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Dynamic Bandstructure and Capacitance Effects in Scanning Tunneling Spectroscopy of Bilayer Graphene

Published in Applied Physics Letters, 2019

We develop a fully self-consistent model to describe scanning tunneling spectroscopy (STS) measurements of Bernal-stacked bilayer graphene (BLG), and we compare the results of our model to experimental measurements.

Recommended citation: Holdman, Gregory R., Zachary J. Krebs, Wyatt A. Behn, Keenan J. Smith, K. Watanabe, T. Taniguchi, and Victor W. Brar. “Dynamic Band Structure and Capacitance Effects in Scanning Tunneling Spectroscopy of Bilayer Graphene.” Applied Physics Letters 115, no. 18 (October 28, 2019): 181601. https://doi.org/10.1063/1.5127078. https://doi.org/10.1063/1.5127078

Electrostatic Modeling of Bilayer Graphene Band Structure for Scanning Tunneling Spectroscopy

Published: March 07, 2019

Abstract R14.00012: Bilayer graphene (BLG) is known to have a dynamic electronic structure including a continuously tunable bandgap, and correlated electron behavior under a variety of conditions. To better understand these phenomena, it is important to develop local probes that can directly determine how these effects manifest in the presence of defects and impurities. In many semiconducting or metallic systems, scanning tunneling spectroscopy (STS) can serve as such a local probe. However, STS necessarily applies a local electric field to the system it measures. For BLG, this field can alter the local band structure by breaking the symmetry of the two layers and simultaneously doping the surface. This dynamic band structure modification makes STS measurements of BLG difficult to interpret and prevents straightforward extraction of the material parameters. In this talk, we show how these effects can be modeled and understood by computing the expected voltage-dependent tunneling spectrum of a BLG sheet between two gate electrodes. We compare this model to STS data taken from BLG/SiO2 and BLG/h-BN systems under UHV conditions at a temperature of 4 K and show how to extract the BLG bandgap from STS measurements performed at different back-gate voltages.

Teaching experience 1

Undergraduate course, University 1, Department, 2014

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Teaching experience 2

Workshop, University 1, Department, 2015

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