Alberto Morpurgo (NS) discovers conduction between two pure insulators

19 June 2008 by TNWToday | M&C

Scientists at TU Delft's Kavli Institute of Nanoscience have observed that a conductive layer does exist on the interface between two non-conducting pure organic materials. In principle, this opens the door to a new class of organic electronic systems. The scientists are to publish their findings in Nature Materials this week.

Scientists at TU Delft’s Kavli Institute of Nanoscience brought two crystals of organic material into contact with each other, simply by pressing them together. They then observed that a highly conductive layer is created on the interface between the two crystals. This is remarkable as the two materials, TTF (tetrathiofulvalene) and TCNQ (tetracyanoquinodimethane), are in themselves electrical insulators, i.e. they do not conduct electricity. As is the case with metals, the resistance on the interface declines as the temperature falls.
According to the researchers, the conductive layer can be explained by some electrons from the outer skin of TTF molecules right on the interface transferring to the TCNQ molecules directly opposite them. The layers are less than 2 nanometres apart.

Dopant
The researchers believe that the results pave the way for new experiments and potential applications. The process observed by the TU Delft scientists, led by Dr Alberto Morpurgo, could probably be used in a large number of organic semiconductor materials.
The process generates a very thin conductive layer to which nothing needs to be added. Today’s electronics still use semiconductor material comprising silicon, containing what are known as dopant atoms. These ‘impurities’ are needed to give the silicon the required electronic properties. Ongoing miniaturisation means that this principle is becoming increasing difficult to apply.
In general, this discovery opens the door to a new class of organic electrical systems with properties which cannot be achieved using conventional materials. The scientists are to publish their findings in Nature Materials this week.

This research was co-financed by the Netherlands Organisation for Scientific Research (NWO).

More information
Alberto Morpurgo, tel. +31 (15) 2786063, e-mail A.Morpurgo@tudelft.nl
Frank Nuijens, science information officer, tel. +31 (15) 2784259, e-mail F.W.Nuijens@tudelft.nl