Abstract
The combination of small dimensions, high stiffness and surface purity enabled carbon nanotube resonators toachieve yoctograms (10-24) mass resolution [1]. Until now, the applicability of such sensors has been hinderedby the use of cryogenics temperatures needed to achieve the signal-to-noise ratio and the high Q-factorsnecessary to achieve this top benchmarking mass resolution.A promising application of CNT resonators relies on the field of nanofluidics, where the study of confinedfluids inside of carbon nanotubes resonators could provide experimental data for theoretical and computationalmodels of confined fluids[2]. The use of cryogenic temperatures impedes most of the practical studies in thisfield.We have fabricated CNT resonators by CVD growing carbon nanotubes over previous fabricated siliconoxide/nitride trenches, Figure 1 a). Theses metalized trenches form the structure of a suspended FET, Figure1b), where the nanotube can be mechanically excited and sensed using electrostatics. The measurement of themechanical vibration mode is achieved by the mixing method, where the CNT FET resonator act as a signalmixer, Figure 2 a). The gate electrode modulates the vibration of the resonator while a source a drain currentcarries the downmixed vibration signal [3]. The distinctive feature of CNT resonators is the wide range offrequency tunability using the DC gate voltage, Figure 2b). The resonance spans from 34 MHz to 70MHzchanging 3V in the DC gate voltage.Aiming towards the use of CNT resonators in nanofluidics, we measured the temporal evolution of theresonator frequency noise at ambient temperature in open and closed loop, Figure 3a). Computing Allandeviation plots, we calculate parameters as the mass sensitivities and the necessary integration times to achievesuch figures. In addition, the mechanism of noise acting in CNT resonators can be inferred from such data,Figure 3 b). We observed that the CNT resonators working in open-loop at ambient temperature presents nonwhitefrequency noise for values of integration time higher than 10-1 s. Measurements in closed-loopconfiguration shows that operating these devices at ambient temperature conserves great part of the outstandingmass resolution, achieving hundreds to tens of yoctograms at specific circumstances.