Detecting sub-nanometer transverse vibrations on a piezo crystal oscillator surface, using time series tunneling current measurements

Vibration characteristics of a piezo crystal oscillator surface are studied using time series measurements of tunneling current. Using this technique, the fluctuations in the tunneling current between a scanning tunneling microscopy tip and the surface of a piezo crystal oscillator are studied, which reveal sub-nanometer vibrations with a sensitivity of 10−2 A°Hz . As the excitation frequency applied to the crystal is varied, the vibrations on the oscillator surface exhibit a resonant response. Furthermore, we detected unconventional sub-nanometer perpendicular vibration modes excited on the crystal surface. These vibrations are in a direction transverse to the surface of the crystal oscillator, whose conventional vibration mode is in a horizontal plane parallel to the surface. We also find near resonance higher harmonics of the perpendicular mode. Thus, the piezo crystal oscillator together with the time series tunneling current measurements offer a convenient simultaneous drive and detection system with a wide operating frequency range.