Observation of Nanosecond Hot Carrier Decay in Graphene

Abstract

An extremely long decay time of hot carriers in graphene at room temperature was observed for the first time by monitoring the photoinduced thermionic emission using a highly sensitive time-of-flight angle-resolved photoemission spectroscopy method. The emission persisted beyond 1 ns, two orders of magnitude longer than previously reported carrier decay. The long lifetime was attributed to the excitation of image potential states at very low laser fluencies.

Picosecond vs Femtosecond: Are All Laser Desorption Ionizations Created Equal?

“…The details of the setup have been described in previous experiments. − Here, we briefly describe modifications to the original instrumentation. For sample preparation, 2,5-Dihydroxybenzoic Acid (98%, Sigma-Aldrich) was prepared in a solution of 50:50 water/acetonitrile.…”

“…Recently, Li and coworkers have developed a 3D momentum imaging system to probe the surface decay dynamics of hot carriers in graphene. 29 The 3D momentum distributions of electrons emitted from the surface provided evidence of delayed photoemission. Conceptually, the same technique can be applied to study the laser desorption/ionization process by measuring the 3D momentum distributions of desorbed ions.…”

“…Utilizing imaging techniques to measure the momentum distributions of photoinduced fragments provides crucial information to the ionization/dissociation dynamics of atomic/molecular systems in gas phase , or from surfaces. − However, all of these systems measure the two-dimensional (2D) momenta of fragments. Recently, Li and co-workers have developed a 3D momentum imaging system to probe the surface decay dynamics of hot carriers in graphene . The 3D momentum distributions of electrons emitted from the surface provided evidence of delayed photoemission.…”

Ultrafast Vibrational Dephasing Times of Modified Graphene

“…7,8 Carrier− carrier relaxation has been investigated in some detail, and there is agreement that it occurs on ultrafast (sub-ps) timescales. 9,10 While there are also a number of studies concerned with the relaxation into optical phonon modes, 11,12 there are few studies on the relaxation dynamics of welldefined vibrational modes.…”

“…Graphene has been in the limelight for almost two decades now, mainly due to its many unusual properties. , Among these properties is the almost ballistic speed with which electrons move through graphene, − making it an almost perfect choice for electronic applications and devices. , Electronic excitations in graphene can relax through two competing mechanisms on ultrafast timescales, namely, carrier–carrier and carrier–phonon relaxation. , Carrier–carrier relaxation has been investigated in some detail, and there is agreement that it occurs on ultrafast (sub-ps) timescales. , While there are also a number of studies concerned with the relaxation into optical phonon modes, , there are few studies on the relaxation dynamics of well-defined vibrational modes.…”