Bruce A. Cook

Superhard self-lubricating AlMgB14 films for microelectromechanical devices

Performance and reliability of microelectromechanical system (MEMS) components can be enhanced dramatically through the incorporation of protective thin-film coatings. Current-generation MEMS devices 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 coating technology for LIGA microdevices. Nanoindentation tests show that the 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 st...

Electrical transport in amorphous semiconducting AlMgB14 films

The electrical transport properties of semiconducting AlMgB14 films deposited at room temperature and 573K are reported in this letter. The as-deposited films are amorphous, and they exhibit high n-type electrical conductivity, which is believed to stem from the conduction electrons donated by Al, Mg, and/or Fe impurities in these films. The film deposited at 573K is less conductive than the room-temperature-deposited film. This is attributed to the nature of donor or trap states in the band gap related to the different deposition temperatures.