|
Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades,
single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors
and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays
of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability.
Nanoscale thermos-capillary flows in thin-film organic coatings followed by reactive ion etching serve as highly
efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays
grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust,
scalable operation, with clear potential for practical use. Especially for the purpose of selective joule heating over only
metallic nanotubes, two representative platforms are proposed and confirmed. One is achieved by selective joule heating
associated with thin film transistors with partial gate structure. The other is based on a simple, scalable, large-area
scheme through microwave irradiation by using micro-strip dipole antennas of low work-function metals. In this study,
based on purified semiconducting SWNTs, we demonstrated field effect transistors with mobility (> 1,000 cm2/Vsec)
and on/off switching ratio (~10,000) with current outputs in the milliamp range. Furthermore, as one demonstration of
the effectiveness over large area-scalability and simplicity, implementing the micro-wave based purification, on large
arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs
that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.
|
