Observation of Boron Vacancy Concentration in Hexagonal Boron Nitride at Nanometer Scale

Abstract

Negatively charged boron vacancy (VB–) ensembles in hexagonal boron nitride (h-BN) have attracted considerable attention as a promising platform for quantum sensing. Current challenges include the experimental validation of the spatial distribution and electronic states of optically active VB–and optically inactive neutral boron vacancy (VB0) defects. To address these issues, we employ electron energy loss spectroscopy (EELS) combined with scanning transmission electron microscopy (STEM) using monochromated 30-keV electrons, effectively reducing background interference. This approach unveils distinct spectral peaks at 2.5 and 1.9 eV, corresponding to VB–and VB0defects, respectively. Furthermore, we achieve nanometer-scale concentration mapping for VB–and VB0defects, advancing insights into spin defect configurations crucial for optimizing quantum sensor performance.