Tunneling spectroscopy of metal-oxide-graphene structure

Abstract

The unique density of states of graphene at the device level is probed via tunneling spectroscopy of macroscopic metal-oxide-graphene structures. Local conductance minima from electrons tunneling into the graphene Dirac point are observed in the dI/dV spectra of both the single-junction and dual-junction configurations. Nonequally-spaced Landau levels, including the hallmark n=0 level, are observed in the presence of a magnetic field. Linear energy-momentum dispersion near the Dirac point, as well as the Fermi velocity, is extracted from both experiments. Local potential fluctuations and interface defects significantly influence these fine physical features, leading to peak broadening and anomalies comparing to the results from the ultra sharp scanning tunneling microscope tip. This study provides important implications for potential tunneling-based graphene devices in the future.

Phonon structures in the electronic density of states of graphene in magnetic field

“…These LLs have been clearly observed in experiments. In particular, tunneling measurements have confirmed the fielddependence [7,8,[25][26][27], and optical conductivity measurements [28] have observed the predicted [23,24] transitions between LLs.…”

Graphene-GaN Schottky diodes

“…The two-dimensional hexagonal carbon array, also known as graphene, has been extensively studied for application as an active or passive layer in electronic and optoelectronic semiconductor devices due to its outstanding physical and optical characteristics, including high intrinsic electron mobility, quantum electronic transport, low optical absorption, and good chemical and mechanical stability [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In particular, its good electrical conductivity and excellent optical transparency across the entire spectrum of wavelengths of graphene made it a promising candidate for use as a transparent contact in optoelectronic devices such as solar cells [15][16][17][18] and light-emitting diodes (LEDs) [19][20][21][22][23][24][25][26][27].…”

Effects of electron-phonon coupling on Landau levels in graphene

“…In a field B perpendicular to the graphene sheet, the linear energy bands are replaced by a set of discrete Landau levels with spacing proportional to |n|B for integral n. The effect of this quantization on the DOS 24 and optical conductivity 25,26 have been calculated in an independent-particle picture, and those predictions have been verified in experiment. 1,10,[27][28][29][30] But we can expect these leading-order predictions to be modified by an assortment of many-body effects made possible by the more complex electronic structure of the quantized system. In particular, we can expect to observe a rich interplay between the LLs and phonons, because for typical magnetic fields used in experiment, the LL spacing is on the scale of the phonon energies in graphene.…”