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Schottky barrier field effect transistors based on individual catalytically-grown and undoped Si-nanowires (NW) have been fabricated and characterized with respect to their gate lengths. The gate length was shortened by the axial, self-aligned formation of nickel-silicide source and drain segments along the NW. The transistors with 10-30 nm NW diameters displayed p-type behaviour, sustained current densities of up to 0.5 MA/cm2, and exhibited on/off current ratios of up to 10(7). The on-currents were limited and kept constant by the Schottky contacts for gate lengths below 1 microm, and decreased exponentially for gate lengths exceeding 1 microm.

Planar field effect transistors (FET) consisting of a large number of parallel single-walled carbon nanotubes (SWCNT) have been fabricated that allow very high on-currents of the order of several milliamperes and on/off ratios exceeding 500. With these devices it is demonstrated, for the first time, that SWCNTs can be used as transistors to control macroscopic devices, e.g., light emitting diodes and electromotors. Those transistors were fabricated by a very simple process that is based on the catalytic chemical vapor deposition (CCVD) growth of SWCNTs at low temperatures, a single lithographic step to define the source and drain contacts, and a bias pulse to eliminate the metallic SWCNTs.

A comparison of different catalysts (Ni, Co, Fe/Mo) has been performed in order to minimize the growth temperature for single-walled carbon nanotubes (SWCNTs). Dense SWCNT networks have been synthesized by thermal chemical vapor deposition (CVD) at temperatures as low as 600 °C using Ni catalyst layers of approximately 0.2 nm thickness. The dependence of the SWCNT growth on the most important parameters will be discussed exemplarily on the Ni catalyst system. On the basis of experimental observations, a phenomenological growth model for CVD synthesis of SWCNTs is proposed which is based on the interactions between the catalyst and its support. Further, it is suggested that only surface diffusion of hydrocarbons on the catalyst support or along the CNTs can explain the fast growth rates of SWCNTs during CVD synthesis.

This work presents a simple and versatile approach for the growth of in-situ contacted single-walled carbon nanotubes (SWCNTs) and subsequent improvement of the contacts using a self-aligned process. We investigated the conditions for the thermal CVD growth of SWCNTs and developed a variety of multilayered metal systems for SWCNT growth at temperatures between 650 °C and 900 °C. The catalytically active layers were either an Fe/Mo bilayer or a Co layer. Further, we report that some of the multilayer systems presented allow lithography free contact improvement by electroless metal deposition.

The synthesis of individual carbon nanotubes (CNTs) with controlled diameters at lithographically predefined locations has been achieved. Employing conventional catalyst-mediated chemical vapor deposition (CVD), isolated CNTs were grown out of nanoholes in silicon dioxide created by optical lithography. This allows the precise placement of individual CNTs on substrates. Furthermore, the diameter of each CNT adjusts to the hole size, which makes it possible to control this important property separately for individual CNTs. This approach is a step toward the parallel manufacture of nanotube-based devices in a scalable batch process. In particular, the integration of CNTs into conventional silicon-technology with potential applications as interconnects, transistors, and memory cells becomes possible.