Electronic and Chemical Properties of Donor, Acceptor Centers in Graphene

Abstract

Chemical doping is one of the most suitable ways of tuning the electronic properties of graphene and a promising candidate for a band gap opening. In this work we report a reliable and tunable method for preparation of high-quality boron and nitrogen co-doped graphene on silicon carbide substrate. We combine experimental (dAFM, STM, XPS, NEXAFS) and theoretical (total energy DFT and simulated STM) studies to analyze the structural, chemical, and electronic properties of the single-atom substitutional dopants in graphene. We show that chemical identification of boron and nitrogen substitutional defects can be achieved in the STM channel due to the quantum interference effect, arising due to the specific electronic structure of nitrogen dopant sites. Chemical reactivity of single boron and nitrogen dopants is analyzed using force-distance spectroscopy by means of dAFM.

Recognizing nitrogen dopant atoms in graphene using atomic force microscopy

“…We should note that Telychko et al found the reverse relationship [24]; however their experiments employed a silicon carbide surface instead of the metallic surfaces presented in this paper. We theoretically investigated the effect of the substrate.…”

“…This effect is not localized on a single atom. This is attributed to the influence of the partially charged N atom on the charge density of the atoms to which it is bound [24]. At the location of the dopant atom there is also some contrast in the z min map.…”

“…Doped graphene has also been studied with STM. For example, it was found that nitrogen-and boron-dopant atoms in graphene have a characteristic appearance in STM images, allowing their identification [22][23][24]. Furthermore, it was found that the nitrogen atoms in graphene, grown by chemical vapor deposition, occupy predominantly one sublattice of graphene [25].…”

“…It has been shown that AFM-based force-distance spectroscopy can provide chemical contrast between the chemically very different atoms Pb, Si, and Sn in a surface alloy [35]. More recently, the chemical reactivity of boron-and nitrogen-doped graphene grown on silicon carbide was investigated with AFM [24]. Chemically passivated tips can also provide different contrast above boron atoms in graphene [5].…”

Transformation of metallic boron into substitutional dopants in graphene on6H−SiC(0001)

“…In our previous work [10] we demonstrated by scanning tunneling microscopy (STM) that, using a suitable doping procedure, the B dopants are homogeneously distributed in the graphene layer. However, STM experiments do not provide any information on their chemical states in terms of local bonding, their activation, and whether the doping procedure itself influences the substrate underneath the graphene layer.…”