Performance and reliability of microelectromechanical
system (MEMS) components enhanced dramatically through the incorporation of protective thin film coatings. Current-generation MEMS devices prepared by the
LIGA technique employ transition metals such as Ni, Cu, Fe, or alloys thereof, and hence lack stability in oxidizing, corrosive, and / or high temperature environments. Fabrication of a superhard, self-lubricating
coating based on a ternary
boride compound AlMgB14 is described in this letter as a potential breakthrough in protective
coating technology for
LIGA microdevices.
Nanoindentation tests show that
hardness of AlMgB14 films prepared by
pulsed laser deposition ranges from 45 GPa to 51 GPa, when deposited at
room temperature and 573 K, respectively. Extremely
low friction coefficients of 0.04-0.05, which are thought to result from a self-lubricating effect, have also been confirmed by nanoscratch tests on the AlMgB14 films.
Transmission electron microscopy studies show that the as-deposited films are amorphous, regardless of substrate temperature; however, analysis of
FTIR spectra suggests that the higher substrate temperature facilitates formation of the B12 icosahedral framework, therefore leading to the higher
hardness.