Direct Transmission Detection of Tunable Mechanical Resonance in an Individual Carbon Nanofiber Relay

Abstract

Nanoelectromechanical systems (NEMS) are attracting increasing attention due to their small size, low power consumption, and fast switching speeds. 1 They are regarded as among the most interesting emerging technologies on the ITRS roadmap. 2 Carbon nanotubes are particularly interesting as NEMS components due to their low mobile mass and high Young's modulus, which enables high speed, combined with their high mechanical strength and ability to withstand extreme conditions of temperature and radiation exposure. The predicted possibility of tuning the resonance frequency over a large range by the application of a gate voltage 3 is particularly promising for many applications. Here we present a direct transmission measurement of the resonance frequency of an individual singly clamped carbon nanofiber relay. The experimental results verify the predictions of a small signal model and provide important information for determining the practicality of using carbon-based NEMS as components in real electrical circuits.Some prototype carbon NEMS have been reported in the literature, 4-11 but there have been relatively few experimental studies of the high frequency properties of carbon NEMS based on individual carbon nanotubes. [12][13][14][15][16] The resonance frequencies of doubly clamped suspended singlewalled nanotubes (SWNT) have been determined using an indirect mixing technique with a lock-in amplifier. [12][13][14] The method requires a semiconducting nanotube and can therefore not be applied to the mechanically more rigid multiwalled nanotubes (MWNT) or nanofibers (CNF) that have been studied as a dc prototype NEMS and allow the fabrication of more varied device geometries. [4][5][6][7][8]10,11 The mechanical resonances of singly clamped MWNT have been observed in a field emission microscope, where the broadening of the field emission spot was observed as the nanotube was brought into mechanical resonance by the application of an ac voltage on a side gate. The resonance frequency of the MWNT could be tuned by an order of magnitude by increasing the bias voltage on the nanotube and thus increasing the tension. 15 The same technique has recently been used to demonstrate a so-called nanoradio. 16 Although all of these studies provide interesting information concerning the resonance properties of individual carbon nanotubes, they do not provide muchneeded information on the feasibility of integrating carbonbased NEMS in useful electronic circuits nor on the signal levels that can be expected. In this letter, we report the first direct transmission detection of the resonant behavior of a two-terminal carbon nanofiber relay. We compare the experimental data with the predictions of a small signal model, treating the CNF as a simple series resonator. Good agreement is obtained concerning the resonance amplitude, shape, and phase. We show that it is possible to measure the transmission of a single relay device; however, the signal level is very low and most practical applications will need to be based on arrays of such st...

Ohmic electromechanical dissipation in nanomechanical cantilevers

“…In Ref. 26 (Eriksson 08), the quality factor was shown to decrease substantially with V DC . However, Fig.…”

Vertically aligned carbon based varactors

“…Therefore, both the device geometry and the growth process conditions are important in determining the operating voltage of a comblike varactor. Based on the device geometries and growth conditions discussed earlier in this paper and taking into account a previous estimation of VACNFs Young's modulus (400 GPa), 118 it should be possible to fabricate comblike varactors with operating voltages in the range of 10 to 30 V. In the case of brushlike varactors, the thickness of the VANTAs can effectively be used to tune the operating voltage. However, the lower limit of the thickness is dictated by the mechanical stability requirements.…”

“…20,21 The achievements during the last few years in reproducible synthesis of high quality VACNFs and VANTAs have extended the boundaries of their application to the realm of nanoelectromechanical systems (NEMS). Although carbon nanotubes and nanofibers had already been used in horizontal configuration as nanoelectromechanical devices, [22][23][24][25][26][27][28][29][30] this time their as-grown vertical alignment was exploited. Good examples of such devices include nanoelectromechanical switches 31 and the nanoscale memory cell 32 based on VACNFs.…”

Suspended Carbon Nanotubes: Applications in Physical Sensors and Actuators

“…Such suspended SWNTs have been shown to act as oscillators, where the resonance frequency was measured using an indirect mixing technique with a lock-in amplifier. More recently, resonance was also observed in metallic MWNTs by using a direct on-chip transmission measurement technique where an RF displacement current was detected as the tube was driven into resonance (Eriksson et al, 2008). Suspended CNTs are attractive as mechanical resonators and have significant promise for mass sensing applications.…”