Spin defects in hexagonal boron nitride for strain sensing on nanopillar arrays

Two-dimensional hexagonal boron nitride (hBN) has attracted much attention as a platform for studies of light-matter interactions at the nanoscale, especially in quantum nanophotonics. Recent efforts have focused on spin defects, specifically negatively charged boron vacancy (V_B⁻) centers. Here, we demonstrate a scalable method to enhance the V_B⁻ emission using an array of SiO₂ nanopillars. We achieve a 4-fold increase in photoluminescence (PL) intensity, and a corresponding 4-fold enhancement in optically detected magnetic resonance (ODMR) contrast. Furthermore, the V_B⁻ ensembles provide useful information about the strain fields associated with the strained hBN at the nanopillar sites. Our results provide an accessible way to increase the emission intensity as well as the ODMR contrast of the V_B⁻ defects, while simultaneously form a basis for miniaturized quantum sensors in layered heterostructures.