Photon Factory Activity Report 2005 #23Part B (2006)
Surface and Interface

15B2/2003S2-001

Structural study of buried Si(111)-5×2-Au by GIXD
Takehiro NOJIMA1. Ryuji YOSHIDA1, Masuaki MATSUMOTO2, Daisuke ARAI1,
1
1
Mitsuhiro HASHIMOTO ,Toshio TAKAHASHI* ,2
3Tatsuo OKANO , Koichi AKIMOTO ,444Hiroshi SUGIYAMA , Xiaowei ZHANG , Hiroshi KAWATA
1
Insititute for Solid State Physics, University of Tokyo, Kashiwanoha, Chiba 277-8581, Japan
2Institure of Industrial Science, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8505
3Department of Quantum Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603
4KEK-PF, Tsukuba, Ibaraki 305-0801, Japan
Introduction
Nanostructuresorlow-dimensionalstructuresfabricated by metal adsorption on semiconductor surfaces
exhibit a variety of exotic physical phenomena and haveattracted considerable interest in recent years bothacademically and technologically[1]. We study theSi(111)-5×2-Au surface which is a superstructure induced
by a submonolayer of gold atoms on the Si(111) substrate,and has one dimensional structure of the Au atoms. The
precise arrangement of the surface atoms, however, has
not been determined yet. Hitherto three structural models
have been proposed; one is the model proposed by Marksand Plass[2] from the measurement of TED, and the othertwo models are proposed by Erwin[3] and Riikonen[4]based on the first principles calculations. Information on
this structure is important for understanding of surface
properties such as kinetics and electronic features.
The systems of metal on Si substrate are expected to beutilized industrially, such as quantum wiring. The
Si(111)-5×2-Au surface is one of the most studiedsurfaces because it has a chained structure of Au atoms.
From the view point of application, it is interesting toinvestigate whether such a one-dimensional structure is
kept when the Si(111)-5×2-Au surface is buried by thedeposition of amorphous material. The surface structure
is widely studied, but the research on its buried structure
is few.
Result and Discussion
In this study, the Si(111)-5×2-Au structure capped withsilicon was investigated by grazing incidence X-ray
diffraction (GIXD). We evaluated the most probablemodel as the interface structure by comparing theexperimental intensities with the calculated intensities forthe three models. The measurements of GIXD wereperformed at BL15-B2, where a six-circle X-ray
diffractometer is installed.
The sample of capped Si(111)-5×2-Au was prepared inan ultra high vacuum chamber. The thickness of thecapped layer was 35Å, which was controlled by a quartz
oscillator.
The intensity distribution of GIXD in two-dimensional
reciprocal space is shown in Fig. 1. We could get
fractional order spots peculiar to 5×2 construction. From

this result, the 5×2 superstructure, at least, is found to be
kept in the interface. However the number of observed
peaks was not enough to construct a new model. We
could not get weak peaks because of large backgrounds.
Least squares fitting analyses were used to compare theobserved intensities of fractional order spots shown in
Fig.1 with the calculated intensities for the three models.
The result indicated that the Erwin model is the mostprobable model at the interface.

Figure1. Intensity distribution of fractional order spots
observed for buried Si(111)-5×2-Au in GIXD.
References[1] I. Matsuda et al., Phys. Rev. B68 (2003) 195319.
[2] L. D. Marks, R. Plass, Phys. Rev. Lett. 75 (1995)
2172.
[3] S. C. Erwin et al., Phys. Rev. Lett. 91 (2003) 206101.
[4] S. Riikonen, D. Sanchez-Portal, Phys. Rev. B71(2005) 235423.
*ttaka@issp.u-tokyo.ac.jp

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