Simulation of inelastic electron tunneling spectroscopy of single molecules with functionalized tips

TL;DR

This paper uses first-principles simulations to explore how chemically functionalized STM tips influence the vibrational spectra in inelastic electron tunneling spectroscopy of single molecules, revealing how tip symmetry affects spectral intensity.

Contribution

It demonstrates how tip functionalization alters IETS signals and provides symmetry-based guidelines for optimizing single-molecule spectroscopy.

Findings

Tip functionalization modifies IETS intensity for adsorbate vibrational modes.

Symmetry considerations explain the propensity rules governing IETS signals.

Selecting the appropriate tip orbital symmetry can optimize single-molecule IETS.

Abstract

The role of the tip in inelastic electron tunneling spectroscopy (IETS) performed with scanning tunneling microscopes (STM) is theoretically addressed via first-principles simulations of vibrational spectra of single carbon monoxide (CO) molecules adsorbed on Cu(111). We show how chemically functionalized STM tips modify the IETS intensity corresponding to adsorbate modes on the sample side. The underlying propensity rules are explained using symmetry considerations for both the vibrational modes and the molecular orbitals of the tip and sample. This suggests that single-molecule IETS can be optimized by selecting the appropriate tip orbital symmetry.