Identification of lattice defects in Cu thin films by positron annihilation spectroscopy

Positron lifetime measurements have been performed for Cu thin films in order to identify lattice defects. Theoretical positron lifetimes of vacancy clusters of Cu are also calculated for identification of the experimental values. Cu thin films were prepared by electro chemical deposition (ECD) and physical vapour deposition (PVD). All of the Cu thin films have longer positron lifetimes than bulk Cu does. This indicates that lattice defects are introduced during deposition. However composition analysis of positron lifetimes shows that whereas vacancy clusters exist in the ECD-Cu thin film, the positron lifetime of defect component in the PVD-Cu thin films is shorter than that of mono-vacancy. On the other hand, the positron lifetime of mono-vacancy was detected in PVD-Cu-0.5 at%Sb thin film prepared by PVD. In order to elucidate the effect of Sb, first-principles calculations have been performed for Cu including Sb and mono-vacancy. The result suggests that mono-vacancies are introduced because of the binding energy between a Sb atom and mono-vacancy. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)