Tip-enhanced sub-diffraction fluorescence imaging of nitrogen-vacancy centers in nanodiamonds

Abstract

This work demonstrates that the gold tip of an atomic force microscope enhances not only the fluorescence of the nitrogen-vacancy centers in nanodiamonds but also improves the optical resolution of the fluorescence image of the particles down to 40 nm in an apertureless near-field scanning optical microscope. With the tip in close contact with 20–30 nm diamonds, the average fluorescence intensity enhancement is 3. By measuring the fluorescence decay lifetime and the saturation intensity, we confirm that the fluorescence enhancement is contributed predominantly by the increase of the radiative decay rate.