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We have performed a quartz crystal microbalance (QCM) study of the nanotribological properties of organophosphate (tricresylphosphate and t-butyl phenylphosphate) layers adsorbed from the vapor phase onto silicon (amorphous silicon and MEMS-like polysilicon), and octadecyltrichlorosilane (OTS) treated silicon and gold surfaces. The latter systems have been studied in order to explore whether organophosphates and OTS in combination might prove synergistic from a tribological point of view [1]. There is a strong possibility that this combination will also exhibit synergistic tribological behaviors when tested on actual MEMS devices. Therefore, it is important to perform QCM measurement on silicon that is as close to that of MEMS devices. In order to perform this study, we have developed a deposition method involving a Si-Ge layer that enables the growth of polycrystalline silicon on top of Cu QCM electrodes. The structural and morphological properties of these samples have been characterized with Raman spectroscopy and atomic force microscopy (AFM), confirming that they are similar in nature to the silicon in actual MEMS devices.

The morphology and bonding characteristics of nanocrystalline diamond films prepared with different Ar:H ratios have been studied and are correlated to tribological performance. A coating made with high Ar:H ratio displayed low friction of 0.05 and very minimal wear, while the low Ar:H film showed high friction (> 0.2), rapid wear, and complete failure after 50 cycles. As both films had the same rms roughness, their different tribology appears to stem from a change in morphology.