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Lecture Andres Castellanos-Gomez


01 juni 2010 FWN-Building 5113.0202, Nijenborgh 4, 9747 AG, Groningen
Speaker: Dr. Andres Castellanos-Gomez
Affiliation: Departamento de Física de la Materia Condensada (C–III), Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid, Spain
Title: Inhomogeneous electronic properties of graphene probed by scanning probe microscopy
Date: Tue Jun 1, 2010
Start: 12.00
Location: FWN-Building 5113.0202
Host: B.J. van Wees
Telephone: +31 50 363 4974


The main topic of my Ph.D. thesis is the study of the electronic properties of graphene using local probe microscopy. We are interested in the changes in the electronic properties of graphene caused by local electric fields like the ones produced by localized charges in the substrate. We have measured the effect of spatial doping inhomogeneities on the local electronic properties of graphene samples by means of scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Two different graphene systems have been studied: exfoliated graphene deposited on a silicon oxide surface (studied at room temperature with a combined STM/AFM) and graphene epitaxially grown on a Ru (0001) surface (low temperature STM). In the first system we have found that trapped charges in the substrate are the main doping inhomogeneities. These trapped charges cause a reduction of the local tunneling barrier height (LBH) producing an unrealistic corrugation in the STM measurement of the topography of graphene. Currently we are investigating the relationship between these changes in the LBH with the ones of the local potential difference measured by electrostatic force microscopy with our STM/AFM. In the second graphene system, the lattice parameter mismatch between the Ru (0001) surface and graphene produces a periodic (Moiré like) graphene corrugation. An STM operated at a temperature of 300mK has been used to measure with high resolution the local density of states (LDOS) by means of scanning tunneling spectroscopy. We have found that both the LDOS and the LBH are also modulated with the same Moiré pattern. We have developed a procedure to disentangle this modulation of the electronic properties from the measured STM topography of graphene.

Laatst gewijzigd:22 oktober 2012 14:31