Range of slow positrons in metal overlayers on Al

This is the authors' abstract. We don't add key points for this paper.

Polycrystalline Pd and amorphous PdTa films on Al substrates were studied by a variable energy positron beam and by Rutherford backscattering. Since positron diffusion in the overlayers is limited, the range follows directly from the Doppler broadening as a function of incident positron energy. To observe possible effects of positron backscattering, a sandwich of Al/Pd/Al was studied as well. It was found that the mean penetration depth is not described well by z̄(E)=A(μg/cm2)×En(E), if A and n are assumed to be material and energy independent.