Tunable electrical transport through annealed monolayers of monodisperse cobalt-platinum nanoparticles

TL;DR

This study demonstrates that annealing monolayers of cobalt-platinum nanoparticles significantly enhances their electrical conductivity, enabling tunable electronic properties through ligand carbonization and nanoparticle interactions.

Contribution

It introduces a method to control electrical transport in nanoparticle monolayers via annealing-induced ligand carbonization and nanoparticle displacement effects.

Findings

Conductivity increases over 4 orders of magnitude after annealing.

Ligand carbonization confirmed by Raman spectroscopy.

Electrical properties can be tuned by thermal treatment.

Abstract

We synthesized monodisperse cobalt-platinum nanoparticles Co(0.14-0.22)Pt(0.86-0.78) of 9 nm in diameter by colloidal chemistry methods and deposited them by the Langmuir-Blodgett technique as highly ordered monolayers onto substrates with e-beam defined gold electrodes. Upon annealing we observe an increase of conductivity over more than 4 orders of magnitude. A first attempt of explanation of this unanticipated effect, a nanoparticle displacement, could not be confirmed for annealing temperatures below 400C. A second approach, a carbonization of the ligands, however, could be confirmed by Raman spectroscopy. The simple thermal treatment allows tuning essential properties of electronic devices based on nanoparticles by the manipulation of the interparticle coupling, namely the electrical conductivity, the Coulomb blockade characteristic, and the activation energy of the system.