Single-walled carbon nanotubes (SWNTs) have been investigated as a key potential candidate for high performance
electronic devices. Two representative device forms are carbon nanotube based field effect transisotors (FETs) and
diodes. In contrast of high popularity of FET devices for the fundamental studies as well as applications, carbon
nanotube based diodes have been rarely studied. Recently, we developed a facile chemical route to realize the SWNT
Schottky diode via mass transport of lithium ions by applying bias voltages on 1-pyrenemethylamine(1-PMA)
functionalized SWNTs in which lithium ions were intercalated. The intercalated Li ions were transported and reduced
on the drain electrode, of which work function was then significantly modulated. Because the modulated work function
induces large Schottky barrier between the drain electrode and SWNT, the current of reversed direction is effectively
blocked while the forward direction current flows through the relatively small Schottky barrier. The migration of lithium
ions was characterized by scanning photoelectron microscopy (SPEM) and space resolved x-ray photoelectron
spectroscopy. To measure the intensity of Li 1s XPS peak, the population of lithium ions was observed along the
nanotube axis from the source to drain electrodes. As a result, the highest population of lithium was observed at near the
drain electrode. This approach using the concept of mass transport of lithium ions to modulate the metal contact
characteristics is a simple and promising process that can be further applied not only to SWNT-based electronics but
also to various nanomaterial-based electronic devices.
Single walled carbon nanotube (SWNT), a potential component of nano-biosensor systems, has been successfully demonstrated as a nanoscale platform of biochips which efficiently accommodate biomolecules, such as proteins and peptides. Highly pure SWNTs directly grown in high yield on a SiO<sub>2</sub>/Si substrate (SWNT film) by chemical vapor deposition (CVD) process have shown that biomolecules are immobilized as their shapes are well retained. Furthermore, SWNT film substrates have embodied a BSA-free chip system by utilizing non-covalent functionalization of SWNT surfaces with 1,1'-carbonyldiimidazole(CDI)-Tween20. Using SWNT films, high specific/nonspecific discrimination ratio has been obtained from biotin-Streptavdin and Protein A (SpA)-Immunoglobulin G (IgG) pairs as well as from small peptide-protein interactions of 3×FLAG-antiFLAG pair. Systematic studies comparing with the state-of-art protein chip have confirmed that the performance of SWNT protein chip is superior in terms of high specific binding efficiency as well as low background signal due to the efficient prevention of nonspecific bindings.