Fast measurement of carbon nanotube resonator amplitude with a heterojunction bipolar transistor

TL;DR

This paper introduces a rapid measurement technique for carbon nanotube resonator amplitudes using a heterojunction bipolar transistor, enabling microsecond response times and potential single-molecule magnetic sensing.

Contribution

It demonstrates a near-device heterojunction bipolar transistor amplifier for fast amplitude measurement and explores non-linear dynamics for improved response times.

Findings

Achieved microsecond measurement timescales.

Modeled non-linear transient behaviors including Duffing effects.

Potential to measure single-molecule magnetic moments within relaxation times.

Abstract

Carbon nanotube (CNT) electromechanical resonators have demonstrated unprecedented sensitivities for detecting small masses and forces. The detection speed in a cryogenic setup is usually limited by the CNT contact resistance and parasitic capacitance. We report the use of a 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 microseconds for the device and circuit presented, potentially enabling the magnetic moments of single molecules to be measured within their spin relaxation and dephasing timescales.