Band Engineering of Carbon Nanotube Field-Effect Transistors via Selected Area Chemical Gating
X. Liu, Z. Luo, S. Han, T. Tang, D. Zhang and C. Zhou
University of Southern California, US
carbon nanotubes, selected area gating, field effect transistor, subthreshold
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