Magnetoresistance (MR) of twisted bilayer graphene on electron transparent substrate

초록

We studied the magnetoresistance (MR) of twisted bilayer graphene (tBLG) on electron transparent substrate. Samples of tBLG were assembled on free-standing silicon nitride (SiNx) membranes (<100 nm thick) by transferring chemical vapor deposition (CVD)-grown single layer graphene (SLG) twice; this allowed the measurement of the angle of rotation between the two layers, the twist angle, by electron diffraction using a transmission electron microscope (TEM). To compare with the previous reports on tBLG, we performed Raman spectroscopy on our samples. We measured the MR of tBLG for two different twist angles: 2 degrees (small) and 18 degrees (large). The MR showed superposition of two Shubnikov de Haas (SdH) oscillations for both angles. An analysis of the oscillation peaks by Landau fan diagrams showed difference as twist angle. While the large twist angle (18 degrees) sample had two anomalous pi Berry's phases, the small twist angle (2 degrees) sample had conventional 2 pi and anomalous pi Berry's phase depending on carrier density. (C) 2016 Elsevier B.V. All rights reserved.

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