Abstract
The nitrogen-vacancy (NV) centre in diamond is a promising candidate for quantum computing applications and magnetic sensing applications, because it is an atomic-scale defect with stable coherence time (T2) and reliable accessibility at room temperature. We demonstrated a method for improving the NV spin properties (the full width half maximum (FWHM) value of the magnetic resonance spectrum and T2) through a near-field (NF) etching method under ambient conditions. The NF etching method, based on a He-Cd ultraviolet laser (325 nm), which is longer than the absorption edge of the oxygen molecule, enabled selective removal of defects on the nanodiamond surface. We observed a decrease in the FWHM value close to 15% and an increase in T2 close to 25%. Since our technique can be easily reproduced, a wide range of NV centre applications could be improved, especially magnetic sensing applications. Our results are especially attractive, because they have been obtained under ambient conditions and only require a light source with wavelength slightly above the O2 absorption edge.
Highlights
The nitrogen-vacancy (NV) centre has emerged as a promising candidate for nanoscale sensing applications in physics and biology[1,2,3,4,5]
The T2 of the NV centre typically lies in the microsecond range[20], with the benchmark currently being 1.8 ms achieved by using an ultrapure isotopically controlled single-crystal chemical vapour deposition (CVD) method[21]
We demonstrated that under sufficiently long-wavelength UV laser-light (325 nm) illumination, it was possible to reduce the dimensions of the nanodiamonds, alongside a decrease in the full width at half maximum (FWHM) value of the ODMR spectrum, and an increase in T2
Summary
The nitrogen-vacancy (NV) centre has emerged as a promising candidate for nanoscale sensing applications in physics and biology[1,2,3,4,5]. It was possible to achieve coherence times well into the minute range, by using ionized donors combined with optical methods and dynamical decoupling[10], it is still of common interest to find a more convenient qubit candidate, which can be used under ambient conditions One of these candidates is the NV centre in diamond, which naturally exhibits excellent characteristics, such as long electron-spin coherence and relaxation times as well as unique optical and magnetic properties[11,12,13,14,15,16]. We demonstrated that under sufficiently long-wavelength UV laser-light (325 nm) illumination, it was possible to reduce the dimensions of the nanodiamonds, alongside a decrease in the full width at half maximum (FWHM) value of the ODMR spectrum, and an increase in T2 These results indicate that the surface etching achieved with the NF etching method results in the removal of parasitic magnetic fields and optical noise from the nanodiamond surface
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