The energies of the substitutional impurities in graphene

Abstract

The properties of the substitutional impurities of the second period of the periodic table incorporated into graphene were investigated. The Green's-functions framework and the tightbinding method without the effect of the lattice distortion were used. We discuss the possibility of the existence of well-defined resonant states in the valence band or the conduction band in the vicinity of the Dirac point. We conclude that in the vicinity of the Dirac point there was a possibility of a coincidence of the Fermi energy levels with impurity resonances (i.e., the Fermi level is pinned to the impurity resonance level.) ß

Edge-Sensitive Semiconducting Behaviour in Low-Defect Narrow Graphene Nanoribbons

“…[35–39]. Indeed, this E a value of ∼35 meV estimated from Figure 3 is close to the impurity levels reported in [35].…”

“…[35–39]. Indeed, this E a value of ∼35 meV estimated from Figure 3 is close to the impurity levels reported in [35]. The observed E a value, thus, could be the activation energy of the electrons emitted from the impurity level to the bottom of the conduction band (Figure 4d) because of the measured V bg = 0V.…”

“…The appearance of such semiconducting behaviour has been understood based on the shifting of the Fermi level (E F ) - which is sensitive to carrier doping via the GNR edges [29–34] - through the 1D electronic density of states (EDOS) with van Hove singularities (VHSs). However, the correlation of semiconducting behaviour with the presence of impurity levels introduced via edge termination by foreign atoms has not thus far been experimentally reported, although there are many theoretical reports (particularly as regards calculating resonant tunnelling via impurity levels originating from edge termination by foreign atoms) [35–38]. In the present study, we observe this correlation in low-defect narrow GNRs (<∼20 nm width).…”

“…However, the correlation of semiconducting behaviour with the presence of impurity levels introduced via edge termination by foreign atoms has not thus far been experimentally reported, although there are many theoretical reports (particularly as regards calculating resonant tunnelling via impurity levels originating from edge termination by foreign atoms) [35][36][37][38]. In the present study, we observe this correlation in low-defect narrow GNRs (<∼20 nm width).…”

“…When E F is pinned around this impurity level, it can cause resonant tunnelling [35–37] and, thus, produce this sharp conductance peak. Here, in Figure 4(a), the conductance peaks exist around V bg = ±3.5 V. This V bg is the voltage applied from the back side of the silicon substrate and, thus, the applied VBG modulates the electronic states of the GNRs via the silicon substrate, so electronic charging in the substrate (Q BG = C BG ΔV BG ) gives rise to the true energy values [15].…”