Energy level alignment of single-wall carbon nanotubes on metal surfaces

Abstract

We studied the electronic configuration of single-wall carbon nanotubes adsorbed on well-defined Au(111) and Cu(111) surfaces. We found opposite behaviors for their energy-level alignment with metal: nanotubes are p-doped on Au(111) and n-doped on Cu(111). The doping level is not uniquely defined for a particular metal surface but rather exhibits a distribution depending on several uncontrolled factors such as nanotube geometry and adsorption configuration.

Electronic modulations in a single wall carbon nanotube induced by the Au(111) surface reconstruction

“…19,43,44 A careful look at the region around the Fermi level reveals that the STS spectrum of a nanotube adsorbed on Au(111) is not symmetrically positioned around the zero bias voltage (Figure 1(e)). The middle of the band gap is measured above the Fermi level by a few tenths of eV in agreement with the previous measurements 16,17,19,23,45 and calculations. 43,46,47 A charge transfer between the nanotube and the surface is responsible for this asymmetry in the gap and was estimated to amount 0.1 electron for an armchair tube.…”

“…[16][17][18][19][20][21][22][23][24][25] In preliminary studies, however, little attention was given to the influence of the adsorption to a metal substrate, partly due to the inherent presence of a large number of co-adsorbed impurities from drop-casting deposition. Recently, important effects arising from the particular adsorption configuration and the local environment of single wall CNTs (SWCNTs) were observed by proper control of the CNT-substrate interface, [23][24][25][26][27][28] like localization of vibronic states, 29 many body effects, 30,31 or local metallization of semiconducting tubes. 32,33 In this letter, we show by STM/STS that for a SWCNT adsorbed on the well-defined Au(111) surface, the herringbone reconstruction of the latter can induce periodic modulations in the nanotube electronic and topographic structure due to charge transfer modulations along the nanotube length.…”

“…48 Variations are found on different nanotubes depending on their geometries as well as their adsorption configurations on the surface. 23 The surface reconstruction of Au(111) consists in a linear contraction of the top atomic layer, where a transition from fcc-to hcp-like sites through bridge positions creates a double line corrugation and a characteristic zigzag pattern. 49 The reconstruction pattern usually influences the adsorption of molecular adsorbates such as C 60 50 or other aromatic molecules, [51][52][53][54] which eventually leads to different self-assembled structures in the fcc and hcp regions.…”

Spatially Resolved Electronic Structures of Atomically Precise Armchair Graphene Nanoribbons

“…The position of AGNR E F as indicated by the green dash-dotted line is shifted toward their unoccupied bands. This is attributed to the smaller work function of Ag(111) (~4.4 eV) and a hybridization between Ag d band and graphene 2 p 2728. The spectra exhibit a sharp peak at ~−240 mV for 21-AGNR, a broad peak at ~−400 mV for 14-AGNR and a broader peak at ~−800 mV for 7-AGNR, as marked by green arrows, respectively.…”

Scanning tunneling spectroscopy of single-wall carbon nanotubes on a polymerized gold substrate

“…STS studies on C60 and graphene revealed that the interplay between the support and the nanostructure may intensely impact the measurement of the fundamental gap [16][17][18]. Recent STS experiments on single-wall carbon nanotubes (SWCNTs) show that the position of the Fermi level shifts differently, depending on the substrate material [19][20][21]. It was pointed out that the electron screening effect of the metal substrate should not be neglected to account for the tunneling spectra [15].…”