This thesis describes new ways of operating high-frequency nanomechanical resonators and using them for sensor applications.
The first part of the thesis is devoted to the techniques of detecting, actuating, and tuning the resonance motion of nanomechanical resonators. First, I consider piezoresistive detection using integrated thin-film piezoresistors made of doped semiconductors or metals. I describe the piezoresistive downmixing technique, which typically results in better performance than the conventional DC biasing technique. I then proceed to the possible ways of actuating the motion of nanomechanical resonators. After describing the challenges of applying the piezoshaker actuation technique to high-frequency resonators, I consider two alternatives: permanent-magnet magnetomotive actuation and Joule-heat-driven thermoelastic actuation. I demonstrate that the combination of thermoelastic actuation and piezoresistive detection can be used to efficiently detect multiple modes of nanomechanical resonators. Finally, I consider two ways of tuning the frequency of nanomechanical resonators: electrostatic tuning and absorptive tuning.
The second part of the thesis is devoted to applications of nanoscale resonators to spin sensing, studies of dissipation of mechanical motion, and gas sensing. I consider possible ways of observing the coupling between mechanical motion and spins, describe our experimental results, and explore the analogy between coupled the spin--resonator system and the quantum-optical model of a laser. I then describe the results of quality-factor measurements in vacuum and air for doubly clamped beams and other resonator geometries. Finally, I describe a way to build better gas sensors by using arrays of nanomechanical resonators and present the preliminary gas-sensing data.</p
