Stability of the Fullerenes Thin Film Deposited on the Si(100) Surface
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STABILITY OF THE FULLERENES THIN FILM DEPOSITED ON THE SI(100) SURFACE H. RAFII-TABAR, Y. KAWAZOE AND H. KAMIYAMA Institute For Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980, JAPAN ABSTRACT We have performed a constant temperature classical molecular dynamics simulation of the epitaxial growth of a C60 monolayer film deposited on the dimerized Si(100) surface. Our simulation, based on non-central many-body inter-atomic potentials, is capable of predicting the structural stability of the C60 film and the Si substrate and provides a theoretical basis for the results of a recently-performed STM- based experiment for this system. Three-dimensional geometries have been generated on computer and used for the animation of the simulation runs. Introduction The discovery of macroscopic quantities of C60 molecules (Buckyballs), and other related fullerenes, as novel forms of carbon in condensed phase laying in between simple carbon clusters and the bulk phase, prompted an intensive research into their physical and morphological properties in both pure and doped compound forms. It has, for instance, been established[l] that C60 crystals can accommodate guest alkali- metal atoms (fullerites) leading to the formation of superconducting states with transition temperatures in excess of 30K. Both experimental investigation[2] and theoretical calculations have been employed to obtain the structural[3], vibrational[4] and orientational[5] properties of this molecule and its synthesised solid phase. It is now well known that the 60 carbon atoms in this cluster reside on the vertices of a truncated icosahedron soccer-ball geometry with an unusual degree of stability. In crystalline phase, the C60 molecules form a strong van der Waals molecular solid[2] having an FCC lattice structure with a centre-to-centre distance of 10.02Aand undergoing independent rotational diffusion at room temperature. The cohesive forces have been estimated from the heat of sublimation and found[6] to be 1.65 eV per molecule. Recently, the study of the nanometer-scale structure and mechanical stability of monolayer and multilayer films of C60 fullerenes adsorbed on metallic and semi-conductor surfaces has become the focus of scientific and technological interests. Employing the Scanning Tunnelling Microscopy(STM) imagining techniques it has been shown that the C60 thin film deposited on the Au(lll) surface[7] displays mobile hexagonal arrays that are structurally unstable with an intercluster spacing of 11.0A, whereas the C60s adsorbed on the GaAs(110) surface[8] reveal large monolayer islands that are locally well-ordered, structurally stable, and commensurate with the GaAs substrate due to the molecule- surface interactions. Due to its great technological importance in nano-scale device fabrication, the research into the mechanism of epitaxial growth and structural properties of C60 molecular film deposited on silicon substrate has, very recently, been initiated and the first field ion STM-based experiment[9] of monolayer and mul
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