Noise and Transport Characterization of Single Molecular Break Junctions with Individual Molecule

TL;DR

This study investigates noise spectra in break junctions with and without molecules, revealing unique Lorentzian noise components linked to single molecules, and proposes a model connecting molecular coupling reconfiguration to charge transport.

Contribution

It introduces a phenomenological model linking molecular coupling reconfiguration to charge transport, supported by experimental noise spectra analysis.

Findings

Lorentzian 1/f^2 noise observed only with single molecules

Characteristic frequency correlates with lock-in current amplitudes

Molecular coupling reconfiguration affects charge transport

Abstract

We studied the noise spectra of molecule-free and molecule-containing mechanically controllable break junctions. Both types of junctions revealed typical 1/ f noise characteristics at different distances between the contacts with square dependence of current noise power spectral density on current. Additional Lorentzian-shape (1/ f 2) noise components were recorded only when nanoelectrodes were bridged by individual 1,4 benzenediamine molecule. The characteristic frequency of the revealed 1/ f 2 noise related to a single bridging molecule correlates with the lock-in current amplitudes. The recorded behavior of Lorentzian-shape noise component as a function of current is interpreted as the manifestation of a dynamic reconfiguration of molecular coupling to the metal electrodes. We propose a phenomenological model that correlates the charge transport via a single molecule with the reconfiguration of its coupling to the metal electrodes. Experimentally obtained results are in good agreement with theoretical ones and indicate that coupling between the molecule metal electrodes is important aspect that should be taken into account.