Direct fabrication of carbon nanotube circuits by selective areachemical vapour deposition on pre-patterned structures

Abstract

We report on a method for self-assembly of integrated carbonnanotube circuits using selective area chemical vapour deposition onpre-patterned catalyst electrodes. The circuits consist of a multi-wallcarbon nanotube bridging a pair of electrodes, forming a metal/carbon nanotube/metal structure. Electron-beam lithographywas used to define electrode sets separated by a desired distance on a500 nm thick SiO2 film on Si substrates. Following metal evaporationand lift-off, chemical vapour deposition was used for selective growthof carbon nanotubes on the catalyst electrodes. The carbon nanotubeseventually form a bridge between nearby electrodes consisting of one,or in some cases more than one, multi-wall nanotube. The resistance ofthe carbon nanotube circuits at room temperature is typically less than100 kΩ. For a few high-resistance samples(>>100 kΩ) transport properties were studied in atemperature range from room temperature to 2 K. At room temperature theI-V is linear. The resistance increases with decreasingtemperature, and the I-V gradually becomes nonlinear. At lowtemperatures a gap appears around V = 0 suggesting semiconductingbehaviour.