A simple shape-free model for pore-size estimation with positron annihilation lifetime spectroscopy

Wada, Ken; Hyodo, Toshio

doi:10.1088/1742-6596/443/1/012003

Cited by 46 publications

(63 citation statements)

References 14 publications

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“…The wellestablished technique of employing radionuclides simultaneously emitting gamma-rays and positrons of typically up to several hundreds of keV is widely applied. Annihilation lifetimes are monotonously related to the void size with a surprisingly low dependence on the material surrounding the void [1]. The quantitative determination of positron annihilation lifetimes nevertheless is hampered when thin films or layered structures with sub-µm thicknesses which are of high technological relevance are considered.…”

Section: Introductionmentioning

confidence: 99%

Positron annihilation lifetime spectroscopy at a superconducting electron accelerator

Wagner

Anwand

Attallah

et al. 2017

J. Phys.: Conf. Ser.

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Abstract. The Helmholtz-Zentrum Dresden-Rossendorf operates a superconducting linear accelerator for electrons with energies up to 35 MeV and average beam currents up to 1.6 mA. The electron beam is employed for production of several secondary beams including X-rays from bremsstrahlung production, neutrons, and positrons. The secondary positron beam after moderation feeds the Monoenergetic Positron Source (MePS) where positron annihilation lifetime (PALS) and positron annihilation Doppler-broadening experiments in materials science are performed in parallel. The adjustable repetition rate of the continuous-wave electron beams allows matching of the pulse separation to the positron lifetime in the sample under study. The energy of the positron beam can be set between 0.5 keV and 20 keV to perform depth resolved defect spectroscopy and porosity studies especially for thin films.

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Section: Introductionmentioning

confidence: 99%

Positron annihilation lifetime spectroscopy at a superconducting electron accelerator

Wagner

Anwand

Attallah

et al. 2017

J. Phys.: Conf. Ser.

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“…A positive correlation between the o-Ps lifetime and cavity size is well-proven and several semi-empirical relations between o-Ps lifetime and cavity size parameters have been proposed to date [16][17][18][19][20][21][22]. In the present paper, we make use of a simple shapefree model suggested recently by Wada and Hyodo [22] for pore size estimation using experimental oPs lifetimes. In their model, the primary measure of pore size is the mean free length of the pore,L, which can be eventually transformed into radius R of a spherical pore as L = 4R/3.…”

Section: Resultsmentioning

confidence: 96%

“…In their model, the primary measure of pore size is the mean free length of the pore,L, which can be eventually transformed into radius R of a spherical pore as L = 4R/3. In what follows, the pore size is expressed in terms of pore radius R estimated from the present oPs lifetime data using the Wada and Hyodo formula [22]. Since the present PLT measurements were conducted in air, a correction of the experimental lifetimes due to the ortho-para quenching of o-Ps was applied.…”

Section: Resultsmentioning

confidence: 99%

Positronium Probing of Pores in Zirconia Nanopowders

et al. 2017

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In the present paper, conventional positron lifetime measurements on selected zirconia-based nanopowders are reported. The nanopowders were doped with various metal cations (Y 3+ , Eu 3+ , Gd 3+ , Lu 3+ and Mg 2+ ). Lifetime experiments were conducted in air and supplemented with mass density measurements. In a range of lifetimes, from a few ns to ≈ 70 ns, up to two individual lifetime components could be identified. Such observations confirmed positronium (Ps) formation with subsequent ortho-Ps pick-off annihilation as well as the occurrence of pores of different size. Pore sizes were estimated using a shape-free model of the correlation between pore size and ortho-Ps lifetime. The origins of pores are discussed on the basis of the ortho-Ps data in combination with the results of mass density measurements.

