Electronics and Optics of Graphene Nanoflakes: Edge Functionalization and Structural Distortions

TL;DR

This study investigates how edge covalent functionalization affects the structural, electronic, and optical properties of armchair graphene nanoflakes, revealing key factors that influence their optoelectronic behavior.

Contribution

It provides a detailed analysis of the impact of various edge functional groups and their distribution on AGNFs' properties using semi-empirical methods, highlighting the role of symmetry and chemical features.

Findings

Electronic gap reduction due to functionalization

Optical peak red shift linked to gap reduction

Edge pattern influences excitations and optical response

Abstract

The effects of edge covalent functionalization on the structural, electronic and optical properties of elongated armchair graphene nanoflakes (AGNFs) are analyzed in detail for a wide range of terminations, within the ramework of Hartree-Fock-based semi-empirical methods. The chemical features of the functional groups, their distribution and the resulting system symmetry are identified as the key factors that determine the modification of structural and optoelectronic features. While the electronic gap is always reduced in presence of substituents, functionalization-induced distortions contribute to the observed lowering by about 35-55%. This effect is paired with a red shift of the first optical peak, corresponding to about 75% of the total optical gap reduction. Further, the functionalization pattern and the specific features of the edge-substituent bond are found to influence the strength and the character of the low energy excitations. All these effects are discussed for flakes of different width, representing the three families of AGNFs.