Real-space Surface Research Articles

AR Digital Workspace: Extending the Workspace of a Mobile Device into Real Space

We propose AR Digital Workspace that extends the workspace of a mobile device in order to solve the narrow display area of mobile devices. The proposed interface allows a user to place multiple application windows on a flat surface in real space through a mobile device. The display area can be changed by moving the mobile device, allowing the user to easily switch between the applications. The user can change the positions and sizes of windows, operate applications in the windows, and copy and paste text between windows by touching the screen of the mobile device. The user can also copy characters in real space by recognizing characters in the images captured by the device’s camera. This interface allows the user to work with a large amount of information displayed in a large workspace. We conducted an experiment to compare the proposed interface with a traditional touchscreen interface using a task that involves switching between multiple applications to explore necessary information and answer questions ( N = 14 ). The results showed no difference in task completion time between the methods, but as trials were repeated, the completion time with the proposed method decreased, and on the last trial, the proposed method took significantly less time than the touchscreen interface. It was also shown that the proposed method was significantly less burdensome for more than half of the NASA-TLX items.

Atomic-scale imaging and spectroscopy via scanning probe microscopy: An overview

Atomic-scale characteristics of surfaces, including their structure, chemical reactivity, and electronic properties, determine their roles in multiple fields of science and technology, e.g., as coatings, catalysts, and device components. As such, it is of utmost importance to study the atomic arrangement and atomic-scale physico-chemical properties of surfaces in real space in a robust and reliable manner. A powerful technique for achieving this goal is scanning probe microscopy (SPM). Here, we present an overview of SPM-based techniques for atomic-resolution surface imaging and spectroscopy and highlight selected advances in the field. We also discuss current challenges of SPM-based techniques for atomic-resolution surface studies.

AR Peephole Interface: Extending the workspace of a mobile device using real-space information

In our previous work, we have proposed a user interface that enables six degrees-of-freedom (6-DOF) peephole interaction with a mobile device using augmented reality technology. This interface allows users to change the display area quickly by moving or tilting the device, and to obtain a lot of information easily. In addition, by fixing a virtual screen on a flat surface in real space, the interface allows users to easily grasp the distance to the virtual screen and to move the device quickly to the desired position. It is also expected that users can easily remember the positions of objects on the virtual screen by associating them with real-space information.In the present study, we conducted a new experiment using a task that requires users to scroll and zoom the screen frequently to evaluate the effectiveness of our proposed interface. The results showed that 6-DOF peephole interaction made it easier for users to change display areas and enabled more comfortable operation than a touchscreen interface. It was also shown that the users’ workload was reduced by fixing a virtual screen on a flat surface in real space.

Superradiance Induced Particle Flow via Dynamical Gauge Coupling.

We study fermions that are gauge coupled to a cavity mode via Raman-assisted hopping in a one-dimensional lattice. For an infinite lattice, we find a superradiant phase with an infinitesimal pumping threshold which induces a directed particle flow. We explore the fate of this flow in a finite lattice with boundaries, studying the nonequilibrium dynamics including fluctuation effects. The short-time dynamics is dominated by superradiance, while the long-time behavior is governed by cavity fluctuations. We show that the steady state in the finite lattice is not unique and can be understood in terms of coherent bosonic excitations above a Fermi surface in real space.

Supramolecular clusters and chains of 2,6-dimethylpyridine on Cu(110): Observation of dynamic configuration change with real-space surface science techniques and DFT calculations

The adsorption of 2,6-dimethylpyridine (2,6-DMP) on Cu(110) has been studied using low temperature scanning tunneling microscopy (LT-STM), time-of-flight electron stimulated desorption ion angular distribution (TOF-ESDIAD), and density functional theory (DFT) calculations. At low temperatures (T<~150K), the 2,6-DMP adsorbs in a flat configuration on Cu(110) producing clusters and extended domains via weak hydrogen bonding (C—H···N) with the molecular symmetry axis aligned along the <001> surface direction. At near-saturation coverage, a c(6×2) long-range ordered structure was observed. Upon annealing to T=200K, the 2,6-DMP molecules adopt an upright configuration with their pyridine ring plane oriented parallel to the <11̅0> azimuth. These upright 2,6-DMP molecules produce extended molecular chains where the repulsive interactions between the molecular chains give rise to coverage-dependent interchain distances. At near-saturation coverage, a 1260 surface structure is observed for the upright configuration. The DFT calculations suggest that the Cu adatom plays an important role in the adsorption configuration change of the 2,6-DMP molecule.

