Paper SS2-MoM10
Gold Nanowire Formation on Si(110) Studied by SPM

Monday, October 15, 2007, 11:00 am, Room 611

Recently, nanostructures such as quantum dots and wires have been focused because of their exotic properties originated from the confinement of electrons, such as Coulomb blockade, charge density waves, spin density waves, etc. Several chain structures have been observed for Au/Si systems such as Au/Si(557).¹ For the Au/Si(110) system, Yamamoto reported a variety of surface phases using reflection high-energy electron diffraction (RHEED),² and only one phase, 2×5 structure, has been investigated in real space by scanning tunneling microscopy (STM).³ In this study, we aim to clarify the relationship between several surface phases of Au/Si(110) by high-resolution STM and atomic force microscopy (AFM). On the basis of high-resolution SPM images, we propose structural models for the phases and discuss the mechanism of nanowire formation. At 0.2-0.3 ML coverage, up-and-down structure of the clean Si(110) surface is destroyed, and 1×2 structure was clearly confirmed by FFT analysis, corresponding to nucleation of the nanowire. It is suggested that (110) facets develop in the Si(110) surface. The density of the nanowires increases with Au coverage to 0.25 ML. The spacing between the wires varies from 5a to 10a (a:unit length along the [-110] direction of Si(110)). At the coverage of 0.30 ML, it becomes constant at 5a, showing 2×5 surface phase. The nanowire consists of double rows with fluctuation character. The detailed atomistic processes of nanowire formation, as well as possible atomic structure models, are discussed.

¹ H. W. Yeom et al., Phys. Rev. B 72, 035323 (2005).
²Y. Yamamoto, Surf. Sci. 271, 407 (1992).
³J. L. McChesney et al., Phys. Rev. B 72, 035446 (2005).