Single-photon emitters (SPE) in hexagonal boron nitride (h-BN) are promising for applications ranging from single-photon sources to quantum sensors. Previous studies exclusively focused on the generation and characterization of SPEs in relatively thick h-BN layers (≥ 30 nm). However, for electrical and magnetic sensing applications, the thickness of the h-BN limits the attainable spatial resolution. Here, we report the observation of blue-wavelength emitters (B-centers) activated by electron beam irradiation in ultra-thin (≃ 3 nm) h-BN. These SPEs in ultra-thin flakes exhibit reduced brightness, broader zero-phonon line, and enhanced photobleaching. Remarkably, upon encapsulation in thicker h-BN, we restore their brightness, narrow linewidth 230μeV at 5K, resolution limited), suppress photobleaching, and confirm single-photon emission with g(2)(0)<0.4 at room temperature. The possibility of generating SPEs in a few-layer h-BN and their subsequent incorporation into a van der Waals heterostructure paves the way for achieving quantum sensing with unprecedented nanometer-scale spatial resolution.
@article{arxiv.2507.02633,
title = {Single Photon Emitters in Ultra-Thin Hexagonal Boron Nitride Layers},
author = {Le Liu and Igor Khanonkin and Johannes Eberle and Bernhard Rizek and Stefan Fält and Kenji Watanabe and Takashi Taniguchi and Ataç Imamoğlu and Martin Kroner},
journal= {arXiv preprint arXiv:2507.02633},
year = {2025}
}