skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Characterization of point defects in CdTe by positron annihilation spectroscopy

Abstract

Positron lifetime measurements on CdTe 0.15% Zn-doped by weight are presented, trapping to monovacancy defects is observed. At low temperatures, localization at shallow binding energy positron traps dominates. To aid defect identification density functional theory, calculated positron lifetimes and momentum distributions are obtained using relaxed geometry configurations of the monovacancy defects and the Te antisite. These calculations provide evidence that combined positron lifetime and coincidence Doppler spectroscopy measurements have the capability to identify neutral or negative charge states of the monovacancies, the Te antisite, A-centers, and divacancy defects in CdTe.

Authors:
 [1];  [2]; ;  [1];  [3]
  1. Carnegie Laboratory of Physics, SUPA, School of Science and Engineering, University of Dundee, Dundee DD1 4HN (United Kingdom)
  2. (Egypt)
  3. Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia (Egypt)
Publication Date:
OSTI Identifier:
22590784
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 108; Journal Issue: 24; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BINDING ENERGY; CADMIUM TELLURIDES; CHARGE STATES; DENSITY FUNCTIONAL METHOD; DISTRIBUTION; DOPED MATERIALS; POSITRONS; TRAPPING; TRAPS; POSITRON ANNIHILATION SPECTROSCOPY

Citation Formats

Elsharkawy, M. R. M., Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia, Kanda, G. S., Keeble, D. J., E-mail: d.j.keeble@dundee.ac.uk, and Abdel-Hady, E. E. Characterization of point defects in CdTe by positron annihilation spectroscopy. United States: N. p., 2016. Web. doi:10.1063/1.4953781.
Elsharkawy, M. R. M., Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia, Kanda, G. S., Keeble, D. J., E-mail: d.j.keeble@dundee.ac.uk, & Abdel-Hady, E. E. Characterization of point defects in CdTe by positron annihilation spectroscopy. United States. doi:10.1063/1.4953781.
Elsharkawy, M. R. M., Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia, Kanda, G. S., Keeble, D. J., E-mail: d.j.keeble@dundee.ac.uk, and Abdel-Hady, E. E. Mon . "Characterization of point defects in CdTe by positron annihilation spectroscopy". United States. doi:10.1063/1.4953781.
@article{osti_22590784,
title = {Characterization of point defects in CdTe by positron annihilation spectroscopy},
author = {Elsharkawy, M. R. M. and Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia and Kanda, G. S. and Keeble, D. J., E-mail: d.j.keeble@dundee.ac.uk and Abdel-Hady, E. E.},
abstractNote = {Positron lifetime measurements on CdTe 0.15% Zn-doped by weight are presented, trapping to monovacancy defects is observed. At low temperatures, localization at shallow binding energy positron traps dominates. To aid defect identification density functional theory, calculated positron lifetimes and momentum distributions are obtained using relaxed geometry configurations of the monovacancy defects and the Te antisite. These calculations provide evidence that combined positron lifetime and coincidence Doppler spectroscopy measurements have the capability to identify neutral or negative charge states of the monovacancies, the Te antisite, A-centers, and divacancy defects in CdTe.},
doi = {10.1063/1.4953781},
journal = {Applied Physics Letters},
number = 24,
volume = 108,
place = {United States},
year = {Mon Jun 13 00:00:00 EDT 2016},
month = {Mon Jun 13 00:00:00 EDT 2016}
}
  • Positrons localize in trapped states at a variety of defect sites in solids, from which they subsequently annihilate with unique observable characteristics. As such, the positron is a valuable probe for the study of these defects. Positron annihilation spectroscopy (PAS) has made significant contributions in recent years to the determination of atomic defect properties in metals and alloys, and in molecular solids as well. It has also been used extensively in the monitoring and characterization of vacancy-like microstructure development, as occurs during post-irradiation annealing. The characterization of defects using PAS is selectively reviewed and some possibilities for using the positronmore » as a localized probe of the atomic and electronic structure of atomic defects and their aggregates are discussed. 32 references, 4 figures.« less
  • The equilibrium equation of point defects in Ll{sub 2} types of intermetallic compounds was established in a new simple method, which is independent of the chemical potentials. The formation energies of the relevant point defects in Ni{sub 3}Al were calculated by EAM potentials and statical relaxations. The concentration of point defects at 1,000 K as a function of bulk composition and the effect of temperature on them were studied for Ni{sub 3}Al alloy. The results show that the Al-antisites are the constitutional defects in hypostoichiometric Ni{sub 3}Al, and the Ni-antisite defects in hyperstoichiometric Ni{sub 3}Al. The two types of vacanciesmore » belong to thermal defects. The positron annihilation technique was also conducted to measure the concentration of vacancies in Ni{sub 3}Al alloys with and without boron. Although vacancies interact with the boron dopant, the changes of vacancy concentration Ni{sub 3}Al alloys can not be considered as the main reason in explaining the effect of stoichiometry on the segregation of boron. The effect of stoichiometry on diffusion in Ni{sub 3}Al alloys was discussed additionally.« less
  • We used Doppler broadening positron annihilation spectroscopy as a nanovoid characterization tool in the study of low dielectric constant (low-[ital k]) hydrogen-silsesquioxane (HSSQ) thin films. The high void sensitivity of this method, combined with depth-resolving capability, enables one to observe changes in the [ital local] electronic environment in a thin film. We established a correlation between the annihilation parameters and the dielectric properties for a series of samples subjected to various annealing conditions in nitrogen. Qualitative differences are found between the pore structures of isochronally and isothermally annealed films, suggesting a complex relationship between the film dielectric constant and poremore » size and pore density. Results showing changes in the chemical environment caused by exposure to various processing environments are also presented. First, the changes in the HSSQ films were determined after a year of exposure to ambient air in which the film properties changed with time due to water absorption. Second, the intentional oxidation of the HSSQ films by exposure to an oxygen plasma were found to propagate from the film surface towards the substrate. A 10 min oxygen-plasma exposure resulted in a 130-nm-thick layer of oxidized HSSQ, with a corresponding high [ital k] (=3.6). A decrease in [ital k] (to 3.3), with a subsequent 400 hthinsp;[degree]C 30 min forming gas anneal was attributed to the void formation at the HSSQ/Si interface. [copyright] [ital 1999 American Institute of Physics.] thinsp« less
  • Near-surface atomic-scale defects in aluminum foils of at least 99.08 % purity were characterized with positron annihilation spectroscopy measurements of the Doppler-broadening parameter S. Profiles of S vs. positron beam energy (i.e., vs. depth into the sample) were analyzed with a model for positron diffusion and trapping in order to characterize the defect layer structure. As-received foils were shown to possess a defect layer within 10 to 100 nm of the oxide film/metal interface. Both dissolution in aqueous sodium hydroxide solution and anodic pitting corrosion in HCl caused significant changes in the positron spectra which were interpreted as increases inmore » the defect population. On the basis of isochronal annealing, the defects were impurity-complexed voids or vacancy clusters, or else interfacial voids at the metal/film boundary located at surface roughness features. Either case suggests a possible role for the defects as pit sites, since both near-surface impurities and surface roughness are known to influence the number of pits on a surface. Defects found after pitting may be present in layers surrounding individual pits, and might have been produced in the process of pit initiation.« less