New Research


How much is the electric resistance of a single molecule ?

-Towards single molecular electronics-

Professor Hirokazu Tada, Associate professor Ryo Yamada, Research assistant Yasuo Azuma, Research as

It is well known that the electrical resistance of a gold wire is inversely proportional to the cross-sectional area of the wire. However, this rule isn\'t right when a diameter of wires is smaller than 1nm. The resistance is restricted to the values proportional to 13,000 ohm in nano-scale. The rule of electrical resistance changes because the way of carrier transport is different. Therefore, we have to know the rules of current flow in nano-scale to make electronic components working in nano-scale,

Organic molecules are the most fascinating material to construct single molecular electronic components because various structures can be designed and synthesized. However, it is not well understood how electric current flows through a single molecule.

We use a scanning tunneling microscope and other original instruments to measure the electrical conductance of oligothiophene derivatives that are developed by collaborators. The mechanism of carrier transport through the molecule was studied by using a series of oligothiophenes with different length. The oligothiophenes were found to be very good electrical conductors as expected. These experimental findings give a clue how to control electrical conductance in single molecules by chemical design of molecules..

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