Reliably counting atomic planes of few-layer graphene (n > 4).
We demonstrate a reliable technique for counting atomic planes (n) of few-layer graphene (FLG) on SiO(2)/Si substrates by Raman spectroscopy. Our approach is based on measuring the ratio of the integrated intensity of the G graphene peak and the optical phonon peak of Si, I(G)/I(Si), and is particularly useful in the range n > 4 where few methods exist. We compare our results with atomic force microscopy (AFM) measurements and Fresnel equation calculations. Then, we apply our method to unambiguously identify n of FLG devices on SiO(2) and find that the mobility (μ ≈ 2000 cm(2) V(-1) s(-1)) is independent of layer thickness for n > 4. Our findings suggest that electrical transport in gated FLG devices is dominated by carriers near the FLG/SiO(2) interface and is thus limited by the environment, even for n > 4.
Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States. mpekyk@nus.edu.sg
Yee Kan
YK
Koh
Myung-Ho
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Bae
David G
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Cahill
Eric
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