Fast diffusers Cu and Ni as the origin of electrical activity in a silicon grain boundary

Grain boundary (GB) electrical activity is increased by heat treatment in silicon; the origin of the phenomenon is a subject of controversy and is often attributed to oxide precipitation. This letter presents microanalytical results (conventional and scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and electron energy loss spectroscopy), obtained on a Σ=25 bicrystal before and after annealing in sealed ampoules at 900 °C. The enhancement of the electrical activity, confirmed by electron beam induced current and deep level transient spectroscopy, is shown to appear at the boundary simultaneously with precipitates containing copper and nickel. The major role of the fast diffusing 3d metals on the GB electrical properties is demonstrated.