Formation of titanium fulleride studied by x-ray spectroscopies

The chemical interaction between titanium and ${\mathrm{C}}_{60}$ in coevaporated titanium-fulleride films has been investigated by x-ray photoelectron spectroscopy, (XPS), x-ray absorption spectroscopy (XAS), and x-ray emission spectroscopy. Two titanium-fulleride films with different Ti concentrations ($x=2.1\mathrm{}$ and 3.6) and a pure ${\mathrm{C}}_{60}$ film were chosen in this study. C $1s$ XPS analyses show a binding-energy shift and a line-broadening effect. C $1s$ XAS study of ${\mathrm{Ti}}_{2.1}{\mathrm{C}}_{60}$ shows a small change of the ${\pi }^{*}$ absorption resonance, with respect to its intensity and energy position, and a variation of the spectral shape in the ${\sigma }^{*}$ absorption region in comparison with pure ${\mathrm{C}}_{60}.$ The C Kα x-ray emission spectra of the films show the same total emission bandwidth as pure ${\mathrm{C}}_{60}.$ For resonant and nonresonant excitations, an x-ray spectral profile similar to pure ${\mathrm{C}}_{60}$ is observed from the ${\mathrm{Ti}}_{2.1}{\mathrm{C}}_{60}$ film, while the ${\mathrm{Ti}}_{3.6}{\mathrm{C}}_{60}$ film results in a spectral profile with some contribution from titanium carbide. All the experimental results indicate that a titanium-fulleride compound has been formed in the coevaporation process of ${\mathrm{C}}_{60}$ and titanium.