Different Types of Quantum Emitters Created by Thermal Annealing in CVD Grown Hexagonal Boron Nitride

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 in Ar gas flow. The thermal annealing 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. Our results provide insight into different types of defects thermally created in CVD-grown hBN films.