Kinetic theory of passing energetic ion transport in presence of the resonant interactions with a rotating magnetic island

The enhanced transport of passing energetic ions (PEIs) in presence of the resonant interactions with a rotating magnetic island is investigated within the drift kinetic framework. When the island rotation plays a role in the resonant interaction, we find that the velocities of PEIs satisfy a constraint relation of resonant flux surface in phase space. The resonant flux surfaces overlap with the magnetic flux surfaces in real space. A new transport channel responsible for the PEIs moving across the magnetic flux surfaces, i.e., continuously overlapping, is found. Two kinds of radial motions can be induced by the surface overlapping: one arises from the coupling between the resonance and the collision with the background plasma and the other from not completely overlapping of the two surfaces. The two radial motions and the symmetry-breaking induced radial motion constitute the total radial motion. When the pitch-angle scattering rate is very weak, the surface-shear induced transport is dominant. Only a small increase in the collision rate can significantly influence the total transport.

Comparative study of the carbide-modified surfacesC/Mo(110)andC/Mo(100)using high-resolution x-ray photoelectron spectroscopy

The preparations of single (monolayer) and bulk carbides on the $\mathrm{Mo}(110)$ and $\mathrm{Mo}(100)$ single crystals are followed in situ at 1200 K using synchrotron-based high-resolution x-ray photoelectron spectroscopy of the $\mathrm{C}\phantom{\rule{0.28em}{0ex}}1s$ and core Mo $3{d}_{5/2}$ levels. By comparing the experimental results to first principles calculations using density functional theory, we suggest real-space surface structures for the carbide-modified surfaces. For a monolayer carbide on $\mathrm{Mo}(110)$, carbon dimers adsorb in the long-bridge site, most likely at a coverage of $3/8\phantom{\rule{0.16em}{0ex}}\mathrm{ML}$ carbon atoms per Mo surface atom. For the bulk carbide, we find a coverage of $\ensuremath{\sim}0.5\phantom{\rule{0.16em}{0ex}}\mathrm{ML}$ on the surface, and the calculations show that single carbon atoms are more stable than dimers on the surface. The monolayer carbide on $\mathrm{Mo}(100)$ exhibits a coverage of $\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{ML}$ and agrees with previous studies, while the bulk carbide preparation probably leads to a faceting of the surface.

Identifying the absolute orientation of a low-symmetry surface in real space

We present atomic-scale force interaction data acquired on an insulating low-symmetry substrate, namely the calcite$(10.4)$ surface. A pronounced asymmetry of the imaged species is apparent along the vertical axis, which will be identified as a tilted band of purely attractive short-range interaction forces. An independent determination of the absolute surface orientation by an optical method suggests that the observed asymmetry is related to the tilt of the carbonate groups within the surface, which, in turn, is linked to the surface orientation. Thus our noncontact atomic force microscopy based work presents the determination of the absolute orientation for a low-symmetry surface.

Temperature-dependent scanning tunneling spectroscopy on the Si(557)-Au surface

Room-temperature and low-temperature (77 K) scanning tunneling spectroscopy (STS) and voltage-dependent scanning tunneling microscopy (STM) data are used to study the local electronic properties of the quasi-one-dimensional Si(557)-Au surface in real space. A gapped local electron density of states near the Gamma-point is observed at different positions of the surface, i.e., at protrusions arising from Si adatoms and step-edge atoms. Within the gap region, two distinct peaks are observed on the chain of localized protrusions attributed to Si adatoms. The energy gap widens on both types of protrusions after cooling from room temperature to T = 77 K. The temperature dependence of the local electronic properties can therefore not be attributed to a Peierls transition occurring for the step edge only. We suggest that more attention should be paid to finite-size effects on the one-dimensional segments.

A pathway between Bernal and rhombohedral stacked graphene layers with scanning tunneling microscopy

Horizontal shifts in the top layer of highly oriented pyrolytic graphite, induced by a scanning tunneling microscope (STM) tip, are presented. Excellent agreement is found between STM images and those simulated using density functional theory. First-principle calculations identify that the low-energy barrier direction of the top layer displacement is toward a structure where none of the carbon pz orbitals overlap, while the high-energy barrier direction is toward AA stacking. Each directional shift yields a real-space surface charge density similar to graphene; however, the low-energy barrier direction requires only one bond length to convert ABA (Bernal) to ABC (rhombohedral).

