Armchair nanoribbons of silicon and germanium honeycomb structures

TL;DR

This study uses first-principles calculations to analyze the structural stability and electronic properties of armchair silicon and germanium honeycomb nanoribbons, revealing family behavior of band gaps and potential for quantum well applications.

Contribution

It provides a comprehensive first-principles analysis of silicon and germanium nanoribbons, including stability, electronic structure, and effects of width modulation, which was not previously detailed.

Findings

Band gaps exhibit family behavior similar to graphene nanoribbons.

Edge reconstruction can be eliminated by hydrogen passivation.

Periodic width modulation creates superlattice structures with confined electronic states.

Abstract

We present a first-principles study of bare and hydrogen passivated armchair nanoribbons of the puckered single layer honeycomb structures of silicon and germanium. Our study includes optimization of atomic structure, stability analysis based on the calculation of phonon dispersions, electronic structure and the variation of band gap with the width of the ribbon. The band gaps of silicon and germanium nanoribbons exhibit family behavior similar to those of graphene nanoribbons. The edges of bare nanoribbons are sharply reconstructed, which can be eliminated by the hydrogen termination of dangling bonds at the edges. Periodic modulation of the nanoribbon width results in a superlattice structure which can act as a multiple quantum wells. Specific electronic states are confined in these wells. Confinement trends are qualitatively explained by including the effects of the interface. In order to investigate wide and long superlattice structures we also performed empirical tight binding calculations with parameters determined from \textit{ab initio} calculations.