Few-Hundred GHz Carbon Nanotube Nanoelectromechanical Systems (NEMS)

We study 23–30 nm long suspended single-wall carbon nanotube quantum dots and observe both their stretching and bending vibrational modes. We use low-temperature DC electron transport to excite and measure the tubes’ bending mode by making use of a positive feedback mechanism between their vibrations and the tunneling electrons. In these nanoelectromechanical systems (NEMS), we measure fundamental bending frequencies <i>f</i>_bend ≈ 75–280 GHz and extract quality factors <i>Q</i> ∼ 10⁶. The NEMS's frequencies can be tuned by a factor of 2 with tension induced by mechanical breakjunctions actuated by an electrostatic force or tension from bent suspended electrodes