Host-guest co-assembly on solid surfaces investigated by scanning tunneling microscopy

The host-guest assembly on solid surface is a representative bottom-up approach to build up functional molecular nanostructures, and has attracted great attention in nanoscience and nanotechnology. With the great feature to get <italic>in-situ</italic>, real-time and real-space surface and interface structure information with sub-molecular resolution, scanning tunneling microscopy (STM) has been widely used to explore the host-guest co-assemblies on solid surfaces and reveal the underlying mechanism of the host-guest assembly process. Host and guest molecules can interact in different modes to form the host-guest assemblies. A common mode is that the host molecules self-assemble into two-dimensional nanoporous networks with well-ordered voids which can be filled with suitable guest molecules. Secondly, guest molecules can epitaxially assemble on the monolayer of host molecules to form a second layer with the structure mirroring that of host molecule adlayer. In some special cases, the nanostructures formed by host molecules can coordinately adjust themselves to accommodate guest molecules with different size and shape. Herein, we review the recent progress of the construction of host-guest co-assemblies on solid surfaces.

Specific Surface Area and Three-Dimensional Nanostructure Measurements of Porous Titania Photocatalysts by Electron Tomography and Their Relation to Photocatalytic Activity

Various porous titania photocatalysts are analyzed three-dimensionally in real space by electron tomography. Shapes and three-dimensional (3D) distributions of fine pores and silver (Ag) particles (2 nm in diameter) within the pores are successfully reconstructed from the 3D data. Electron tomography is applied for measuring the specific surface area of the porous structures including open and closed porosity. Calculated specific surface areas of 22.8 m(2)/g for a conventional sol-gel TiO(2) sample and 366 m(2)/g for a highly porous TiO(2) sample prepared using the Pluronic P-123 self-assembly process are compared with those measured by the general BET method. The real-space surface measurement indicates that the highly porous TiO(2) produced by the present method using block copolymers has a greater number of effective reaction sites for the degradation of methylene blue. Electron tomography shows a great potential to contribute considerably to the nanostructural analysis and design of such catalyst materials for photocatalysis.

Seeing the Fermi Surface in Real Space by Nanoscale Electron Focusing

The Fermi surface that characterizes the electronic band structure of crystalline solids can be difficult to image experimentally in a way that reveals local variations. We show that Fermi surfaces can be imaged in real space with a low-temperature scanning tunneling microscope when subsurface point scatterers are present: in this case, cobalt impurities under a copper surface. Even the very simple Fermi surface of copper causes strongly anisotropic propagation characteristics of bulk electrons that are confined in beamlike paths on the nanoscale. The induced charge density oscillations on the nearby surface can be used for mapping buried defects and interfaces and some of their properties.

An instrument to investigate femtochemistry on metal surfaces in real space

A newly established combination of a femtosecond laser with a low temperature scanning tunneling microscope is described, which facilitates one to analyze femtochemistry on metal surfaces in real space. The combined instrument enables focusing the laser to some tens of micrometers and guiding it reproducibly into the tunneling gap with the aid of in situ movable mirrors. Furthermore, a method to determine the focus size on the sample is presented. The focus size is used to calculate the electron and phonon temperatures at the surface. Despite the additional noise introduced by laser operation the vertical resolution of the microscope lies below 1 pm. The potential of the instrument is demonstrated on para-chloronitrobenzene clusters adsorbed on Au(111). Single chloronitrobenzene molecules diffuse upon femtosecond laser irradiation; some smaller clusters rotate by multiples of 30 degrees ; clusters of less compact form rearrange to close-packed clusters.

Structural and morphological characterisation of hybrid Cu/Si(0 0 1) structures

The structural and morphological properties of epitaxial Cu/Si(0 0 1) type of structures have been investigated by a combination of electron, X-ray and scanning probe imaging techniques. Auger electron spectroscopy measurements indicate the presence of Si in the Cu layer for Cu thicknesses up to 10 nm. In addition, X-ray scattering results show that there is a mosaic spread in the Cu(0 0 1) crystal which decreases as the Cu thickness increases, from 8° at 15 nm to 4.5° at 100 nm. This behaviour is corroborated by reflection high energy electron diffraction patterns of the Cu surface measured during growth, which exhibit a twinning in the diffraction spots for the 15 and 30 nm Cu films. Atomic force and scanning electron microscopy imaging of Cu(4 nm)/Co(7,17 nm)/Cu(100 nm)/Si(0 0 1) structures allow one to visualise and characterise the sample surface in real space; from these measurements, an average roughness amplitude of ∼0.5 nm and a correlation length of ∼50 nm are obtained. Our results provide a better understanding of an important system which has been widely used as a template for the growth of epitaxial ultrathin magnetic films.

