Inelastic and elastic mean free paths from FIB samples of metallic glasses

Abstract

We have used focused ion beam (FIB) milling and scanning electron microscopy (SEM) to prepare samples of known thickness for measurement of the electron scattering elastic and inelastic mean free paths (EMFP and IMFP respectively) of three metallic glasses, Cu(64.5)Zr(35.5), Zr(50)Cu(45)Al(5), and Al(87)Y(7)Fe(5)Cu. After measuring the EMFP and IMFP in a scanning transmission electron microscope, we used the FIB to coat the lamellae with carbon on the top and bottom surfaces, which eliminated secondary electron emission from those surfaces and made SEM measurements of their thickness more reliable. At 200 kV, we find IMFP/ EMFP values of 146±2/43±1, 163±1/41±1, and 149±1/85±1 nm, respectively for the three glass compositions. Our results differ from available models for the IMFP by as much as 50%.