Simulations of atomic resolution tip-enhanced optical microscopy

Optical techniques can access a wealth of information but traditionally their resolution has been restricted by the diffraction limit. Near-field techniques, which used nanoscale apertures or nanotip electric field enhancement, have succeeded in circumventing Abbe's law. We show that atomic resolution is theoretically achievable for tip enhanced optical microscopy. Using finite element analysis of the electromagnetic field around a small radius metallic scanning probe microscopy tip, we modelled various tip radii and materials, and an aqueous environment as well as ambient air. For a 1 nm gold tip we predict a strong red shift, and surprisingly high values for the enhancement of the intensity of scattered light - over 10(7). For this tip, we predict that 0.2 nm lateral resolution in optical imaging is achievable - good enough to resolve individual atomic bonds. The promise of optical data at these spatial scales offers great potential for nanometrology and nanotechnology applications. (c) 2006 Optical Society of America.