The research group used metal nanoparticles which were so small they no longer showed their metallic character under current flow but instead exhibited an energy gap caused by the Coulomb repulsion of the electrons among one another.
Via a controlling voltage, this gap can be shifted energetically and the current can thus be switched on and off as desired. The nanoparticles are not deposited as individual structures, which according to the researchers renders the production very complex and the properties of the corresponding components unreliable.
Instead, they are deposited as thin films with a height of only one layer of nanoparticles. Employing this method, the electrical characteristics of the devices are said to become adjustable.
"Scientifically interesting is that the metal particles inherit semiconductor-like properties due to their small size,” says Dr Christian Klinke. "The devices developed in our group can not only be used as transistors, but they are also very interesting as chemical sensors because the interstices between the nanoparticles, which act as tunnel barriers, react to chemical deposits."
The team claims these Coulomb transistors have three main advantages that make them interesting for commercial applications: the synthesis of metal nanoparticles is controllable and scalable; it provides very small nanocrystals that can be stored in solvents and are easy to process; and the Langmuir-Blodgett deposition method provides high-quality monolayered films and can also be implemented on an industrial scale.
The resulting transistors are said to show a switching behaviour of more than 90% and function up to room temperature. The researchers therefore believe that inexpensive transistors and computer chips with lower power consumption are possible in the future.