Core-level spectroscopy of point defects in single layer h-BN.

Electron energy-loss spectroscopy (EELS) is used to analyze single-layered hexagonal boron-nitride with or without point defects. EELS profiles using a 0.1 nm probe clearly discriminate the chemical species of single atoms but show different delocalization of the boron and nitrogen K edges. A monovacancy at the boron site is unambiguously identified and the electronic state of its nearest neighboring nitrogen atoms is examined by energy-loss near edge fine structure analysis, which demonstrates a prominent defect state. Theoretical calculations suggest that the observed prepeak originates from the 1s to lowest unoccupied molecular orbital excitation of dangling nitrogen bonds, which is substantially lowered in energy with respect to the three coordinated nitrogen atoms.