Deterministic generation of spin defects in van der Waals materials for quantum sensing applications

Quantum sensing is a revolutionary technology that is already advancing from a laboratory-based fundamental research field to real-world applications. Quantum sensing allows us to understand how we interact with the world around us by detecting small changes in electric or magnetic fields and other physical quantities with superior accuracy over classical sensing techniques. This is possible as quantum sensors utilize quantum resources to analyze data at the atomic level, whereas classical sensors can only extract data from a large collection of atomic systems. High-quality, on-demand quantum emitters (QE) are essential for integrated on-chip quantum sensing applications. Until recently, QEs were mostly confined in the bulk of solid-state materials, for example, the bright NV⁻ centers in diamond and silicon carbide. 2D materials such as transition metal dichalcogenides (TMD) and hexagonal boron nitrides (hBN) have become promising new bases for generating on–demand QEs. hBN is a wide band gap 2D material that can house color centers consisting of the negatively charged boron vacancy defect (VB⁻) which is optically and spin active at room temperature. In this work, we deterministically fabricate optically active spin defects in hexagonal boron nitride (hBN) using focused ion beam irradiation of few-layer hBN flakes, with the goal to exploit these defects for quantum sensing applications. The ion bombardments knock off boron atoms in the irradiated zones, generating the negative boron vacancy (VB⁻) defect, which has been shown to have an appreciable optically driven magnetic resonance (ODMR) contrast in several studies. In addition to hBN, this work will explore similar techniques together with strain engineering to fabricate inherent spin defects in monolayer TMDs like tungsten diselenide (WSe2) and study the origin of these defects through a series of defect generation and passivation experiments.