title: Anisotropy in conductance of a quasi-one-dimensional metallic surface state measured by a square micro-four-point probe method.
abstract: We have devised a "square micro-four-point probe method" using an independently driven ultrahigh-vacuum four-tip scanning tunneling microscope, and succeeded for the first time to directly measure anisotropic electrical conductance of a single-atomic layer on a solid surface. A quasi-one-dimensional metal of a single-domain Si(111)4 x 1-In had a surface-state conductance along the metallic atom chains (sigma(axially)) to be 7.2(+/-0.6) x 10(-4) S/square at room temperature, which was larger than that in the perpendicular direction (sigma(radially)) by approximately 60 times. The sigma(axially) was consistently interpreted by a Boltzmann equation with the anisotropic surface-state band dispersion, while the sigma(radially) was dominated by a surface-space-charge-layer conductance.
authors.affiliation: Department of Physics, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Taizo
authors.initials: T
authors.lastname: Kanagawa
authors.forename: Rei
authors.initials: R
authors.lastname: Hobara
authors.forename: Iwao
authors.initials: I
authors.lastname: Matsuda
authors.forename: Takehiro
authors.initials: T
authors.lastname: Tanikawa
authors.forename: Akiko
authors.initials: A
authors.lastname: Natori
authors.forename: Shuji
authors.initials: S
authors.lastname: Hasegawa