▎ 摘　　要

We describe charging a quantum dot induced electrostatically within a semiconducting graphene nanoribbon by electrons or holes. The applied model is based on a tight-binding approach with the electron-electron interaction introduced by a mean-field local-spin-density approximation. The numerical approach accounts for the charge of all the p(z) electrons and screening of external potentials by states near the charge-neutrality point. Both a homogeneous ribbon and a graphene flake embedded within the ribbon are discussed. The formation of transport gaps as functions of the external confinement potential (top-gate potential) and the Fermi energy (back-gate potential) are described in a qualitative agreement with the experimental data. For a fixed number of excess electrons, we find that the excess charge added to the system is, - depending on the voltages defining the work point of the device, (i) delocalized outside the quantum dot, - in the transport gap due to the top-gate potential; (ii) localized inside the quantum dot, - in the transport gap due to the back-gate potential; or (iii) extended over both the quantum dot area and the ribbon connections, - outside the transport gaps. The applicability of the frozen valence-band approximation to describe charging the quantum dot by excess electrons is also discussed.