Single and multilayer graphene systems are promising for nanoelectronic applications because of their high carrier mobility and large current-carrying capacities. While electron transport studies have led to a better understanding of the physical mechanism responsible for the carrier mobility and electron scattering at low electric fields, more experiments are needed for elucidating the physics of transport at high electric fields. In this talk, I will discuss research efforts of my group in investigating hot carrier transports in multilayer graphene produced by both chemical vapor deposition and mechanical exfoliation methods. Two notable features were observed in differential conductance (dI/dV) spectra as a function of drain-source voltage Vd. First, a dip of dI/dV was found to be fixed at Vd = 0 regardless of the gate voltage, which can be attributed to the hot electron effect due to the weak electron-acoustic phonon coupling in graphitic layers. Second, anomalies in dI/dV were observed at higher energies (> 8 meV), likely induced by intrinsic electron-phonon scattering through phonon-emission process in graphitic systems. The evidence of such phonon-emission processes has been demonstrated by a direct comparison of the dI/dV spectrum with calculated phonon density of states for graphite. Furthermore, we have investigated the evolution of such hot carrier transport behavior under magnetic filed up to 15T. Our research results not only shed light on the physical mechanism responsible for high-current transport in graphitic systems, but also offer new perspectives for optimizing device performance for graphitic nano-electronic devices.

Single and multilayer graphene systems are promising for nanoelectronic applications because of their high carrier mobility and large current-carrying capacities. While electron transport studies have led to a better understanding of the physical mechanism responsible for the carrier mobility and electron scattering at low electric fields, more experiments are needed for elucidating the physics of transport at high electric fields. In this talk, I will discuss research efforts of my group in investigating hot carrier transports in multilayer graphene produced by both chemical vapor deposition and mechanical exfoliation methods. Two notable features were observed in differential conductance (dI/dV) spectra as a function of drain-source voltage Vd. First, a dip of dI/dV was found to be fixed at Vd = 0 regardless of the gate voltage, which can be attributed to the hot electron effect due to the weak electron-acoustic phonon coupling in graphitic layers. Second, anomalies in dI/dV were observed at higher energies (> 8 meV), likely induced by intrinsic electron-phonon scattering through phonon-emission process in graphitic systems. The evidence of such phonon-emission processes has been demonstrated by a direct comparison of the dI/dV spectrum with calculated phonon density of states for graphite. Furthermore, we have investigated the evolution of such hot carrier transport behavior under magnetic filed up to 15T. Our research results not only shed light on the physical mechanism responsible for high-current transport in graphitic systems, but also offer new perspectives for optimizing device performance for graphitic nano-electronic devices.