Raman Spectroscopy
Raman-AFM and TERS Application Examples
AFM-Raman is now a well established technique offering a multi-technique platform for deeper understanding of materials at the nanoscale. Tip-enhanced Raman scattering (TERS) takes advantage of that same platform combined with surface plasmon resonance effects localized at the probe-tip to bring chemical information with nanometric spatial resolution. These techniques have the potential to transform spectroscopic research and sample characterisation in many varied fields, including biology, semiconductors, nanomaterials. The examples given below illustrate the power of AFM-Raman and TERS analysis to provide new insights into sample structure. These examples should not be considered exhaustive. Please contact us if you would like to understand how Raman-AFM and TERS could be applied to your research.
Co-localized Raman and AFM imaging of carbon nanotubes
Raman high-speed confocal imaging allows to easily locate a single carbon nanotube among other type of carbon, and AFM provides topography as well as other physical parameters (like conductance or thermal information). Images were acquired over a 10um x 10um area, with a step size of 250nm for the Raman map.
The spectra (bottom) shows the carbon D and G band region, illustrating the clear differences between the high quality nanotube (red) and disordered material (green).
Tip Enhanced Raman Spectroscopy of Multiwall Carbon Nanotubes (MWCNTs)
(a) AFM topographic image of two multiwall carbon nanotubes. (b) AFM topography profile through the line indicated in the image. (c) the tip-enhanced Raman intensity profile through the same line. The adjacent nanotubes can be spatially resolved in the Raman profile. The full width half maximum (FWHM) values of the nanotube signal from the TERS Raman profile are calculated as 48nm and 29nm respectively.
Data courtesy of Professor Razvigor Ossikovski, and Dr Marc Chaigneau, CNRS Ecole Polytechnique, Palaiseau, France.
[Reference: Chemical Physics Letters, 2009, 469, 161–165]
TERS Imaging of Nano-structured Silicon
SiOX features on a silicon substrate have been imaged using TERS, based on a LabRam HR combined Raman-AFM system. The sample structure is shown (top). An image based on Raman intensity clearly shows the sub-micron structure, and illustrates how TERS can be used to analyse features on the sub-50nm scale. The line profiles for both AFM and TERS (near field Raman) show the correlation between AFM tip height and TERS Raman intensity.
Data courtesy of Professor Alexei Sokolov, University of Tennessee, Knoxville, USA.
[Reference: Journal of Raman Spectroscopy, 2007, 38, 789]
Strained silicon layer on SiOX and Si
TERS analysis of a 30 nm strained silicon layer on SiOX and Si. When the tip away from the surface, the spectrum (blue) shows signal from both the strained silicon top layer in addition to the silicon wafer substrate. However, as the tip is lowered to the sample (red), there is a significant increase in contribution from the 30 nm top layer of strained silicon, illustrating the nanometer spatial resolution which TERS provides.
Data courtesy of Professor Alexei Sokolov, University of Tennessee, Knoxville, USA.
To learn more about this technology and how you can integrate all your needs into one powerful instrument, please fill out the contact form or call or email your local HORIBA Scientific representative.
