Nonlinear resistivity and heat dissipation in monolayer graphene

We have experimentally studied the nonlinear nature of electrical conduction in monolayer graphene devices on silica substrates. This nonlinearity manifests itself as a nonmonotonic dependence of the differential resistance on applied dc voltage bias across the sample. At temperatures below similar to 70 K, the differential resistance exhibits a peak near zero bias that can be attributed to self-heating of the charge carriers. We show that the shape of this peak arises from a combination of different energy dissipation mechanisms of the carriers. The energy dissipation at higher carrier temperatures depends critically on the length of the sample. For samples longer than 10 mu m the heat loss is shown to be determined by optical phonons at the silica-graphene interface.