All existing transistors are based on the use of semiconductor junctions formed by introducing dopant atoms into the semiconductor material. As the distance between junctions in modern devices drops below 10 nm, extraordinarily high doping concentration gradients become necessary. Because of the laws of diffusion and the statistical nature of the distribution of the doping atoms, such junctions represent an increasingly difficult fabrication challenge for the semiconductor industry. Here, we propose and demonstrate a new type of transistor in which there are no junctions and no doping concentration gradients. These devices have full CMOS functionality and are made using silicon nanowires. They have near-ideal subthreshold slope, extremely low leakage currents, and less degradation of mobility with gate voltage and temperature than classical transistors.

We have made electrical measurements on a system using carbon nanotubes as the dopant material. A semiconjugated, organic polymer was mixed with carbon nanotubes to form a wholly organic composite. Composite formation from low to high nanotube concentration increases the conductivity dramatically by ten orders of magnitude, indicative of percolative behavior. Effective mobilities were calculated from the spacecharge regions of the current-voltage characteristics for the 0-8 % mass fractions. After an initial rise these were seen to fall from 1-8 % doping levels as predicted by theory. From the values for conductivity and mobility, an effective carrier density was calculated. This was seen to decrease between 0% and 1%, before rising steadily. ͓S0163-1829͑98͒51536-6͔

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Hybrid systems of a semiconjugated organic polymer and single-wall nanotubes have been characterized by optical absorption spectroscopy, electron microscopy, and Raman spectroscopy. It is demonstrated that solutions of the polymer are capable of suspending nanotubes indefinitely while the majority of the accompanying amorphous graphite precipitates out of solution. Electron microscopy and Raman scattering indicate that through an intercalation process, the ropes of nanotubes are destroyed, resulting in individual nanotubes being well dispersed within the polymer matrix. Moreover, Raman and absorption studies suggest that the polymer interacts preferentially with nanotubes of specific diameters or a range of diameters.

Production of stable polymer-nanotube composites depends on good wetting interaction between polymer and nanotube, which is polymer specific, and depends in particular on chain conformation. In this paper, we examine this interaction for a conjugated, semiconducting polymer by a range of microscopic and spectroscopic techniques, to gain a greater understanding of the binding. Several interesting effects are observed, including an order to the interaction between the polymer and nanotube, the tendency of defects in the nanotube structure to nucleate crystal growth, and substantial changes in the spectroscopic behavior of the polymer due to the effect of the nanotubes on polymer conformation. This is substantiated by computational modeling, which demonstrates that these conformational modifications are due to the interaction with the nanotubes.

ring overnight at room temperature, monomer and initiator were readily absorbed in the vesicle bilayer. Photoinitiated polymerizations were performed in a thermostatted quartz reactor using either an UV-lamp (HPR 125 W, Philips) or a pulsed excimer laser (Lambda Physics XeF, 351 nm, 2 Hz pulse frequency, 30 mJ energy per pulse) as irradiation source. Conversions were determined by HPLC analysis of the residual monomers.Details concerning the use of cryo-electron microscopy have been described earlier [19].

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We report the fabrication of junctionless SOI MOSFETs. Such devices greatly simplify processing thermal budget and behave as regular multigate SOI transistors.