Simulations of tip-enhanced optical microscopy reveal atomic resolution.

We have performed finite element electromagnetic analysis of ‘apertureless’ scanning near-field optical microscope tips. A variety of radii was considered, from 40 nm down to 1 nm, and the enhancement of optical scattering from the region beneath the probe apex was modelled in air and water. We observed sizeable spectral shifts when the radius decreases, together with a surprising increase in the amount of scattering from small tips. The lateral resolution is considered, which is shown to be always smaller than the tip radius, and for 1-nm-radius tips can allow atomic resolution imaging with sufficient optical enhancement. Gold, silver, copper and aluminium were modelled as tip materials. [ABSTRACT FROM AUTHOR]