Electron-state engineering of bilayer graphene by ionic molecules

Abstract

Based on the first-principles total-energy calculations, we demonstrate the possibility of controlling the band-gap and carrier type of bilayer graphene using ionic molecules. Our calculations suggest that bilayer graphene sandwiched by a pair of cation-anion molecules is a semiconductor with a moderate energy gap of 0.26 eV that is attributable to the strong local dipole field induced by the cation-anion pair. Furthermore, we can control the semiconducting carrier type—intrinsic, p-type, or n-type—of bilayer graphene sandwiched by ionic molecules by changing the cation-anion pair.

Field-induced structural control of COx molecules adsorbed on graphene

“…[1][2][3] With this peculiar electronic structure around the Fermi level, graphene exhibits remarkable carrier mobility [4][5][6] of up to 200 000 cm 2 V -1 s -1 that enables high-speed switching within electronic devices. 7 Nevertheless, the electronic structure of graphene is fragile against the formation of hybrid structures with foreign materials, such as insulating substrates, [8][9][10][11] metal electrodes, 12 molecular/atomic adsorbates, [13][14][15][16][17][18][19][20][21] and structural defects. [22][23][24][25][26] Furthermore, an external electric field can tune the electronic structure of graphene and its hybrids.…”

Geometric structures of Al nanoparticles adsorbed on graphene under an external electric field

“…8) In addition to its intrinsic unique electronic properties, graphene exhibits further variation in its electronic structure by forming hybrid structures with foreign materials and the external environment. [9][10][11][12][13] Graphene no longer possesses linear dispersion bands when it is adsorbed on insulating substrates, [14][15][16][17] metal surfaces, 18) and defective graphene layers, 19) owing to the modulation of the electrostatic potential on graphene by foreign materials. An external electric field also modulates the electronic structure of graphene and its hybrids.…”

Effect of charged metal nanoparticles on carrier injection in graphene by an external electric field

“…In practical applications of graphene, graphene inherently possesses hybrid structures with foreign materials in its device structures, such as an insulating substrate, metal electrode, and atoms=molecules, which affect the electronic structure of graphene. [11][12][13][14][15][16][17] It has been demonstrated that graphene physically adsorbed on insulating substrates does not possess the Dirac cone but quadratic dispersion band with a finite energy gap, which depends on the surface morphology and atom species. [11][12][13][14] Atoms and molecules adsorbed on graphene also modulate the Dirac cone of graphene by covalent and van der Waals interactions between adsorbates and graphene.…”

“…[11][12][13][14] Atoms and molecules adsorbed on graphene also modulate the Dirac cone of graphene by covalent and van der Waals interactions between adsorbates and graphene. [15][16][17] Although carrier accumulation in pristine graphene and graphite under an external electric field has been steadily elucidated, 18,19) the microscopic mechanism of carrier injection into graphene under such hybrid structures has yet been elucidated. In particular, for further advancing device applications, it is important to unravel whether foreign materials prevent or assist carrier injection into graphene in hybrid structures.…”