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Understanding electronic and ionic transport across interfaces is crucial for designing high-performance electric devices. The adjustment of work functions is critical for band alignment at the interfaces of metals and semiconductors. However, the electronic structures at the interfaces of metals and mixed conductors, which conduct both electrons and ions, remain poorly understood. This study reveals that a Schottky barrier is present at the interface of the Nb-doped SrTiO3 metal and a LiCoO2 mixed conductor and that the interfacial resistance can be tuned by inserting an electric dipole layer. The interfacial resistance significantly decreased (by more than 5 orders of magnitude) upon the insertion of a 1 nm thick insulating LaAlO3 layer at the interface. We apply these techniques to solid-state lithium batteries and demonstrate that tuning the electronic energy band alignment by interfacial engineering is applicable to the interfaces of metals and mixed conductors. These results highlight the importance of designing positive electrode and current collector interfaces for solid-state lithium batteries with high power density.

The van der Waals (vdW) materials with low dimensions have been extensively studied as a platform to generate exotic quantum properties. Advancing this view, a great deal of attention is currently paid to topological quantum materials with vdW structures. Here, we provide a new concept of designing topological materials by the vdW stacking of quantum spin Hall insulators (QSHIs). Most interestingly, a slight shift of inversion center in the unit cell caused by a modification of stacking is found to induce the topological variation from a trivial insulator to a higher-order topological insulator (HOTI). Based on that, we present the first experimental realization of a HOTI by investigating a bismuth bromide Bi4Br4 with angle-resolved photoemission spectroscopy (ARPES). The unique feature in bismuth halides capable of selecting various topology only by differently stacking chains, combined with the great advantage of the vdW structure, offers a fascinating playground for engineering topologically non-trivial edge-states toward future spintronics applications.

The origin of electrical resistance at the interface between the positive electrode and solid electrolyte of an all-solid-state Li battery has not been fully determined. It is well known that the interface resistance increases when the electrode surface is exposed to air. However, an effective method of reducing this resistance has not been developed. This report demonstrates that drastic reduction of the resistance is achievable by annealing the entire battery cell. Exposing the LiCoO

A multi-beam X-ray optics that can image a sample from different directions in a large angular range simultaneously without sample rotation is reported. It consists of 28 thin silicon crystals that are arranged in a σ-polarization diffraction geometry so that the diffracted X-rays from an incident white synchrotron radiation beam pass through the sample. A tomogram of a simple test sample was calculated from projection images recorded with the optics, showing that an alignment accuracy sufficient for X-ray tomography can be achieved.

A multi-beam optics consisting of curved crystals with blades for a white synchrotron X-ray beam from a bending magnet was developed, and millisecond-order temporal-resolution X-ray tomography with a voxel size of 20 μm was successfully realized without sample rotation. The multi-beam optics opens the spatio-temporal frontier of X-ray tomography for unrepeatable and nonequilibrium systems and is expected to be applied to various fields in materials and life sciences.

The major breakthroughs in understanding of topological materials over the past decade were all triggered by the discovery of the Z2-type topological insulator-a type of material that is insulating in its interior but allows electron flow on its surface. In three dimensions, a topological insulator is classified as either 'strong' or 'weak'1,2, and experimental confirmations of the strong topological insulator rapidly followed theoretical predictions3-5. By contrast, the weak topological insulator (WTI) has so far eluded experimental verification, because the topological surface states emerge only on particular side surfaces, which are typically undetectable in real three-dimensional crystals6-10. Here we provide experimental evidence for the WTI state in a bismuth iodide, β-Bi4I4. Notably, the crystal has naturally cleavable top and side planes-stacked via van der Waals forces-which have long been desirable for the experimental realization of the WTI state11,12. As a definitive signature of this state, we find a quasi-one-dimensional Dirac topological surface state at the side surface (the (100) plane), while the top surface (the (001) plane) is topologically dark with an absence of topological surface states. We also find that a crystal transition from the β-phase to the α-phase drives a topological phase transition from a nontrivial WTI to a normal insulator at roughly room temperature. The weak topological phase-viewed as quantum spin Hall insulators stacked three-dimensionally13,14-will lay a foundation for technology that benefits from highly directional, dense spin currents that are protected against backscattering.

