Complex edge effects in zigzag graphene nanoribbons due to hydrogen loading

Abstract

We have performed density functional calculations as well as employed a tight-binding theory, to study the effect of passivation of zigzag graphene nanoribbons (ZGNR) by Hydrogen. We show that each edge C atom bonded with 2 H atoms open up a gap and destroys magnetism for small widths of the nanoribbon. However, a re-entrant magnetism accompanied by a metallic electronic structure is observed from 8 rows and thicker nanoribbons. The electronic structure and magnetic state are quite complex for this type of termination, with sp 3 bonded edge atoms being non-magnetic, whereas the nearest neighboring atoms are metallic and magnetic. We have also evaluated the phase stability of several thicknesses of ZGNR, and demonstrate that sp 3 bonded edge atoms, with 2 H atoms at the edge, should be stable at temperatures and pressures which are reachable in a laboratory environment.

Conductance gap induced by orbital symmetry mismatch in inhomogeneous hydrogen-terminated zigzag graphene nanoribbons

“…One can see that a sharp conductance peak presents right at the Fermi level of the H-zGNR as the result of the highly conductive edge states [3]. A gap about 0.48 eV presents around the Fermi level of the H2-zGNR as expected [24]. By introducing sp 3 -edges ðN H2 Þ in a pure sp 2 -edges, the conductance spectra show two drastic changes, namely the significant decrease of the conductance around the Fermi level and the presence of some conductance dips.…”

“…While H2-terminations can only induce a band gap in ultrathin H2-zGNRs. Such a gap rapidly decreases to zero when the width increases to only 7-zigzag rows (about 1.5 nm) [24]. At the same time, the zGNRs with mixed H-and H2-terminations have also been studied [26][27][28].…”

“…Careful computational studies of hydrogen terminated ribbons [20,24] have demonstrated that the H2-terminated zGNRs (H2-zGNRs), with sp 3 edges, are more stable than the H-terminated zGNRs (H-zGNRs), with sp 2 edges. The sp 2 edge geometry is favored only at extremely low hydrogen partial pressures and it can not generate a band gap at all [25].…”

Study of Nitrogen terminated doped zigzag GNR FET exhibiting negative differential resistance

“…selective doping [9], edge modulation (defective boundaries and edge disorder) [10,11], enabling each edge Carbon (C) atom to two Hydrogen (H) atoms [12], terminating the edge C atoms of the ribbon by Nitrogen (N) atoms [13].…”

First principles calculations of pentaheptite graphene and boronitrene derivatives

“…[16][17][18][19][20][21][22][23] Concerning the former, first principles electronic structure calculations and experiments have reported that graphene can be transformed into an insulating sheet, named graphane, 15 by complete hydrogenation. Graphane has been recently synthesized by Elias et al, 9 following initial predictions by Sofo et al 15 Quantum confinement effects have also shown the possibilities of band gap engineering, as in graphene nanoribbons [24][25][26][27] and nanomeshes 28 passivated with hydrogen. However, the resulting electronic properties are strongly dependent on the type of edge termination.…”