Structure and Electrical Properties of Atomic-scale In-Bi Nanowire Arrays
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1080-O03-06
Structure and Electrical Properties of Atomic-scale In-Bi Nanowire Arrays James Hugh Gervase Owen1,2, Osamu Kubo2, and David Bowler2,3 1 Dept. de Physique de la Matière Condensée, Université de Genève, 24 Quai Ernest Ansermet, Genève, 1211, Switzerland 2 National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan 3 London Centre for Nanotechnology and Dept. of Physics and Astronomy, University College London, Gower St, London, WC1E 6BT, United Kingdom The 1-nm-wide Bi nanoline has been proposed as a possible template for the growth of very-high-density arrays of atomic-scale nanowires, grown epitaxially on the technologically important Si(001) surface. Indium reacts with the Bi dimers, forming a unique zigzag atomic chain structure. Simulations of the appearance in STM of the lowest-energy isomer of this structure match experimental filled-states images. Calculation of the LDOS for the single-layer islands, finds that the nanowires are semiconducting, with a band gap smaller than that of the substrate, in good agreement with STS. A delocalised LUMO state is created, which may provide a conduction pathway along the nanowire. We have performed dual-probe STM conduction measurements along the In-Bi nanowires to test this prediction. INTRODUCTION Although there are many ways to produce single-nm nanowires, their arrangement onto a surface remains a significant challenge. Self-assembly of an array of nanowires on a surface is one solution. The Bi nanoline [1,2], has been proposed as a possible template for the growth of very-high-density arrays of atomic-scale nanowires, grown epitaxially on the technologically important Si(001) surface. However, although structurally very suitable as a nanowire – it is always 1.54 nm wide, can grow to lengths well over 1µm, and has no kinks and virtually no defects – it has no delocalized electronic states, and a band gap larger than the surrounding Si surface [3,4]. Therefore we have proposed that it might be used as a template for the formation of nanowires of other materials. Deposited metal atoms will adsorb onto background silicon dimers rather than the Bi nanoline[5]. However, after passivation of the background silicon dangling bonds with hydrogen or ammonia, the nanoline becomes a preferential adsorption site for many different metals. The H passivation layer blocks direct interaction between metal atoms and the Si substrate, even for otherwise reactive metals such as Ni and Co[6, 7]. On the template, therefore, the metal atoms remain on the surface, attacking Bi-Si bonds, or the Si-Si rebonding within the top layer of the nanoline.
Over the last three years, considerable knowledge of the deposition of Al, In, Ag, Au, Pt, Pd, Fe and Co has been accumulated [8]: In most cases, these atoms form clusters on the nanolines as for Ag [9], only Group III metals of those studied so far form flat epitaxial islands[10,11]. Indium (and Al) reacts with the Bi dimers, forming a semiconducting atomic chain with a unique structure, described previously[10,11],
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