Tuning Carbon Nanotube Resonance Frequencies

Tuning carbon nanotube resonance frequencies can be achieved by varying a static voltage applied between the nanotubes and a counter electrode. This was demonstrated for several nanotubes (NT) grown on a nickel support tip. The natural resonant NT frequencies are those where the NT oscillates with a large amplitude, a motion that can be monitored directly by watching the pattern of electrons spraying out the end of the tubes (like water spraying out of a wiggling garden hose). The vibration is excited by applying an additional sinusoidal voltage of the correct frequency to one of the electrodes (see figure). This technique gives researchers yet another handle for manipulating the versatile NT's for what promises to be wide variety of applications. According to Stephen Purcell of the University of Lyon (stephen.purcell@dpm.univ-lyon1.fr), one of the co-authors on a new paper reporting the results, carefully excited and tuned NT's may act as the core for future nanometric oscillator circuitry, nano-balances or nano-force sensors. (Purcell et al., Physical Review Letters, 30 December 2002; for a past summary of NT thermal, electrical, and optical emissions, see Update 580.)