Nanoscale Surface Elemental Analysis by Synchrotron Radiation Based Scanning Tunneling Microscope

Scanning Tunneling Microscope (STM) combined with Synchrotron Radiation (SR) allowed to analyze solid surfaces in real space with nanometer scale by inner-shell excitation of a specific energy level under the STM observation. Elemental analysis was successfully accomplished for Ge nano-islands on a Si(111) 7×7 surface by SR-STM. As a next step, remaining diffculties of instability and inaccuracy during measurements were improved. After renewal of a dumper system, a key to solve the diffculties was reduction of emitted electrons. Thus, an insulator-coated tip to shut out the electrons coming from a wide area was developed. Further surface analysis was performed for Cu domain on a Ge(111) 2×8 surface using the new tip. As a result, elemental analysis between Cu domains and the surrounding Ge surface was achieved. It has been shown that SR-STM provides new possibilities of nanoscale surface analysis.

Single-Atom Contact Mechanics: From Atomic Scale Energy Barrier to Mechanical Relaxation Hysteresis

The potential energy landscape of surfaces governs the dynamics of adsorbed molecules, as well as atomic scale friction processes. We measure the potential energy landscape of a single-atom tip interacting with a vicinal nonconducting NaCl(100) surface in real space using noncontact atomic force microscopy. We find that the shape of the potential energy profile is of sinusoidal form with a barrier height of 48 meV. Furthermore, we observe a discontinuity in the force curves at specific lattice sites, indicating the onset of reversible yet hysteretic mechanical relaxations.

Scanning tunneling microscopy study of the structural phase transformation in manganese nitride: θ-MnN → η-Mn 3 N 2

The phase transformation of a (001)-oriented θMnN thin film grown by molecular beam epitaxy to ηMn3N2 has been investigated using a combination of diffraction analysis and real-space surface analysis by scanning tunneling microscopy. The θMnN thin film is prepared by growth at 450 °C; it is then annealed at 550 °C. It is found that the phase transformation results in three different orientations of the ηMn3N2 phase within the annealed film. The phase transformation is attributed to diffusion and loss of N atoms and ordering of the N-vacancies into parallel sheets. A schematic model of the annealed film structure is presented.

Blocking map of He+ scattered from a Si(001)-(2×1) surface

Abstract Scattering and recoiling imaging spectrometry (SARIS) in the “blocking configuration” for the system of 5 keV He+ scattering from a Si(0 0 1)-(2 × 1) surface has been used to measure a two-dimensional blocking map. The map demonstrates that this real-space surface crystallographic technique is sensitive to interatomic spacings in the surface and subsurface layers of a crystal. Classical ion trajectory simulations using the scattering and recoiling imaging code (SARIC) and “two-atom” molecular dynamics (MD) simulations are used to interpret the blocking patterns and to provide quantitative interpretations of the experimental data. The “blocking configuration”, in which atomic trajectories scattered from subsurface layers are blocked by atoms in layers nearer to the surface, is demonstrated to be a viable method for simultaneous acquisition of data from the surface and individual surface layers. It is found that the blocking map is representative of the crystal geometry. The results show that the major blocking cones for 5 keV He+ on Si(0 0 1)-(2 × 1) originate from fourth to seventh-atomic layer scattering, while cones of lesser intensity are observed from as deep as the 12th-atomic layer.

Molecular quantum theory: Separable electronuclear wave functions and vibronic states—A generalized diabatic approach

AbstractThe linear superposition principle is used to represent chemical and physical processes. A quantum state representation is obtained for model molecular systems. An exact Hamiltonian is first introduced and thereafter approximated by a sum of Coulomb Hamiltonian, electron–phonon (e–ph), relativistic effects, and coupling to external fields. A sharp separability ansatz is used to study the Coulomb Hamiltonian first; the electronic part is fully represented in Hilbert space (q space); a background of positive charge replaces nuclei in real space (ξ space). This QC model leads to diabatic electronic functions and diabatic potential energy (DPE) surfaces in real space. Next, the nuclear masses are introduced via a kinetic energy operator and added to the DPEs. The attractor property of the diabatic electronic functions is used to study mass fluctuation regimes. Fluctuations, if quantized, lead to the Q2C model; mass dynamics takes place in real space. The set of product functions {ϕj(q)ζjl(ξ)} provides a base to represent arbitrary electronic states. In this context, the linear superposition principle is naturally introduced. The formulation of chemical reactions, pump–probe experiments and a detailed study of H are topics examined from the present perspective. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004