A setup for fast multi-energy X-ray tomography is reported. Projection images of a sample using X-ray beams with energies below and above an absorption edge of an element of interest were recorded simultaneously with a multi-beam detector. The sample was rotated to obtain a data set for tomography. In a proof-of-principle multi-energy tomography experiment with a measurement time of 0.25 s, the neighboring elements Ag and Pd could be clearly distinguished.

Solid-state lithium (Li) batteries using spinel-oxide electrode materials such as LiNi0.5Mn1.5O4 are promising power supplies for mobile devices and electric vehicles. Here, we demonstrate stable b...

This paper presents polarity reversal of the charge carrier in tetragonal TiH${}_{x}$ ($x$ = 1.6-2.0) at low temperatures. The volume change leads to the change in the aspect ratio of the tetragonal lattice, altering the contribution of electron and hole at the Fermi surface and the sign of the Hall coefficient.

Materials that possess nontrivial topology and magnetism is known to exhibit exotic quantum phenomena such as the quantum anomalous Hall effect. Here, we fabricate a novel magnetic topological heterostructure Mn4Bi2Te7/Bi2Te3 where multiple magnetic layers are inserted into the topmost quintuple layer of the original topological insulator Bi2Te3. A massive Dirac cone (DC) with a gap of 40–75 meV at 16 K is observed. By tracing the temperature evolution, this gap is shown to gradually decrease with increasing temperature and a blunt transition from a massive to a massless DC occurs around 200–250 K. Structural analysis shows that the samples also contain MnBi2Te4/Bi2Te3. Magnetic measurements show that there are two distinct Mn components in the system that corresponds to the two heterostructures; MnBi2Te4/Bi2Te3 is paramagnetic at 6 K while Mn4Bi2Te7/Bi2Te3 is ferromagnetic with a negative hysteresis (critical temperature ~20 K). This novel heterostructure is potentially important for future device applications., T.H. was supported by JSPS KAKENHI Grant Number 18H03877, the Murata Science Foundation (No. H30-084), the Asahi Glass Foundation, Tokyo Tech. Challenging Research Award, and the Iketani Science and Technology Foundation (No. 0321083-A). M.K. was supported by the Spintronics Research Network of Japan (Spin-RNJ). The ARPES measurements were performed under the UVSOR proposal Nos. 29-837, 30-571, 30-860 and the SARPES measurements were performed under the HiSOR proposal No. 16BG001. The XMCD measurements were performed at JAEA beamline BL-23SU in SPring-8 (Proposal No. 2018B3843) and also at PF-KEK (PF PAC No. 17P006). The work at SPring-8 was performed under the Shared Use Program of JAEA Facilities (Proposal No. 2018B-E21) with the approval of Nanotechnology Platform project supported by the Ministry of Education, Culture, Sports, Science and Technology (Proposal No. A-18-AE-0039). The support by Tomsk State University competitiveness improvement program (No. 8.1.01.2018), the Saint Petersburg State University (Project ID 51126254), the Russian Science Foundation (Grant No. 18-12-00169) and the Government research assignment for ISPMS SB RAS, project No. III.23.2.9 is gratefully acknowledged. M.M.O. acknowledges the support by Spanish Ministerio de Ciencia e Innovación (Grant No. PID2019-103910GB-I00).

Additional information about the design of the multi-beam optical elements and the 3D reconstruction; transmittance images; tomogram of the tungsten wire sample; resolution

Using synchrotron surface X-ray diffraction, we investigated the atomic structures of the interfaces of a solid electrolyte (Li3PO4) and electrode (LiCoO2). We prepared two types of interfaces with high and low interface resistances; the low-resistance interface exhibited a flat and well-ordered atomic arrangement at the electrode surface, whereas the high-resistance interface showed a disordered interface. These results indicate that the crystallinity of LiCoO2 at the interface has a significant impact on interface resistance. Furthermore, we reveal that the migration of Li ions along the interface and into grain boundaries and antiphase domain boundaries is a critical factor reducing interface resistance.

Pentacene, one of the most studied organic semiconductors, crystallizes in different structures depending on the growth conditions. The structure is usually classified into one of the three polymorphs, the so-called single crystal phase, bulk phase, and thin film phase. In this report, we show that epitaxial crystalline pentacene thin films on Bi(0001), which have been believed to be the bulk phase, have a distinct molecular orientation in the same crystal lattice as the bulk phase. The calculated band structures are clearly different from those of the bulk phase and show an excellent agreement with the experimental data for the bandwidth.(21) A tight-binding model indicates that one of the two main intermolecular interactions is almost identical to that of the single crystal phase, while the other one is almost identical to that of the bulk phase. The results implies that polymorphs in the same crystal lattice can be formed by a molecular-substrate interaction.

