First adhesion measurements of conductive ultrananocrystalline diamond MEMS sidewalls

We present the first measuremenst of adhesion between two micro-electromechanical systems (MEMS) surfaces, fully fabricated with boron doped ultrananocrystalline diamond (B-UNCD). This research allows us to explore the potential of conductive UNCD MEMS for the solution of issues like adhesion and friction in micro-devices and describe with accuracy the effects involved. By means of standard lithographic techniques, we have fabricated a diamond micro thermal actuator (chevron type), which is used as a platform for tribological testing. A peculiar effect has been observed in the adhesion phenomenon of UNCD. It involves with high probability, an interaction between hydrocarbon/amorphous carbon layers (a-C) that cover the two diamond contacting surfaces. The as-etched device shows a `chewing-gum' effect in the adhesion curve, probably due to the formation of hydrocarbon/a-C chains after the interaction of the surfaces. This effect disappears when the device is treated in oxygen plasma and the hydrocarbon/a-C is removed. The study of this phenomenon will be followed by more accurate analysis and atomistic simulation and the results will be compared with nitrogen-incorporated UNCD (N-UNCD) fabricated devices.