Nonlinear resistivity and heat dissipation in monolayer graphene

Abstract

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 ∼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 μm the heat loss is shown to be determined by optical phonons at the silica-graphene interface. Graphene is a promising material for electronic applications because of its high electrical and thermal conductivities. 1 A limiting intrinsic room-temperature mobility of graphene fieldeffect transistors of ∼2 × 10 5 cm 2 /V s has been estimated 2 and approached experimentally. 3 Its high thermal conductivity, 4 far exceeding that of copper, holds great promise for heat management in electronics. 5 Fully realizing this potential requires an understanding of the scattering mechanisms in graphene, particularly electron-phonon scattering, which becomes increasingly important with increasing temperature and device currents.Several different techniques have been used to study the coupling between charge carriers and phonons in graphene. Measurements of the temperature dependence of the resistance have shown that at low temperatures, T < 150 K, electronphonon scattering is dominated by longitudinal acoustic phonons, 2,6-8 resulting in a linear temperature dependence of the resistivity. At higher temperatures the resistivity becomes strongly temperature dependent, possibly due to ripples in the graphene membrane 8 or coupling with remote interfacial phonons (RIPs) at the SiO 2 surface. 2,9 This latter scattering mechanism has been put forward as an important heat dissipation mechanism in carbon nanotube and graphene devices. [10][11][12] Measurements of the current saturation in graphene lend support to the hypothesis that these RIPs are an important scattering mechanism, 13 although another study identifies scattering with optical phonons intrinsic to the graphene lattice 14 as the dominant saturation mechanism.In this Rapid Communication, we report electrical measurements of monolayer graphene field-effect transistors in the high-current regime at temperatures between 4 and 200 K. We show that overheating of the charge carriers results in a nonmonotonic dependence of the differential resistance on source-drain bias. By correlating this dependence with the measured temperature dependence of the differential resistance, we test different models of thermal transport and electron-phonon coupling, and demonstrate that energy dissipation is dominated by coupling to the remote interfacial phonons in the silica substrate.Graphene flakes were mechanically exfoliated onto ...

Role of Remote Interfacial Phonon (RIP) Scattering in Heat Transport Across Graphene/SiO2 Interfaces

“…As a result, electrons and holes could play a significant role in heat conduction across graphene interfaces via RIP scattering. 9,14 In fact, this remote heat transfer via RIP scattering is thought to dominate heat dissipation from CNTs to dielectric substrates. 7,11 Specifically, Rotkin et al calculated that RIP scattering contributes thermal conductance per unit length of g RIP  0.1 W m -1 K -1 to interfacial heat transfer of a single-walled CNT (~1.3 nm in diameter) with a carrier concentration of 0.1 e/nm.…”

Effects of optical and surface polar phonons on the optical conductivity of doped graphene

“…Besides the aforementioned studies on the optical conductivity, the role played by different phonons has also been studied in the context of heat dissipation mechanisms [34][35][36] and current/velocity saturation in graphene, 37 which plays an important role in electronic RF applications 11 and also for transport 38,39 in the similar system of carbon nanotubes. Inelastic scattering either by intrinsic graphene optical phonons 40 or surface polar phonons 37,[41][42][43][44][45] (SPPs) is thought to give rise to the saturation of the current in graphene and affect the low field carrier mobility.…”

Universal scaling of weak localization in graphene due to bias-induced dispersion decoherence

“…(Notable exceptions include early works that demonstrated the inability of an electric field to break time reversal during coherent backscattering 2,33,34 , and later experiments on the differential conductance of GaAs/AlGaAs quantum dots 35 and short metallic nanobridges 36,37 .) While there have been a few investigations of the nonlinear differential conductance of graphene [38][39][40][41][42][43] , there is still relatively little that is understood about the manner in which the quantum corrections in this material (and in other Dirac materials) are affected under nonequilibrium conditions. It is this specific problem that we address here, from both experimental and theoretical perspectives.…”