The structure of the Si(111)- 21 × 21 -(Ag + Au) surface is studied using surface X-ray diffraction and fluorescence yield measurements. The fluorescence measurements indicate that there are three gold atoms in the unit cell. From the analysis of the diffraction data, it is shown that the gold atoms form a trimer with an interatomic distance of 2.8 A and that the sides of the trimer are almost parallel to the Si(111)-1 × 1 fundamental vectors, similar to that in the Si(111)- 3 × 3 -Au structure.

Determining the atomic structure across electrolyte–electrode interfaces with a sufficient temporal resolution is crucial to understanding how electrochemical reactions proceed. Surface X-ray diffraction is a well-established method for determining interface structures at the atomic scale. However, existing measurement methods are often incapable of quantifying time-dependent structural changes during electrochemical processes because acquiring a diffraction rod profile sufficient for structure determination usually takes a longer time than the rate of the structural changes. This report demonstrates that the wavelength-dispersive method, which can acquire a range of the diffraction rod profile at once, is capable of the time-resolved analysis of electrochemical dynamics on a time scale of seconds and less, using electrochemical reactions on Pt(111) electrode surface as examples. In the case of the electrochemical oxidation of methanol, the quantitative analysis of the transient vertical displacement of t...

An X-ray reflectometer, using a laboratory X-ray source, that can measure the specular X-ray reflectivity curve with a time resolution of 10 s or less was developed. Low reflectivities can be measured accurately because the background can be subtracted from the signal., An X-ray reflectometer using a laboratory X-ray source for quick measurements of the specular X-ray reflectivity curve is presented. It uses a bent–twisted crystal to monochromatize and focus the diverging X-rays (Cu Kα1) from a laboratory point source onto the sample. The reflected X-rays are recorded with a two-dimensional detector. Reflectivity curves can be measured without rotating the sample, detector or X-ray source during measurements. The instrument can separate the specularly reflected X-rays from the diffuse scattering background, so low reflectivities can be measured accurately. For a gold thin film on silicon, the reflectivity down to the order of 10−6 was obtained with a measurement time of 100 s and that down to 10−5 with a measurement time of 10 s. Reflectivity curves of a silicon wafer and a liquid ethylene glycol surface are shown as well. Time-resolved measurements of a TiO2 surface during UV irradiation are also reported.

The surface structural change of the rutile–TiO2(110) during the UV-light-induced wettability conversion was studied with atomic resolution using the X-ray crystal truncation rod (CTR) scattering method. We confirmed that an atomic-scale surface structural change occurs during the UV-light irradiation by using time-resolved CTR profile measurements. Quantitative structural analysis on static CTR data, which were measured before and after the conversion, shows that on the hydrophobic (nonphotoirradiated) surface the five-coordinated Ti atom is covered with an O atom likely in a form of water molecule, for which the bridging O atom is not likely hydroxylated, and that large atomic positional fluctuations occur on the hydrophilic (photoirradiated) surface possibly due to the photoinduced proton transfer from the intact water molecule to the bridging oxygen atom. The resulting surface OH groups might be active sites for water adsorption to make the surface superhydrophilic.

We have investigated the atomic structure of the “multilayer silicene” grown on the Ag(111) single crystal surface by using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). We measured the intensity of the LEED spot as a function of the incident electron energy (I–V curve) and analyzed the I–V curve using a dynamical LEED theory. We have found that the Si(111)( 3 × 3 )-Ag model well reproduces the I–V curve whereas the models consisting of the honeycomb structure of Si do not. The bias dependence of the STM image of multilayer silicene agrees with that of the Si(111)( 3 × 3 )-Ag reconstructed surface. Consequently, we have concluded that the multilayer silicene grown on Ag(111) is identical to the Si(111)( 3 × 3 )-Ag reconstructed structure.

