|Our new organic device fabrication
laboratory on the Lower Ground corridor of the Old Main Building
Plastics are generally considered to be poor conductors of electricity.
However, polymers can be made conductive by engineering them to
contain alternating single and double carbon bonds. Organic electronics
is of growing interest because while they are appearing in commercial
applications, much of the electronic properties of conductive organic
materials are still poorly understood. Presently we have two projects
in this area – the first studies the electronic properties
of transistors based on organic molecular crystals and the second
involves using ion-implantation to engineer the conductivity of
An important challenge in developing organic transistors is to
improve the electrical mobility (how easily current can flow through
the device). One way to achieve this is to use organic molecules
that form highly ordered crystals. The polyacenes, which consist
of molecules containing up to 5 benzene rings fused together into
a linear chain, have shown considerable promise. These molecules
readily form flat hexagonal crystals up to 1cm in diameter and have
the requisite alternating single-double bond structure that allows
them to conduct electricity effectively.
We produced our first working organic crystal transistors (FETs)
in late 2004, and in 2005 we further optimized these devices using
a newly developed technique where a prefabricated flexible transistor
structure is laminated against the crystal. This eliminates the
need to perform damaging fabrication processes on the fragile organic
crystals. By the end of 2005 we were able to routinely fabricate
organic FETs with channel lengths up to a few mm and mobilities
of order 10 cm2/Vs. Such high mobilities are state-of-the-art for
We have also continued our measurements on the electronic properties
of ion-implanted plastics as part of an ongoing collaboration with
the soft condensed matter group at the University of Queensland.
We are currently measuring a new series of samples aimed at better
understanding this new material system.
Finally, in 2005 we also completed our new laboratories. These
labs included a wet chemistry lab (shared with Mike Gal) and a device
fabrication cleanroom for fabricating organic crystal FETs, silicone
rubber transistor stamps and ion-implanted polymer films. With support
from UNSW facilities, the new device fabrication lab has been made
one of the showcase research labs in the school.
Laurence Bell, Adam Micolich,
Alex Hamilton and Jack Cochrane