POSITRON INTERACTION IN POLYMERS

2004 ◽  
Vol 19 (23) ◽  
pp. 3951-3959 ◽  
Author(s):  
CORINE BAS ◽  
N. DOMINIQUE ALBÉROLA ◽  
MARIE-FRANCE BARTHE ◽  
JÉRÉMIE De BAERDEMAEKER ◽  
CHARLES DAUWE
Keyword(s):  
Positron Annihilation ◽  
Chemical Structure ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Hole Size ◽  
Doppler Broadening ◽  
Positron Source ◽  
Positron Annihilation Lifetime ◽  
Doppler Broadening Spectra ◽  
Variable Energy

A series of dense copolyimide membranes was characterized using positron annihilation spectroscopy. The positron annihilation lifetime spectroscopy performed on film with a classical positron source gives informations on the positronium fraction formed and also on the hole size within the film. The Doppler broadening spectra (DBS) of the gamma annihilation rays coupled with a variable energy positron beam allow the microstructural analyses as a function of the film depth. Experimental data were also linked to the chemical structure of the polyimides. It was found that the presence of the fluorine atoms strongly affects the positron annihilitation process and especially the DBS responses.

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.

Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production

2012 ◽  
Vol 331 ◽  
pp. 41-52 ◽  
Author(s):  
Andreas Wagner ◽  
Wolfgang Anwand ◽  
Maik Butterling ◽  
Thomas E. Cowan ◽  
Fine Fiedler ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Linear Accelerator ◽  
Electron Accelerator ◽  
Positron Annihilation Spectroscopy ◽  
Doppler Broadening ◽  
Electron Linear Accelerator ◽  
Positron Annihilation Lifetime ◽  
Electron Bremsstrahlung ◽  
New Type ◽  
Set Up

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

scholarly journals Study of multiblock polyamide-6/Poly-(isoprene) copolymers by positron annihilation spectroscopy

2008 ◽  
Vol 6 (4) ◽  
pp. 575-580 ◽  
Author(s):  
R. Bryaskova ◽  
R. Mateva ◽  
N. Djourelov ◽  
M. Krasteva
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Main Chain ◽  
Positron Annihilation Spectroscopy ◽  
Polyamide 6 ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Degree Of Crystallinity ◽  
Doppler Broadening ◽  
Annihilation Line ◽  
Positron Annihilation Lifetime

AbstractPositron annihilation lifetime spectroscopy (PALS) has been used to determine the free volume in multiblock polyamide-6/poly-(isoprene) copolymers (PA-6/PI), synthesized via activated anionic bulk copolymerization. The diisocyanate functionalized telechelic PI, blocked with caprolactam (CL) has been used as a commoner and an activator at the same time. The elastic PI block incorporated into the main chain of PA-6 affects the amorphous and crystal phase of the copolymer leading to changing in degree of crystallinity. The positron annihilation lifetime spectroscopy (PAL) and Doppler broadening of annihilation line (DBAL) technique in a set of pure PA-6 and PA-6/PI copolymers with two different compositions have been applied and evaluation of the size of free-volume holes (pores), localized mainly in the disordered regions of the PA-6/PI copolymer by measuring the o-Ps lifetime (τ3) and o-Ps intensity (I3) has been performed.

Temperature Dependence of Radiation Damage in ODS Steel Studied by Triple Beam Irradiation and Positron Annihilation Techniques

2017 ◽  
Vol 373 ◽  
pp. 91-95 ◽  
Author(s):  
Da Qing Yuan ◽  
Qiao Li Zhang ◽  
Ping Fan ◽  
Xian Ping Wang ◽  
Bin Long ◽  
...  
Keyword(s):  
Radiation Damage ◽  
Positron Annihilation ◽  
Ion Beam ◽  
Positron Beam ◽  
Doppler Broadening ◽  
Beam Irradiation ◽  
Single Beam ◽  
Positron Annihilation Lifetime ◽  
Ods Steel ◽  
S Parameter

The oxide dispersed strengthened (ODS) ferritic-martensitic steel was irradiated by 100MeV iron ion whose energy was degraded by using a Ta foil of 4 μm thick, 100 keV Hydrogen and 200 keV Helium at 480, 515, 550 and 580 °C. The irradiation fluences were 1×1016, 1.1×1015 and 6.8×1013/cm2, respectively for Fe, H and He. The techniques of positron annihilation lifetime and Doppler broadening of slow positron beam were utilized to examine the produced radiation damage. At 550 °C the maximal positron annihilation lifetime and S parameter of Doppler broadening were observed, implyin g tha t 550 °C is the pea k temperature of swelling. The S parameter and annihilation lifetime of the sample irradiated at 515 °C by the single Fe ion beam were smaller compared to the triple beam irradiation at the same temperature, implying that the triple beam irradiation caused more severe damage than the single beam irradiation.

scholarly journals A new approach to near-surface positron annihilation analysis of ion irradiated ferritic alloys

2021 ◽  
Author(s):  
Vladimir Krsjak ◽  
Petr Hruška ◽  
Jarmila Degmova ◽  
Stanislav Sojak ◽  
Pavol Noga ◽  
...  
Keyword(s):  
Positron Annihilation ◽  
Ion Beam ◽  
Positron Beam ◽  
Ion Beam Irradiation ◽  
Near Surface ◽  
Slow Positron ◽  
New Approach ◽  
Ferritic Alloys ◽  
Positron Annihilation Lifetime ◽  
Variable Energy

The present work provides an innovative approach to the near-surface slow-positron-beam (SPB) study of structural materials exposed to ion-beam irradiation. This approach enables the use of variable-energy positron annihilation lifetime...

