High‐Temperature Cs x C 58 Fullerides

Cs doped non‐IPR fullerides (IPR: isolated pentagon rule) have been grown by co‐depositing C 58 cations and Cs atoms on highly oriented pyrolytic graphite (HOPG). The C 58 cages, as building blocks of the material, form a predominantly covalently stabilized scaffold, C 58 –C 58 , which is doped by Cs atoms thermally diffusing across the bulk. The heating of the solid Cs x C 58 sample is accompanied by sublimation of Cs, C 58 , and C 60 species from the topmost layers of the sample. However, the major part (>94%) of the material survives the heating procedure and constitutes a doped high‐temperature carbon solid, HT‐Cs x C 58 . The new non‐IPR material exhibits surprisingly high thermal stability. It survives a heating flash up to 1100 K at which the classic IPR‐Cs x C 60 phase does not exist anymore. However, the thermally treated HT‐Cs x C 58 phase exhibits a considerably depleted Cs content ( x  < 2) and a significantly modified carbon scaffold. The apparent stability of the scaffold results from covalent C–C bonds interlinking adjacent carbon cages. Cs atoms in the HT‐Cs x C 58 phase contribute to this stability only as minority species, forming comparably weak ionic bonds with C 58 –C 58 oligomers. However, this interaction facilitates the formation of structural defects (new non‐IPR sites) in carbon cages. The surface topography of the HT‐Cs x C 58 as monitored by scanning photoemission microscopy, atomic force microscopy, and scanning electron microscopy is governed by islands standing out by their elevated Cs/C ratio.