화학공학소재연구정보센터
Applied Surface Science, Vol.157, No.4, 320-325, 2000
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)(1/2), 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 10(-1) and 10(2) N/m. The strength of the nanometric neck was 10(8) N/m(2) 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.