Sub-nanometer level vibration detection of a piezo crystal oscillator's surface, using time series tunneling current measurement.*

We study the vibration characteristics of a piezo crystal oscillator surface using time series measurement of tunneling currents. We determine the fluctuations in the tunneling current between an STM tip and the surface of a vibrating piezo crystal oscillator. These fluctuations reveal sub-nanometer vibrations on the piezo crystal oscillator’s surface with a sensitivity of 10^-2 Å/√Hz. The vibrations on the surface of the oscillator exhibit a resonant response as we vary the excitation frequency. An unconventional sub-nanometer perpendicular vibrations mode excited on the crystal surface is detected. The direction of these vibrations is perpendicular to the surface whereas the conventional vibration mode is in a direction parallel to the crystal surface. We find that this perpendicular mode also has higher harmonics near resonance. We can conveniently call the piezo crystal oscillator together with the time series tunneling current measurements a simultaneous drive and detection system.