Self-assembled Nanoline Template for Growth of Nanoparticles and Nanowires on Si(001)
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0901-Ra13-02.1
Self-assembled Nanoline Template for Growth of Nanoparticles and Nanowires on Si(001) J.H.G.Owen* and K.Miki International Center for Young Scientists (ICYS) and Nanomaterials Laboratory (NML), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba. Ibaraki 305-0044, Japan. *[email protected], www: http://homepage.mac.com/jhgowen/research/research.html ABSTRACT Long, straight self-assembled nanolines of Bismuth are used as an atomic-scale nonlithographic template for the deposition of different metals. The Bi nanolines are 15 Å wide and can grow to lengths exceeding 1µm, limited only by the substrate terraces. We describe the method of formation of these templates, and demonstrate strongly preferential adsorption of different metals. We observe both wetting behaviour, in which elongated metal islands form nanowires along the template, and nonwetting behaviour, in which arrays of metal clusters of uniform size are produced. INTRODUCTION The next generation of electronic devices is likely to be based on nanometre-scale components, such as switchable molecules[1] between two perpendicular arrays of metallic contacts, as in the “crossbar” architecture[2]. For the foreseeable future, the fabrication of practical devices will require that these components be integrated into conventional silicon-based architectures, and hence arrangement of these components onto the Si(001) surface, and the interconnection of these components, is of great importance. Conventional lithographic techniques are currently reaching their limits at 90 nm, while electron-beam lithography[3] and nanoimprint lithography[4] can achieve linewidths of, at minimum, 5-10 nm. Even then, wires formed by metal deposition in this way are composed of a string of randomly-orientated metal crystals, with a grain size comparable to the wire's width, and thus are inherently nonuniform, and prone to failure. Direct-writing techniques based on scanning probes can, in principle, pick out single atoms to generate arrays of nanoclusters, and write highly-uniform lines one atom across[5-7], to make atomic-scale nanowires, but the writing process is impracticably slow. Nanoscale components can be fabricated ex-situ, and the challenge then is to arrange them on a surface. Metal nanoclusters, which have a variety of interesting magnetic and optical properties, can be made by a laser ablation process, with a time-of-flight mass spectrometer providing control over the size of the nanoclusters produced[8]. However, they will typically aggregate on deposition onto a surface, forming islands or adsorbing along step edges[9]. Carbon nanotubes[10] and semiconductor nanowires[11] can be arranged on a surface using microfluidic methods. Self-assembly processes are an attractive possibility for in-situ fabrication of nanostructures. Atomic-scale wires can be formed by step edge reconstruction on vicinal Si(111) surface after adsorption of metals such as Au[12]. Heteroepitaxial strain allows the growth of 0D systems as in III-V quantum dots, and by
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