Superhard self-lubricating AlMgB14 films for microelectromechanical devices

Abstract

<p>Performance and reliability of microelectromechanical system(MEMS) components can be enhanced dramatically through the incorporation of protective thin-filmcoatings. Current-generation MEMSdevices prepared by the lithographie-galvanoformung-abformung (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 described in this letter has great potential in protective coatingtechnology for LIGA microdevices. Nanoindentation tests show that the hardness of AlMgB14films 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 AlMgB14films. Transmission electron microscopy studies show that the as-deposited films are amorphous, regardless of substrate temperature; however, analysis of Fourier transform infrared spectra suggests that the higher substrate temperature facilitates the formation of the B12 icosahedral framework, therefore leading to the higher hardness.</p>