Authors: Ulrich Starke, J. Bernhardt, J. Schardt, A. Seubert, K. Heinz
415
Authors: Filippo Giannazzo, Ioannis Deretzis, Antonino La Magna, Salvatore di Franco, Nicolò Piluso, Patrick Fiorenza, Fabrizio Roccaforte, Patrick Schmid, Wilfried Lerch, Rositza Yakimova
Abstract: Two dimensional maps of the electronic conductance in epitaxial graphene (EG) grown on SiC were obtained by conductive atomic force microscopy (CAFM). The correlation between morphological and electrical maps revealed the local conductance degradation in EG over the SiC substrate steps or at the junction between monolayer (1L) and bilayer (2L) graphene regions. The effect of steps strongly depends on the charge transfer phenomena between the step sidewall and graphene, whereas the resistance increase at 1L/2L junction is a purely quantum mechanical effect, due to the weak coupling between 1L and 2L electron wavefunctions.
113
Authors: Toby Hopf, Konstantin Vassilevski, Enrique Escobedo-Cousin, Peter King, Nicholas G. Wright, Anthony G. O’Neill, Alton B. Horsfall, Jonathan Goss, George Wells, Michael Hunt
Abstract: Top-gated field-effect transistors have been created from bilayer epitaxial graphene samples that were grown on SiC substrates by a vacuum sublimation approach. A high-quality dielectric layer of Al2O3 was grown by atomic layer deposition to function as the gate oxide, with an e-beam evaporated seed layer utilized to promote uniform growth of Al2O3 over the graphene. Electrical characterization has been performed on these devices, and temperature-dependent measurements yielded a rise in the maximum transconductance and a significant shifting of the Dirac point as the operating temperature of the transistors was increased.
937
Authors: Xin Gong, Yue Hui Jia, Pei Peng, Zi Dong Wang, Zhong Zheng Tian, Li Ming Ren, Yun Yi Fu
Abstract: PMMA is commonly used for graphene transfer and device processing. However, it leaves a thin layer of polymer residues after standard acetone cleaning and causes electrical and thermal performance degradation of graphene devices. In this paper, we present a research of the impact of polymer residues on surface morphologies and electronic properties of bilayer graphene using Raman spectroscopy in combination with atomic force microscopy (AFM). The electronic structure of bilayer graphene is well captured in its Raman spectrum, of which the 2D band reveals four double resonance Raman scattering processes. The Raman analyses show universal blueshifts of the G band and the four 2D sub-bands P11, P12, P21, P22, as well as reduced intensity ratios of the sub-bands to the G band I(Pij)/I(G) after surface contamination by polymer residues, implying an electronic structure modulation in bilayer graphene. The effects are mainly attributed to p-type doping and extrinsic scattering induced by residual impurities and defects.
417