Defect engineering of hBN for quantum light sources

Shih-Chu Lin^1*, Ya-Ching Tsai¹, Yu-Chen Chen², Wen-Hao Chang²

¹Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan

* Presenter:Shih-Chu Lin, email:linsc81893@gmail.com

Solid-state single photon emitters (SPEs) play an important role in photonic quantum technologies. Recently, SPEs based on defects in hexagonal boron nitride (hBN) have been demonstrated, exhibiting outstanding optical properties at room temperature. In this work, we created SPEs in chemical vapor deposition (CVD) grown 2.5-nm-thick hBN films by high temperature annealing and using electron beam irradiation to locally create defect arrays in exfoliated hBN. The thermally created defects in the CVD grown hBN films can be classified into two types. The photoluminescence (PL) spectra of type-I defects show a broadened zero phonon line (ZPL) near 575 nm with a strong phonon sideband (PSB). The ZPL of type-II defects is distributed in 650-750 nm, exhibiting a relatively narrower ZPL linewidth with a much weaker PSB. Temperature dependent PL measurements show that the ZPL linewidth of type-II defects exhibits a weak temperature dependence, indicating less phonon coupling. Polarization dependent measurement and Fourier plane imaging have also been performed to identify the dipole orientation of the two defect types. However, sites of SPEs created by thermal annealing are uncontrollable. In order to deterministically create SPEs in hBN, we used electron beam irradiation. The PL map shows the localized defects after electron beam irradiation. The PL emission from the defects exhibits a ZPL at 437 nm which is bright and stable at room temperature. We demonstrate two different methods to create defects in the hBN. Our results provide insight into different types of defects thermally created in CVD-grown hBN films and a method for site-controlled defect formations in hBN.

Keywords: 2D material, hexagonal boron nitride, single photon emitter