“Surface Science of 2-Dimensional Crystals Probed by Optical Spectroscopy”
Two-dimensional crystals (2DX) represented by graphene
hold substantial potentials both in fundamental research and industrial
applications owing to novel electronic and optical properties enabled by
dimensional confinement. In addition, their intrinsic properties are readily
manipulated by chemical entities in direct contact because of their high
fraction of surface atoms. To uncover and control emerging properties, my group
has explored surface and interfacial science of low dimensional materials and
developed optimized spectroscopic methods. In particular, Raman spectroscopy
has proven to be a versatile analytical probe because of the varying spectral
features for different thickness, stacking, defect density, charge density,
mechanical strain, temperature, etc. Such multimodal sensitivity, however,
turns into difficulty when multiple unknown variables are to be determined simultaneously.
In this talk, I will explain that the effects of strain and charges in graphene
can be optically separated from each other by correlation analysis of the two
modes, enabling simple quantification of both. Employing the analysis, I will present
our recent findings on important surface scientific problems in 2-dimension
such as structural deformation caused by substrates and thermal perturbation, interfacial charge transfer, and molecular diffusion through
2DX-substrate interface. References
1. J. E. Lee, G. Ahn, J. Shim, Y. S. Lee, and S. Ryu,*
“Optical Separation of Mechanical Strain from Charge Doping in Graphene”,
Nature Commun. 3, 1024
(2012)
2. J. Shim, C. H. Lui, T. Y. Ko, Y.-J. Yu, P. Kim, T. F.
Heinz, and S. Ryu,* “Water-Gated Charge Doping of Graphene Induced by Mica
Substrates”, Nano Lett. 12,
648 (2012)
3.
D. Lee, G. Ahn and S. Ryu,*
“Two-Dimensional Water Diffusion at a Graphene-Silica Interface”, J. Am. Chem.
Soc. 136, 6634
(2014)