| This thesis strives toward the understanding and prediction of friction for micro- and nano-scale devices, and fundamental improvements of the understanding of friction. A multiscale approach understanding to friction is employed through friction experiments on both the nano- and micro-scales to fully understand behavior of MicroElectroMechanical Systems (MEMS). Atomic Force Microscopy (AFM) is used with rigorous calibration techniques to yield useful, quantitative information of single asperity friction at the nanoscale. Sophisticated techniques such as tilt-compensation and lateral stiffness measurements are employed to extract useful information about the tribological systems under study.; Single asperity friction results for a SiN/diamondlike carbon (DLC) interface measured using AFM reveals that friction is proportional to the contact area, where the interfacial shear strength increases by ∼40% with increasing humidity. The increase in friction with relative humidity suggests that the adsorption of water on the DLC surface is a key factor influencing friction. Microscale experiments are performed using a MEMS device known as the nanotractor, which is a promising vehicle for in-situ wear studies on MEMS devices. A monolayer lubricant coating significantly enhances the wear resistance of the silicon MEMS surfaces, while surface roughness does not strongly affect wear.; Friction measured between silicon tips and on alkylsilane self-assembled monolayer samples varies significantly with tip use, which can be attributed to tip wear or contamination. Transfer of SAM molecules or other contaminants to uncoated tips is common phenomenon, and run-in is an important technique to equilibrate tip geometry and chemistry. Adhesion of coated vs. uncoated interfaces varies by a factor of two, while the adhesion of surfaces coated with different types of monolayers varies to a much lower extent. Two phases of the OTS monolayer-coated surfaces are observed, which demonstrates that lower friction is associated with higher packing density of the molecules. Lateral stiffness measurements indicate stiffening of the interface due to molecular nonlinearity, and/or interaction with the stiffer substrate. The significant role of frictional plowing of SAMs is discussed.; This thesis makes substantial and novel contributions to progress in both the understanding of the fundamental origins of friction, and the application of that knowledge to technologies such as MEMS. |
