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EPSRC Reference: EP/J010944/1
Title: Atomic Layer Interface Engineering for Nanoelectronics (ALIEN): Contacts
Principal Investigator: O'Neill, Professor A
Other Investigators:
Cumpson, Professor P
Researcher Co-Investigators:
Project Partners:
Analog Devices Inc National Physical Laboratory Oxford Instruments Ltd
PETEC
Department: Electrical, Electronic & Computer Eng
Organisation: Newcastle University
Scheme: Standard Research
Starts: 01 July 2012 Ends: 30 June 2015 Value (£): 593,072
EPSRC Research Topic Classifications:
Electronic Devices & Subsys.
EPSRC Industrial Sector Classifications:
Electronics
Related Grants:
EP/J011592/1
Panel History:
Panel DatePanel NameOutcome
26 Oct 2011 EPSRC ICT Responsive Mode - Oct 2011 Announced
Summary on Grant Application Form
This research considers the intriguing prospect of using insulators to improve electrical conductivity. The revolution in electronics over the last 50 years is due in large part to semiconductors, including silicon for microchips, III-V semiconductors for optical components such as lasers or LEDs and organic semiconductors for large area displays. Electrical contact from a metal to these semiconductors is fundamental. Conventional theory, developed by Schottky and Mott in the 1930's and still taught today, says that the potential energy barrier that electrons encounter at the junction between a metal and a semiconductor is simply the difference in energy needed to take electrons from each material (the workfunction difference). Thus by a suitable choice of semiconductor and metal, the energy to remove electrons from either will be the same and there should be no barrier to current between them. But experience shows this is generally not the case, particularly for semiconductors of commercial interest. In fact, the potential energy barrier (the Schottky barrier) tends to be about the same for all metal contacts to any given semiconductor. The effect is called Fermi level pinning and arises because electrons from the metal spill into the semiconductor at the junction. The barrier gives rise to an electrical resistance, which may be different depending on the direction of current (a Schottky diode). The resistance can belowered by making the contact surface area large and/or by increasing doping in the semiconductor so that the potential energy barrier becomes thin enough that electrons can easily tunnel through. But this is not always possible or sufficient.

A novel approach to improving the electrical contact is to add a thin insulator in between the metal and the semiconductor. The effect is to prevent electrons spilling from the metal into the semiconductor and so prevent Fermi level pinning. The correct choice of metal and semiconductor will allow a reduction in potential energy barrier height, as Schottky-Mott theory suggests. A complication is that the insulator itself may block current and so needs to be thin (~ nm scale). This research will deposit nm scale insulating layers between semiconductors and metals to improve conduction across the contact. A range of experimental techniques will be used to measure the change in electrical properties brought about by the thin insulator films and the film thickness will be optimised for a range of important semiconductors. Modelling of the atomic structure of the metal, insulator and semiconductor will help to unravel to competing factors that are at play in improving current flow. The research will also address integrating this type of contact into a manufactured device, 3D structures and to test its applicability to organic semiconductors.

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Potential use in non-academic contexts
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Organisation Website: http://www.ncl.ac.uk