Deposition of catalyst for carbon nanotube growth

Researchers in the Eriksson and Lagally research groups at the University of Wisconsin have used a Microplotter to direct the growth of carbon nanotubes at specific locations on a surface by depositing microscale spots of catalyst. Carbon nanotubes are composed of single-atom-thick sheets of carbon that have been formed into a tube only nanometers wide. They can be grown by flowing a high-temperature carbon-rich gas over specific catalyst materials. For electronic applications and research, it is desirable to be able to grow or place carbon nanotubes at specific locations, such as over a gap between electrodes. Normally, targeted growth of nanotubes is achieved by patterning catalyst spots using semiconductor photolithography techniques, which can require expensive masks, equipment, and facilities, and take days to complete.

Catalyst solution was deposited in spots as small as 5 microns using a Microplotter. This direct dispensing was fast and required no cleanroom processing before the samples could be used to grow nanotubes. New designs could be drawn up and tested on the fly, without requiring the generation of photolithographic masks. From this, carbon nanotubes were grown on electronic structures and used for research into their electrical properties.