Multiple negative resistances in trenched structures bridged with carbon nanotubes

Field effect transistor (FET)-like structures with a trench as “gate” were fabricated on GaAs substrates. The bottom of the trench as well as the “source” and “drain” regions were metallized. Bundles of nanotubes were then suspended over the trench. At a certain threshold, these trenched FET-like structures display an S-shaped negative resistance, which breaks into parallel branches when the voltage is increased in equal steps. Several such steps were observed at room temperature and under normal pressure. The steps were reversibly enabled and disabled via changes in the applied voltage. A maximum stable gain with a quasilinear behavior was observed between 0.5 and 3.25GHz.