  Imaging and spectroscopy performed in a low-voltage scanning transmission
electron microscope (LV-STEM) are used to characterize the structure and
chemical properties of boron-terminated tetravacancies in hexagonal boron
nitride (h-BN). We confirm earlier theoretical predictions about the structure
of these defects and identify new features in the electron energy-loss spectra
(EELS) of B atoms using high resolution chemical maps, highlighting differences
between these areas and pristine sample regions. We correlate our experimental
data with calculations which help explain our observations.
