Fluorescence imaging of submicrometric lattices of colour centres in LiF by an apertureless scanning near-field optical microscope

Abstract : We report fluorescence imaging of colour centres in Lithium Fluoride (LiF) using an apertureless Scanning Near Field Optical Microscope (SNOM). The sample consists of periodically spaced submicrometric coloured areas F2 laser-active colour centres produced by low-energy electron beam lithography on the surface of a LiF thin film. A silicon Atomic Force Microscope (AFM) tip is used as an apertureless optical probe. AFM images show a uniform surface roughness with a RMS of 7.2 nm. The SNOM images of the red fluorescence of colour centres excited at λ=458 nm with an argon ion laser show that the local photon emission is unambiguously related to the coloured areas and that topographic artefacts can be excluded.