Band Engineering of Carbon Nanotube Field-Effect Transistors via Selected Area Chemical Gating

Keywords:
carbon nanotubes, selected area gating, field effect transistor, subthreshold

Abstract:
Since carbon nanotube field-effect transistors were reported, great effort has been devoted to understanding the operation of these transistors and improving their performance. Here we present a new approach to engineer the band structure of carbon nanotube field-effect transistors via selected area chemical gating, which provides a way to tailor the device performance without the complexity of extra gate electrodes. By exposing the center part or the contacts of the nanotube devices to oxidizing or reducing gases, a good control over the threshold voltage and subthreshold swing has been achieved. Our experiments reveal that NO2 shifts the threshold voltage higher while NH3 shifts it lower for both center-exposed and contact-exposed devices. However, modulations to the subthreshold swing are in opposite directions for center-exposed and contact-exposed devices: NO2 lowers the subthreshold swing of the contact-exposed devices, but increases that of the center-exposed devices; In contrast, NH3 reduces the subthreshold swing of the center-exposed devices, but increases that of the contact-exposed devices. A model has been developed based on Langmuir isotherm, which can explain the experimental results well. Our concept of selected area doping can be readily applied to solid-phase doping techniques and render stable nanotube devices mimicking conventional metal-oxide-semiconductor field-effect transistors.

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Nanotech 2005 Conference Program Abstract