Dynamics of Vapor-phase Organophosphates on Silicon and OTS

We have performed a quartz crystal microbalance (QCM) study of the uptake and nanotribology of organophosphate (tricresylphosphate (TCP) and t-butyl phenyl phosphate (TBPP)) layers adsorbed from the vapor phase onto amorphous and polycrystalline silicon and octadecyltrichlorosilane (OTS) treated silicon substrates. The materials were selected for their relevance to MEMS applications. About 3–5 monolayer-thick organophosphate films are observed to form readily on both silicon and OTS-treated silicon. The coatings moreover exhibit mobility in the form of interfacial slippage or viscoelasticity in response to the oscillatory motion of the QCM, implying that enhanced tribological performance may be expected in MEMS applications.