Surface nanostructuring and optical activation of lithium fluoride crystals by ion beam irradiation

We present results on simultaneous nanostructuring and optical activation of lithium fluoride crystals by 800 eV off-normal Ar+ sputtering at different ion doses. The samples were studied by atomic force microscopy and optical spectroscopy. After ion irradiation smoothening of the initial random roughness is achieved and well-defined self-organized ripple structures appear, having a mean periodicity of 30 nm and a mean height of 3 nm. The simultaneous optical activation of the irradiated samples is due to the stable formation of electronic defects with intense photoluminescence in the visible spectral range. These results demonstrate the possibility to simultaneously modify the optical and topographical properties of LiF crystals by off-normal ion irradiation. Though none of the usual optical measuring devices have the required resolution to study the spatial distribution of the produced electronic defects, therefore allowing us to collect information on the possible “optical nanostructuring” of the irradiated surface, the efficient production of color centers with intense and stable photoluminescence in the visible spectral range on the periodically nanostructured surface seems anyhow very promising for the production of advanced substrates. Our findings seem to indicate that further work could be successfully done to obtain, in a controlled way, functionalized substrates with regular patterns of lithiumenriched and light-emitting areas at the nanoscale level.