Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 5: Rastersondentechniken I

O 5.1: Vortrag

Montag, 24. März 2003, 11:15–11:30, FOE/ORG

Apertureless near-field scanning optical microscopy: depth of field and vertical resolution — •Markus Raschke and Christoph Lienau — Max-Born-Insitut, Berlin

Scattering type ("aperturelessNo-dq) near-field scanning optical microscopies currently emerge as promising techniques due to their ability to achieve all-optical resolution in the nanometer range. Here, we investigated systematically in a linear light scattering experiment the influence of substrate dielectric properties, tip characteristics and their correlations on image formation, resolution and signal strength. It is found that the information obtained about the probed surface is related to a vertical average over a surface layer with a thickness that is determined by the metal tip geometry. Using wedged metal films depths of field as small as ∼ 5 nm can be demonstrated. The results can be described by a the optical field induced coupling between the tip and the sample (active probe). The resulting consequences for the image formation in apertureless microscopy will be discussed.

Furthermore, for optimized illumination and detection conditions non-interferometric detection was made possible. Strongly tip-enhanced near-field signals nearly comparable to the far-field Rayleigh scattered light intensities were found. This indicates that this detection scheme is directly applicable for spectroscopic scattering experiments using ultrafast and/or spectrally broad band light sources.