Hopping Domain Wall Induced by Paired Adatoms on an Atomic Wire: $\mathrm{Si}(111)\mathrm{\text{\ensuremath{-}}}(5\ifmmode\times\else\texttimes\fi{}2)\mathrm{\text{\ensuremath{-}}}\mathrm{Au}$

Hopping Domain Wall Induced by Paired Adatoms on an Atomic Wire: $Si (111) − (5 \times 2) − Au$

Pil-Gyu Kang, Hojin Jeong, and Han Woong Yeom

Phys. Rev. Lett. 100, 146103 – Published 11 April 2008

Abstract

We observed an inhomogeneous fluctuation along one-dimensional atomic wires self-assembled on a Si(111) surface using scanning tunneling microscopy. The fluctuation exhibits dynamic behavior at room temperature and is observed only in a specific geometric condition; the spacing between two neighboring adatom defects is discommensurate with the wire lattice. Upon cooling, the dynamic fluctuation freezes to show the existence of an atomic-scale dislocation or domain wall induced by such “unfavorably” paired adatoms. The microscopic characteristics of the dynamic fluctuation are explained in terms of a hopping solitonic domain wall, and a local potential for this motion imposed by the adatoms is quantified.

Received 15 October 2007

DOI:https://doi.org/10.1103/PhysRevLett.100.146103

Authors & Affiliations

Pil-Gyu Kang, Hojin Jeong, and Han Woong Yeom^*

Institute of Physics and Applied Physics and Center for Atomic Wires and Layers, Yonsei University, Seoul 120-749, Korea

^*yeom@yonsei.ac.kr

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Vol. 100, Iss. 14 — 11 April 2008

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Figure 1
(a) STM image ( $11 \times 14 {nm}^{2}$ ) of $Si (111) − (5 \times 2) − Au$ at RT and its close-ups in (b) empty and (c) filled states. Bias voltages are (a), (b) $+ 1.0$ and (c) $- 1.0 V$ and the tunneling current is 50 pA. (d) The schematics of one structure model [15], where large (yellow) and small (open) circles represent Au and Si atoms, respectively. Schematics of the characteristic features of the empty-state STM images are overlapped in the right. The $5 \times 2$ unit cell is depicted by boxes in (a) and (d).Reuse & Permissions
Figure 2
STM images (top) in (a) empty and (b) filled states and sequential line profiles (lower 4 curves) along dashed lines of the images, respectively. Bias voltages are (a) $+ 1.0 V$ and (c) $- 1.0 V$ and the tunneling current is 50 pA. Within the gray area, over $3 a_{0}$ from adatoms, the line profile is time dependent.Reuse & Permissions
Figure 3
Length distribution of the bare wire segments between two neighboring adatoms obtained from STM images (total 1836 Si adatoms are sampled). The distribution of the segment with a length of an even multiple of $a_{0}$ (solid circles) is fitted by a simple exponential function (solid line) of Poisson behavior except for a rarely observed one of $2 a_{0}$ length. The segments with a length of an odd multiple of $a_{0}$ feature the DF without an exception, as shown in STM images ( $+ 1.0 V$ , 50 pA).Reuse & Permissions
Figure 4
(a) STM image ( $9.5 \times 10.5 {nm}^{2}$ ) of $Si (111) − (5 \times 2) − Au$ at 25 K. The dual-bias scanned STM images [empty-state in (b) and filled-state in (c)] for an odd-length ( $19 a_{0}$ ) segment include a new atomic feature. (d) Schematics of the empty-state STM image with two possible positions of the domain wall (the center of the strongly bright contrast in empty-state and the dark trench in filled-state), $13.5 a_{0}$ and $15.5 a_{0}$ from the left adatom. Large (yellow) circles represent Si adatoms. (e) An empty-state STM image for a $19 a_{0}$ segment at RT. Bias voltages are (a),(b),(e) $+ 1.0 V$ and (c) $- 1.0 V$ and the tunneling current is 50 pA.Reuse & Permissions
Figure 5
(a) Time-dependent height at the centers of a few oval protrusions along dashed lines of Fig. 4e at RT after filtering small amplitude noise out. (b) The simple potential energy assumed for the domain wall hopping motion with the hopping events at a specific site. (c) (Upper) The occupation probability (both experiment and simulation) and (lower) the relative energy deduced as a function of distance from the center of the segments. The experimental data were taken for three different segments with lengths of 15, 19, and $27 a_{0}$ , but only one ( $19 a_{0}$ ) is shown. The gray solid line represents the envelope (apparent height) along the center of the DF in the time-averaged STM image.Reuse & Permissions

Physical Review Letters

Hopping Domain Wall Induced by Paired Adatoms on an Atomic Wire: Si(111)−(5×2)−Au

Pil-Gyu Kang, Hojin Jeong, and Han Woong Yeom

Phys. Rev. Lett. 100, 146103 – Published 11 April 2008

Abstract

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Hopping Domain Wall Induced by Paired Adatoms on an Atomic Wire: $Si (111) − (5 \times 2) − Au$