THE ION-BEAM MIXING OF TI AND CR FILMS ON SILICA GLASS

The effects of ion implantation dose-PHI and substrate temperature have been examined for the 75 keV Ar+ ion beam mixing of thin Ti and Cr films on silica. The dose dependence could be described in three distinct regions: (1) at low doses the amount of metal mixed into the silica was approximately proportional to PHI-1/2 indicating that isotropic cascade mixing was dominant; (2) above a dose of approximately 5 X 10(16) Ar+ cm-2 this changed to a PHI-2 dependence; (3) at approximately 2 X 10(17) Ar+ cm-2 surface erosion by sputtering became important and reduced the concentration of metal mixed into the substrate. Optical measurements were performed on the etched surfaces of the specimens and indicated that chemical reactions may have occurred at the mixed interfaces. The ion beam mixing of Ti was found to be independent of temperature throughout the experimental temperature range of 300 to 600 K whereas the mixing of Cr was temperature dependent above 440 K. It exhibited an activation energy of approximately 0.2 eV, due to radiation enhanced diffusion.