Variable Energy Positron Annihilation Spectroscopy of Perovskite Oxides

2012 ◽  
Vol 331 ◽  
pp. 201-233 ◽  
Author(s):  
David J. Keeble
Keyword(s):  
Positron Annihilation ◽  
Oxygen Deficiency ◽  
Single Layer ◽  
Positron Annihilation Spectroscopy ◽  
Perovskite Oxide ◽  
Near Surface ◽  
Vacancy Defects ◽  
Positron Annihilation Lifetime ◽  
Primary Focus ◽  
Variable Energy

The application of variable energy positron annihilation spectroscopy (VE-PAS) methods to the study of perovskite oxide, ABO3, material thin films and near-surface regions is reviewed. The primary focus is on ferroic perovskite titanate oxide materials SrTiO3and Pb (ZrxTi1-x)O3, but studies of BaTiO3, LaxSr1-xCoO3, La0.67Sr0.33MnO3and YBa2CuO7-δare also included. Characterization of single layer and multilayer structures is discussed. The methods, in particular positron annihilation lifetime spectroscopy, allow the identification of cation vacancy defects at both the A-and B-sites with parts per million sensitivity. Varying oxygen deficiency is often observed to result in marked changes in PAS spectra; these effects are reviewed and discussed.

Hydrogen interaction with oxidized Si(111) probed with positrons

1989 ◽  
Vol 67 (8) ◽  
pp. 818-820 ◽  
Author(s):  
K. G. Lynn ◽  
Bent Nielsen ◽  
D. O. Welch
Keyword(s):  
Positron Annihilation ◽  
Momentum Distribution ◽  
Electron Pair ◽  
Positron Beam ◽  
Thermally Grown Oxide ◽  
Doppler Broadening ◽  
Hydrogen Binding ◽  
Hydrogen Interaction ◽  
Hydrogen Exposure ◽  
Variable Energy

A variable-energy positron beam was utilized to study the interface action of hydrogen with Si(111) covered by an ultrahigh-vacuum thermally grown oxide of 2–3 nm thickness. It was observed that positrons implanted at shallow depth (<100 nm) after diffusion are trapped either at the interface between the oxide and the Si or in the oxide. The positron-annihilation characteristics of these trapped positrons are found to be very sensitive to hydrogen exposure. The momentum distribution of the annihilating positron–electron pair, as observed in the Doppler broadening of the annihilation line, broadens considerably after exposure to hydrogen. The effect recovers after annealing at [Formula: see text], suggesting a hydrogen binding at the interface of ~3 ± 0.3 eV.

scholarly journals Microscopy studies on magnetron sputtered thin films with preferred orientation for positron moderation

2019 ◽  
Vol 1 (1) ◽  
pp. 62-63
Keyword(s):  
Thin Films ◽  
Positron Annihilation ◽  
Branching Ratio ◽  
Positron Beam ◽  
Positron Annihilation Spectroscopy ◽  
Structure Characterization ◽  
Near Surface ◽  
Positron Annihilation Lifetime ◽  
Pass Through ◽  
Intrinsic Characteristic

Doppler-broadening Spectroscopy (DBS) and positron annihilation lifetime spectroscopy (PALS) are two positron annihilation spectroscopy techniques used for identifying near surface vacancies and lattice dislocations. Positrons manifest a broad energy distribution of about several MeV and in order to generate a low-energy positron beam, the positrons need to pass through a material called “moderator” so that a narrow positron kinetic energy bandwidth can be obtained, without losing too much intensity. The moderator must possess certain properties, among which a large negative positron work function and a large branching ratio to free positrons. The first can be assessed to an intrinsic characteristic of the material, that is usually correlated to the material bandgap, and in order to attain the second, a defect free, epitaxial thin film should be obtained. Due to its 3.4 eV bandgap, GaN represents a very promising candidate for positron moderation and field assisted moderation, that might manage longer average positron diffusion lengths. The aim of the present study is to obtain semi-insulating GaN thin films by magnetron sputtering GaN on different substrates (ZnO, TiO2, Al2O3) with fewer impurities incorporated, which should hold promises of increasing the positron diffusion length in the material. Preliminary depositions made in this study are to be discussed, highlighting both their advantages and limitations derived from their structure characterization.

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