Structural properties of chlorinated epitaxial ${\mathrm{C}}_{60}$ films

The interaction of chlorine gas with epitaxially grown ${\mathrm{C}}_{60}$ films was investigated by combined scanning tunneling microscopy (STM) x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XANES). The STM measurements of chlorinated fullerene surfaces on ${\mathrm{VSe}}_2$ reveal an inhomogeneous ${\mathrm{C}}_{60}$ and chlorine coverage in an area up to 200 nm from the fullerene island edges but showed no influence to the fullerene (111) coordination in the inner regions of the layers. In accordance with the STM data the XPS spectra of C $1s$ and Cl $2p$ core levels, which were taken at different emission angles, provide evidence for chlorine aggregation on the fullerite surface. As valence band and XANES spectra show that all ${\mathrm{C}}_{60}$ features derived from the highest occupied and lowest unoccupied molecular orbitals are preserved, a noncovalent interaction between fullerene and halogen can be concluded. As monitored by STM subsequent fullerene deposition on the chlorinated samples prove the perturbed island areas to serve as growth seeds so that a chlorine incorporation into the fullerite lattice can be achieved by an alternating preparation sequence.