E.A. Kazantsevac aNational Research Center "Kurchatov Institute", Alikhanov Institute of Theoretical and Experimental Physics, ul. B. Cheremushkinskaya 25, Moscow, 117218, Russian Federation bNT-MDT Spectrum Instruments, Zelenograd, Russian Federation cMoscow Technological University, prosp. Vernadskogo 78, Moscow, 119454, Russian Federation
This paper discusses the operating principles of the Apertureless Scanning Near-field Optical Microscope (ASNOM), in which the probe acts as a rod antenna and its electromagnetic radiation plays a role of the registered signal. The phase and amplitude of the emitted wave vary depending on the 'grounding conditions' of the antenna tip at the sample point under study. The weak radiation from a tiny (2—15 μm long) tip is detected using optical homo- and heterodyning and the nonlinear dependence of the tip polarizability on the tip-surface distance. The lateral resolution of ASNOM is determined by the tip curvature radius (1—20 nm) regardless of the wavelength (500 nm—100 μm). Capabilities of ASNOM are shown to provide surface optical map with nanometer resolution and to carry out spectral- and time-resolved measurements in a selected point of sample.
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