Purification and Separation of Carbon Nanotubes

The problems posed by the synthesis and purification of single-walled carbon nanotubes (SWNTs) have inhibited progress in the field. In this article, we review the methods available for measuring the purity of SWNTs and the current status of processes designed to purify them.We emphasize the hierarchy of the purification steps that must be developed in order to obtain high-quality material suitable for the full range of advanced applications that are envisioned for the ultimate carbon nanofiber.We review two strategies for SWNT purification, the assessment of SWNT purity by use of near-IR spectroscopy and its application to the thermal oxidation of thin films of SWNTs, as well as recent advances in the separation of metallic and semiconducting SWNTs. While substantial progress has been made in the purification and separation of SWNTs, we note the need for quality control and quality assurance within the industry. Much work remains before pure SWNTs of specific lengths, diameters, and chirality can be made available for applications.

Interface morphologies in the polysilicon-SiO2 materials system

The fabrication of increasingly complex integrated circuit devices represents one of the most challenging areas of applied materials research. As layout geometries are reduced, device operation becomes more readily influenced both by the presence of various materials defects and by the structural integrity of the interfaces involved. Critical to the manufacture of such devices are the technologies associated with the deposition, doping, and oxidation of thin films of polycrystalline silicon (polysilicon). The strong interrelationship between the last two of these processes can result in the formation of unusual morphologies at the interface between the polysilicon and its thermally grown oxide. Conventional TEM has been applied to establish the nature of several such structures. Because their spatial extent is sometimes extremely small (e.g. 20A), high resolution lattice imaging was utilized in order to gain crystallographic information of a very fine scale.