Comparison of positron-lifetime spectroscopy and differential dilatometric measurements of equilibrium vacancies in copper and alpha -Cu-Ge alloys.

Abstract

Thermally generated vacancy formation in copper and \ensuremath{\alpha}-CuGe alloys was investigated with both high-resolution positron-lifetime spectroscopy and the absolute technique. The formation enthalpies extracted from positron-annihilation experiments by means of the \ensuremath{\mu}${\mathit{C}}_{\mathit{V}}$=${\mathit{I}}_{2}$(${\ensuremath{\lambda}}_{1}$-${\ensuremath{\lambda}}_{2}$) method show significant deviations from those determined from differential dilatometric measurements using ${\mathit{C}}_{\mathit{V}}$=3(\ensuremath{\Delta}l/${\mathit{l}}_{0}$-\ensuremath{\Delta}a/${\mathit{a}}_{0}$). By adopting the model of Warburton and Shulman, the deviation becomes calculable and is seen to vanish. In addition, this investigation allows to extract directly the absolute value and its temperature dependence of the specific trapping rate as well as the influence of vacancy bound impurities on the trapping behavior.