Ion beam deposition of fluorinated amorphous carbon

We have studied the growth and the properties of (t)a-C:F films prepared by the deposition of mass separated C-12(+) and F-19(+) ions as a function of the F concentration. The films are always strongly F deficient due to the formation of volatile F-2 and CFx molecules during the deposition process. A maximum F content of about 25 at. % is obtained for an ion charge ratio o f C+:F+ = 1:1. The observed mechanical, optical, electrical, and structural properties as well as the thermal stability of the films are strongly infl uenced by the F content. A three step progression of the film structure is evident for increasing F concentration: the amorphous three-dimensional net work of tetrahedrally bonded carbon atoms of pure carbon films (ta-C) with diamondlike properties is doped for very low F concentrations (ta-C:F). A f urther increase of the F content results first in transformation to a graph itelike amorphous structure (a-C:F) before the deposited films become porou s and to a polymerlike one for the highest F content. (C) 2001 American Ins titute of Physics.