Abstract
We investigate the structural and electronic properties of nitrogen-doped epitaxial monolayer graphene and quasifreestanding monolayer graphene on 6H-SiC(0001) by the normal incidence x-ray standing wave technique and by angle-resolved photoelectron spectroscopy supported by density functional theory simulations. With the location of various nitrogen species uniquely identified, we observe that for the same doping procedure, the graphene support, consisting of substrate and interface, strongly influences the structural as well as the electronic properties of the resulting doped graphene layer. Compared to epitaxial graphene, quasifreestanding graphene is found to contain fewer nitrogen dopants. However, this lack of dopants is compensated by the proximity of nitrogen atoms at the interface that yield a similar number of charge carriers in graphene.
Highlights
We investigate the structural and electronic properties of nitrogen-doped epitaxial monolayer graphene and quasifreestanding monolayer graphene on 6H-SiCð0001Þ by the normal incidence x-ray standing wave technique and by angle-resolved photoelectron spectroscopy supported by density functional theory simulations
N-doped epitaxial monolayer graphene (EMLG) and H-intercalated quasifreestanding monolayer graphene (QFMLG), both grown on 6H-SiCð0001Þ, are investigated by the normal incidence x-ray standing wave (NIXSW) technique, which determines the vertical positions of the individual chemical
The effects of the structural changes on the electronic bands are checked by angle-resolved photoelectron spectroscopy (ARPES) and density functional theory (DFT)
Summary
We first present the structures of N-doped graphene as determined by the NIXSW technique. We measured a set of XPS spectra (C 1s, Si 2p, N 1s) over a photon energy range of 2 eV around the (0006) Bragg energy (2462 eV) of 6H-SiC. The spectra of the three samples present different sets of components, revealing the distinct chemical states of N. Using the vertical positions derived from the NIXSW technique, summarized, we will show below that these chemical components can be associated with N incorporation into the different constituents of the samples. Before considering the results for EMLG and QFMLG, it is worth studying the effect of N doping on the BL sample, because the buffer layer on SiC is the support for graphene in EMLG. The main component is present for the EMLG and QFMLG samples [Figs. The main component is present for the EMLG and QFMLG samples [Figs. 1(b) and 1(c)]
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