Comparison of surface layers on copper, titanium and tantalum created by methane plasma-based ion implantation

Two carbide forming metals, titanium and tantalum, and a typical non carbide former, copper, were treated by methane plasma immersion ion implantation. The polished metal samples were exposed to high voltage pulses at –20 kV in an atmosphere of methane. The lateral distribution of the carbon was investigated via electron probe microanalysis, the depth distribution of the respective metal, carbon and hydrogen was determined by secondary ion mass spectrometry. X-ray photoelectron spectroscopy in conjunction with argon sputtering showed the evolution of the binding conditions with depth. The phase composition of the samples was also analyzed by glancing incidence X-ray diffraction. The generated carbon layers exhibited considerable differences depending on the respective substrate. Although there was no carbide formation with the copper samples, some carbon was incorporated into the surfaces. On copper the lateral carbon distributions showed inhomogeneities whereas the appearances of the ones on titanium and tantalum were uniform. The resulting thickness of the carbon layer was not only dependent on the substrate material, but also on the process parameters