Oct 2, 2002
New technique creates narrow inter-electrode gaps
Scientists from Cambridge University, UK, and CEMES-CNRS in France have come up with a reliable method for making pairs of electrodes that incorporate narrow gaps. The co-planar metal-insulator-metal junctions have gaps less than 5 nm wide and could have applications in single molecule electronics.
"This is a high yield and reliable way to fabricate sub-5 nm co-planar gaps," Dr Saifullah of Cambridge University told nanotechweb.org. "The advantage of our technique is its simplicity."
The scientists used electron-beam nanolithography to make the junctions. By studying the actual gap distance that resulted from a given designed distance, they were able to compensate for exposure and processing factors, increasing the reliability of the technique. They also developed the exposed resist with a weak developer under ultrasonic agitation, which improved the patterning resolution.
"Once the relationship between the actual gap distance achieved for a designed distance is established, the narrow-gap electrodes can be produced with a very high yield using the same set of parameters," added Saifullah.
For a designed inter-electrode distance of 0 nm, the yield of gaps with a spacing of < id= 5 nm was roughly 75%. The smallest gap measured was about 2 nm - the size of a single molecule. Typically, the difference in height between the electrodes and the silica surface was less than 1 nm over 1 square micron. p>The leakage resistance of the gaps, meanwhile, was of the order of 1012 ohms. According to the scientists, this indicates that the gaps have very good insulating properties and suit use in molecular electronics.
Now, Saifullah says that work is under way at CEMES-CNRS to put molecules on top of the junctions and study their electrical characteristics.
The team reported its work in Nanotechnology.
About the author
Liz Kalaugher is editor of nanotechweb.org.