LAUSR

We investigate the electronic transport properties of Au-contacted graphene on Ge/Si(001). Kelvin probe force microscopy at room temperature with an additionally applied electric transport field is used to gain a comprehensive understanding of macroscopic transport measurements. In particular, we analyze the contact pads including the transition region, perform local transport measurements in pristine graphene/Germanium, and explore the role of the semiconducting Germanium substrate. We connect the results from these local scale measurements with the macroscopic performance of the device. We find that a graphene sheet on a 2 μm Ge film carries approximately 10% of the current flowing through the device. Moreover, we show that an electronic transition region forms directly adjacent to the contact pads. This transition region is characterized by a width of >100 μm and a strongly increased sheet resistance acting as the bottleneck for charge transport. Based on Rutherford backscattering of the contact pads, we suggest that the formation of this transition region is caused by diffusion.