Internal reflection mode scanning near-field optical microscopy with the tetrahedral tip on metallic samples |
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Authors: | J Ferber UC Fischer N Hagedorn H Fuchs |
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Institution: | Physikalisches Institut, Westf?lische Wilhelms-Universit?t, Wilhelm-Klemm-Str. 10, D-48149 Münster, DE
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Abstract: | An internal reflection mode is introduced for scanning near-field optical microscopy (SNOM) with the tetrahedral tip. A beam
of light is coupled into the tip and the light specularly reflected out of the tip is detected as a photosignal for SNOM.
An auxiliary STM mode is used to control the distance during the scanning process and to record the topography of the sample
simultaneously with the SNOM image. Images were obtained of different metallic samples which show a contrast in the order
of 10% of the total reflected photosignal. In images of metallic samples an inverted contrast is consistently obtained compared
to images previously obtained of comparable samples in a transmission mode. The contrast shows a pronounced dependence on
the polarization of the incident beam with respect to the orientation of the edges of the tip. In the case of gold surfaces,
the photosignal as a function of distance between the tip and the surface shows a pronounced peak in the near-field range
of 0–20 nm which is tentatively attributed to the excitation of surface plasmons on the gold surface. The pronounced near-field
effects and the strong contrast in the near-field images and the resolution well below 50 nm are an indication of a highly
efficient coupling of the incident beam to a local excitation of the tip apex which is essential for the function of the tip
as a probe for SNOM.
Received: 17 May 1999 / Accepted: 18 May 1999 / Published online: 21 October 1999 |
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Keywords: | PACS: 07 79 C 61 16 C |
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