On the electric conductivity of highly ordered monolayers of monodisperse metal nanoparticles

TL;DR

This study investigates the electric conductivity of highly ordered monolayers of monodisperse cobalt-platinum nanoparticles, revealing thermally activated hopping and Coulomb blockade phenomena, with a novel method to determine particle charging energies.

Contribution

It introduces a new experimental approach to measure particle charging energies in nanoparticle monolayers, highlighting the role of self-capacitance and permittivity.

Findings

Electron hopping occurs at room temperature.

Coulomb blockade observed at low temperatures.

Charging energies depend on particle size, not interparticle distance.

Abstract

Monolayers of colloidally synthesized cobalt-platinum nanoparticles of different diameters characterized by TEM (transmission electron microscopy) were deposited on structured silicon oxide substrates and characterized by SEM (scanning electron microscopy), GISAXS (grazing incidence x-ray scattering), and electric transport measurements. The highly ordered nanoparticle films show a thermally activated electron hopping between spatially adjacent particles at room temperature and Coulomb blockade at low temperatures. We present a novel approach to experimentally determine the particles charging energies giving values of 6.7-25.4 meV dependent on the particles size and independent of the interparticle distance. These observations are supported by FEM (finite element method) calculations showing the self-capacitance to be the determining value which only depends on the permittivity constant of the surrounding space and the particles radius.