Hexagonal boron nitride (hBN) is gaining interest as a wide bandgap van der
Waals host of optically active spin defects for quantum technologies. Most
studies of the spin-photon interface in hBN focus on the negatively charged
boron vacancy (VB-) defect, which is typically fabricated by ion irradiation.
However, VB- fabrication methods often lack robustness and reproducibility when
applied to thin flakes (less than 10 nm) of hBN. Here we identify mechanisms
that both promote and inhibit VB- generation and optimize ion beam parameters
for site-specific fabrication of optically active VB- centers. We emphasize
conditions accessible by high resolution focused ion beam (FIB) systems, and
present a framework for VB- fabrication in hBN flakes of arbitrary thickness
for applications in quantum sensing and quantum information processing.Comment: 11 pages, 5 figure