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Optical Spectroscopy of Nanostructures

Summary

We develop novel spectroscopic measurement techniques to probe key physicochemical properties of advanced materials (i.e., 2D…) that will enable future technologies to move past conventional digital computing. Determining the fundamental processes of carriers, excitons, and related charge migration phenomenon are key aspects of our project. Additionally, we study alternative-state variables or information carriers, such as spin, phase, valley, etc., which will provide the foundation for lower-power electronics, optical switching, non-volatile memory, neuromorphic computing, and other technologies that are not possible with present material systems. Visible, infrared, and terahertz measurement systems, both in the linear and non-linear regime, enable detection of scattering, absorption, emission, and magnetism in these materials. 

Description

Raman map of the G peak intensity from exfoliated graphene  where layer numbers between 1 and 6 can be identified.

Raman map of the G peak intensity from exfoliated graphene where layer numbers between 1 and 6 can be identified.

The Raman facility is unique. Multiple laser lines, two spectrometers including a triple grating, cryostats, magnetic field, and an atomic force microscope combined instrument, provide the basis for the measurement capabilities. Through our extensive in-house engineering and synthesis capabilities, we are able to uniquely synthesize the nanomaterials, fine tune their properties and isolate specific parameters for study. This cycle of production, isolation, and characterization is fundamental to a meaningful, detailed analysis.

Multidisciplinary collaborations, both those inside of NIST and beyond, are crucial to the group's success. By working in research teams, we learn more and contribute more fully to the physics of nanotechnology. NIST teams with which we actively collaborate include Carbon Nanotube Metrology and Graphene. 

Raman excitation profile of single-wall carbon nanotube dispersion.
Raman excitation profile of single-wall carbon nanotube dispersion.
 

Major Accomplishments

2016

  • Improved AFM/Raman reproducibility and usability to routinely resolve 100 nm (sub diffraction limit) spatial features.
  • New physics revealed in carbon nanotubes.  First on the cross section of the specific modes; radial breathing mode and G graphite mode and then on the defect (D) peaks response to laser frequency-i.e., dispersiveness-is not an inherent phenomenon.

2015

  • Developed Raman metrology for measuring carbon nanotubes, graphene, and other 2D materials.
  • Developed unique instrumentation on magneto-Raman and TERS
Created September 23, 2014, Updated January 30, 2018