A multiscale study of electronic structure and quantum transport in $C_{6n^2}H_{6n}$-based graphene quantum dots

TL;DR

This study combines multiscale modeling and quantum transport calculations to analyze defect effects in graphene quantum dots, highlighting the importance of accurate parameterization and defect modeling for electronic properties.

Contribution

It introduces a multiscale approach integrating density functional theory and semiempirical methods to study defect localization and quantum transport in graphene quantum dots.

Findings

Vacancies exhibit impurity-like behavior affecting electronic structure.

Proper parameterization is crucial for accurate transport predictions.

Vacancies induce wavefunction localization impacting conduction.

Abstract

We implement a bottom-up multiscale approach for the modeling of defect localization in $C_{6n^2}H_{6n}$ islands, i.e. graphene quantum dots with a hexagonal symmetry, by means of density functional and semiempirical approaches. Using the \textit{ab initio} calculations as a reference, we recognize the theoretical framework under which semiempirical methods describe adequately the electronic structure of the studied systems and thereon proceed to the calculation of quantum transport within the non-equilibrium Green's function formalism. The computational data reveal an impurity-like behavior of vacancies in these clusters and evidence the role of parameterization even within the same semiempirical context. In terms of conduction, failure to capture the proper chemical aspects in the presence of generic local alterations of the ideal atomic structure results in an improper description of the transport features. As an example, we show wavefunction localization phenomena induced by the presence of vacancies and discuss the importance of their modeling for the conduction characteristics of the studied structures.