In Search of Metallic Nanowires on Si(001)
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J18.29.1
In Search of Metallic Nanowires on Si(001) Inder P. Batra, Bikash C. Gupta and Aakanksha A. Panjwani Department of Physics, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7059, USA ABSTRACT Electronic structures of several atomic wires of metals like Al, Ga and In on hydrogen passivated Si(001):1×1 surface have been examined in search of nanowires with metallic properties. The dihydrogenated Si(001) is patterned by depassivating only one row of Si atoms along the [1ī0] direction. Various structures of adsorbed metals and their electronic properties have been studied. With our present effort it was observed that Al and Ga nanowire configurations with metallic property are unstable towards the formation of buckled metal dimers leading to semiconducting behaviour. However, indium atomic wire is close to the metallic limit and shows marginal preference for the formation of symmetric dimers. It is encouraging that In metallic wires on a patterned dihydrogenated Si(001) may be realized. INTRODUCTION Tremendous current interest in nanotechnology has led to the investigations of atomic dimension wires with metallicity. Our ability to manipulate atoms, placing them at will on different surface sites to fabricate atomic-scale structures has led to further investigations of electronic and transport properties of free and supported nanowires [1-10]. The placement of trivalent atoms (Al, Ga and In) on Si(001) can lead to the formation of low-dimensional structures exhibiting significant new electronic properties. One can easily compute the electronic properties of free-standing nanowires. For this, one computes the total energy to determine the possible stable structures. Such calculations have been carried out for nanowires consisting of a wide variety of atoms e.g. K, Al, Cu, Ni, Au and Si [1-5]. A general finding is that a zig-zag structure in the form of an equilateral triangle is the most stable. In general, free-standing nanowires tend to be metallic (finite density of states at the Fermi level) but these wires in practice have to be supported. Silicon is the most widely used substrate for practical applications and the low index surfaces; Si(001) is the surface of choice. It is desireable to investigate the electronic properties at the lowest possible metal coverages to from metallic nanowires. Thus the study of metals like Al, Ga and In on Si(001) at sub-monolayer coverages becomes significant. The interaction of metal nanowires with substrate can significantly alter the electronic properties. There has been a continual quest [6-10] for conducting wires of atomic widths deposited on Si(001):2×1 with and without H-passivation. For example, as early as in 1989, Batra [6] identified a metastable zig-zag atomic chain of Al on Si(001):2×1 with semi-metallic properties. Recent attempts have shifted towards H-passivated Si(001):2×1 largely due to the pioneering efforts of Watanabe and coworkers [7-8]. Here H atoms are removed from a selected row from an otherwise fully passivated su
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