Dissipation factor and frequency dependence of graphene quantum Hall devices

Quantum Hall resistors made from epitaxial graphene measured with alternating current exhibit an unusual negative frequency dependence. To test the hypothesis that parasitic capacitances between contact pads cause this effect, we studied capacitance and dissipation factor in the quantum Hall regime for various in-plane electrode configurations. The largest dissipation factor is found for configurations where a strong electric field penetrates the bulk of the graphene. The measured effect of different electrode configurations on the frequency dependence of the quantized Hall resistance confirms our hypothesis. The findings are important for modeling and optimization of a future graphene-based quantum impedance standard.