Surface-induced charge state conversion of nitrogen-vacancy defects in nanodiamonds

TL;DR

This study investigates how the surface of nanodiamonds influences the charge states of nitrogen-vacancy defects, revealing size-dependent effects and methods to enhance negatively-charged NV centers for quantum applications.

Contribution

It introduces a surface trap model explaining charge state conversion and demonstrates thermal oxidation as a technique to increase NV$^{-}$ defect proportion in nanodiamonds.

Findings

NV$^{-}$ proportion decreases with ND size

Surface traps influence charge states

Thermal oxidation increases NV$^{-}$ in 10-nm NDs

Abstract

We present a study of the charge state conversion of single nitrogen-vacancy (NV) defects hosted in nanodiamonds (NDs). We first show that the proportion of negatively-charged NV$^{-}$ defects, with respect to its neutral counterpart NV$^{0}$, decreases with the size of the ND. We then propose a simple model based on a layer of electron traps located at the ND surface which is in good agreement with the recorded statistics. By using thermal oxidation to remove the shell of amorphous carbon around the NDs, we demonstrate a significant increase of the proportion of NV$^{-}$ defects in 10-nm NDs. These results are invaluable for further understanding, control and use of the unique properties of negatively-charged NV defects in diamond