Localized state and charge transfer in nitrogen-doped graphene

Abstract

Nitrogen-doped epitaxial graphene grown on SiC(000?1) was prepared by exposing the surface to an atomic nitrogen flux. Using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS), supported by Density Functional Theory (DFT) calculations, the simple substitution of carbon by nitrogen atoms has been identified as the most common doping configuration. High-resolution images reveal a reduction of local charge density on top of the nitrogen atoms, indicating a charge transfer to the neighboring carbon atoms. For the first time, local STS spectra clearly evidenced the energy levels associated with the chemical doping by nitrogen, localized in the conduction band. Various other nitrogen-related defects have been observed. The bias dependence of their topographic signatures demonstrates the presence of structural configurations more complex than substitution as well as hole-doping.Comment: 5 pages, accepted in PR

Self-consistent tight-binding model of B and N doping in graphene

“…(7), (12), and (13), we compare in Fig. 3 the local density of states computed using either numerical or analytical methods.…”

“…Note, however, that interactions among impurities in neighboring supercells will affect the results if N is not sufficiently large. 12,13 The resulting matrix problem reads (H 0 + H 1 ) · c n, k = E n, k S · c n, k , where n and k label band and k-vector, respectively, S is the overlap matrix, and E n, k and c n, k denote eigenvalues and eigenvectors. If a total of N k k-points in the irreducible Brillouin zone are sampled, the local density of states L(ω) on the impurity site is evaluated numerically as…”

“…Donor or acceptor levels may subsequently be identified as resonances in the local density of states. Several publications have investigated this problem at ab initio [11][12][13] and tight-binding [13][14][15][16][17][18][19][20][21] levels. The tight-binding approach is obviously highly suited for analysis of localized impurity states.…”

“…Moreover, the long-range nature of impurity-impurity interactions requires rather large simulation cells, making firstprinciples calculations challenging. 12,13 A simple, orthogonal nearest-neighbor tight-binding model is capable of qualitatively modeling several impurity-related properties. 15,16,18 The implicit assumptions, such as perfect electron-hole symmetry, are problematic, however.…”

Tuning the Optically Bright and Dark States of Doped Graphene Quantum Dots

“…19,20 Other methods have also been used successfully to produce nitrogen doped graphene fragments. 21,22 There has been many works on the optical response of graphene and truncated graphene i.e. graphene quantum dots (GQD) and for GQD the excitonic features are more exotic than their 2D analogue.…”