Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.susc.2021.121905

researchmap

Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)  

© 2020 Elsevier B.V. Triangular islands with uniform size are observed on the Ge(111)-Ag surface after the formation of the 3×3 structure by scanning tunneling microscopy (STM) at 77 K. The triangular islands disappear at room temperature, and do not form on the 4 × 4 surface of Ge(111)-Ag at 77 K. These results indicate that, when the 3×3 structure is formed, excess Ag atoms exist on the Ge(111)-Ag surface, which are assembled into the triangular islands at low temperature. From the bias dependence of the STM images for the triangular islands, we conclude that the triangular island is composed of six Ag adatoms with a triangular configuration. In addition, after additional deposition of Ag at room temperature, structural evolution from the triangular islands to 39×39 and 6 × 6 superstructures is also observed.

DOI： 10.1016/j.susc.2020.121724

Scopus

researchmap

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In addition to the well-known double-helix structure of deoxyribonucleic acid (DNA), theoretical simulations have predicted structural variants, such as cross and T-shaped formations. The direct visualization of individual DNA molecules by scanning probe microscopy should be able to identify these structures. In this study, we examine various structures of DNA deposited on Au(111) by using an electrospray method and analyzing with a low-temperature scanning tunneling microscope. We could identify in detail several interesting structures. In particular, we found that double-stranded DNAs are partially unraveled into single-stranded DNAs and we confirmed the presence of T-shaped DNA structures.

DOI： 10.1021/acs.jpcb.8b12100

Web of Science

researchmap

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Self-assembly of tetracene on an anisotropic surface of Ag(110) has been investigated using scanning tunneling microscopy and low-energy electron diffraction. We observe multistage structural transformations of the self-assembled tetracene on Ag(110) as a function of molecular coverages, which are accompanied by the changes in molecular orientations. They are analyzed by a balance between multiple molecule-molecule and anisotropic substrate-molecule interactions. (C) 2016 AIP Publishing LLC.

DOI： 10.1063/1.4943576

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The adsorption and self-assembled structures of alpha-sexithiophene (alpha-6T) have been investigated on a Si(111)-Ag surface using scanning tunneling microscopy (STM), low-energy electron diffraction, and density functional theory calculations. The adsorbed alpha-6T molecules are arranged into unidirectional molecular rows with a side-by-side orientation. The molecular rows reveal three kinds of appearances in the filled-state STM images, which reflect the distinct adsorption sites. From tunneling spectroscopy, we find that the filled-state STM images of alpha-6T should be influenced by the surface states of Si(111)-Ag. At one monolayer coverage, sequentially ordering of the triple molecular rows results in the close-packed arrangement of the alpha-6T overlayer. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4921568

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Asymmetric electronic structures within a single molecule have been investigated by scanning tunneling microscopy and spectroscopy. Inside of a phenyl-linked porphyrin dimer, the asymmetric electronic structures are achieved by the incorporation of a cobalt ion in one porphyrin moiety. We find that a p-n junction between two pi-conjugated segments is formed within the porphyrin dimer. The understanding of the local electronic structures of the intramolecular p-n junction should represent a fundamental step to realizing single molecular devices.

DOI： 10.1021/jz500511w

Web of Science

researchmap

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The surface electrostatic potential of Au(111) has been evaluated by using site-specific barrier-height measurements in a scanning tunneling microscope. From the spatial variation of the barrier height, sharp enlargement and reduction of the surface potential are obtained at the upper and lower step edges, respectively, which are characterized as the Smoluchowski effect. We also observe the potential with oscillatory decay away from the step, known as the Friedel potential oscillation. In addition, the periodic potential modulation induced by the surface reconstruction is evaluated quantitatively, which is confirmed by the energy shift of the bulk electronic states.

DOI： 10.1103/PhysRevB.89.155423

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Structural and conformational determination of large and functional organic molecules is of great importance to understand their physical and chemical properties. Here we report on the length dependence of molecular shapes of long oligothiophene wires adsorbed on Au(111), which has been directly visualized by low-temperature scanning tunneling microscopy (STM). The controlled vacuum deposition of the oligothiophene wires from 10 to 120 nm in length has been accomplished by using an electrospray ionization technique. From the high-resolution STM images, we have observed that the oligothiophene molecules longer than around 60 nm tend to form folded (or looped) structures in order to keep compact shapes, which should reflect the molecular shapes in solution or in gas phase.

