Nanometer to micrometer scaled inhomogeneous etching of bulk metallic glasses by ion sputtering

In order to faithfully investigate the microscopic and mesoscopic structures of bulk metallic glass (BMG) materials, inhomogeneous contrast in nanometer to micrometer scale in BMG specimens has been throughoutly studied by transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). It is found that ion-milling induced surface roughening and pattern formation are the source of the inhomogeneous contrast in TEM images of BMG samples. Additionally, high resolution TEM and X-ray energy dispersive spectroscopy investigations rule out structure or composition changes in the specimens. The dynamic roughening process during ion-milling as well as saturated pattern sizes are revealed from Zr-, Cu-, Fe- and Mg-based BMGs. The understanding of this inhomogeneous etching in BMG specimens is critical for recently intensive TEM studies on microscopic and mesoscopic inhomogeneities of BMGs.