Anomalous resonant frequency changes in piezoelectric microcantilevers by monolayer formation of Au films

Although the resonant frequency of a microcantilever has been reported to be changed by surface stress and/or flexural rigidity, the reasons still remained unclear. Here, we present an observation of anomalous resonant frequency change with positive values at 3.25 angstrom thickness of Au, where it represents the monolayer formation of Au films. This result illustrates the surface stress-dependence of the resonant frequency. The thickness at where the resonant frequency shift would become zero through the compensation of the mass, and the surface stress is expected to be approximately three monolayers (9.7 angstrom). (C) 2011 American Institute of Physics. [doi: 10.1063/1.3621825]