Figure 3.
Schematic for proposed mechanism. (a) The acid-refluxed diamond sample (NVD) has a shallow NV-doped layer up to 5 nm from the surface, which consists of nondiamond carbon (gray region) and oxygen functionalities (orange dots) on the surface. (b) Laser exposure under different environments can cause desorption of nondiamond carbon- and oxygen-containing functional groups (in vacuum) or an increase in oxygen termination on the surface (in air). These changes lead to the charge state conversion between NV– and NV0.