An investigation was made of  the effect of surface termination on the charge state of nitrogen-vacancy (NV) centers, which were ion-implanted a few nanometers below the surface of diamond. It was found that, when changing the surface termination from oxygen to hydrogen, previously stable NV- centers converted into NV0 and subsequently into an unknown non-fluorescent state. This effect was found to depend strongly on the implantation dose. Simulations of the electronic band structure confirm the disappearance of NV- in the vicinity of the hydrogen-terminated surface. The band bending, which induces a p-type surface conductive layer, leads to a depletion of electrons in the nitrogen-vacancies close to the surface. Therefore, hydrogen surface termination provides a chemical way to control the charge state of nitrogen-vacancy centers in diamond. Furthermore, it opens the way to electrostatic control of the charge state with the use of an external gate electrode.

Chemical Control of the Charge State of Nitrogen-Vacancy Centers in Diamond. M.V.Hauf, B.Grotz, B.Naydenov, M.Dankerl, S.Pezzagna, J.Meijer, F.Jelezko, J.Wrachtrup, M.Stutzmann, F.Reinhard, J.A.Garrido: Physical Review B, 2011, 83[8], 081304