This summer marks my fourth year participating in the Research Experience for Teachers (RET) program at the University of Notre Dame. I am fortunate to have been able to work with the same research group all four summers. My work this summer deals with 2d materials, specifically the growth and characterization of graphene. Graphene, like many other novel 2d materials, exhibits unique properties that are useful for high frequency energy efficient electrical devices.
The graphene that I study is grown in a chemical vapor deposition oven in the Stinson-Remick cleanroom on campus. Essentially, methane is flowed under very low pressure at high temperature over a copper substrate. The copper provides nucleating sites for the decomposition of the methane, and consequently the sp2 hybridized carbon sheet forms radially at these nucleating sites.
Once the graphene is grown, it must be characterized. We do this by removing the copper substrate and transferring the graphene to a silicon wafer. This is done because you can optically resolve the graphene when using certain types of silicon due to a small index of refraction. Once the samples have been transferred to silicon, we utilize kelvin probe microscopy to characterize the surface as well as the electric field of the graphene, which provides details to the amount of defects on the graphene sheet. Another tool we use to confirm the presence of single layer or multiple layer graphene is Raman Spectroscopy. Graphene has characteristic absorbance peaks that make it quite easy to identify if you have grown single layer or multiple layer graphene.