One-Dimensional Electrical Contact to a Two-Dimensional Material

We report a contact geometry in which we metalize only the 1D edge of a 2D graphene layer

L. Wang; I. Meric; P. Y. Huang; Q. Gao; Y. Gao; H. Tran; T. Taniguchi; K. Watanabe; L. M. Campos; D. A. Muller; J. Guo; P. Kim; J. Hone; K. L. Shepard; C. R. Dean

2013

Scholarcy highlights

  • Heterostructures based on layering of two-dimensional materials such as graphene and hexagonal boron nitride represent a new class of electronic devices
  • We demonstrate a new device topology where 3D metal electrodes are connected to a 2D graphene layer along the 1D graphene edge
  • We fabricated graphene devices with unprecedented performance exhibiting room-temperature mobility up to 140,000 cm2/Vs and sheet resistivity below 40 ohms per square at n > 4 × 1012 cm−2, comparable to the theoretical limit imposed by acoustic phonon scattering
  • Beginning with a boron nitride-G-BN heterostructure, a hard mask is defined on the top BN surface by electron-beam lithography of a hydrogen-silsesquioxane resist
  • Within the resolution of the scanning transmission electron microscope image, there is no evidence of metal diffusion into the graphene/BN interface, confirming the truly edge nature of the contact
  • RC was remarkably low, reaching ~150 ohm·μm for n-type carriers at high density. This value is ~25% lower than the best reported surface contacts without additional engineering such as chemical or electrostatic doping
  • The contact resistance is asymmetric, being lower by a factor of 2 to 3 when the device is gated to be n-type versus p-type. This asymmetry is consistent with electrical contact being made primarily to the Cr adhesion layer, as suggested by the cross-section energy-loss spectroscopy map, because the Cr work function is ~0.16 eV lower than that of graphene
  • Even higher mobility could be expected for larger-area devices, which may be realized by combining recent progress in scalable growth techniques together with the edge-contact geometry described here

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