Continuous‐Wave Laser Induced Formation of Carbon‐Related Defects in Hexagonal Boron Nitride Enhanced by Surface Plasmons and Strain

Abstract Hexagonal boron nitride (hBN), a 2D van der Waals material, has garnered significant attention for its applications in optoelectronic devices and quantum photonics, primarily due to its remarkable stability and wide bandgap. The hetero‐integration of graphene within the hBN lattice to form nano‐heterostructure and carbon‐related emitters is of particular interest due to the engineered bandgap, defect states and magnetic properties. However, achieving such heterostructures remains challenging. In this work, it is demonstrated that continuous‐wave laser irradiation of pristine hBN flakes induces the aggregation of carbon atoms, forming graphene fragments that result in carbon‐related defect emitters at the hBN/graphene boundaries with excellent repeatability and stability. By capping metal nanoparticles with hBN, it is shown that the synergistic effects of localized surface plasmon resonances and strain effectively lower the irradiation threshold required to achieve these structures, while enhancing and stabilizing fluorescence from defect emitters at the boundaries. Furthermore, selective enhancement of specific wavebands within the broad emission spectrum of carbon‐related defects is achieved by nanoparticle‐on‐mirror nanocavities. This work presents a straightforward and efficient approach to introducing graphene fragments and carbon‐related defect emitters in 2D pristine hBN flakes, paving the way for integrated circuitry and on‐chip quantum nanophotonic devices.