Single molecule transistors work at room temperature

　　For the first time a team of researchers from Columbia University in the city of New York claims to have reproducibly demonstrated current blockade – the ability to switch a device from the insulating to the conducting state where charge is added and removed one electron at a time – using atomically precise molecular clusters at room temperature.

　　According to the research team, this could enable smaller electrical components and improve data storage and computing power.

　　To create the transistor, the researchers developed a single cluster of geometrically ordered atoms with an inorganic core made of 14 atoms and positioned linkers that wired the core to two gold electrodes.

　　The researchers then used a scanning tunneling microscope technique to make junctions comprising a single cluster connected to the two gold electrodes, which enabled them to characterise its electrical response as they varied the applied bias voltage. The technique is said to allow them to fabricate and measure thousands of junctions with reproducible transport characteristics.

　　"We found that these clusters can perform very well as room-temperature nanoscale diodes whose electrical response we can tailor by changing their chemical composition," says Professor Latha Venkataraman.

　　"Theoretically, a single atom is the smallest limit, but single-atom devices cannot be fabricated and stabilised at room temperature. With these molecular clusters, we have complete control over their structure with atomic precision and can change the elemental composition and structure in a controllable manner to elicit a certain electrical response."

　　"Most of the other studies created single-molecule devices that functioned as single-electron transistors at 4K, but for any real-world application, these devices need to work at room temperature. And ours do," says postdoctoral researcher Giacomo Lovat.

　　The team evaluated the performance of the diode through the on/off ratio. At room temperature, they observed an on/off ratio of about 600 in single-cluster junctions, which they claim is higher than any other single-molecule devices measured to date.