NASA’s Jet Propulsion Laboratory has developed a nano-electro-mechanical resonator (NEMR) based on vertically aligned carbon nanofibers (CNFs) that is suitable for applications requiring high sensitivity, broad tenability, low loss (high Q), low power consumption, and small size. Other nanoscale resonators have been demonstrated using top-down fabrication approaches, but these generally involve complicated and expensive electron beam lithography. JPL’s bottom-up fabrication approach yields robust, vertically oriented CNFs that can be used to form high-Q, high-frequency NEMRs. In addition, the resonant frequency of these NEMRs can be tuned by selecting the length and diameter of the CNFs. This allows for a highly integrated, ultra-low-power, high-data-rate, and wide-bandwidth NEMR-based transceiver architecture.
The NEMR comprises a vertically aligned CNF in a solution, positioned with a gap width and a coupling length to a nanoprobe. The CNF can be fabricated on a silicon wafer substrate with pre-patterned nickel catalyst islands in a plasma-enhanced chemical vapor deposition (PECVD) growth system, and the nanoprobe can be used to mechanically deflect the CNF. The CNF significantly couples to an AC signal when the frequency of that signal is near or equal to its mechanical resonant frequency, and insignificantly couples at other frequencies. This resonance behavior can be turned on and off by adjusting the DC bias on the nanoprobe. For high-elastic-modulus CNFs, resonant frequencies in the hundreds of MHz to the tens of GHz are possible, and a CNF has been demonstrated having a resonant frequency around five times larger than the resonant frequencies of aluminum and mild steel.
A vertically oriented CNF has been simulated using COMSOL Multiphysics. These simulations show that the CNF vibration amplitude increases with increasing coupling length, but decreases with increasing gap width.
Potential applications include nanoelectro-mechanical components, nonvolatile memory, computer chips, and electronics for use in harsh environments.