tellurium

2021 ◽  
Author(s):  
Ricardo Domínguez-Reyes
Keyword(s):  
High Purity ◽  
Positron Lifetime ◽  
Theoretical Calculations ◽  
Positron Annihilation Spectroscopy ◽  
Basic Information ◽  
Spectroscopy Technique ◽  
Experimental Knowledge ◽  
Wide Range ◽  
Positron Lifetime Spectroscopy ◽  
Range Of Values

AbstractHigh-purity crystalline Tellurium has been investigated using positron lifetime spectroscopy technique in order to determine basic information missing in the current experimental knowledge of the positron annihilation spectroscopy field. Three different pairs of samples have been studied in the as-received state and, in order to eliminate the vacancy-type defects, after consecutive isothermal treatments at 300 °C. Lifetime corresponding to the annihilation in the Tellurium bulk has been determined as 282(1) ps. Previous theoretical calculations present in the bibliography that used different methods and parameterization provided a wide range of values for the annihilation lifetime of the positron in the bulk of Tellurium. The obtained result has been used to identify the most accurate results among them.

Defects Distribution of Pr2Fe14B Hard Magnetic Magnet from Amorphous to Nanostructures Characterized by Positron Annihilation Spectroscopy

2005 ◽  
Vol 475-479 ◽  
pp. 2123-2126
Author(s):  
Yu Cheng Wu ◽  
W. Sprengel ◽  
K. Reimann ◽  
K.J. Reichle ◽  
D. Goll ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Grain Growth ◽  
Melt Spinning ◽  
Positron Lifetime ◽  
Positron Annihilation Spectroscopy ◽  
Amorphous Structure ◽  
Defect Distribution ◽  
Positron Lifetime Spectroscopy ◽  
Positron Lifetimes ◽  
Shape And Size

The defect distributions have been investigated using positron lifetime spectroscopy on amorphous and nanocrystalline Pr2Fe14B samples, produced by melt-spinning and nanocrystallization route. The main two components can be concluded that were ascribed to vacancy-like defects in the intergranular layers or the interfaces, and microvoids or large free volumes with size compared to several missing atoms at the interactions of the atomic aggregates or the crystallites. The remarkable changes in the positron lifetimes from the amorphous structure to the nanocrystalline with varied sizes can be interpreted, indicating that the structural transformation and the grain growth induce the defect distribution changes occurring at the interfaces with different shape and size.

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.

A Study of Defects in Czochralski-Grown Silicon by Positron Annihilation Spectroscopy

1992 ◽  
Vol 262 ◽  
Author(s):  
S. C. Sharma ◽  
N. Hozhabri ◽  
R. G. Hyer ◽  
T. Hossain ◽  
S. Kim ◽  
...  
Keyword(s):  
Positron Lifetime ◽  
Single Crystal Silicon ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Crystal Silicon ◽  
Different Depths ◽  
Positron Lifetime Spectroscopy ◽  
Doppler Broadening Spectra ◽  
Variable Energy

ABSTRACTWe have studied defects in Cz-grown single crystal silicon by utilizing a variable energy positron beam and positron lifetime spectroscopy in conjunction with surface photovoltage measurements. We present results for the depth profile of defects obtained from the Doppler broadening spectra measured by implanting variable energy positrons at different depths ranging from the surface down to ∼ 1 /xm deep. We have also measured positron lifetime spectra at different locations on a wafer and have obtained a radial variation in the density of the vacancy-type defects.

Study the Effect of Plastic Deformation in 8006 Al-Alloys by Positron Lifetime Spectroscopy, Vickers Hardness and X-Ray Diffraction

2017 ◽  
Vol 373 ◽  
pp. 142-145 ◽  
Author(s):  
Emad A. Badawi ◽  
M.A. Abdel-Rahman ◽  
Mohammed Salah ◽  
Mohamed Abdel-Rahman
Keyword(s):  
Plastic Deformation ◽  
Vickers Hardness ◽  
Positron Lifetime ◽  
Positron Annihilation Spectroscopy ◽  
Al Alloys ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
Degree Of Deformation ◽  
X Ray ◽  
Positron Lifetime Spectroscopy

Due to the great effect of defects on the properties of the material including strength, ductility, resistivity and opacity, there are many techniques that are used in defect detecting. Positron annihilation spectroscopy (PAS), Vickers hardness, and X-ray diffraction were used to study the influence of plastic deformation on the properties of 8006 Al-alloy in this work. An increase in the positron lifetime and Vickers hardness with a bit Broadening of XRD peaks was observed with increasing the degree of deformation reflecting a large dislocation density produced by plastic deformation.

Point Defect Study in Fe72Al28 Alloy as a Function of Thermal Treatment by Positron Lifetime Spectroscopy

2010 ◽  
Vol 666 ◽  
pp. 50-53 ◽  
Author(s):  
Jerzy Kansy ◽  
Aneta Hanc ◽  
Magdalena Jabłońska ◽  
E. Bernstock-Kopaczyńska ◽  
Dawid Giebel
Keyword(s):  
Positron Lifetime ◽  
Vacancy Concentration ◽  
Theoretical Calculations ◽  
Cast State ◽  
Slow Cooling ◽  
Positron Annihilation Lifetime ◽  
Trapping Model ◽  
Positron Lifetime Spectroscopy ◽  
Rate Of Cooling ◽  
Nearest Neighborhood

