Super-rolloff electron tunneling transduction of nanomechanical motion using frequency downmixing

A downmixed transduction technique is demonstrated which eliminates the high-frequency cutoff problem in traditional electron tunneling instrumentation. We measure the ∼1 MHz vibrational modes of a micromechanical beam two orders of magnitude above the electronic bandwidth of our readout circuitry with no fundamental limitations anticipated up to microwave frequencies. The displacement sensitivity of 40 fm/Hz1/2 demonstrates the viability of this technique as a sensitive displacement transducer for high-frequency nanoelectromechanical systems. Backaction from the tunneling tip on the device induces resonance frequency shifts of order 1%.