Colloidal Coulomb Transistor...

Thin films made of metal nanoparticles (grey spheres) are electrically contacted by gold electrodes. The current flowing through the films (in blue) is adjustable by the voltage of a local electrode located below the film. For the characterization, needle-shaped probes are applied to the electrodes, which provide the corresponding voltages and measure the current. Credit: Christian Klinke, University of Hamburg

Topics: Electrical Engineering, Nanotechnology, Semiconductor Technology

Researchers at the University of Hamburg in Germany have succeeded in making the first Coulomb transistor from structured thin films of colloidal metal nanoparticles. Instead of having only two states, ON and OFF, as in classic transistors based on semiconductors, the new device has sinusoidal ON/OFF characteristics.

Modern-day transistors are based on semiconducting-type materials, usually silicon. In the quest for cheaper, less power-hungry microelectronics devices, such as those in laptops, tablets and smartphones, researchers are looking into alternatives to these materials.

A team led by Christian Klinke has now made transistors from metal nanoparticles. The small size of the particles means that they no longer show metallic characteristics under current flow but instead have an energy bandgap (akin to that in semiconductors) that arises from the Coulomb repulsion between electrons in the material. This effect is known as the Coulomb blockade, and it exists even at room temperature in the materials employed in the new devices (in this case cobalt-platinum nanoparticles).

Colloidal metal nanoparticles make Coulomb transistor, Belle Dumé, Nanotech Web