Molecular transistors that run on single electrons now work at room temperature. Dutch scientists achieved the feat by buckling carbon nanotubes with an atomic force microscope.
鈥淲e鈥檝e added another important piece to the toolbox for molecular electronics鈥� said lead researcher Cees Dekker of Delft University. 鈥淚t鈥檚 only four years ago since we measured for the first time any electronic transport through a nanotube. Now, we are exploring what can be done in terms of single-molecule devices.
鈥淭he next step will be to think about how to combine these elements into complex circuits,鈥� he says. Molecular computers would be high speed and low power.
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Other experts say the method is too fiddly to lend itself to the mass-production of nanoscopic transistors immediately, but they believe it demonstrates new possibilities.
鈥淚t鈥檚 a different way to get this sort of transistor,鈥� says James Tour of Rice University鈥檚 Centre for Nanoscale Science and Technology in Houston, Texas. 鈥淚t shows that you can bring this up to room temperature鈥�
Leaky circuit
The transistors inside normal computers control the flow of thousands of electrons at a time. Transistors capable of manipulating individual electrons could potentially do the same work faster and more efficiently.
However, functioning at this tiny scale can be difficult as heat can cause electrons to leak in and out of the molecular components. To avoid this, previous molecular transistors were cooled to near absolute zero.
The Delft researchers wanted to create a device that worked at more practical temperatures. By buckling a metallic carbon nanotube, they formed a small area from which a single electron cannot escape at room temperature unless a current is applied via an electrode.
Quantum tricks
Although the process in ingenious, Tour believes there are still a number obstacles between producing single electron circuits.
These include finding a way to reproduce the effect for thousands of transistors at a time and the fact that molecular computer components cannot be manufactured using current lithographic techniques. Another problem involves scaling down other parts of the new transistor鈥檚 architecture.
鈥淚t鈥檚 a beautiful lab experiment,鈥� says Tour. 鈥淏ut on the flip side, it鈥檚 going to be difficult to do anything more than in a lab.鈥�
An interesting and unexpected quantum phenomena also came from the experiment. Dekker says that pushing a single electron through the transistor caused it to exhibit quantum coherence.
This means that the electron maintains some of the quantum state it obtained whilst inside the transistor when it leaves. The effect is not found within normal electronics.