Strength measurement and calculations on silicon-based nanometric oscillators for scanning force microcopy operating in the gigahertz range

For an oscillator having a structure that can be modeled as a concentrated mass–spring model with constant Q factor, its minimum detectable force gradient is proportional to KM.1r2, where M is the mass and K is the spring constant. Miniaturization of the oscillator acts favorably in increasing the force resolution, since drastic decrease of the mass can then be achieved. With the aim of increasing the force and mass resolution of the oscillator used for force detection in scanning force microscopy SFM., we have developed a novel fabrication technique of nanometric oscillators by selective etching of laminated silicon substrates such as SOI silicon on insulator.or SIMOX separation by implanted oxygen.. The oscillator has a tetrahedral or a conical tip supported by an elastic neck, and the tip serves as the mass. Typical size of the oscillator lies in the range of 100–1000 nm. The oscillator could be tailored to have its natural frequency in the range of 0.01–1 GHz, and a spring constant between 10y1 and 102 Nrm. The strength of the nanometric neck was 108 Nrm2 for both shear and normal forces, indicating that a neck 10 nm in diameter can withstand forces up to around 50 nN. Calculations on the different vibrational modes of the oscillator gave a better guideline to the design of the oscillators. q2000 Elsevier Science B.V. All rights reserved