Search results for "Positron Lifetime Spectroscopy"

Positronics of radiation-induced effects in chalcogenide glassy semiconductors

2015

Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.

Positron states in Si and GaAs.

1988

Study of the e<sup>+</sup> Distribution in a Layered Stack Sample Using Positron Lifetime Spectroscopy

2010

The results of the Monte Carlo (MC) simulations, using GEANT4 codes, indicate the enhancement of the fraction of the e+ in the denser regions of the sample embedded by the less dense environment. The positron lifetime measurements, performed for two stacks of layers consisting of pure aluminum and silver do not seem to reveal this effect. Some features of the e+ distribution detected in the experiments are not reproduced by the MC simulations.

The positron distribution in a layered stack sample studied with the use of positron lifetime spectroscopy

2011

Abstract Computer simulation using GEANT4 codes indicates an enhancement of the fraction of implanted positrons stopped in the denser regions of a layered sample. However, positron lifetime measurements performed for layers of pure aluminum, silver and gold foils do not reveal this effect, indicating instead that backscattering plays an important role in determining the positron implantation profile in layered and/or heterogeneous samples.

Positron studies of hydrogen-defect interactions in proton irradiated molybdenum

1985

Molybdenum single crystals are irradiated at 20 K with 6 MeV protons. The radiation damage and lattice defect annealing is studied by positron lifetime spectroscopy in the temperature range from 15 to 720 K. Loss of vacancies due to recombination with mobile interstitials is observed at 40 K (Stage I) in agreement with resistivity measurements. This is the first time Stage I is observed by positrons below 77 K. The implanted hydrogen decorates the vacancies around 100 K, which is consistent with a hydrogen migration energy in molybdenum:E H = 0.3–0.4 eV. Clustering of spatially correlated vacancies takes place in a wide temperature region below the usual vacancy clustering stage (Stage III)…

Temperature- and illumination-induced charge-state change in divacancies of GaTe

2010

Temperature-dependent positron annihilation lifetime spectroscopy measurements have been performed in GaTe samples, with and without illumination. The average lifetime shows a monotonous temperature evolution but the lifetime decomposition shows a rich behavior. It is produced by two types of vacancy defects. The vacancy-type defects characterized by their shorter lifetime change their charge state below 100 K and when illuminating with light of an energy of 0.8 eV.

Positron implantation profiles in layered samples

2009

The paper presents theoretical and experimental studies of the positron implantation profiles in layered samples. The Monte Carlo simulations performed using the GEANT4 toolkit reveal accumulation of positrons in the denser layer embedded between two less dense layers. That effect is significant not only for low energy positrons at slow monoenergetic positron beams but also for high energy positrons which are emitted from radioactive nuclei in conventional experiments. Measurements of the positron implantation profile into the samples which consist of silver and aluminium foils of different thickness show profile features which correspond well with those simulated by the GEANT4 toolkit for …