Near-surface nitrogen-vacancy (NV) centers in diamond have been successfully employed as atomic-sized magnetic field sensors for external spins over the last years. A key challenge is still to develop a method to bring NV centers at nanometer proximity to the diamond surface while preserving their optical and spin properties. To that aim we present a method of controlled diamond etching with nanometric precision using an oxygen inductively coupled plasma process. Importantly, no traces of plasma-induced damages to the etched surface could be detected by X-ray photoelectron spectroscopy and confocal photoluminescence microscopy techniques. In addition, by profiling the depth of NV centers created by 5.0 keV of nitrogen implantation energy, no plasma-induced quenching in their fluorescence could be observed. Moreover, the developed etching process allowed even the channeling tail in their depth distribution to be resolved. Furthermore, treating a ¹² C isotopically purified diamond revealed a threefold increase in T ₂ times for NV centers with <4 nm of depth (measured by nuclear magnetic resonance signal from protons at the diamond surface) in comparison to the initial oxygen-terminated surface.

Reference: Effect of low-damage inductively coupled plasma on shallow nitrogen-vacancy centers in diamond, Felipe Fávaro de Oliveira, S. Ali Momenzadeh, Ya Wang, Mitsuharu Konuma, Matthew Markham, Andrew M. Edmonds, Andrej Denisenko and Jörg Wrachtrup, Appl. Phys. Lett. 107, 073107 (2015); Link (extern): http://dx.doi.org/10.1063/1.4929356