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Measuring structural damping due to internal friction in deposited thin films can provide useful guidelines for the design of high-Q micro/nanomechanical resonators utilized used for sensing, communications and vibration energy harvesting. Such measurements can also generate valuable insights into the effects of size and confinement on the mechanisms of damping in these films. Typically, these measurements are carried out by depositing a thin film on a relatively thick cantilevered substrate and measuring the change in damping in the substrate/film composite. However, the measured damping is due to losses from several sources including support losses, clamping losses, thermoelastic damping (TED) and internal friction losses in the substrate/film composite. Accurately identifying the magnitude of internal friction in the film has been a long-standing difficulty in this field. This thesis presents the design and development of a silicon microcantilever platform to resolve this difficulty. At the core of the platform is the ability to reduce the damping in single crystal silicon microcantilevers to low levels of damping approaching the fundamental limits of dissipation established by thermoelastic damping (TED). This demonstrates that all other sources of damping (viscous losses, support losses and internal friction losses) are sufficiently low. These cantilevers can then be coated with the thin film of interest and the damping in the substrate/film composite measured. The measured damping is comprised of the thermoelastic damping in the substrate/film composite and the internal friction in the film. The former can be calculated using accurate models and the initial damping can be substracted from the measured damping in the composite to obtain an accurate estimate of the internal friction in the film. ) with values approaching the TED limit. Subsets of these beams are then used to carry out the first calibrated iii measurements on the effects of thickness and frequency on internal friction in thin films of aluminum, gold and silver at room temperature. The films ranged in thickness from 60 nm to 450 nm and were studied over frequencies from 100 Hz to 1.5 kHz. The results of this study provide two valuable guidelines for the design of low dissipation (high Q) layered composite resonators: gold leads to a smaller increase in damping than either aluminum or silver, and damping in the composite resonators can be decreased by reducing the film thickness. As a third design guideline, a strategy to control and minimize the damping by selective patterning of thin films on the resonator is described. In this work, a simple model is developed to predict the damping in partially metalized cantilevered beams and experimentally validated using the platform. The silicon microcantilever platform, and the results obtained using this platform establish a foundation for studying internal friction in thin films.iv vi

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