Keynote Talk  


Dr. Ilka Hermes: "Visualizing the electronic properties of topographical anomalies on wafer-scale graphene"

Ilka M. Hermes,¹,² Simonas Krotkus,³ George Sarau,⁴ Abdul Rauf,² Sergej Pasko³, Silke Christiansen,⁴ Michael Heuken,³ Ben Conran,⁵ Clifford McAleese,⁵ Xiaochen Wang,⁵ Oliver Whear⁵

¹ Leibniz Institut für Polymerforschung Dresden e.V., Dresden, Germany

² Park Systems Europe GmbH, Mannheim, Germany

³ AIXTRON SE, Herzogenrath, Germany

⁴ Fraunhofer-Institut für Keramische Technologien und Systeme IKTS, Forchheim, Germany

⁵ AIXTRON Ltd, Cambridge, United Kingdom

Wafer-scale fabrication of graphene on insulating substrates without transfer is a prerequisite for the materials’ industrial application in high-performance nanoelectronics [1]. Chemical vapor deposition (CVD) enables direct monolayer graphene growth on sapphire. The use of high temperature H2-annealed sapphire substrate instead of pristine sapphire improves the resulting graphene film by reducing the overall density of strain-induced wrinkles and increasing the crystal quality [2]. However, using Kelvin probe force microscopy (KPFM) imaging we observed that the annealing induced underlaying sapphire terraces introduce a heterogeneous surface potential distribution on the graphene monolayers. Moreover, we correlated the surface potential distribution to the nanomechanical behavior of graphene film, including its stiffness and adhesion, which was supplemented by micro-Raman measurements. Particularly, the correlation of the surface potential and the sample’s nanomechanical response indicates that the heterogeneous electronic properties are likely to originate from a film straining at underlying step edges.

[1] S. J. Kim, K. Choi, B. Lee, Y. Kim and B. H. Hong, Annu. Rev. Mater. Res., 45 (2015), 63–84

[2] N. Mishra, S. Forti, F. Fabbri, L. Martini, C. McAleese, B. R. Conran, P. R. Whelan, A. Shivayogimath, B. S. Jessen and L. Buß, Small, 15 (2019), 1904906