To organize nanoparticles into structures that are useful in electronics, researchers have turned to DNA scaffolds that self-assemble into patterns and attract the nanoparticles into functional arrangements.
Now researchers at the Nanoscience Center (NSC) of the University of Jyväskylä and BioMediTech (BMT) of the University of Tampere, both in Finland, have used these DNA scaffolds to organize three gold nanoparticles into a single-electron transistor. DNA scaffolds have previously been used to organize gold nanoparticles into patterns. But this work represents the first time that these DNA scaffolds have been used to construct precise, controllable DNA-based assemblies that are fully electrically characterized for use in single-electron nanoelectronics. The immediate benefit: There’s no longer a need to keep these structures at cryogenic temperatures in order for them to work.
The way that electron transport occurs in single-electron devices is altogether different than in conventional electronics. With single-electron devices, the electron is governed by quantum mechanics. In these devices, there is what is known as an “island” where electrons are contained and isolated by tunnel junctions that control electron tunneling. The tunnel junctions operate under the quantum mechanical phenomenon known as the Coulomb Blockade, in which electrons inside the device produce a strong repulsion preventing other electrons from circulating.
The Finland-based scientists observed a clear Coulomb Blockade phenomenon with their device—all the way up to room temperature. While this is not the first time that Coulomb Blockade has been observed at temperatures that high, its demonstration in a single-electron device should prove significant for these devices. But, more importantly, the use of a self-assembling DNA scaffold could make the production of these devices far more scalable.
“Such a device based on DNA self-assembly would be a vast improvement due to fully parallel fabrication easily scaled for mass-production, which is the property not possible with previous methods demonstrating Coulomb Blockade up to room temperature,” explained Jussi Toppari, a Senior Lecturer at the NSC and a member of the research team, in an e-mail interview with IEEE Spectrum.
In research described in the journal Nano Letters, the researchers fabricated a single-electron transistor (SET) that can visualize the effect of single electrons leaving or arriving to the islands of the device via tunneling.
“The device was electrically characterized and proven to work at a basic level,” says Toppari. “However, gate dependency could not be fully demonstrated due to technical reasons. A fully working device could be utilized as a transistor or an extremely sensitive electrometer at the nanoscale.”
Of course, realizing a full-fledged single-electron device is still going to require some substantial efforts. The main sticking point preventing the full utilization of this method for builing single electron nanoelectronic circuits is the difficulty associated with growing gold nanoparticles, says Toppari. “Otherwise only the DNA-self-assembly sets the limits, and those have been pushed very far already.”
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.