title: Transient absorption and photocurrent microscopy show that hot electron supercollisions describe the rate-limiting relaxation step in graphene.
abstract: Using transient absorption (TA) microscopy as a hot electron thermometer, we show that disorder-assisted acoustic-phonon supercollisions (SCs) best describe the rate-limiting relaxation step in graphene over a wide range of lattice temperatures (Tl = 5-300 K), Fermi energies (E(F) = ± 0.35 eV), and optical probe energies (~0.3-1.1 eV). Comparison with simultaneously collected transient photocurrent, an independent hot electron thermometer, confirms that the rate-limiting optical and electrical response in graphene are best described by the SC-heat dissipation rate model, H = A(T(e)(3) - T(l)(3)). Our data further show that the electron cooling rate in substrate-supported graphene is twice as fast as in suspended graphene sheets, consistent with SC model prediction for disorder.
authors.affiliation: Laboratory for Atomic and Solid State Physics, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Matt W
authors.initials: MW
authors.lastname: Graham
authors.forename: Su-Fei
authors.initials: SF
authors.lastname: Shi
authors.forename: Zenghui
authors.initials: Z
authors.lastname: Wang
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Ralph
authors.forename: Jiwoong
authors.initials: J
authors.lastname: Park
authors.forename: Paul L
authors.initials: PL
authors.lastname: McEuen
mesh_terms: D000042:Absorption; D004583:Electrons; D006108:Graphite / Q000737:chemistry*; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry*
chemical_list: D006108:Graphite