We present a high-speed multi-beam X-ray imaging realized using a detector system and the recently developed multi-beam X-ray optics [Voegeli et al., Optica 7, 514 (2020)]. The detector utilized optical relay lenses and mirrors for connecting four scintillator screens to a CMOS camera, enabling the high-speed simultaneous acquisition of multiple projection images. We successfully acquired nine projection images in 0.5 ms with a spatial resolution of 70 μm. Dynamical behaviors of a light-bulb filament and a living ladybug were captured with a temporal resolution of 0.5 ms, demonstrating the potential for high-speed and high-spatial-resolution 4D X-ray tomography.

Twisted bilayer graphene (TBG), in which two monolayer graphene are stacked with an in-plane rotation angle, has recently become a hot topic due to unique electronic structures. TBG is normally produced in air by the tear-and-stack method of mechanical exfoliation and transferring graphene flakes, by which a sizable, millimeter-order area, and importantly clean interface between layers are hard to obtain. In this study, we resolved these problems by directly transferring the easy-to-exfoliate CVD-grown graphene on SiC substrate to graphene in a high vacuum without using any transfer assisting medium and observed electronic band modulations due to the strong interlayer coupling.

X-ray tomography is a powerful method for visualizing the three-dimensional structure of an object with a high spatial resolution. Conventional time-resolved x-ray tomography using synchrotron radiation requires fast rotation of the object, which limits the temporal resolution and hampers its application to, e.g., fluids and in vivo observation of living beings. Here, we present a multibeam x-ray optical system for high-speed 4D tomography, which can obtain projection images of a sample in a wide angular range simultaneously. It consists of about three dozen single-crystalline blades oriented with different angles to the incident beam, which each Bragg-reflect a part of the incident x-rays in the direction of the sample position. Thirty-two projection images covering an angular range of more than ± 70 ∘ were obtained without moving the sample or optical system, with an exposure time of 1 ms. The data set was successfully used for reconstructing the three-dimensional structure of two test samples. The optical system provides the basis for realizing millisecond time resolution x-ray tomography of nonrepeatable phenomena, and can be expected to be useful for other applications as well, for example, for time-resolved element-specific imaging.

Solid-state Li batteries that use spinel LiNi0.5Mn1.5O4 as a positive electrode are promising energy-storage devices for portable electronics and electric vehicles. For practical applications of su...

Low-energy electron diffraction (LEED) provides structural information of crystalline surfaces. The discovery of LEED goes back to the Davisson and Germer experiments in 1927. Later on, LEED evolved to a surface analysis tool in the 1960s, mainly due to the rapid evolution of ultra-high vacuum techniques and the efficient detection techniques such as a screen display LEED system. The successful theory of LEED was established in the late 1960s and early 1970s. Nowadays LEED is used as the common tool for the surface structure analysis. It is still developing in new directions such as ultrafast structural dynamics. An overview of LEED, from fundamental principles to recent advances, is presented.

X-ray CTR scattering is a rod-shaped X-ray scattering appearing in the direction perpendicular to a crystalline surface (Fig. 130.1a) (Feidenhans’l in Surf Sci Rep 10:105–188, 1989[1]). Sharp truncation of the electron density of crystalline materials at the surface results in the CTRs.

Inducing magnetism into topological insulators is intriguing for utilizing exotic phenomena such as the quantum anomalous Hall effect (QAHE) for technological applications. While most studies have focused on doping magnetic impurities to open a gap at the surface-state Dirac point, many undesirable effects have been reported to appear in some cases that makes it difficult to determine whether the gap opening is due to the time-reversal symmetry breaking or not. Furthermore, the realization of the QAHE has been limited to low temperatures. Here we have succeeded in generating a massive Dirac cone in a MnBiSe/BiSe heterostructure, which was fabricated by self-assembling a MnBiSe layer on top of the BiSe surface as a result of the codeposition of Mn and Se. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the fabricated MnBiSe/BiSe heterostructure shows ferromagnetism up to room temperature and a clear Dirac cone gap opening of ∼100 meV without any other significant changes in the rest of the band structure. It can be considered as a result of the direct interaction of the surface Dirac cone and the magnetic layer rather than a magnetic proximity effect. This spontaneously formed self-assembled heterostructure with a massive Dirac spectrum, characterized by a nontrivial Chern number C = -1, has a potential to realize the QAHE at significantly higher temperatures than reported up to now and can serve as a platform for developing future >topotronics> devices., This work has been supported by Grants-In-Aid from Japan Society for the Promotion of Science (Nos. 15H05453, 16K13683, 19340078, and 23244066), the Toray Science Foundation, the Basque Country Government, Departamento de Educacion, Universidades e Investigacion (Grant No. IT-756-13), the Spanish Ministry of Science and Innovation (Grant Nos. FIS2010-19609-C02-01, FIS2013- 48286-C02-02-P, and FIS2013-48286-C02-01-P), the Tomsk State University Academic D.I. Mendeleev Fund Program (Grant No. 8.1.05.2015), and Saint Petersburg State University (project 15.61.202.2015). The ARPES experiments were performed under the UVSOR Proposal Nos. 25-808, 26-531, 27-533, 28-526, and S-15-MS-0034, and the SARPES experiments were performed under the HiSOR Proposal No. 15-A14. The XMCD measurements were performed under the UVSOR proposal number S-16-MS-2017. The LEED measurements were performed under the ISSP Proposal number H17-A250. The SQUID measurements were performed using facilities of the Cryogenic Research Center, the University of Tokyo.

