Cleaving silicene-terminated calcium disilicide in the transmission electron microscope

Silicene, a monolayer of silicon atoms arranged in a honeycomb lattice, is excellently compatible with the materials used in today's semiconductor manufacturing. In this paper, silicene-terminated CaSi₂ is cleaved inside a transmission electron microscope using an in situ manipulator. HRTEM studies on a standard lift-out lamella performed from several crystallographic orientations confirm the cell parameters of a = 3.7 Å and c = 30.60 Å, and allow to determine its exact orientation in the SEM/FIB system. A FIB procedure with corrected tilting and rotating angles has been developed to ensure that the tensile force applied by the manipulator is perpendicular to the (0 0 1) plane, and that the [1 0 0] pole axis could be used for HRTEM imaging. A sharp and flat cleavage interface with a length of more than 1 μm was observed in one in situ experiment. HRTEM images from multiple regions confirm that the flat cleavage follows the (0 0 3) plane of the CaSi₂ crystal. The current in situ study demonstrates that a surface sheet with silicene-like atomic arrangement can be mechanically exfoliated from silicide compounds.