Local atomic order of a metallic glass made visible by scanning tunneling microscopy

Abstract

Exploring the atomic level structure in amorphous materials by STM becomes extremely difficult due to the localized electronic states. Here we carried out STM studies on a quasi-low-dimensional film of metallic glass ZrCuAl which is 'ultrathin' compared with the localization length and/or the length scale of short range order. The local electronic structure must appear more inherent, having states at E available for tip-sample tunneling current. To enhance imaging contrasts between long-range and short-range orders, the highly oriented pyrolytic graphite was chosen as substrate, so that the structural heterogeneity arising from competition between the glass former ability and the epitaxy can be ascertained. A chemical order predicted for this system was observed in atomic ordered regimes (1-2 monolayers), accompanied with a superstructure with the period Zr-Cu(Al)-Zr along three hexagonal axes. The result implies a chemical short range order in disordered regimes, where polyhedral clusters are dominant with the solute atom Cu(Al) in the center. An attempt for the structural modelling was made based on high resolution STM images, giving icosahedral order on the surface and different Voronoi clusters in 3D space.

Local mechanical properties of an ultrastable metallic glass

“…It is tempting to assign these findings to a potentially varying and preparation parameter dependent amount of reactive gas atoms in the different samples incorporated during sputtering. However, this is neglectable for the short overall deposition times and the low base pressure as was shown on an atomic scale using STM techniques [25].…”

“…In this work we produce ultrastable metallic glasses [24,25] of Cu 50 Zr 50 . We investigate relevant samples using x-ray diffraction measurements (XRD) and AFAM-techniques to connect preparation parameters with local mechanical properties and the stability of the metallic glass.…”