Electronic and optical properties in graphane

TL;DR

This paper develops a tight-binding model to analyze the electronic and optical properties of graphane, revealing unique band structures and optical excitations distinct from graphene.

Contribution

It introduces a detailed tight-binding approach to study graphane's properties, highlighting the effects of sp3 bonding on optical spectra and electronic structure.

Findings

Optical absorption peaks are insensitive to polarization direction.

Shoulder structures at ~3.5 eV relate to 2px and 2py orbitals.

High-frequency peaks involve hybridization of carbon and hydrogen orbitals.

Abstract

We develop the tight-binding model to study electronic and optical properties of graphane. The strong sp3 chemical bondings among the carbon and hydrogen atoms induce a special band structure and thus lead to the rich optical excitations. The absorption spectrum hardly depends on the direction of electric polarization. It ex- hibits a lot of shoulder structures and absorption peaks, which arise from the extreme points and the saddle points of the parabolic bands, respectively. The threshold op- tical excitations, only associated with the 2px and 2py orbitals of the carbon atoms, are revealed in a shoulder structure at ?3.5 eV. The first symmetric absorption peak, appearing at ~11 eV, corresponds to energy bands due to the considerable hybridiza- tion of carbon 2pz orbitals and H 1s orbitals. Also, some absorption peaks at higher frequencies indicate the bonding of 2s and 1s orbitals. These results are in sharp contrast to those of the sp2 graphene systems.