Order and disorder in C60 Langmuir-Blodgett films: Direct imaging by scanning tunneling microscopy and high-resolution transmission electron microscopy

C60 forms very rigid insoluble films (open-quotes monolayersclose quotes) at the air-water interface (collapse pressure IIc = 62.5 mN/m). The open-quotes area per moleculeclose quotes A0 = 21.6 Angstrom 2 (at zero pressure) and Ac = 11.5 Angstrom 2 (at IIc) are too small for a single C60 molecule and suggest 4-7.5 C60 molecules piled n top of each other, per open-quotes monolayerclose quotes. C60 forms Langmuir-Blodgett (LB) films on glass and HOPG and Langmuir-Schaefer (LS) films on a Cu grid. The ellipsometric LB film thickness is about 2 molecules per open-quotes monolayerclose quotes. The STM (LB) and HRTEM (LS) images show that the C60 films have 2-dimensional and 3-dimensional crystalline regions. The STM image shows a slightly distorted (013) projection of an face-centered cubic (fcc) pattern of roundish, atomically unresolved peaks, with a cell constant of 14.2 Angstrom. The HRTEM micrographs and a selected-area electron diffraction pattern show that, at optimum crystallinity, the C60 molecules pack in an fcc pattern with a cell constant of 14.20 ± 0.05 Angstrom. No hexagonal close-packed structures were found. 21 refs., 6 figs