| Electron pumps are devices that can transfer a certain number of electrons during each pumping cycle. Besides being of fundamental interest to physicists, single-electron pumps have a potential for practical application in metrology, acting as an accurate frequency-current converter. | |
| The general goal of this field is to build a current standard based on the electrical charge of a single electron in order to achieve high accuracy for current measurement. A device called single-electron transistor (SET) can confine charges down to single electron level and hence is applicable for quantized current generation (current that consists of only one or a few electrons). | |
| Experimentally, this concept was mostly tested on devices made by III-V semiconductor heterostructures or metallic nanoparticles. In principle, the smaller the device is, the better the performance will be. However, the size of the devices made by either semiconductor heterostructures or metal particles is limited by current lithography technologies. | |
| Most implementations of single electron pumps employ a very small region weakly coupled to electron reservoirs, usually described in metallic systems as an island. The island is sufficiently small that the addition or removal of a single electron makes an appreciable energetic difference. Researchers have proposed to modify this structure by replacing the normal-metal island with an individual single-walled carbon nanotube (SWCNT), which already possess nanoscale dimensions with diameters of about 1 nm. | |
| Attempts to generate quantized current in SWCNTs have been made with various methods over the past few years, but were not very successful in obtaining a high degree of current quantization, especially when trying to generate current with more than one electron (read more: "Quantum dot nanodevices with carbon nanotubes"). | |
| A research team in Germany has now demonstrated the feasibility of using a single molecule – in this case, a single-walled carbon nanotube – for the generation of quantized electric current. |
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