Reactive and nonreactive ion mixing of Ti films on carbon substrates

The influence of nonreactive and reactive ion beam mixing on the interfacial chemistry, morphology, and adhesion of Ti films on glassy carbon, a-face pyrolytic graphite, and c-face pyrolytic graphite was examined and compared to thermal processing. Nonreactive ion beam mixing was performed with 180-keV 84Kr+ at doses of 1 to 5×1016 Kr/cm2. Reactive ion beam mixing was performed with 150-keV 28Si+ at doses of 1 to 5×1017 Si/cm2. Vacuum annealing was performed at 1000 °C for 1 h. Both 84Kr+ and 28Si+ implantation induced substantial intermixing between the Ti films and each of the carbon substrates. The 1000 °C anneal produced little interfacial reaction. Ion beam mixing produced adhesion increases of up to 1000× while no adhesion enhancement was observed following the anneal. Adhesion increases were attributed primarily to mechanical interlocking for both the 28Si+ and the 84Kr+ implantation. There were indications of ion induced film/substrate chemical bonding (Ti–C and Ti–O–Si-C), but this bonding did not appear to greatly influence the observed adhesion. Ion induced topographical changes included void and bubble formation, cracking, erosion, and carbon aggregation. Topographical modifications were at a minimum on the glassy carbon specimens and at a maximum on the c-face pyrolytic graphite specimens. Film characterization was performed using secondary ion mass spectrometry, Auger electron spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive x-ray analysis, and x-ray diffraction. Adhesion was examined using a scratch test.