There is an increasing demand for device size miniaturisation, especially in the consumer electronic industry.
Estimates however, suggest that current technology will be unable to satisfy future miniaturisation requirements and this has led to a number of researchers looking toward nanotechnology as a possible solution.
In this regard, Frost & Sullivan has taken note of work conducted by researchers from ETH Zurich and the University of California at Berkeley. The researchers have demonstrated the ability to print microelectronic circuits by laser-treating ink consisting of nano-sized gold particles.
Though gold has preferable electrical properties, it is rarely used in electronics because of its high cost and high melting point, which makes it difficult to manipulate. The researchers, however, have shown that nano-sized gold particles have a much lower melting point.
The team has successfully analysed this effect and prepared conductor tracks consisting of coated gold particles measuring two nanometres, which melt at temperatures as low as 150°C. A coating of self-organising organic molecules containing sulphur is also employed to prevent the gold from coagulating and becoming lumpy.
Initially, the nanoink is applied to an organic substrate by using either a special ink-jet printer or a special pipette. The gold-based nanoink is then sintered (converted into the solid phase) by an argon ion laser. This is a vital step as it allows for the actual formation of individual electronic structures.
An argon ion laser is employed as its beam is efficiently absorbed by the metal, allowing for complete solidification at that point. After writing, the residual ink is washed away. If metallic conductor structures at various levels are needed, another layer of organic material can be applied and written on again with ink and laser.
In a recent paper published by the team, the researchers demonstrated the method of fabrication of a transistor. They printed an organic field-effect transistor in which the source, drain and gate elements consisted of gold. The dielectric layer between them is made of polymer, and so is the semiconductor.
Initial testing showed that the transistor is capable of functioning for extended periods of time. Transistor fabrication has opened up the possibility of creating other more complex devices using different metals or by using carbon nanotubes as the semiconductor. The method is also suitable for additional applications such as radio frequency identification (RFID) chips or flexible sensors.
Apart from being extremely versatile and flexible in terms of device design, this method also provides the additional benefit of being very cost effective. Nanoink-based printed electronics do not require a clean room environment and can be manufactured at room temperature. This would greatly reduce time to market and overall operating costs.
For more information contact Patrick Cairns, Frost & Sullivan, +27 (0)21 680 3274, patrick.cairns@frost.com
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