ACTA

Positron Lifetime Spectroscopy of Nanocrystalline Copper

J. C̆ížek^a, I. Procházka^a, P. Vostrý^a, F. Chmelík^a and R.K. Islamgaliev^b
^a Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
^b Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000, Russia

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Positron lifetime spectroscopy was applied to investigate the thermal stability of nanocrystalline copper prepared by severe plastic torsion deformation. Positrons annihilating in as prepared specimens exhibited free positron component τ₁ and two defect components τ₂=164 ps and τ₃=255 ps. Evolution of the lifetimes and relative intensities of all the three components with increasing annealing temperature during step-by-step isochronal annealing up to 630°C was studied. Behaviour of positrons in nanocrystalline copper could not be interpreted in the frame of conventional 3-state trapping model due to highly inhomogeneous defect distribution. Therefore a modified trapping model was developed and applied to explain the experimental results.

DOI: 10.12693/APhysPolA.95.487
PACS numbers: 78.70.Bj, 79.60.Jv