Near-field Raman spectral measurement of monocrystalline silicon by apertureless SNOM in feflection geometry

Abstract

The combination of scanning near field optical microscopy (SNOM) and Raman spectroscopy provides specific spectra information with nanometer spatial resolution beyond the diffraction limit, which has a wide range of potential applications and can help to understand the interactions between light and matter in nanometer scale. In this paper, a near-field Raman spectroscopy experimental setup has been developed by using an apertureless SNOM system. An Ar+ laser (514nm ) is focused at an angle onto the sample surface. The metallized tip is an Au-layer-coated cantilever of an atomic force microscopy and working in the contact mode. The near field Raman spectra signal can be detected when the tip approached the sample surface. In addition, the apertureless SNOM appears to have greater potential resolution than aperture-type SNOM system. Furthermore, the reflection geometry employed in this experiment allows no need for specific sample preparation, making near field spectrum study a reality for any samples. The reflected near field Raman spectra signal is collected by a microscope objective. Finally, the near field Raman spectra of monocrystalline silicon are presented.