Nanoline Templating of Metals and the Underlying Surface Processes
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0961-O15-07
Nanoline Templating of Metals and the Underlying Surface Processes James Hugh Gervase Owen1 and Kazushi Miki2 1 International Centre for Young Scientists, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0051, Japan 2 Nanomaterials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 3050051, Japan Bi nanolines, which self-assemble on Si(001), have been used as templates for the deposition of a variety of metals: noble metals, transition metals, and Gr. III metals. The different metals show a variety of behaviours on this surface, from a strong interaction in the case of In and Al, to a very weak interaction in the case of Ag. The different phenomena are discussed in terms of a balance of different competing surface mechanisms, such as diffusion and nucleation, which drives the observed behaviours. INTRODUCTION Self-assembled nanoscale templates have been proposed as an alternative to conventional lithographic techniques, which reach their limits at around 50 nm, or to direct-writing techniques based on scanning probes[1] or electron beams[2], which do not offer scalability. The Bi/Si(001) system[3,4] has many features appropriate for a nanoscale template[5,6]. The spacing of the nanolines is random, but can be varied to some extent by control of the growth conditions, or choice of a vicinal wafer. The nanolines have a constant width, 15 Å, unlike the silicide nanowires[7]. They have virtually no defects or kinks, and can grow more than 500 nm in length, limited only by the flatness of the Si wafer. The chemical difference between the Bi and the surrounding Si, and the remarkable passivity of the Bi dimers, allow for the passivation of the substrate with H[8], leaving the Bi nanolines clean and thus forming a template. The use of a selfassembled nanoline as a nanoscale template requires that the deposited material adsorbs preferentially onto the nanoline[9]. Alternatively, in the scheme described here, the background is passivated using a suitable masking material (hydrogen or ammonia), making the nanoline into a more attractive adsorption site. In order to test the principle of nanoline templating, a wide range of different metals have been deposited onto Bi nanoline templates: noble metals, Au, Ag, Pd; transition metals, Fe, Co; and Gr. III metals, Al, In. Two of these, Ag and In, have been the subject of detailed studies. Indium was found to interact strongly with the Bi dimers of the nanoline, breaking the Bi-Bi bonds and the Bi-Si bonds, and forming a unique In-Bi 1-D atomic chain structure[5,10], while Ag interacted only weakly with the Bi nanolines, forming arrays of nanoclusters, with a peak size of around 6 Å[6,11]. These two behaviours might be described as ‘wetting’ and ‘non-wetting’, and hence form the extremes of templating behaviour. In this paper, we describe the behaviour of all the above metals on the Bi nanoline templates, and draw out the common growth mechanisms. The various processes which are involved in nanoline templating are shown schemati
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