Haidong Liang1,Yuan Chen1,Chengyuan Yang1,Goki Eda1,Andrew Bettiol1
National University of Singapore1
Haidong Liang1,Yuan Chen1,Chengyuan Yang1,Goki Eda1,Andrew Bettiol1
National University of Singapore1
Recently the negatively charged boron vacancies ( V<sub>B</sub><sup>-</sup>) in hexagonal boron nitride (hBN) have been shown as spin defects that have great potential in quantum sensing. However, so far the sensitivity is limited by either photoluminescence (PL) brightness or the optically detected magnetic resonance (ODMR) contrast, and linewidth. In this work, we demonstrate the generation of these spin defects using high energy helium ion beams and perform ODMR measurements with different laser and microwave powers. The spin defects generated by high energy helium ions exhibit a high PL brightness and ODMR contrast while keeping a small linewidth, hence a good sensitivity. By comparing different fluences of helium irradiations, we determine an optimal fluence which is sufficient in creating spin defects without damaging the overall crystal lattice structure. With this optimal fluence, we can obtain a high signal-to-noise ratio ODMR spectrum with an accurate measurement of zero field splitting frequency, and a best sensitivity as ~2.55μT/sqrt (Hz). Moreover, with a focused beam, we can deterministically create such spin defects with nanometer precision.<br/>Hexagonal boron nitride (hBN) has been a centre of interest due to its ability to host several bright quantum emitters at room temperature. However, the identification of the observed emitters remains challenging due to spectral variability as well as the lack of atomic defect structure information. In this work, we report two new blue quantum emitters with zero phonon line (ZPL) centred around 460 nm and 490 nm in hBN powders. We further demonstrate that the new emissions can be created by high temperature annealing or high energy ion irradiation in exfoliated hBN flakes. Scanning transmission electron microscopy (STEM) reveals that the dominant defect structures present in ion irradiated sample are vacancy type and adatom (intercalant) type. Through first principle GW-BSE (Bethe-Salpeter equation) calculation, we attribute the observed emissions at 460nm and 490nm to originate from boron intercalant and nitrogen intercalant respectively. Our results not only discover a new group of blue quantum emissions in hBN, but also provide an insight on the physical origin of the emissions by correlating the emission wavelength with local atomic structures in hBN.