We discuss the central issues to be addressed for realizing carbon nanotube (CNT) nanoelectronics. We focus on selective growth, electron energy bandgap engineering and device integration. We have introduced a nanotemplate to control the selective growth, length and diameter of CNTs. Vertically aligned CNTs are synthesized for developing a vertical CNT-field effect transistor (FET). The ohmic contact of the CNT/metal interface is formed by rapid thermal annealing. Diameter control, synthesis of Y-shaped CNTs and surface modification of CNTs open up the possibility for energy bandgap modulation. The concepts of an ultra-high density transistor based on the vertical-CNT array and a nonvolatile memory based on the top gate structure with an oxide–nitride–oxide charge trap are also presented. We suggest that the deposited memory film can be used for the quantum dot storage due to the localized electric field created by a nano scale CNT-electron channel.

Single-walled carbon nanotubes (SWNTs) were successfully grown on SiO 2 /Si substrates at 450 °C by remote plasma enhanced chemical vapor deposition with a plasma power of 15 W. The ratio of D-band (disorder-induced mode) to G-band (tangential stretching mode) in the Raman spectra, an indicator of nanotube quality, is about 0.1 owing to their good quality. Even at 400 °C, SWNTs were also grown with low plasma power (<40 W), although the I D /I G ratios are higher than those at 450 °C. It is discussed that for low-temperature growth of SWNTs, the plasma power should be held at a low level to avoid the formation of disordered or amorphous carbons. The low-temperature growth of SWNTs may enable compatible integration of SWNTs with current complementary metal-oxide-silicon technology.

A chemical route to single-walled carbon nanotubes (SWCNTs) under ambient conditions has been developed. Silica powder was immersed in a mixture solution of ferrocene and p-xylene. After sonication at atmospheric pressure and room temperature, we obtained high-purity SWCNTs. Sonochemical effects may lead to producing high-purity SWCNTs. The process could be readily generalized to synthesize other forms of carbon-based materials, such as fullerenes, multiwalled nanotubes, carbon onions, and diamond, in liquid solution under ambient conditions.

We investigate ambipolar to unipolar transition by the effect of ambient air on the carbon nanotube field-effect transistor. A unipolar transport property of the double-walled nanotube field-effect transistor and its conversion from ambipolar behavior are observed. We suggest that adsorptions of oxygen molecules, whose lowest-unoccupied-molecular-orbital state is around the midgap of the carbon nanotube, could suppress the electron channel formation and, consequently, result in the unipolar transport behavior.

Vertically aligned carbon-nanotube (CNT) arrays were fabricated in the thin-film anodic aluminum oxide (AAO) templates on silicon wafers utilizing a niobium (Nb) thin film as the source electrode. The average diameter of the CNTs was 25 nm, and the number density was 3 x 10(10) cm(-2). The CNT arrays synthesized at 700 degrees C and above exhibited Schottky behavior even at 300 K, with energy gaps between 0.2 eV and 0.3 eV. However, individual CNTs obtained by removal of the template behaved as resistors at 300 K. The CNT/Nb oxide/Nb junction is thought to be responsible for the Schottky behavior. This structure can be a useful cornerstone in the fabrication of nanotransistors operating at room temperature.

The effect of the crystallographic orientation of underlying poly-Si film on the thermal stability of the TiSi2 film was studied. Different preferred orientations of the poly-Si film were obtained by annealing poly-Si or amorphous Si films at various temperatures. The TiSi2 film was formed by the solid-state reaction of the Ti film sputtered on the poly-Si film. The thermal stability of the TiSi2 film was evaluated by changes in the sheet resistance and microstructural evolution during furnace anneals. The TiSi2 film on poly-Si with the <110> preferred orientation shows more stable conductivity during high temperature anneals than with the <111> orientation. The surface energy of underlying poly-Si is expected to influence the thermal stability of the TiSi2/poly-Si structure significantly. Better thermal stability of the TiSi2 film can be obtained by the higher surface energy of underlying poly-Si.