December 7, 2011
FRONTIERS IN MATERIALS SCIENCE
VINSE COLLOQUIUM SERIES
Professor Jie Liu
"Growth Mechanism of Well Aligned Semiconducting Single-walled Carbon Nanotubes on Quartz"
Abstract. Even though the devices made from individual nanotubes have shown outstanding performances such as high mobility, high current, high thermal conductivity, good chemical and mechanical stability, the high hope for the next generation of carbon nanotube based electronics is hampered by several major problems. Among them are the lack of reliable methods to control the alignment and position of nanotubes as well as and perhaps most problematically, the simultaneous growth of nanotubes with different chiralities, yielding random mixtures of metallic and semiconducting nanotubes. Even though the post-growth separation of metallic from semiconducting SWNTs have made good progress, the alignment and assembly of the separated nanotubes into devices are still challenging and not suitable for large scale fabrication. Consequently, a method that can directly produce well aligned arrays of pure semiconducting nanotubes is thought to be the ideal choice for large scale fabrication of nanotubes FETs. In this talk, we show that such a method is not a dream. We developed a chemical vapor deposition (CVD) approach, which allows selective growth of high-density arrays of well-aligned SWNTs with almost exclusively semiconducting SWNTs. Analysis of the samples shows that at least over 95% of nanotubes are semiconducting. This method demonstrates great promise to solve two of the most difficult problems which limit application of carbon nanotubes in nanoelectronics – the coexistence of metallic and semiconducting nanotubes in samples produced by most, if not all, growth methods and the simultaneous control of the alignment of the nanotubes.