Structural change in amorphous carbon on core excitations induced by soft x-ray illumination

Effects of carbon 1s core excitations on the structure of tetrahedral amorphous carbon films were investigated by illuminating samples with intense soft X-rays from a synchrotron radiation source in the photon energy range of 240 eV to 310 eV. The structural changes detected in the X-ray absorption spectra obtained before and after the intense illumination are characterized by graphitic ordering, similar to the effect of high-energy electron irradiation. The excitation spectrum for the photo-stimulated structural changes was found to consist of a non-resonant component and a resonant component peaking at 289 eV close to the 288 eV XAS peak characteristic of ta-C films. The microscopic mechanisms are discussed for the non-resonant and the resonant effects.

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