Mesoscopic Patterning Induced by Co-deposition of C 60 and Ni on the MgO(100) Single Crystal
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Mesoscopic Patterning Induced by Co-deposition of C60 and Ni on the MgO(100) Single Crystal Jiri Vacik1,*, Hiroshi Naramoto1, Kazumasa Narumi1, Shunya Yamamoto2, Kiyoshi Myashita3 1 Advanced Science Research Center, Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan 2 Department of Materials Development, Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan 3 Gunma Prefecture Industrial Technology Research Laboratory, 190 Toriba Maebashi, Gunma 371-0845 Japan * On leave from Nuclear Physics Institute, CZ – 250 60 Rez, Czech Republic ABSTRACT We report on an unusual phenomenon of pattern formation in the mixture of Ni and C60 codeposited on the single crystal of MgO(100). Under certain deposition kinetics an array of periodic stripes was formed. The stripes consist of sub-half-micrometer Ni droplets (embedded in the complex Ni-C base) and encompassed with a polymerized C60 rind. The stripes are bound to the thin double-layer platform consisting of the epitaxial Ni and amorphous C (a-C) layers. During co-deposition the C60 molecules partly disintegrate and transform towards the a-C structures. Accumulation of a-C (immiscible with Ni) may induce thermodynamic instability in the system and trigger the process of spontaneous partitioning. As a principal mechanism of the stripe formation a sequential drift and co-ordinate release of the incited instability was proposed.
INTRODUCTION Self-organization of matter is a phenomenon commonly observed in nature. It appertains to various mono- or multi-componential systems and sets in a broad range of spatio-temporal scales. There exists a rich gallery of engrossing self-made structures in nature, which are grown in complex physico-chemical processes. Patterns are formed, e.g., in the Turning reactiondiffusion systems [1], oscillating Belousov-Zhabotinsky catalytic reactions [2] or RayleighBénard convection of fluids [3]. The manifestation of the creative ability of in-organic matter provokes questions about pattern growth determining mechanisms. Though the universal theory of pattern formation does not exist many self-organized systems have similar structures and evolution mechanisms and by understanding one the other can be better comprehended. Most of the self-organized structures have common denominator – non-equilibrium conditions, under which they were formed. Generally, the systems grown far away from thermodynamic equilibrium may reach a critical point where onset of the pattern formation can occur. At this point the patterns arise suddenly as ‘an elegant solution of conflicting processes evolving in the system’ [4]. In this paper we report on the pattern formation observed in a thin Ni+C60 mixture deposited on MgO(100). The spontaneously formed structure points out the peculiar nature of the fullerene/metal composites. These systems exhibit unusual transport properties which have already been utilized in several targeted applications [5]. P3.50.1
EXPERIMENTAL DETAILS As a substrate for deposition of t
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