Irradiation of solid C60 films with pulsed UV-laser-light: Fabrication of a periodic submicron C60 structure and transformation of C60 into a different carbon phase

A thin solid C60 film has been irradiated under a fix incident angle with pulsed UV light at the wavelength of 266 nm. With scanning electron microscopy and atomic force microscopy, a surface transformation of the irradiated films has been observed to a periodic surface structure at low laser fluences in air as well as in vacuum and to strong morphology changes at higher laser fluences only in air. For both structural transformations the occuring surface chemistry has been studied with Raman spectroscopy and X-ray photoelectron spectroscopy. In the case of the periodical lines, these results in addition to a detailed discussion of the existing models for laser induced surface structures have shown that the C60 film remains a van der Waals solid but with much oxygen incorporation in the lattice and does not polymerize as it is known to happen during continuous wave irradiation. The case of strong morphology changes could be explained by detailed comparison of the obtained Raman and X-ray photoelectron spectroscopy data as the formation of a new carbon phase with diamond-like sp3 bondings through an oxygen-assisted fullerene cage opening.