Few-hundred GHz Carbon Nanotube NEMS
  We study 23 to 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 nano-electro-mechanical-systems (NEMS), we measure fundamental bending frequencies $f_{bend}\approx$ 75 - 280 GHz, and extract quality factors $Q \sim 10^{6}$. The NEMS' frequencies can be tuned by a factor of two with tension induced by mechanical breakjunctions actuated by an electrostatic force, or tension from bent suspended electrodes. 
J. O. Island, V. Tayari, A. C. McRae, and A. R. Champagne
cond-mat.mes-hall cond-mat.mtrl-sci