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“…we assume that at t = 0 the positrons are uniformly distributed and there are no positrons trapped at interfacial defects and nanovoids. Thus, the diffusion equation is solved subjected to the boundary conditions: where V  is the volume of the grain having radius R. Thus, we obtain the solution of equation (1). When a beam of monoenergetic positrons is implanted from vacuum into the grain, the positron survives before annihilation either as a free positron or trapped at the grain boundary or into the thermally induced vacancy.…”

Section: Formulation Of the Diffusion Trapping Modelmentioning

confidence: 99%

“…While the annihilation lifetime yields characteristic information about the size of open-volume defects ranging from single atomic vacancies up to nanovoids, the kinematical Doppler-broadening of annihilation radiation tells about the local electron momentum distribution at the annihilation site. Annihilation lifetimes are monotonously related to the void size with a surprisingly low dependence on the material surrounding the void [1]. The semiconducting nanocrystalline thin films have great applications in electronic industry, solar cells, solar energy storage and biomedical industries.…”

Section: Introductionmentioning

confidence: 99%

S-Parameter and Positron Lifetime Studies of Mn Doped Zn1-Xox

Rathore¹

2018

IJRASET

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Zinc Oxide (ZnO) is an fascinating material and have potential applications as a transparent conductive electrodes for solar cells, light emmitting diodes as well as for gas sensors. Interaction between dopant, impurities and intrinsic defects plays an essential role to enhance the electrical and optical properties of ZnO thin films. Positron annihilation spectroscopy (PAS) is a non destructive technique to study thin films and nanocrystalline materials. The mechanism of positron annihilation in oxide thin films has been discussed in terms of diffusion of positrons inside the grain boundaries, nanovoids and thermally generated vacancies. The mean positron lifetime and S-parameter as a function of grain size in pure and Mn doped ZnO thin films has been calculated by using positron diffusion model. The samples are prepared by Spray pyrolysis method and temperature dependent measurements revels information about the presence of shallow positron traps like grain boundaries and interfacial defects. The calculations of shows that mean positron lifetime decreases as the grain grows. While the S-parameter increases with the increase in the siza of grains. This increase in  has been ascribed to the increase in the number of thermally generated vacancies at higher temperatures. diffusion can also be closely linked with thermal defect formation at higher temperatures. Thus, information regarding grain boundaries in thin films and nano composites can be gathered by DTM (diffusion Trapping Model). I. INTRODUCTIONPositron annihilation lifetime spectroscopy (PALS) serves as a unique tool for the characterization of lattice defects in materials science. While the annihilation lifetime yields characteristic information about the size of open-volume defects ranging from single atomic vacancies up to nanovoids, the kinematical Doppler-broadening of annihilation radiation tells about the local electron momentum distribution at the annihilation site. Annihilation lifetimes are monotonously related to the void size with a surprisingly low dependence on the material surrounding the void [1]. The semiconducting nanocrystalline thin films have great applications in electronic industry, solar cells, solar energy storage and biomedical industries. Among the nanocrystalline semiconducting materials the preparation and characterization of doped and undoped ZnO films has assumed much importance during recent years. ZnO is an important wide band gap semiconductor having wide applications in various fields such as transducers, gas sensors, transport conduction electrodes and surface acoustic wave devices etc. [2][3][4]. Zinc oxide (ZnO) is a material with great potential for a variety of practical applications due to the unique physical and chemical properties such as wide and di-rect energy band gap (~3.37 eV), large exciton binding energy (~60 meV), high electron mobility, high thermal conductivity, high radiation damage resistance and biocompatibility. The recent progress in nanoscaling of ZnO structures attracts also attention t...

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A simple shape-free model for pore-size estimation with positron annihilation lifetime spectroscopy

Cited by 46 publications

References 14 publications

Positron annihilation lifetime spectroscopy at a superconducting electron accelerator

Positron annihilation lifetime spectroscopy at a superconducting electron accelerator

Positronium Probing of Pores in Zirconia Nanopowders

S-Parameter and Positron Lifetime Studies of Mn Doped Zn1-Xox

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