We have investigated the structure of silicene forming into the (4 × 4) superstructure on Ag(111) by using the low-energy electron diffraction. We found that Si atoms form a buckled honeycomb structure on Ag(111), which fully matches with the structure optimized with the density functional theory calculations. The Si Si bond lengths range from 2.29 to 2.31 A, which are close to the upper limit of Si Si double bond and shorter than the bond length in the bulk diamond structure. The buckling in the silicene layer causes the displacement of Ag atoms in the first substrate layer with 0.3 A perpendicular to the surface, which is a compelling evidence of the strong couplings at the interface between the silicene and the substrate.

A totally anisotropic peculiar Rashba-Bychkov (RB) splitting of electronic bands was found on the Tl/Si(110)-(1×1) surface with C_{1h} symmetry by angle- and spin-resolved photoelectron spectroscopy and first-principles theoretical calculation. The constant energy contour of the upper branch of the RB split band has a warped elliptical shape centered at a k point located between Γ[over ¯] and the edge of the surface Brillouin zone, i.e., at a point without time-reversal symmetry. The spin-polarization vector of this state is in-plane and points almost the same direction along the whole elliptic contour. This novel nonvortical RB spin structure is confirmed as a general phenomenon originating from the C_{1h} symmetry of the surface.

Silicon carbide (SiC) has the potential to serve as an extremely important semiconductor material in next-generation electronics. However, a major stumbling block for its practical application has been the preparation of high-quality interfaces with insulating materials. We have discovered a way to prepare a 0.6-nm thick silicon oxynitride (SiON) layer having an epitaxial interface with the SiC(0 0 0 1) surface. This review article focuses on the atomic and electronic structures of the SiON layer. Based on various experimental techniques and theoretical studies, we understand the SiON layer to be a complex but unique hetero-double-layered structure: a topmost Si 2 O 5 monolayer is connected to an interfacial Si 2 N 3 monolayer via Si–O–Si linear bridge bonds. The most striking feature of the SiON structure is that there is no dangling bond in the unit cell, rendering it remarkably robust to air exposure. Stability and processes for the formation of the SiON on SiC(0 0 0 1) are discussed on the basis of the structural features obtained. Scanning tunneling spectroscopy measurements of the SiON exhibit a bulk SiO 2 -like band gap of ∼9 eV as well as first-principles calculations. The remarkable band-gap opening of such a thin insulator film is investigated by the combination of element-specific soft x-ray absorption/emission spectroscopies and by first-principles calculations, revealing the Si 2 N 3 and Si 2 O 5 monolayers to have band gaps of corresponding bulk-like values. Promising applications of the SiON to electronic devices are discussed.

The epitaxial silicon oxynitride (SiON) layer grown on a 6H-SiC(0001) surface is studied with core level photoemission spectroscopy. Si 2p spectra show three spectral components other than the bulk one. Chemical shifts and emission angle dependence of these components are well explained within a framework of a determined structure model of the SiON layer.

Atomic and valence-band electronic structures of a recently discovered epitaxial silicon oxynitride (SiON) layer on a 6H-SiC(0001) surface were investigated with x-ray diffraction (XRD) and angle-resolved photoemission spectroscopy (ARPES). The atomic structure optimized by XRD analysis well agrees with a previous low-energy electron diffraction analysis and a first-principles calculation. Band dispersions of surface states observed by ARPES can be explained by the previous calculation. Interface states intrinsic to the SiON layer were not observed above the valence-band maximum of SiC, but a diffuse, non-dispersive state was found by ARPES. Its origin is suggested to be a by-product of graphite-like clusters formed on the SiON layer during heat treatment.

