Vibrational features in inelastic electron tunneling spectra

TL;DR

This paper presents a theoretical analysis of inelastic electron tunneling spectroscopy (IETS) in molecular junctions, examining how vibronic coupling, phonon energy, and temperature influence the spectra, with insights into asymmetry effects.

Contribution

It introduces a nonperturbative computational scheme to analyze IETS spectra considering various parameters and asymmetry effects in molecular junctions.

Findings

Vibronic coupling strength significantly affects IETS features.

Phonon energy influences the spectral shape and intensity.

Weak bias asymmetry arises from electrode connection asymmetry.

Abstract

A theoretical analysis of inelastic electron tunneling spectroscopy (IETS) experiments conducted on molecular junctions are presented, where the second derivative of the current with respect to voltage is usually plotted as a function of applied bias. Within the nonperturbative computational scheme, adequate for arbitrary parameters of the model, we consider the virtual conduction process in the off-resonance region. Here we study the influence of few crucial factors on the IETS spectra: the strength of the vibronic coupling, the phonon energy, and the device working temperature. It was also shown that weak asymmetry in the IETS signal with respect to bias polarity is obtained as a result of strongly asymmetric connection with the electrodes.