Langmuir-Blodgett films of C60: structure of pure films and their superconductivity after exposure to potassium vapor

C60 forms very rigid insoluble films (''monolayers'') at the air-water interface (collapse pressure Πc=62.5 mN/m). The ''area per molecule'' values Ao=21.6 A2 (at Π=0) and Ac=11.5 A2 (at Πc) suggest that more than 4 C60 molecules are piled atop each other, per ''monolayer''. These films were transferred to glass and HOPG as Langmuir-Blodgett (LB) films, and to a Cu grid as Langmuir- Schaefer films. These films have 2-D and 3-D crystalline regions, seen by scanning tunneling microscopy (STM) and high resolution electron microscopy (HRTEM). The STM image is a {013} face-centered cubic (FCC) projection, a=14.2 A. The HRTEM micrographs and a selected-area diffraction pattern show an FCC lattice, a = 14.20 ± 0.05 A. When optimally ''doped'' with potassium, an LB film of 50 ''monolayers'' of C60 on polyethylene terephthalate shows a low-field susceptibility signal (LFS) at or below 8.1 K: this is the first report of superconductivity in an LB film. (orig.)