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In the XRD spectra, apart from the peaks of Ti and Ta, small peaks of the respective
carbide phases MeC can be identified. Carbon implantation led to formation of the
carbide phase. The peaks are rather weak and broad, which is assumed to be a
consequence of small grain sizes and the shallowness of the implanted zone. XPS
combined with Ar sputtering showed the development of the binding conditions with
depth. In the C1s spectrum, on top of the sample, a thin film of elemental carbon was
found. After 1 min sputtering, a chemical shift to carbide was detected. With
increasing sputtering time, i.e. depth, the C signal became smaller and vanished,
when the thickness of the implant region was exceeded. The Ti2p signal appeared at
the position of the carbide and shifted to the position of elemental Ti upon sputtering.
This showed that the TiC phase had been formed, in accordance with XRD.
Basically, the same result was found for Ta in the C1s and Ta4f spectra.
Fig. 4: SIMS
carbon profiles of
Ti samples,
treated for 0.5, 1,
or 2 h, extracted
from the Ta-181
C-12 signals
It can be
concluded that pulse biasing titanium and tantalum in an atmosphere of methane in
an appropriate pressure range leads to formation of a methane plasma from which
ions are accelerated towards the metal targets. Thus, thin gradient films of implanted
carbon are formed. Carbide phase formation has been shown by X-ray diffraction,
indicating the presence of small carbide crystallites, and by the shifted photoelectron
energy states of metal and carbon. Depth profiling by sputter etching in combination
with photoelectron spectroscopy and by secondary ion mass spectrometry showed
thin carbon films on top and gradient carbide films below.
Acknowledgments
The authors would like to thank Deutsche Forschungsgemeinschaft (DFG) for
financial support with the project EN207/19-1.
The fruitful collaboration with Drs. K. Baba and R. Hatada from Industrial Technology
Center of Nagasaki is gratefully acknowledged.
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