A single crystal CVD diamond component comprising: a surface, wherein at least a portion of said surface is formed of as-grown growth face single crystal CVD diamond material which has not been polished or etched and which has a surface roughness Ra of no more than 100 nm; and a layer of NV− defects, said layer of NV− defects being disposed within 1 μm of the surface, said layer of NV− defects having a thickness of no more than 500 nm, and said layer of NV− defects having a concentration of NV− defects of at least 105 NV−/cm2.