DOI： 10.1021/jp405411f

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The conformation and self-assembly of tertiary-butylphenyl substituted free-base and metal porphyrins (M-TBPP) on Ag(110) have been investigated as a function of the central metals (M = 2H, Cu, Pt, Ni, Zn, and Co) using scanning tunneling microscopy and low-energy electron diffraction. In the case of M = Cu, Pt, Ni, and Zn, a metastable adsorption structure is formed by the deposition below about 270 K and irreversibly transformed into a stable one after thermal annealing above 280 K. Nevertheless, we find that 2H- and Co-TBPP molecules do not exhibit structural transformation even after thermal annealing. The distinct adsorption behaviors should be related mainly to the porphyrin-substrate interactions depending on the central metal in M-TBPP. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4770501]

DOI： 10.1063/1.4770501

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Adsorption and diffusion behavior of dipolar Ir(ppy)(3) molecules on Cu(111) has been investigated by low-temperature scanning tunneling microscopy (STM). At low coverages, highly dispersed structures of Ir(ppy)(3) are formed on the Cu(111) surface, which result from the repulsive dipole-dipole interactions. The two-dimensional surface diffusion of single Ir(ppy)(3) molecules is directly observed in a temperature range from 65 to 94 K, the hopping rate of which is systematically derived from STM images. We also extract the corresponding activation energy, pre-exponential factor, and jump length for the diffusion of Ir(ppy)(3) on Cu(111).

DOI： 10.1103/PhysRevB.82.155414

Web of Science

researchmap

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A checkerboard pattern of alpha-sexithiophene (alpha-6T) with an approximate lattice size of 2.6x3.3 nm(2) has been achieved on a Ag(110) surface at monolayer coverage, which is formed through a lateral ordering of two oriented molecules and vacancy defects. We find that this self-assembled pattern provides a template structure for the formation of molecular nanodots and nanocolumns. Second and third-layer islands of alpha-6T are formed within the checkerboard lattice, leading to a uniform molecular nanodot array, and a nanosized columnar structure is expected if growth is continued into the multilayer regime.

DOI： 10.1063/1.3308512

Web of Science

researchmap

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

By using low-temperature scanning tunneling microscopy, we show that long linear chains of Alq(3) are formed on a Cu(111) surface at a temperature of less than 250 K. The linear chains include an identical width, composed of double rows separated by about 0.75 nm, and are enlarged in the [112] direction and its equivalent directions of Cu(111). Above this critical deposition temperature, isolated single molecules are randomly distributed and are very mobile on the surface even at 78 K. The formation of the linear chains should be associated with the metastable adsorption structures of Alq(3) existing only at low temperature.

DOI： 10.1021/jp811454t

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The conformation and self-assembly of tertiary butyl-phenyl substituted Pt-porphyrin (Pt-TBPP) on an Ag(110) surface have been studied as a function of deposition and annealing temperatures using scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). While a stable two-dimensional arrangement is formed by room-temperature deposition, one-dimensional chains of Pt-TBPP along the [1 (1) over bar0] direction are assembled by decreasing the deposition temperature, wherein the molecular orientation is orthogonal to that formed at room temperature. From a careful comparison of STM images and molecular orbital calculation results, the molecular conformations within these assembled structures were determined by the bending angles of the tertiary butyl-phenyl substituents, as well as the rotation angles, which result from conformational adaptation of the adsorbed Pt-TBPP to the substrate lattice. We also observed the structural transformation from one-dimensional chains formed at low temperature to the two-dimensional arrangement by thermal annealing at 280-310 K. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3001609]

DOI： 10.1063/1.3001609

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Selective discriminating and indiscriminating assembly of isomeric oligothiophene derivatives is performed on a Ag(110) surface. The self-assembled structures are directly analyzed by using scanning tunneling microscopy. We demonstrate that the phase separation and phase mixing of s-cis- and s-trans-oligothiophenes can be controlled by shape-complementary intermolecular interactions associated with the overall molecular shapes. The overall shapes of the s-cis- and s-trans-oligothiophenes are tuned by the length of alkyl side chains.

DOI： 10.1021/jp805116v

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Highly dispersed superstructures of a dipolar iridium complex are formed on a Cu(111) surface. We show that the dilute superstructures with density-controlled intermolecular separations are stabilized by the strong and long-range repulsive intermolecular interactions. The repulsive intermolecular interactions are quantitatively evaluated by using low-temperature scanning tunneling microscopy, which are characterized by the surface-enhanced dipole-dipole interactions.

DOI： 10.1103/PhysRevLett.98.206102

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A direct conformational analysis using scanning tunneling microscopy (STM) has been performed for individual adsorbed alpha-octithiophene molecules on Cu(100). s-cis and s-trans conformational isomers are induced by the rotational flexibility of individual thiophene rings. By adding bulky N-silyl substituents to octithiophene, we successfully identify the s-cis and s-trans conformational isomers using STM. The obtained relative abundances of the s-cis and s-trans conformations are analyzed using ab initio molecular orbital calculations.

