M. Takahasi

Pseudomorphic growth of Pd monolayer on Au(111) electrode surface

Abstract The surface structure of a Pd layer electrochemically deposited onto Au(111) from PdCl 2− 4 solution has been studied by surface X-ray diffraction. By combining the measurements of the specular and non-specular rod profiles, both in-plane and out-of-plane structures have been determined. On the Au(111) electrode surface, Pd occupies the cubic closest packing site and forms a pseudomorphic smooth monolayer. The formation of the stable Pd overlayer is explained by the lifting of the surface reconstruction of the Au substrate. The Pdue5f8Au bond length at the Pd/Au(111) interface has been found to be 2.82xa0A, which is close to the sum of the atomic radii of Pd and Au in each bulk.

A novel spectroelectrochemical cell for in situ surface X-ray scattering measurements of single crystal disk electrodes

A newly designed spectroelectrochemical cell was constructed for surface X-ray scattering (SXS) to study single crystal electrodes. Electrochemical characteristics of a specific face of a single crystal electrode can be investigated in the meniscus mode, and SXS measurement can be easily carried out using the spectroelectrochemical cell. The usefulness of the present cell was demonstrated by studying the electrochemical deposition of thin Pd layers on Au(111) and Au(100) that require precise amounts of Pd deposits.

In situ monitoring of internal strain and height of InAs nanoislands grown on GaAs(001)

A monitoring technique for molecular beam epitaxial growth of InAs∕GaAs(001) nanoislands is presented. With the help of synchrotron radiation, x-ray diffraction intensity mapping in reciprocal space has been measured during growth. The internal strain distribution and height of the Stranski-Krastanov islands were monitored at a temporal resolution of 9.6s. The relaxation process of internal strain inside the Stranski-Krastanov islands displayed significant dependence on the growth temperature.

Coverage of the Cd Underpotential Deposited Layer Formed on an Au(111) Substrate Effect of the Electrolytic Conditions

The surface-normal structure of a Cd layer formed on an Au(111) substrate using underpotential deposition (UPD) in a sulfuric acid solution has been investigated by specular X-ray reflectivity measurements. The measurements were carried out for the Cd UPD layers which were formed at the first and second UPD potential in electrolytic solutions of I mM CdSO 4 with 10 mM and 100 mM H 2 SO 4 . In all cases, a Cd atomic layer is positioned on the Au(111) surface, which is similar to the reconstructed structure, and also a sulfuric acid anion layer is positioned on the Cd atomic layer. Contrary to results of the previous literature, the Cd coverage of the UPD layer depends not on the UPD potential but on the concentration of H 2 SO 4 . The coverage of the Cd atoms increases from approximately 0.50 to approximately 0.60 monolayer as the concentration of H 2 SO 4 increases from 10 to 100 mM, and the coverage of the sulfuric acid anions is approximately half the Cd coverage.

Time-resolved X-ray diffraction study on surface structure and morphology during molecular-beam epitaxy growth

Summary form only given. Reflection high energy electron diffraction (RHEED) oscillation has been widely adopted for studies on growth kinetics and dynamics in molecular beam epitaxy (MBE). Recent developments in brilliant X-ray sources has enabled similar experiments with X-rays, which has great advantage in a straightforward interpretation of results and in a high angular resolution. In general, the diffracted intensity from surface is proportional to the surface structure factor associated with the surface reconstruction, F, multiplied by a damping factor associated with the surface roughness, m. We show that the two factors, F and m, can be obtained separately by measuring diffuse scattering around the two-dimensional Bragg peak during growth. The experiments were performed with a six-axis surface diffractometer coupled to an MBE chamber at the synchrotron radiation facility, SPring-8. This apparatus allows the sample to be subjected to X-ray measurements at the same position as prepared. The diffracted intensity of X-rays was measured during the homoepitaxial growth of GaAs[001] at a substrate temperature of 700 K. Under the condition used, the RHEED pattern changed from the c(4x4) to the 2x1 symmetry on starting the growth.

Time-resolved X-ray diffraction study on surface structure and morphology during molecular beam epitaxy growth

Summary form only given. Reflection high energy electron diffraction (RHEED) oscillation has been widely adopted for studies on growth kinetics and dynamics in molecular beam epitaxy (MBE). Recent developments in brilliant X-ray sources has enabled similar experiments with X-rays, which has great advantage in a straightforward interpretation of results and in a high angular resolution. In general, the diffracted intensity from surface is proportional to the surface structure factor associated with the surface reconstruction, F, multiplied by a damping factor associated with the surface roughness, m. We show that the two factors, F and m, can be obtained separately by measuring diffuse scattering around the two-dimensional Bragg peak during growth. The experiments were performed with a six-axis surface diffractometer coupled to an MBE chamber at the synchrotron radiation facility, SPring-8. This apparatus allows the sample to be subjected to X-ray measurements at the same position as prepared. The diffracted intensity of X-rays was measured during the homoepitaxial growth of GaAs[001] at a substrate temperature of 700 K. Under the condition used, the RHEED pattern changed from the c(4x4) to the 2x1 symmetry on starting the growth.