  The controlled creation and manipulation of defects in 2D materials has
become increasingly popular as a means to design and tune new material
functionalities. However, defect characterization by direct atomic imaging is
often severely limited by surface contamination due to a blanket of
hydrocarbons. Thus, analysis techniques are needed that can characterize atomic
scale defects despite the contamination. In this work we use electron energy
loss spectroscopy to probe beneath the hydrocarbon blanket, characterizing
defect structures in 2D hexagonal boron nitride (hBN) based on fine structure
in the boron K-edge. Since this technique is performed in a transmission
electron microscope, imaging can also be used to assess contamination levels
and other factors such as tears in the fragile 2D sheets, which can affect the
spectroscopic analysis. Furthermore, by locally probing individual areas,
multiple regions on the same specimen that have undergone different defect
engineering treatments can be investigated for systematic studies at increased
throughput. For 2D hBN samples irradiated with different ions for a range
doses, we find spectral signatures indicative of boron-oxygen bonding that can
be used as a measure of sample defectiveness depending on the ion beam
treatment.
