Electron Beam Restructuring of Quantum Emitters in Hexagonal Boron Nitride

Abstract

Hexagonal boron nitride (hBN) holds promise as a solid state, van der Waals host of single photon emitters for on-chip quantum photonics. The B-center defect emitting at 436 nm is particularly compelling as it can be generated by electron beam irradiation. However, the emitter generation mechanism is unknown, the robustness of the method is variable, and it has only been applied successfully to thick flakes of hBN (≫ 10 nm). Here, it is used in situ time-resolved cathodoluminescence (CL) spectroscopy to investigate the kinetics of B-center generation. It is shown that the generation of B-centers is accompanied by quenching of a carbon-related emission at ≈305 nm and that both processes are rate-limited by electromigration of defects in the hBN lattice. It identifies problems that limit the efficacy and reproducibility of the emitter generation method and solve them using a combination of optimized electron beam parameters and hBN pre-and postprocessing treatments. It is achieved B-center quantum emitters in hBN flakes as thin as 8 nm, elucidate the mechanisms responsible for electron beam restructuring of quantum emitters in hBN, and gain insights toward the identification of the atomic structure of the B-center quantum emitter.