Parametric resonance based scanning probe microscopy

We propose a mode of dynamic scanning probe microscopy based on parametric resonance for highly sensitive nanoscale imaging and force spectroscopy. In this mode the microcantilever probe is excited by means of a closed-loop electronic circuit that modulates the microcantilever stiffness at a frequency close to twice its natural resonance frequency. Under ambient conditions this parametric pumping leads to self-sustained oscillations in a narrow frequency bandwidth thereby resulting in exquisitely sharp, controllable, and non-Lorentzian resonance peaks. We discuss and demonstrate the potential of imaging and force spectroscopy using this mode. (c) 2006 American Institute of Physics.