Coulomb blockade based field-effect transistors exploiting stripe-shaped channel geometries of self-assembled metal nanoparticles

Abstract

Metallic nanoparticles offer possibilities to build basic electric devices with new functionality and improved performance. Due to the small volume and the resulting low self-capacitance, each single nanoparticle exhibits a high charging energy. Thus, a Coulomb-energy gap emerges during transport experiments that can be shifted by electric fields, allowing for charge transport whenever energy levels of neighboring particles match. Hence, the state of the device changes sequentially between conducting and non-conducting instead of just one transition from conducting to pinch-off as in semiconductors. To exploit this behavior for field-effect transistors, it is necessary to use uniform nanoparticles in ordered arrays separated by well-defined tunnel barriers. In this work, CoPt nanoparticles with a narrow size distribution are synthesized by colloidal chemistry. These particles are deposited via the scalable Langmuir-Blodgett technique as ordered, homogeneous monolayers onto Si/SiO2 substrates with pre-patterned gold electrodes. The resulting nanoparticle arrays are limited to stripes of adjustable lengths and widths. In such a defined channel with a limited number of conduction paths the current can be controlled precisely by a gate voltage. Clearly pronounced Coulomb oscillations are observed up to temperatures of 150 K. Using such systems as field-effect transistors yields unprecedented oscillating current modulations with on/off-ratios of around 70%.

Metal nanoparticle film–based room temperature Coulomb transistor

“…Even at room temperature, the characteristic is still slightly nonlinear. The monolayer system is well suited to investigate the temperature transition of the transport mechanism ( 31 – 33 ). In accordance with previous observations, electrical transport at low temperatures takes place mainly through tunneling (direct or Nordheim-Fowler tunneling), where the current is strongly dependent on the source-drain voltage ( 37 ).…”

Impact of a charged neighboring particle on Förster resonance energy transfer (FRET)

“…where 0 is the permittivity of vacuum. We ignore the capacitance of the submerged medium (C sur = 0), reasoning that it is smaller in orders of magnitude compared to the self capacitance of the particle [47,48]. Hence, the capacitance of the MNP is proportional to the radius R and depends on the relative permittivity of the dielectric medium, b .…”

Electrical transport through self-assembled colloidal nanomaterials and their perspectives

“…The Coulomb charging energy of the individual nanoparticles adopts a similar function like the semiconductor bandgap. Since the charging energy depends on the size of the nanoparticles, a reduction of the diameter and further device engineering can lead to higher working temperatures up to room temperature and larger on/off ratios [127,128]. Due to the involved Coulomb energy ladder, these new types of transistors possess sinusoidal transfer characteristics which are tunable by the size of the particles, the interparticle distances, the used ligands, and the device architecture.…”