Chemical functionalization on planar polysilane and graphane

TL;DR

This study uses density functional theory to explore how fluorine and other groups modify the electronic properties of planar polysilane and graphane, revealing how surface chemistry and doping configurations influence their electronic structures.

Contribution

It provides new insights into the effects of chemical functionalization on the electronic structures of planar polysilane and graphane, highlighting differences between carbon and silicon surfaces.

Findings

Fluorine turns the indirect gap of polysilane into a direct gap.

Fluorine coverage determines the gap width regardless of distribution.

Electronic structure of fluorine-doped graphane is highly sensitive to doping configuration.

Abstract

Two dimensional materials are important for electronics applications. A natural way for electronic structure engineering on two dimensional systems is on-plane chemical functionalization. Based on density functional theory, we study the electronic structures of fluorine substituted planar polysilane and graphane. We find that carbon and silicon present very different surface chemistry. The indirect energy gap of planar polysilane turns to be direct upon fluorine decoration, and the gap width is mainly determined by fluorine coverage regardless of its distribution on the surface. However, electronic structure of fluorine doped graphane is very sensitive to the doping configuration, due to the competition between antibonding states and nearly-free-electron (NFE) states. With specific fluorine distribution pattern, zero-dimensional and one-dimensional NFE states can be obtained. We have also studied the chemical modification with -OH or -NH$_2$ group. Carbon seems to be too small to accommodate big functional groups on its graphane skeleton with a high concentration.