Probing phonon emission via hot carrier transport in suspended graphitic multilayers

Abstract

We study hot carrier transport under magnetic fields up to 15 T in suspended graphitic multilayers through differential conductance (dI/dV) spectroscopy. Distinct high-energy dI/dV anomalies have been observed and shown to be related to intrinsic phonon-emission processes in graphite. The evolution of such dI/dV anomalies under magnetic fields is further understood as a consequence of inter-Landau level cyclotronphonon resonance scattering. The observed magneto-phonon effects not only shed light on the physical mechanisms responsible for high-current transport in graphitic systems, but also offer new perspectives for optimizing performance in graphitic nano-electronic devices.Description: Figure 1S shows the phonon dispersion and phonon density of states (ph-DOS) of graphite calculated using the Density Functional Perturbation Theory (DFTP) [1] as implemented in the CASTEP code.[2] The first-principles energy calculations were done within the generalized-gradient approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) exchangecorrelation functional [3] using the norm-conserved pseudopotential plane-wave method . The non-bonding interaction between graphene planes were accounted for by dispersion corrections of the form C 6 R -6 included in the DFT formalism by using Tkathcenko and Scheffer scheme. [4] We used a graphite crystal structure obtained from the experimental one by energy minimization and convergence tolerances 1.8 × 10 −7 eV/atom for energy, 2.0 × 10 −7 eV/Å for forces, 0.009 GPa for stresses, and 4.7 × 10 −10 Å for displacements. The phonon dispersion and ph-DOS were calculated over 23 × 23 × 8 Monkhorst-Pack grid in the k-space along the lines connecting the high symmetry points in the Brillouin zone.

Tunable magnetoresistance behavior in suspended graphitic multilayers through ion implantation

“…An earlier attempt was directed to a quantum origin at high B-field where all carriers condense into the lowest Landau level, [8] but this deviates from the experimental observation of a linear MR over a B field range even before the onset of SdH oscillations. [1,25] The persistence of a nearly linear positive MR at higher effective temperature (higher V d from Fig. 2c) also excludes a potential quantum origin suggested by Ref.…”

“…2c). [24] We note that for some other devices [25] no appreciable weak localization was observed, but we present here a device showing significant negative MR at low B in order to clearly distinguish the physical origins of the negative MR at low B and the positive MR at high B. Now we discuss the physical mechanism for the main feature: the nearly linear positive MR non-saturating even at B = 15 T. A suspected linear positive MR background on top of SdH oscillations has been noted in graphitic structures for decades, [1,[5][6][7] yet its physical origin is still in debate.…”

AB-Stacked Multilayer Graphene Synthesized via Chemical Vapor Deposition: A Characterization by Hot Carrier Transport

“…Such four-terminal transport results unambiguously demonstrate a distinct differential conductance dip at V = 0, an intrinsic transport behavior of multilayer graphene attributable to the presence of hot electron effect. We further observed that magnetic fields attenuate the hot electron effect and thus provide a way for its control by enhancing cyclotron phonon scattering. , …”

“…We further observed that magnetic fields attenuate the hot electron effect and thus provide a way for its control by enhancing cyclotron-phonon scattering. 16,17…”

Phonon recycling

“…The sources of these hot optical phonon are presented in Fig. 2 and include the electric field induced acceleration of charges in high-power electronic devices (Matulionis, et al, 2004), nonradiative decay of hot electrons in optoelectric devices (Conibeer et al, 2010), lattice electron-stoppage of charged fission fragments (Goland and Paskin, 1964), frustrated-vibration relaxation of chemisorbed molecules (Sakong, et al, 2008), and magnetic field Landau splitting (Diaz-Pinto, et al, 2011). Some of these sources directly emit phonons, while others first excite an electric or magnetic entity which in turn decays, emitting phonons.…”