DOI： 10.1021/jp064217c

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

We have investigated effects of the vacancies on the order-disorder phase transition by a Monte Carlo simulation using an Ising system, where two states of a buckled dimer were regarded as spins up and down. First, we calculated the correlation length in the model. In the following, we introduced single-dimer vacancies into the model. As a result, a new local structure appeared in the vicinity of an isolated vacancy near a critical temperature TMCc (≈320 K) due to a strain field. The strain was considered to be a local next nearest neighbor (n.n.n.) antiferromagnetic (AF) one, where the strain energy (A) was deduced to be about 20 meV. Since our model without any vacancies shows the nearest neighbor (n.n.) AF structure to be the ordered state, we concluded that competition between the overall n.n. AF coupling and the local n.n.n. AF coupling induced by the defect occurred near Tc, which agreed with the STM experiment (T. Yokoyama, K. Takayanagi, Phys. Rev. B 56 (1997) 10483). © 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0039-6028(97)00978-3

Scopus

researchmap

researchmap

researchmap

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

researchmap

researchmap

researchmap

Language：English   Publisher：ELSEVIER SCIENCE BV  

We studied the atomic structure of the Si(001)-c(4 x 12)-Al surface, which appears in scanning tunneling microscopy (STM) images as an array of clusters in the four-fold direction. Transmission electron diffraction (TED) patterns showed (h/4, k/12) fractional-order spots after depositing about four monolayers of aluminum on clean Si(001) surfaces at a substrate temperature of 600 degreesC. A model, which accords with the TED intensity and the observed STM images, consists of a periodical terrace-and-trench geometry in the 12-fold direction. In the four-fold direction, an aluminum ad-dimer is adsorbed every 4a distance (a=0.384 nm) on the terraces terminated by double-height steps, making up the cluster array corresponding to bright protrusions in STM images. In addition to ad-dimers, rebonded atoms at the double-height step edge and zigzag isolated dimers in the trench are found to be the building blocks of the c(4 x 12) structure. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0039-6028(00)00668-3

Web of Science

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

researchmap

Language：English  

The unoccupied π* surface band of the Si(001)-c(4×2) surface has been determined from standing-wave patterns using low-temperature scanning tunneling microscopy. A straight chain of Al ad-dimers, formed by deposition at room temperature, works as a one-dimensional (1D) barrier that scatters the surface-state electrons. The standing waves have been observed along Si dimer rows in a sample voltage range of 0.9-1.3 V at T = 63K. The relationship between their wavelengths and the sample voltages gives the dispersion relation of the π* surface band. The height and width of the potential barrier have been estimated according to the 1D Schr�dinger equation. © 1998 The American Physical Society.

DOI： 10.1103/PhysRevLett.81.3423

Scopus

researchmap

Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

researchmap

Language：English  

We have studied an order-disorder phase transition of a vicinal Si(001) surface from a (Formula presented) to a (Formula presented) structure using low-temperature scanning tunneling microscopy (STM). The order parameter for the (Formula presented) structure is derived from the Fourier transform of the atomically resolved STM images in the 65-300 K temperature range. The order parameter on the (Formula presented) terrace bounded with an (Formula presented) step is found to reach only 0.7, even at 65 K, while the (Formula presented) structure is almost complete on the (Formula presented) terrace bounded with an (Formula presented) step. In the STM images at 65 K, dimers at the lower side of the (Formula presented) step still appear symmetric, resulting in an order-parameter reduction of the (Formula presented) terrace. © 1998 The American Physical Society.

DOI： 10.1103/PhysRevB.57.R4226

Scopus

researchmap

Language：English  

We used a low-temperature scanning tunneling microscope to observe a single-dimer vacancy ((Formula presented)-type defect) induce buckling of the dimers on a Si(001) surface near (Formula presented) This dimer buckling always occurs in rows adjacent to the (Formula presented)-type defects near (Formula presented) which simultaneously forms an out-of-phase boundary in the domain of a (Formula presented) structure. However, the out-of-phase boundaries around the (Formula presented)-type defects disappear on the surface at 78 K. We discuss the nucleation and growth behavior of the dimer buckling around the (Formula presented)-type defect and the influence of the defects on the structural phase transition of a Si(001) surface. © 1997 The American Physical Society.

DOI： 10.1103/PhysRevB.56.10483

Scopus

researchmap

Language：Japanese  

researchmap

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Language：English   Presentation type：Poster presentation  

researchmap

Language：English   Presentation type：Poster presentation  

researchmap

Language：Japanese  

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

Language：English   Presentation type：Poster presentation  

researchmap

Language：English   Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

Language：Japanese   Presentation type：Poster presentation  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Language：English  

researchmap

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

Language：Japanese  

researchmap

Language：Japanese  

researchmap

researchmap

researchmap