Electron-beam analysis of polymerizedKC60

We have conducted high-resolution transmission electron microscopy (HRTEM) and electron-energy-loss spectroscopy (EELS) studies on polymerized ${\mathrm{KC}}_{60}$. The chainlike structure proposed for the polymerized material is confirmed. Lattice constants extracted from the HRTEM images are consistent with those determined earlier by x-ray diffraction. The fine structure in the EELS spectrum of ${\mathrm{KC}}_{60}$ shows the ${\mathit{sp}}^2$ nature of the carbon bonds along with features which distinguish the bonding in this alkali fulleride from that of other fullerenes. Both the HRTEM and EELS studies show that polymerized ${\mathrm{KC}}_{60}$ is exceedingly resilient against damage induced by a 200-keV electron beam, in sharp contrast to the behavior of pristine ${\mathrm{C}}_{60}$. © 1996 The American Physical Society.