AVS 46th International Symposium
    The Science of Micro-Electro-Mechanical Systems Topical Conference Wednesday Sessions
       Session MM-WeA

Paper MM-WeA9
Nanofabrication and Electrostatic Operation of Single-crystal Silicon Paddle Oscillators

Wednesday, October 27, 1999, 4:40 pm, Room 620

Session: Micro-Science and Tribology
Presenter: L. Sekaric, Cornell University
Authors: D.W. Carr, Cornell University
S. Evoy, Cornell University
L. Sekaric, Cornell University
A. Olkhovets, Cornell University
J.M. Parpia, Cornell University
H.G. Craighead, Cornell University
Correspondent: Click to Email
Nanoelectromechanical systems (NEMS) are of interest from both scientific and technological standpoints. Such structures are being considered for use as sensors, force gauges and for various optomechanical and biomedical applications. Small resonant structures also open avenues for mesoscopic studies of the mechanical properties of materials. We have recently reported the fabrication and excitation of single wires with resonant frequencies as high as 380 MHz. Here we report the fabrication and characterization of paddle oscillators with nanometer-scale supporting rods. The devices are electrostatically driven and are detected at room temperature using an optical interferometric technique. The devices show two resonances in the f =1-10 MHz range. We have measured the frequency of both resonances for a series of devices of varying paddle length, d. A fit of data to a f = Kd^b power law reveals experimental power coefficients of b1=-0.5±0.1 and b2=-1.6±0.15 for the two resonances. These coefficients agree with the values expected for translational and torsional modes of motion, respectively. Our model of the torsional mode suggests that the external drive induces an angular dependent electrostatic torque, resulting in a modulation of the torsional constant. This results in a shift of the resonant frequency under the application of a DC bias. Dependence of this shift on the bias allows us to extract a mechanical torsional constant of tau= 4.21±0.04 x 10-12 N.m. This modulation also results in parametric amplification effects that are under investigation. The translational motion shows non-linear behavior at low driving RF amplitudes. A model based on the mechanical stretching of the beams predicts the onset of non-linearity at such amplitudes. Finally, we will discuss the effects of material and surface properties on the dissipative processes in these structures. We are also looking at alternative geometries and potential chemical sensing applications.