Carbon Nanotube Nanomechanical Mass Sensor

Hsin-Ying Chiu
Department of Physics, California Institute of Technology

Single-walled carbon nanotubes (SWNT) are arguably the lightest and smallest wires in the world, and have recently been shown to act as nanomechanical resonators. As a result, SWNT resonators are excellent candidates for highly sensitive mass sensing. My talk will present our most recent results concerning the ultimate sensitivity of SWNT nanomechanical mass sensors at cryogenic temperatures and high vacuum. The nanotube resonant motion is sensed capacitively using a mixing technique. We have clear line of slight to inject gases onto nanotube resonators in our customized cryostat. When injecting Xenon atoms, we observed "stepped" resonant frequency shifts of carbon nanotube resonator which are due to the Xenon atoms adsorbing at different positions along the nanotube length. We can resolve the sub-zeptogram mass of a few Xenon atoms. Atomic shot noise and variable step sizes of random walk for the frequency will be discussed as well. I will also talk about some additional interesting phenomena, such as the nonlinearity of our SWNT resonators and some unexpected features of quantized frequencies that should originally attribute to the coulomb blockade oscillation at low temperature.