Frequency-Tunable Micromechanical Oscillator

An experimental method, employing a scanning tunneling microscope (STM) as an actuator and a scanning electron microscope (SEM) as a motion detector, was developed to study microelectromechanical systems (MEMS) and has been applied to study microfabricated cantilever beams. Vibrations actuated by an ac voltage applied to the piezodrive are transferred to the sample by the STM tip, which also provides a constraint at the drive location, altering the fundamental mode of the oscillation. A continuous change in the resonant frequency of the cantilever is achieved by varying the position of the STM tip. In contrast to the few percent tunability previously demonstrated for MEMS oscillators, we have varied the cantilever frequency over a 300% range. (C) 2000 American Institute of Physics. [S0003-6951(00)03146-6].