Studying the local character of Raman features of single-walled carbon nanotubes along a bundle using TERS

Here, we show that the Raman intensity of the G-mode in tip-enhanced Raman spectroscopy (TERS) is strongly dependent on the height of the bundle. Moreover, using TERS we are able to position different single-walled carbon nanotubes along a bundle, by correlating the observed radial breathing mode (RBM) with the AFM topography at the measuring point. The frequency of the G- mode behaves differently in TERS as compared to far-field Raman. Using the RBM frequency, the diameters of the tubes were calculated and a very good agreement with the G--mode frequency was observed

Strain and composition effects on Raman vibrational modes of silicon-germanium-tin ternary alloys

We investigated Raman vibrational modes in silicon-germanium-tin layers grown epitaxially on germanium/silicon virtual substrates using reduced pressure chemical vapor deposition. Severalexcitation wavelengths were utilized to accurately analyze Raman shifts in ternary layers with uniform silicon and tin content in 4–19 and 2–12 at. % ranges, respectively. The excitation using a633 nm laser was found to be optimal leading to a clear detection and an unambiguous identification of all first order modes in the alloy. The influence of both strain and composition on these modes is discussed. The strain in the layers is evaluated from Raman shifts and reciprocal space mapping data and the obtained results are discussed in the light of recent theoretical calculations