Coulomb blockade detected in organic conductors

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In experiments, a team of researchers from Osaka University claims to have detected Coulomb blockades in two dimensional organic conducting polymer films. The group says its work could change the conventional understanding of organic conductors and help in the design of organic and molecular devices, such as single-electron transistors or a memory in which information is stored by just a few electrons.

Previously, it was thought that Coulomb blockades only occurred in inorganic materials at extremely low temperatures. However, the team not only showed that it can take place in organic materials, but also that Coulomb blockades can affect conductivity at room temperature.

The researchers, led by Assistant Professor Megumi Akai-Kasaya and Professor Yuji Kuwahara, created a sheet of two-dimensional films of regularly arranged hexylthiophene monolayers. The sheet was then attached to an electrode with a gap of less than 1µm and its electrical conductivity was measured. The current flowing through the film was found to be temperature dependent over temperatures ranging from 4K to 150K and to vary according to the charge on the electrode and the thermal energy of the system. The team also found the effect produced a temperature dependent threshold voltage.

The group claims it theoretically verified the Coulomb blockade in the organic thin film through the delocalisation of electric charge and the distribution of conductivity in the two-dimensional film.