Nano-materials

Nanomaterials are considered as materials which have at least one of the three dimensions reduced down to nanometer scale.

Following this definition, there are 2D materials, which are essentially single layers, like including graphene, or other similar materials like transition metal dichalcogenide (TMDC) monolayers: MoS2, MoSe2, WS2, and WSe2. Another example can be all atomically thin layers, having often an importance in electronic, material or biological applications. Quasi-2D structures are also possible, for example heterostructures, comprising a stack of very thin layers and exhibiting for this reason new physical properties.
Carbon nanotubes, nanowires, and nanorods are examples of 1D materials and quantum dots or nanoparticles are 0D materials.

Raman image of graphene
Raman image of graphene, illustrating distribution of monolayer, bilayer and trilayer regions on a silicon substrate

Classical Raman micro-spectroscopy offers a diffraction limited spatial resolution in the order of a few hundreds of nanometers.  Despite the difference between this resolution and the actual dimensions of the nanomaterials, Raman remains an excellent tool to answer many questions about their structure and properties.  Furthermore, advances in methods such as Tip Enhanced Raman Spectroscopy (TERS) have also brought significant in achievable spatial resolution for Raman, down to 20 nm and below, more closely matching the actual dimensions of the nanomaterials.

Hyphenation

A step further is a combination of Raman spectroscopy with Scanning Probe Microscopy (SPM) techniques. Such combination allows the user to take advantage of these two analysis methods within a single experiment platform. The colocalized Raman-SPM measurements give separate information from Raman spectroscopy (chemical characterization and imaging) and SPM (physical properties), acquired from the same region of the sample. In contrast to this, Tip Enhanced Raman Spectroscopy (TERS) measurements provide the chemical information (like Raman) with nanometer spatial resolution (like SPM). Find more information on this subject on our pages related to NanoRaman.

Areas which benefit from Raman spectroscopy include:

  • Identification of materials constituting nanostructures
  • Number of layers for graphene and TMDC layers
  • Thickness of heterostructure layers
  • Diameter and chirality of carbon nanotubes
  • Stress/strain characterization
  • Electronic properties of materials (metallic/semiconductive, doping)
  • Localization of separated carbon nanotubes or quantum dots
Classical least square deconvolution of a Raman image of Carbon nanotubes and Graphene Oxide flakes
Classical least square deconvolution of a Raman image of Carbon nanotubes and Graphene Oxide flakes

Application Notes

Nano-materials Application Notes
  • Carbon03 : Carbon NanoTubes - What information does Raman bring?
  • RA50 : Perspectives on Raman spectroscopy of graphene.
  • RA54 : Number of layers of MoS2 determined using Raman Spectroscopy.
  • RA 67 : Combined Raman and Photoluminescence Imaging of 2D WS2