Nanoscale electron diffraction and plasmon spectroscopy of single- and few-layer boron nitride

Boron nitride (BN) sheets were exfoliated, and proof of the presence of single and double layers was obtained via electron diffraction and plasmon electron energy loss spectroscopy. A plasmon structure unique to mono- and bi-layer BN was established, and was accompanied by WIEN2K DFT calculations. The latter reproduced plasmon energies and general plasmon structure well; however, the detailed shape of the pi-plasmon of the calculated pure BN spectra shows discrepancies with the experimental data. The theoretical models were then modified to include impurity atoms. Both oxygen and carbon impurities were considered, as well as different structures, including singular oxygen atoms and oxygen next to carbon atoms. These various configurations were obtained by analyzing atomic-resolution high-angle annular dark field (HAADF) images. Using these modified models, a pi-plasmon structure close to the experimentally observed structure could be simulated.