The defect structure of Fe28Al samples is examined with the Positron Annihilation Lifetime Spectroscopy. The studies are carried out for samples in as-cast state and after heat treatments: annealing for 24 hours at 900°C (or 1050°C) and either slow cooling with furnace or quenching to oil. The PALS spectra are analyzed using two-state trapping model. Only one type of defects is detected. The positron lifetime in these defects (V) suggests that they are quenched-in Fe-monovacancies (VFe). The vacancy concentration strongly depends on the rate of cooling. Besides, V also depends slightly on the rate of cooling of the material. This fact suggests, according to the predictions of latest theoretical calculations, that V is sensitive to the atomic configuration in the nearest neighborhood of VFe, which give hope to estimate the degree of atomic ordering in alloys by the PALS technique.

scholarly journals Undoped gallium antimonide studied by positron annihilation spectroscopy

2003 ◽  
Vol 799 ◽  
Author(s):  
S. K. Ma ◽  
C. C. Ling ◽  
H. M. Weng ◽  
D. S. Hang
Keyword(s):  
Ionization Energy ◽  
Gallium Antimonide ◽  
Positron Lifetime ◽  
Positron Annihilation Spectroscopy ◽  
Lifetime Data ◽  
Temperature Dependent ◽  
Lifetime Component ◽  
Grown Sample ◽  
Related Defect ◽  
Positron Lifetime Spectroscopy

ABSTRACTPositron lifetime spectroscopy has been used to study the vacancy type defects in undoped gallium antimonide. Temperature dependent positron trapping into the VGa-related defect having a characteristic lifetime of 310ps was observed in the as-grown sample. The lifetime data were well described by a model involving the thermal ionization (0/-) of the VGa-related defect and its ionization energy was found to be E(0/-)=83meV. For the electron irradiated sample, the VGa-related defect with lifetime of 310ps that was found in the non-irradiated samples was also identified. Moreover, another lifetime component (280ps) was only observed in the electron irradiated sample but not in the non-irradiated sample. It was also attributed to the VGa-related defect. The two identified VGa-related defects should have different microstructures because of their difference in characteristic lifetimes. The 280ps component remains thermally stable after the 500°C annealing while the 310ps component anneals at 300°C.

Positron Annihilation Spectroscopy of Defects in Commercially Pure Titanium Saturated with Hydrogen

2014 ◽  
Vol 880 ◽  
pp. 134-140 ◽  
Author(s):  
Roman S. Laptev ◽  
Yuriy S. Bordulev ◽  
Viktor N. Kudiiarov ◽  
Andrey M. Lider ◽  
Georgy V. Garanin
Keyword(s):  
Gas Phase ◽  
Positron Lifetime ◽  
Pure Titanium ◽  
Metal Structure ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Commercially Pure Titanium ◽  
Commercially Pure ◽  
Hydrogen Interaction ◽  
Positron Lifetime Spectroscopy

The experimental study of the structure of commercially pure titanium after saturation with hydrogen from the gas phase by means of positron lifetime spectroscopy (PLS) and Doppler broadening spectroscopy (DBS) was carried out. In the result of penetration and accumulation of hydrogen, significant changes of annihilation characteristics occurred due to the defect structure changing. The investigated samples contained hydrogen in concentrations varying from 0 to 0.961 wt.%. Several stages of hydrogen interaction with the metal structure were revealed.

Microstructure and Defects of MgO/ZrO2 Nanocrystals Investigated by Positron Annihilation Spectroscopy

2017 ◽  
Vol 373 ◽  
pp. 249-253
Author(s):  
Jia Heng Wang ◽  
Jian Jian Shi ◽  
Wei Yang ◽  
Zhe Jie Zhu ◽  
Yi Chu Wu
Keyword(s):  
Single Phase ◽  
Annealing Temperature ◽  
Positron Lifetime ◽  
Positron Annihilation Spectroscopy ◽  
X Ray Diffraction ◽  
Mgo Nanoparticles ◽  
Vacancy Defects ◽  
X Ray ◽  
Vacancy Clusters ◽  
Positron Lifetime Spectroscopy

Pure MgO, ZrO2 and mixture MgO/ZrO2 nanocrystals were annealed in air from 100 to 1200°C. Variation of the microstructure and defects was investigated by positron lifetime spectroscopy and X-ray diffraction. The experiment results showed that the average positron lifetime of mixture MgO/ZrO2 was more larger than that of single phase MgO and ZrO2, and decreased with the increasing annealing temperature. Thermal annealing below 600°C, the movement of grain boundaries mainly led a reduce of the number of microvoids, and vacancy defects began to recover due to the growth of MgO nanoparticles after annealing between 600 to 900°C. Furthermore, ZrO2 nanoparticles began to grow above 900°C, meanwhile the recovery of vacancy and vacancy clusters in MgO/ZrO2 nanoparticles are restrained because of synergic effect between MgO and ZrO2 nanoparticles.

scholarly journals Entanglement entropy in cubic gravitational theories

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Elena Cáceres ◽  
Rodrigo Castillo Vásquez ◽  
Alejandro Vilar López
Keyword(s):  
Entanglement Entropy ◽  
Gravitational Theory ◽  
Riemann Tensor ◽  
Holographic Entanglement Entropy ◽  
Gravitational Theories ◽  
Entropy Functional ◽  
Wide Range ◽  
Splitting Problem ◽  
Range Of Values

Abstract We derive the holographic entanglement entropy functional for a generic gravitational theory whose action contains terms up to cubic order in the Riemann tensor, and in any dimension. This is the simplest case for which the so-called splitting problem manifests itself, and we explicitly show that the two common splittings present in the literature — minimal and non-minimal — produce different functionals. We apply our results to the particular examples of a boundary disk and a boundary strip in a state dual to 4- dimensional Poincaré AdS in Einsteinian Cubic Gravity, obtaining the bulk entanglement surface for both functionals and finding that causal wedge inclusion is respected for both splittings and a wide range of values of the cubic coupling.

Sign in / Sign up

Export Citation Format

Share Document