MODIFICATION OF TETRAHEDRAL AMORPHOUS-CARBON FILM BY CONCURRENT AR ION-BOMBARDMENT DURING DEPOSITION

The surface morphology, mechanical and optical properties of tetrahedr al amorphous carbon (ta-C) films by concurrent Ar ion bombardment duri ng filtered cathodic vacuum are (FCVA) deposition are investigated. Th e Ar ions were produced by an RF ion beam source at different ion ener gies ranging from 60 eV to 500 eV, in order to study the Ar ion-induce d modification of ta-C films. Atomic force microscopy shows that all f ilms are atomically smooth, with roughnesses (RMS) ranging from 0.17 t o 0.43 nm. A rougher film surface has been attributed to a higher Ar i on energy. The compressive stress in the ta-C films ranges from 6.6 to 11.2 GPa and the microhardness from 34 to 67 GPa. A lower compressive stress and microhardness were observed at a higher Ar ion energy. The optical absorption spectrum shows that the edge has shifted to the lo wer photon energy side with the increasing Ar ion energy. The optical band gap decreases from 2.61 to 1.52 eV as the Ar ion energy is increa sed from 60 eV to 500 eV. The compressive stress, microhardness, optic al absorption and optical band gap information suggests that the sp(2) -bonded carbon atoms in the sp(3) matrix increase with the increasing Ar ion energy. (C) 1998 Elsevier Science S.A.