Probing the non-linear transient response of a carbon nanotube mechanical oscillator

Carbon nanotube (CNT) nano-electromechanical systems have demonstrated unprecedented sensitivities for detecting small masses and forces. In cryogenic measurement setups, the detection speed of the mechanical resonator amplitude is usually limited by the CNT contact resistance and parasitic capacitance of cabling. We report the use of a cold heterojunction bipolar transistor (HBT) amplifying circuit near the device to measure the mechanical amplitude at microsecond timescales. A Coulomb rectification scheme, in which the probe signal is at much lower frequency than the mechanical drive signal, allows investigation of the strongly non-linear regime. The behaviour of transients in both the linear and non-linear regimes is observed and modeled by including Duffing and non-linear damping terms in a harmonic oscillator equation. We show that the non-linear regime can result in faster mechanical response times, on the order of 10 µs for the device and circuit presented. (arXiv: 1707.03025)