Mitigation of nitrogen vacancy photoluminescence quenching from material integration for quantum sensing

Abstract

The nitrogen-vacancy (NV) color center in diamond has demonstrated
great promise in a wide range of quantum sensing. Recently, there have been a series of
proposals and experiments using NV centers to detect spin noise of quantum materials
near the diamond surface. This is a rich complex area of study with novel nanomagnetism
and electronic behavior, that the NV center would be ideal for sensing.
However, due to the electronic properties of the NV itself and its host material,
getting high quality NV centers within nanometers of such systems is challenging.
Band bending caused by space charges formed at the metal-semiconductor interface
force the NV center into its insensitive charge states. Here, we investigate optimizing
this interface by depositing thin metal films and thin insulating layers on a series
of NV ensembles at different depths to characterize the impact of metal films on
different ensemble depths. We find an improvement of coherence and dephasing times
we attribute to ionization of other paramagnetic defects. The insulating layer of
alumina between the metal and diamond provide improved photoluminescence and
higher sensitivity in all modes of sensing as compared to direct contact with the metal,
providing as much as a factor of 2 increase in sensitivity, decrease of integration time
by a factor of 4, for NV T1 relaxometry measurements.