Investigation of spin defects in hexagonal boron nitride generated via ion implantation

Spin-active defects in layered hexagonal boron nitride (hBN) crystals have attracted increased attention in quantum sensing. Notably, the recently discovered negatively charged boron vacancy (V B − ) center stands out due to its optical addressability and coherent controllability. Among the various methods reported for generating such defects, ion implantation is notable as a readily accessible technique. In this paper, the properties of V B − defects in hBN generated via ion implantation are extensively studied. We achieve a ubiquitous distribution of highly stable defects across the crystal sample, and find that the ion beam current density, rather than fluence, plays a critical role in determining the uniformity and density of defects. The generated defects display bright and stable photoluminescence, and we explicitly investigate the dependence of spin properties on factors such as laser, microwave power, and duration. An intriguing phenomenon is observed wherein the peak contrast exceeds 20% without any enhancing techniques in the optically detected magnetic resonance spectrum for some special defects. Our results provide valuable insights and suggestions for the controlled generation of V B − defects in hBN through ion implantation.