Scanning tunneling microscopy simulations of poly(3-dodecylthiophene) chains adsorbed on highly oriented pyrolytic graphite

TL;DR

This paper introduces a new simulation method combining tight binding and density-functional calculations to efficiently model STM images of molecules on surfaces, specifically applied to poly(3-dodecylthiophene) on graphite.

Contribution

It presents a novel hybrid simulation scheme that accounts for structural relaxation effects in STM modeling of adsorbed molecules.

Findings

Accurately predicts STM images and spectra of P3DDT on HOPG.

Shows good agreement with experimental data.

Highlights the importance of including structural relaxation effects.

Abstract

We report on a novel scheme to perform efficient simulations of Scanning Tunneling Microscopy (STM) of molecules weakly bonded to surfaces. Calculations are based on a tight binding (TB) technique including self-consistency for the molecule to predict STM imaging and spectroscopy. To palliate the lack of self-consistency in the tunneling current calculation, we performed first principles density-functional calculations to extract the geometrical and electronic properties of the system. In this way, we can include, in the TB scheme, the effects of structural relaxation upon adsorption on the electronic structure of the molecule. This approach is applied to the study of regioregular poly(3-dodecylthiophene) (P3DDT) polymer chains adsorbed on highly oriented pyrolytic graphite (HOPG). Results of spectroscopic calculations are discussed and compared with recently obtained experimental dat