Thermal properties of DLC thin films bombarded with ion beams

We have studied the change in the thermal annealing properties of diamond-like carbon (DLC) films bombarded with ion beams. The carbon films were deposited on silicon wafers by evaporating a glassy carbon material. After the depositions, the carbon films were bombarded with argon, nitrogen or helium ions. The bombardments were performed with doses ranging from 5 x 10(15) to 5 x 10(17) ions cm(-2) at acceleration voltages ranging from 20 to 40 kV. The bombarded carbon films were annealed at 673 K, 773 K or 873 K in a vacuum. The chemical structure and mechanical properties were evaluated by measuring Raman spectra and microhardness testing, respectively. The results are as follows: (1) The carbon structure changes to a graphitic structure after annealing. Correspondingly the hardness of the films decreases. (2) Ion bombardment causes a decrease in the temperature at which the structure of the carbon films begins to become graphitic. (3) Bombardment with light ions, such as helium ions, makes the structure of carbon films change more to a graphitic structure than bombardment with heavier ions. (C) 1998 Elsevier Science S.A.