Scanning tunneling microscopy and spectroscopy of graphene on insulating substrates

Abstract

Graphene is a truly two-dimensional (2D) material with exceptional electronic, mechanical, and optical properties. As such, it consists of surface only and can be probed by the welldeveloped surface science techniques such as, e.g., scanning tunneling microscopy (STM). This method bridges the gap between the surface science community and the electronic device community and might lead to novel combined approaches. Here, I review some of the STM and scanning tunneling spectroscopy (STS) experiments on monolayer graphene samples. I will concentrate on graphene samples deposited on insulating substrates, since these are related to graphene device concepts. In particular, I will discuss the morphology of graphene on SiO 2 and other emerging substrates, some nanomechanical manipulation experiments using STM, and spectroscopic results. The latter can map the disorder potentials as well as the interaction of the electrons with the disorder, which is most pronounced in the quantum Hall regime.Three-dimensional representation of a STM image of graphene; the atomic resolution is displayed as color code, while the rippling is shown in three dimensions (courtesy of M. Pratzer, RWTH Aachen).

Mesoscopic fluctuations of the local density of states in interacting electron systems

“…We note that our theoretical results are consistent with available data on scanning tunneling microscopy in disordered interacting systems, in particular, for a strongly disordered 3D system [68], for various 2D semiconductor systems and graphene [69][70][71][72], for a magnetic semiconductor Ga 1−x Mn x As near metal-insulator transition [9], for metallic and insulating phases near superconductorinsulator transition in TiN, InO, and NbN films [73][74][75][76][77][78].…”

Artificial honeycomb lattices for electrons, atoms and photons

“…Electromagnetic waves propagating in such a periodic structure, composed of metallic cylinders with radius R = 0.25 a, where a is the lattice constant, exhibit a dispersion relation with several Dirac points. In the vicinity of a Dirac point, the measured reflection spectra resemble the STM spectra of graphene flakes [50,51]. In a subsequent work [52] extremal transmission through a microwave photonic crystal and the observation of edge states close to Dirac points were also demonstrated.…”

Evolution of Landau levels into edge states in graphene

“…Graphene, a one-atom-thick crystal of carbon atoms arranged in a honeycomb lattice [25][26][27] , provides unprecedented opportunities to revisit the physics of QH edge states. The fact that its structure is strictly 2D, with electrons residing right at the surface, provides flexibility in choosing the distance to the screening plane.…”