Limiting Damage to 2D Materials during Focused Ion Beam Processing

Abstract

2D materials are by definition just a few atomic layers thick. They are therefore ideal samples for transmission electron microscopy, in the plan‐view geometry. However, 2D materials are typically placed or grown on substrates, which in some cases requires analysis to be performed on cross sections. In this case focused ion beam preparation is often the technique of choice for producing thin lamellae, but damage to the surface of 2D material during imaging and milling must be mitigated. Herein, it is demonstrated that the typically applied electron beam‐assisted deposition of platinum and carbon prior to milling does not provide sufficient protection, and results in significant damage. Instead, it is found that arc‐evaporated carbon—deposited with a standard carbon coater designed for scanning electron microscopy (SEM) samples—can provide sufficient protection, enabling cross‐sectional analysis without detectable damage to monolayer or bilayer samples subsequently prepared by standard focused ion beam preparation procedures.