The origin of high-resolution IETS-STM images of organic molecules with functionalized tips

TL;DR

This paper explains how high-resolution IETS-STM imaging of organic molecules is achieved using decorated tips, particularly CO-functionalized tips, which act as nanoscale sensors revealing molecular structure and charge transfer details.

Contribution

The authors extend existing models to explain high-resolution IETS imaging with decorated tips, highlighting the role of CO as a nanoscale sensor and including electrostatic interactions.

Findings

CO-decorated tips enable high-resolution imaging of molecular structures.

The model accounts for electrostatic forces affecting IETS signals.

Imaging reveals intramolecular charge transfer phenomena.

Abstract

Recently, the family of high-resolution scanning probe imaging techniques using decorated tips has been complimented by a method based on inelastic electron tunneling spectroscopy (IETS). The new technique resolves the inner structure of organic molecules by mapping the vibrational energy of a single carbonmonoxide (CO) molecule positioned at the apex of a scanning tunnelling microscope (STM) tip. Here, we explain high-resolution IETS imaging by extending the model developed earlier for STM and atomic force microscopy (AFM) imaging with decorated tips. In particular, we show that the tip decorated with CO acts as a nanoscale sensor that changes the energy of the CO frustrated translation in response to the change of the local curvature of the surface potential. In addition, we show that high resolution AFM, STM and IETS-STM images can deliver information about intramolecular charge transfer for molecules deposited on a~surface. To demonstrate this, we extended our numerical model by taking into the account the electrostatic force acting between the decorated tip and surface Hartree potential.