Incorporating C2 into C60 films

The material formed by depositing C-2(-) anions onto/into thin C-60 films (on graphite) at room temperature has been studied by means of thermal desorption mass spectroscopy, ultraviolet photoionization spectroscopy, atomic force microscopy (AFM), and surface enhanced Raman spectroscopy. As-prepared, C-2/C-60 films manifest thermal desorption behaviour which differs significantly from pure C-60 films. Whereas the latter can be fully sublimed, we observe decomposition of C-2/C-60 films to a high-temperature-stable material while predominantly C-60, C-62, and C-64 are desorbed in parallel. Deposition of C-2(-) also leads to significantly modified electronic and vibrational properties. Based on DFT model calculations of the Raman spectra, we suggest that as-prepared C-2/C-60 films contain appreciable amounts of polymeric networks comprising -C-2-C-60-C-2-C-60-chains. Detection of sublimed C-62 and C-64 upon heating implies that thermal decomposition of C-2/C-60 films involves addition/uptake of C-2 units into individual fullerene cages. Correspondingly, annealing films up to various intermediate temperatures results in significant modifications to valence-band UP spectra as well as to surface topographies as imaged by AFM. The novel carbonaceous material obtained by heating to T > 950 K has a finite density of states at the Fermi level in contrast to as-prepared C-2/C-60. It comprises fused fullerene cages. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3673887]