Reflection-mode scanning near-field optical microscopy using an apertureless metallic tip

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Abstract
Recently, a reflection-mode near-field optical microscope with an apertureless tungsten tip has been introduced and 100-nm resolution has been achieved [R. Bachelot, P. Gleyzes, and A. C. Boccara, Microsc. Microanal. Microstruc. 5, 389–397 (1994)]. The optical signal is recorded in parallel with a tapping-mode atomic force microscope signal. By showing several images here, we confirm the capabilities of this device and clearly demonstrate a 20-nm (∼λ/35) resolution that has been achieved with smaller tips. A study of these images shows that both the topography and the near electromagnetic field of the sample can be independently probed by this device. Additionally, we discuss the principle of our approach, notably on the basis of interference phenomena between a Rayleigh scatterer and its image through the reflecting surface, and some of the setup’s experimental characteristics are presented.