Fabrication and characterization of a double torsional mechanical oscillator and its applications in gold micromass measurements
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We report the design and fabrication of a micro-mechanical oscillator for use in extremely small force detection experiments such as transverse force measurements of a moving vortex and Nuclear Magnetic Resonance Force Microscopy (NMRFM). We study the basic physics of the double torsional mechanical oscillator, and pursue double torsional oscillators with small spring constants, high resonance frequencies, and high quality factors. Using a series of semiconductor manufacturing techniques, especially using the electron-beam lithography technique, we successfully micro-fabricate double torsional mechanical oscillators from silicon-on-insulator wafers. We conduct characterization experiments to extract important parameters of a mechanical oscillator, including the resonance frequencies, spring constants, and quality factors. We focus on the four typical resonance modes of these oscillators, and then compare the force detection sensitivity of each mode. Eventually we apply these force sensitive oscillators to gold micro-mass measurements, and achieve very small mass detection. In the future we are going to continue to micro-fabricate thinner oscillators to reduce the spring constants, and improve the quality factors by designing more suitable geometric shapes and by pursuing annealing studies. Thus, we might be able to achieve single nuclear spin measurements using NMRFM.