| AVS 57th International Symposium & Exhibition | |
| Graphene Focus Topic | Tuesday Sessions |
| Session GR+TF-TuM |
| Session: | Characterization, Properties, and Applications |
| Presenter: | N.N. Klimov, CNST/EEEL/NIST and Maryland NanoCenter UMD |
| Authors: | N.N. Klimov, CNST/EEEL/NIST and Maryland NanoCenter UMD G.M. Rutter, CNST/NIST S. Jung, CNST/NIST and Maryland NanoCenter UMD D.B. Newell, EEEL/NIST N.B. Zhitenev, CNST/NIST J.A. Stroscio, CNST/NIST |
| Correspondent: | Click to Email |
It has been shown recently, both theoretically [1] and experimentally [2-3], that a bandgap can be opened and even tuned continuously in bilayer graphene (BLG) in the presence of a strong electrical field, which induces asymmetry of the electrostatic potential of the two graphene layers. This makes BLG an attractive material for future digital electronic applications, infrared nanophotonics, pseudospintronics, and terahertz technology. On the other hand a complete understanding of the physics of BLG and the effect of disorder on a microscopic scale is missing. In this work, we present local tunneling measurements of bilayer graphene exfoliated on SiO2/Si using scanning tunneling spectroscopy at a temperature of 4.3 K. The graphene bilayer is probed with both the application of a perpendicular magnetic field and with an external gate voltage applied to the Si substrate. We study the effect of disorder potential induced by SiO2/Si on the electronic properties of bilayer graphene. We find that disorder potential causes a bandgap opening in BLG, while a backgate voltage has a secondary effect on the density of states. We also find that the magnetic quantization of the carriers, evidenced by the formation of Landau levels (LL), does not obey the simple scaling of LL energy versus magnetic field for an ideal graphene bilayer.[4] The LL spectra are seen to vary greatly depending on the local potential variation and associated charge density. We have investigated these variations with detailed spectroscopic maps of the LL spectra as a function of energy, gate voltage, and local potential variation. We find the assignment of the spectral features to be much more complex than expected, and may require the introduction of an intrinsic electrical bias in the bilayer system. In this talk, we will discuss the possible theoretical models that may account for our observations.
[1] E. McCann, V. I. Fal’ko, Phys. Rev. Lett. 96, 086805 (2006).
[2] J. B. Oostinga, et. al., Nature Mater. 7, 1510157 (2008).
[3] E. V. Castro Phys. Rev. Lett. 99, 216802 (2007).
[4] E. A. Henriksen et al., Phys. Rev. Lett. 100, 087403 (2008).