Résumé
Substantial progress on field effect transistors ͑FETs͒ consisting of semiconducting single wall carbon nanotubes ͑s-SWNTs͒ without detectable traces of metallic nanotubes and impurities is reported. Nearly perfect removal of metallic nanotubes is confirmed by optical absorption, Raman measurements, and electrical measurements. This outstanding result was made possible in particular by ultracentrifugation (150 000 g) of solutions prepared from SWNT powders using polyfluorene as an extracting agent in toluene. Such s-SWNTs processable solutions were applied to realize FET, embodying randomly or preferentially oriented nanotube networks prepared by spin coating or dielectrophoresis. Devices exhibit stable p-type semiconductor behavior in air with very promising characteristics. The on-off current ratio is 10^5, the on-current level is around 10 µA, and the estimated hole mobility is larger than 2 cm2 / V s.