MODIFICATION OF TRIBOLOGICAL PROPERTIES OF SILICON BY BORON ION-IMPLANTATION

Friction and wear properties of silicon used in the fabrication of microelectromechanical systems (MEMS) are important for their long-term reliability. In the present study, the authors have implanted single-crystal and polycrystalline silicon wafers with boron ions to improve their mechanical and tribological properties. The authors have studied the effects of ion implantation on the crystallinity, microstructure, nanohardness, and friction and wear properties and have found that silicon remains crystalline after ion bombardment at doses up to 2 x 10(17) ions . cm-2 but with a large amount of defects. The ion bombardment modifies elastic/plastic deformation characteristics and crack nucleation that occurs during indentation. There is a minor increase, approximately 10-15 percent, in the nanohardness as a result of boron-ion implantation. Ion bombarded single-crystal silicon exhibits very low friction (0.05) and low wear factor (10(-6) mm3.N-1m-1) while slid against a 521 00 steel ball. The coefficient of friction of bombarded silicon in dry air and dry nitrogen is even lower.