Graphene Characterization with Microscale UV-VIS and Raman!
As CRAIC Technologies specializes in optical tools for spectroscopic characterization from the ultraviolet to the short-wave infrared with microscale sampling areas, there are a multitude of applications for both our microspectrophotometers (MSP) and Raman microspectrometers in the study of low dimension materials and devices. This is especially true as they can both be used on the same microscope to quickly and easily collect Transmission, Reflection, or Photoluminescence microspectra from the same area as Raman microspectra, and these spectra can be mapped over 2-dimensional areas of the sample or device!
A microspectrophotometer can be used to measure the number of layers present with microscale sampling areas ranging from 1x1 micron up to 100x100 microns. Pristine graphene absorbs 2.29% per layer in the visible wavelengths, so the thickness of the sample at that position can be easily determined with just the transmission intensity.
In graphene (or other carbon based low dimension materials), there are three characteristic peaks that are typically observed in the Raman spectra, referred to as the D-peak at 1360 cm-1, the G-peak at 1600 cm-1, and the 2D peak at 2700 cm-1. The exact frequency of these vibrations will be influenced by the local environment, such as substrate, solvents, and localized defects, which is a major reason why Raman is such a great analysis tool.
The G-peak is due to the carbon-carbon bond stretching, while the D-peak is indicative of disorder or impurities in the Graphene sample. The 2D peak is common to all Graphite samples, and the intensity, width, and location of this peak can be used in order to determine the number of layers of the sample. The presence of the D peak in this spectrum indicates disorder in the sample, and the intensity of this peak can be used to measure the disorder in the sample.
To learn more about applications of CRAIC instruments to Graphene and other low-dimension materials, please reach out to us by phone or email!