Hybrid density-functional theory calculations of electronic and optical properties of mercaptocarboxylic acids on ZnO $(10{\overline 1}0)$ surfaces

TL;DR

This study uses density functional theory to analyze how mercaptocarboxylic acids adsorb on ZnO surfaces, revealing stable monodentate binding modes that introduce optically active states, with properties unaffected by chain length, useful for opto-electronic applications.

Contribution

It demonstrates that mercaptocarboxylic acids can stabilize ZnO surfaces and modify their optical properties independently of chain length, using advanced hybrid DFT calculations.

Findings

Monodentate adsorption mode is most stable.

Adsorption introduces optically active states in ZnO.

Properties are insensitive to chain length.

Abstract

In this work we investigate the electronic properties of mercaptocarboxylic acids with several carbon chain lengths adsorbed on ZnO-(10-10) surfaces via density functional theory calculations using semi-local and hybrid exchange-correlation functionals. Amongst the investigated structures, we identify the monodentate adsorption mode to be stable. Moreover, this mode introduces optically active states in the ZnO gap, is further confirmed by the calculation of the dielectric function at PBE0 and TD-PBE0 levels. One interesting finding is that adsorption mode and the dielectric properties of the hybrid system are both rather insensitive to the chain length, since the acceptor molecular state is very localized on the sulphur atom. This indicates that even small molecules can be used to stabilize ZnO surface and to enhance its functionality for opto-electronic applications.