High resolution Raman imaging of single wall carbon nanotubes using electrochemically etched gold tips and a radially polarized annular beam
(Color online) Schematic diagram of the tip-enhanced Raman system.
Based on our observation of few hundreds of electron microscopy images (SEM and TEM) of chemically etched tips, a representative transmission electron microscopy (TEM) image of a tip having a tip radius of curvature of is presented.
(Color online) Schematic diagram showing the polarization of the beam before and after passing through the composite wave plate and the fast axes of the quadrants of the composite wave plate (top). Ray diagram showing the polarization of the beam at the focal point (bottom).
(Color online) (a) Raman spectrum of bulk single wall carbon nanotubes (SWNT) sample. (b) Far-field Raman image of a single wall carbon nanotubes sample on glass cover slip using the G-peak intensity. The sample is a mixture of isolated single tubes and bundles of tubes. (c) Topography and (d) TERS images of single wall carbon nanotubes. The sizes of the images are . Line correction was performed on the topography image. Gauss filtering was applied to the Raman image. The white dots in the Raman image are due to artifacts arising from noise and filtering. The cross section of the TERS image marked by the black line is shown as inset; the full width half maxima of the profile is .
(Color online) Raman images with radially polarized circular beam and radially polarized annular beam: (a) TERS image with a radially polarized circular beam and (b) corresponding topography image, (c) TERS image with a radially polarized annular beam and (d) corresponding topography image. The sizes of the images are . Line corrections were performed on the topography images. Gauss filtering was applied to the Raman image. The beam shape and radial polarization are shown in the inset of the images.
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