Keywords: mechanical oscillations, nanocantilevers, multi-wall carbon nanotubes, nanotechnology, cantilevers, parasitic capacitance, electrical actuation, harmonic resonance
Electrical actuation and detection of mechanical oscillations in cantilevered multi-walled carbon nanotubes
A novel detection scheme, called the Harmonic Detection of Resonance (HDR) method, is described for measuring mechanical oscillations in nano-sized cantilevers under ambient conditions. HDR overcomes the problem of parasitic capacitance, which in the past has significantly limited the performance of capacitive sensors, by measuring resonances at higher harmonics (integer multiples) of the driving frequency. Individual multi-wall carbon nanotubes (MWNTs) were manipulated to serve as single-end clamped (diving board geometry) cantilevers and driven into resonance using a sharpened tungsten probe tip as the counter electrode. Two geometries between the MWNT and the probe tip were tested and HDR was found to work equally well for both geometries. Importantly, the HDR method has the advantage of being entirely electrical, both in actuation and detection, and thus is straightforward to integrate into standard CMOS technology.