“After fabrication, the nanoparticles float in an aqueous solution and need to be organised into the desired form and connected to the auxiliary circuitry,” explained researcher Kosti Tapio. “DNA-based self-assembly together with its ability to be linked with nanoparticles offer a suitable toolkit for this purpose.”
Gold nanoparticles were attached directly onto a DNA structure within the aqueous solution. The whole process yielded countless structures within a single patch and ready structures are further trapped for measurements by electric fields.
According to the team, even the addition of a single electron into a nanoscale piece of metal can increase its energy enough to prevent conduction. The addition of electrons happens via a quantum-mechanical effect called tunnelling, where electrons tunnel through an energy barrier. In this study, the electrons tunnelled from the electrode connected to a voltage source, to the first nanoparticle and onwards to the next particle and so on, through the gaps between them.
“The weakness of single-electron devices has been the cryogenic temperatures needed for them to work,” commented senior lecturer Jussi Toppari from the NSC. “Usually, the operation temperature of these devices scales up as the size of the components decreases. Our ultimate aim is to have the devices working at room temperature, which is hardly possible for conventional nanofabrication methods – so new venues need to be found.”