Surface modification of single crystal silicon by Ar+ ion implantation and vacuum deposition of amorphous carbon coating

Single crystal silicon wafers (Si (100) ) were implanted with 110 keV Ar+ ions at a fluence of 1 × 1016 ions/cm2. Then the unimplanted and ion-implanted Si surfaces were coated with an amorphous carbon coating of 50 ± 5 nm thick making use of vacuum vapor deposition. The microstructures of the unimplanted and Ar+ ion implanted Si wafers were analysed by means of transmission electron microscopy (TEM). The hardness and elastic modulus of the unimplanted and Ar+ ion implanted Si wafers were measured using a nano-indentation device. The adhesion strengths of the amorphous carbon coatings on the unimplanted and Ar+ ion implanted Si surfaces were determined making use of scratch test. The friction and wear behaviors of the samples were evaluated using a ball-on-disk reciprocating friction and wear tester. The morphologies of the wear and scratch tracks of the Si samples were observed using a scanning electron microscope (SEM). It was found that Ar+ ion implantation alone led to little effect on the friction and wear behavior of the Si sample. However, the amorphous carbon coating deposited on the Ar+ ion implanted Si surface showed much better friction-reducing and antiwear ability than that on the unimplanted Si surface. The formation of a mixed nano-crystal and amorphous silicon structure during the Ar+ ion implantation improves the ability of the amorphous carbon coating to resist plastic deformation, and hence increase the adhesion strength and antiwear-life of the amorphous carbon film.