Research of Low-Dimensional Semiconductor Nanostructures by Optical Methods (Scanning Near-Field Optical Microscopy, Raman Scattering)

The text presents the study of semiconductor structures using apertureless scanning near-field optical microscope (sSNOM). The extraction of the signal corresponding to the light wave scattered by the scanning tip is performed using optical homodyning in the Michelson interferometer scheme. Modulation of the phase of the homodyning beam accompanied by the corresponding demodulation of the signal from the photodetector, allows to measure not only the amplitude but also the phase of the optical signals caused by the near-field tip-sample interaction. We have investigated InSb/GaSb quantum dots. The material-contrast imaging provided by sSNOM allows us to obtain images of quantum dots with a resolution of ~10-20 nm in the sample plane at the CO2 laser wavelength (935 cm-1, 10.6 μm). The surface SNOM images distinguish the materials forming the quantum dots and the substrate. Phonon-polariton waves on the surface of crystalline SiC excited by a plane coherent wave incident on the sample (in the wavelength range of the CO2 laser) have been investigated. The laser lines are in the frequency range of the region of existence of surface phonon-polariton states in crystalline SiC. This allows us to observe the excitation by light of running and standing phonon-polariton waves in the presence of metal masks, of special shape, applied to the exposed surface of the crystal. A lattice of parallel strips with an optimal period allows the formation of a wave packet of surface phonon-polariton waves under the action of incident light in the direction corresponding to Bragg scattering.