Project Description

Figure: Valence Band (VB) and VB-1 dispersion for a pristine 7-AGNR (left) and transmission function (right) for a pristine ribbon (red), a single boron pair (dashed green) and for the confined system formed by two boron pairs (blue). The transmission function shows the strong reflectivity of a single boron pair and the Fabry−Perot behavior of the double 2B-barrier system. (d) Real part of the eigenchannel functions taken at the energies corresponding to the N = 2, 3, 4, and 5 quantum well levels. The figure is taken from E. Carbonell-Sanromà et al. Nano Lett. 2017, 17, 50−56.

Quantum Dots Embedded in Graphene Nanoribbons – Electronic Transport

Eduard Carbonell-Sanromà, Pedro Brandimarte, Richard Balog, Martina Corso, Shigeki Kawai, Aran Garcia-Lekue, Shohei Saito, Shigehiro Yamaguchi, Ernst Meyer, Daniel Sánchez-Portal, and Jose Ignacio Pascual, Nano Letters 2017, 17 (1), 50-56, DOI: 10.1021/acs.nanolett.6b03148

Motivation of the modeling:

Bottom-up chemical reactions of selected molecular precursors on a gold surface can produce high quality graphene nanoribbons (GNRs). In this study it is reported the formation of quantum dots embedded in an armchair GNR by substitutional inclusion of pairs of boron atoms into the GNR backbone. First-principles simulations are used to understand the origin of the discretization of the valence band into confined modes shown by the nanoribbons in the pristine region between two boron pairs.

Achievements of the model:

First-principles calculations qualitatively reproduce the experimental results and evidence that the band selective nature of the confinement is due to the different symmetry of the bands of the pristine ribbon and the scattered states.

Model system/Software:

A free-standing 7-AGNR with two B-substituted subunits. The electronic structure calculations were performed using the SIESTA/TranSIESTA package.

The SIESTA simulations provided the following main information:

  • Charge distribution (Mulliken population analysis)
  • PDOS profile
  • Wave functions and corresponding energy levels
  • Band Structure
  • Electrostatic Potential
  • Transmission functions

Daniel Sánchez-Portal, SIMUNE’s collaborator within the RETOS project and member of the core development team of the SIESTA code, is one of the authors of this work.