Non-Local Conductance Modulation by Molecules: STM of Substituted Styrene Heterostructures on H-Terminated Si(100)

TL;DR

This study uses STM and simulations to show how substituents on styrene molecules can modulate local conductance in organic heterostructures on silicon, revealing a method to tune molecular and substrate transport.

Contribution

It demonstrates how different molecular substituents influence local conductance and substrate transport in organic heterostructures on silicon, combining experimental STM and ab initio simulations.

Findings

OCH3 groups enhance conduction near heterojunctions

CF3 groups suppress silicon transport

Substituent choice allows tuning of molecular-scale conductance

Abstract

One-dimensional organic heterostructures consisting of contiguous lines of CF3- and OCH3-substituted styrene molecules on silicon are studied by scanning tunneling microscopy and ab initio simulation. Dipole fields of OCH3-styrene molecules are found to enhance conduction through molecules near OCH3-styrene/CF3-styrene heterojunctions. Those of CF3-styrene depress transport through the nearby silicon. Thus choice of substituents and their attachment site on host molecules provide a means of differentially tuning molecule and substrate transport at the molecular scale.