The recent developments in synchrotron optics, X-ray detectors, and data analysis algorithms have enhanced the capability of the surface X-ray diffraction technique. This technique has been used to clarify the atomic arrangement around surfaces in a non-contact and nondestructive manner. An overview of surface X-ray diffraction, from the historical development to recent topics, is presented. In the early stage of this technique, surface reconstructions of simple semiconductors or metals were studied. Currently, the surface or interface structures of complicated functional materials are examined with sub-A resolution. As examples, the surface structure determination of organic semiconductors and of a one-dimensional structure on silicon are presented. A new frontier is time-resolved interfacial structure analysis. A recent observation of the structure and dynamics of the electric double layer of ionic liquids, and an investigation of the structural evolution in the wettability transition on a TiO2 surface ...

The atomic structures of the Bi/Si(111)-( 3 × 3 ) reconstructed surfaces obtained at different adsorbate coverages were studied by dynamical low-energy electron diffraction (LEED) I–V analysis. The experimentally obtained I–V curves of the β-Bi/Si(111)-( 3 × 3 ) surface, which is formed by a Bi coverage of 1 ML, showed good agreement with the curves calculated for the milk stool model, a model proposed in the literature. In contrast to this result, the I–V curves of the α-phase obtained at a coverage of 1/3 ML do not agree with those reported in early LEED studies. We found that the I–V curves reported in the former LEED studies resemble closely to the results obtained for the surface on which the β and α-phases coexist. Based on the obtained I–V curves, we propose a more reliable structural model for the α-phase, and present the way to determine the presence of a high quality α-phase by using LEED.

The adsorption of calcium (Ca) atoms on a Cu(0 0 1) surface has been studied by low-energy electron diffraction (LEED) at 130, 300 and 400 K. It is found that a (4 × 4) was the only LEED pattern appeared at 400 K while a quasi-hexagonal structure was formed in a wide range of submonolayer coverage at 130 K. At 300 K, the (4 × 4) LEED spots were broad and weak. The (4 × 4) structure formed at 400 K was determined by a tensor LEED I–V analysis. It is a new-type of surface alloys consisting of five substitutional Ca atoms, nine surface Cu atoms, and two atomic vacancies in the unit cell. In spite of a quite large size-difference between Ca (3.94 A) and Cu (2.55 A) atoms, all Ca atoms are located at the substitutional sites. Among surface alloys so far reported, the atomic size ratio between Cu and Ca in the (4 × 4), 1.54, is the largest. Optimized structural parameters reveal that large lateral displacements of surface Cu atoms, being enabled by the appearance of the vacancies, allow the formation of the (4 × 4) structure.

An X-ray holographic method that reconstructs a single layer of atoms at the interface between ultra-thin film and substrate crystal is studied. We applied the method to the analysis of the interface structure of iron-silicide grown on the Si(111) surface, the structure of which is considered to be the CsCl-type FeSi. First we confirmed by simulations that the method is useful to discriminate whether an additional layer at the interface exists or not, using calculated X-ray intensities. Next we applied the method to the analysis of experimental data obtained for Si(111)-2×2-Fe. The result indicated the existence of the interface atoms, corresponding to the B8 model for CsCl-type FeSi. [DOI: 10.1380/ejssnt.2009.525]

When gold is deposited onto the Si(553) surface, a highly ordered surface with a quasi-one-dimensional electronic structure can be prepared. This Si(553)-Au surface was investigated by surface X-ray diffraction to determine the surface structure. A structure model was constructed from the Patterson function of the experimental diffracted intensities. There is one gold atom in the primitive unit cell. It substitutes for a top-layer silicon atom on the terraces. The silicon atoms near the step edge reconstruct to form a honey-comb chain. [DOI: 10.1380/ejssnt.2009.533]

The structure of buried Si(1 1 1)-5 × 2-Au capped with amorphous Si was investigated using surface X-ray diffraction. It was found that the 5 × 2 structural periodicity is kept under the amorphous Si from the in-plane measurement. Furthermore, the intensity variation along the fractional-order rod indicates that Au atoms are located almost on the same plane.