Atomic-Scale Charge Distribution Mapping of Single Substitutional p- and n-Type Dopants in Graphene

Abstract

Tuning the chemical properties of graphene by controlled doping is a widely investigated strategy. The effect of a substitutional single dopant on graphene local reactivity is much less explored. To improve the understanding of the role of p-and n-type dopants in graphene's local chemical activity and quantification of its interaction with single molecules, we report an atomic-scale investigation of single boron (B) and nitrogen (N) dopants in graphene and their interactions with CO molecules by means of atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) experiments and theoretical calculations. We infer that N/B doping significantly increases/ lowers the chemical interaction of graphene with individual CO molecules as a result of weak electrostatic forces induced by distinct charge distribution around the dopant site. High-resolution AFM images allow dopant discrimination and their atomic-scale structural characterization, which may be crucial for the atomic-scale design of graphene derivatives with relevant potential applications in molecular sensing and catalysis.

On‐Surface Synthesis of a Dicationic Diazahexabenzocoronene Derivative on the Au(111) Surface

“…Specifically, we observe a substantial variation of the local contact potential difference (LCPD), which shifts toward lower values with respect to the reference LCPD recorded on the bare Au(111) surface (Figure 4 b). This LCPD shift concurs very well with the positive net charge of 2 [44–48] . Moreover, simulated KPFM images of fully relaxed 2 on the Au(111) match very well the experimental KPFM images acquired in a close tip‐sample distance revealing submolecular resolution (see Figure S6 and methods section for further details) [48, 49] …”

On‐Surface Synthesis of a Dicationic Diazahexabenzocoronene Derivative on the Au(111) Surface

“…This LCPD shift concurs very well with the positive net charge of 2. [44][45][46][47][48] Moreover,s imulated KPFM images of fully relaxed 2 on the Au(111) match very well the experimental KPFM images acquired in ac lose tip-sample distance revealing submolecular resolution (see Figure S6 and methods section for further details). [48,49]…”

Measuring and Tuning the Potential Landscape of Electrostatically Defined Quantum Dots in Graphene

“…In a KPFM measurement, the local contact potential difference (LCPD) between the surface of a material and the conductive tip of an atomic force microscope (AFM) is spatially mapped across the sample . For graphene, KPFM measurements have been used to characterize several phenomena: the dependence of work function on carrier density, Moirè pattern potentials, quantum Hall edge states, screening clouds near defects, potential drops across biased samples, , and near electrical contacts . One complication of KPFM measurements is that the tip can have both a sharp (∼10 nm) apex and a large (∼1–10 μm) body which can measure different short- and long-range, respectively, CPD values .…”