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Philipp Schmidt: Band gap opening in dual-gated bilayer graphene heterostructure devices

posted 14 Aug 2019, 05:44 by info admin   [ updated 14 Aug 2019, 05:45 ]

P. Schmidt1, E. T. Icking1,2, L. Banszerus1,2, C. Steiner1, C. Rogge1, K. Watanabe3, T. Taniguchi3,
B. Beschoten1 and C. Stampfer1,2

1JARA-FIT and 2nd Institute of Physics, RWTH Aachen University, Germany, EU
1,2Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich, Germany, EU
3National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan

One of the most unique characteristics of bilayer graphene (BLG) is the possibility to tune the low-energy electron dispersion relation by applying an external electric field. This allows for opening up a band gap, modifying the band curvatures and even changing the topology of the Fermi surface. It has been shown that local graphite gates improve the device quality significantly compared to devices equipped with a global silicon back gate [1]. This can be explained by the formation of conductive edge channels due to fringe fields of the far separated global back gate and a lower disorder potential for local graphite gates efficiently screening charge disorder in the SiO2. While this current technology already allows for the confinement of charge carriers in zero or one dimensions [2], novel, more complex device geometries require structured top and back-gates [3]. This requires structuring of the graphite gate, which results in contaminated interfaces and therefore could lead to a reduced device quality. On the other hand, using a lithographically defined local gold gate results in a high disorder potential due to its rough surface. To avoid both problems, we present a technique to flip the encapsulated graphene with a pre-defined gate structure so that the rough surface of the gold is not at the interface to the graphene stack. Bias spectroscopy and temperature dependent transport measurements of a flipped gold gate device are also presented and compared to the graphite counterpart.

[1] H. Overweg, et al.: Nano Lett. 2018, 18, 1, 553-559

[2] L. Banszerus et al.: Nano Lett. 2018, 18, 8, 4785-4790

[3] J. Li, et al.: Science 2018, 362, 6419, 1149-1152


Philipp Schmidt is currently a Master student in the group of Christoph Stampfer at RWTH Aachen University. He is interested in mesoscopic electron transport in bilayer graphene nanostructures and the nanofabrication of 2D heterostructures.

During his bachelor studies he investigated the dephasing properties of a graphene-based nanomechanical resonator coupled to a microwave cavity.