Vibrational spectroscopy, including Raman spectroscopy can be used for identifying molecular species, which is
not possible by a scanning probe microscopy or an electron microscopy. Moreover, vibrational spectra contain structural
information, such as intermolecular interactions, molecular orientations, and symmetry distortions of each species.
Therefore, Raman spectroscopy is a powerful tool for studying the chemical composition of matter.
By employing Tip-enhanced Raman spectroscopy (TERS), we can perform Raman spectroscopy with nano-scale
spatial resolution. Our approach relies on the enhanced filed near a laser irradiated metal tip which works as the Raman
excitation source. We have investigated nano-composite materials by TERS. Near-field Raman spectra revealed the
nano-scale properties of molecules encapsulated in single-wall carbon nanotubes (SWNT). The enhanced field act on
encapsulated molecules through the wall of SWNT to extract chemical information inside. &bgr;-carotene which has strong
Raman intensities under visible light illuminations is used as an encapsulated molecule. The advantage of Raman
spectroscopy is that the information of both SWNT and &bgr;-carotene can be obtained at the same time. So, it is possible to
discuss the interaction between SWNT and the encapsulated molecules. Near-field Raman spectra measured at several
different positions on SWNT bundle show that &bgr;-carotenes inside the tube are not uniformly distributed. We also find
that the filling rates and the peak positions of the radial breathing mode of SWNT are linearly correlated.