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The creation of three-dimensional (3D) geometrical shapes with atomically ordered surfaces and the investigation of their physical properties are major steps contributing to the development of a new paradigm in surface science. We produced a 3D-patterned Si sample with atomically flat and reconstructed {111} facet surfaces, and investigated its structural and physical properties. To apply the conventional techniques in surface science to 3D samples with various oriented surfaces, instead of two-dimensional planar samples, an appropriate relationship between the crystallographic surface ordering on the 3D-architected surfaces and the angle-resolved photoelectron spectroscopy (ARPES) setup considering the configuration in 3D space is indispensable. The distinctive and complex low-energy electron diffraction (LEED) patterns reflecting the 3D-arranged facet surfaces showed the realization of atomically reconstructed facet surfaces on 3D-patterned Si. Surface states of the 3D-patterned Si{111} surfaces are mapped by ARPES by considering the 3D geometrical relationship. The selection of the appropriate alignment of the incident electron beam (light) for the target surfaces allows the clear observation of the band dispersion from the produced {111}7×7 facet surfaces in 3D space. Our demonstration of accessibility of ARPES technique could provide useful guidelines for new methodologies, giving a fundamental understanding of 3D-shape-induced novel functionalities.

Spatially arranged surfaces on the micro-rod structure, which was three-dimensionally (3D) architected on a Si(110) substrate have been thoroughly investigated by a system with micro-beam reflection high-energy electron diffraction (μ-RHEED) and scanning electron microscopy (SEM). The combination of μ-RHEED and SEM realized analytical structure investigation of 3D surfaces with the spatial resolution of sub micrometer for the 3D rectangular shaped rod consisting of a (110) top surface (20 μm wide) and {111} vertical side surfaces (10 μm wide). Exhaustive mapping revealed the peculiar reconstructed surface structures: Si(110) “16 × 2” single domain and {35 47 7} facet surfaces locally appeared on the interconnected edge region on the 3D structure in addition to the “16 × 2” and 7 × 7 super structures on flat top (110) and side {111} surfaces, respectively. The formation mechanism for “16 × 2” single-domain structure near the corner edge of the (110) surfaces and {35 47 7} facets on the corner edges between (110) and {111} surfaces were discussed from the viewpoint of the surface stability on the 3D geometrical shaped Si structure.

The control of three-dimensional (3D) geometrical shapes is one of important approaches that contribute the development of new functionalities in material science. We produced 3D Si pyramids with a...

Neodymium nickelate (NdNiO3: NNO), which is a typical strongly correlated metal oxide, has attracted considerable attention because of its large resistance changes due to its metal-insulator transi...

New fitting analyses for peak shapes in a 2D reciprocal-space map are demonstrated to evaluate the strain, strain distribution and domain size of a crystalline ultra-thin (15 Å) film of β-FeSi2(100) grown epitaxially on an Si(001) substrate, using grazing-incidence X-ray diffraction. A 2D Laue-fit analysis taking into account instrument broadening and the double-domain effect provides residual maps as a function of the inequivalent strains ɛ b and ɛ c along the b and c axes of β-FeSi2, respectively (and domain size D), reflecting the probability of existence of homogeneous domains with fixed ɛ b , ɛ c and D, in addition to the most probable minimum residual. A 2D Laue fit with an inhomogeneous domain distribution provides a population map with ɛ b and ɛ c , reflecting strain components contributing to the film. The population map also leads to a reference residual as a guide for the strains contributing to the residual map. The advantages of the 2D Laue fits are discussed by comparison with the Scherrer, Williamson–Hall and Gaussian fitting methods for equivalent systems. The analyzed results indicate that the β-FeSi2 nanofilm was considerably small strained, which was also confirmed by transmission electron microscopy, implying a weak interface interaction between the film and the substrate.

The realization of three-dimensional (3D)-architected nanostructures, that is, the transformation from novel two-dimensional (2D) film-based devices to 3D complex nanodevices, is of crucial importance with the progress of scaling down devices to nanometer order. However, little attention has been devoted to controlling the atomic ordering and structures of side-surfaces on 3D structures, while techniques for controlling and investigating 2D surfaces, namely, surface science, have been established only for planar 2D surfaces. We have established an original methodology that enables atomic orderings and arrangements of surfaces with arbitrary directions to be observed on 3D figured structures by developing diffraction and microscopy techniques. An original technique, namely, directly and quantitatively viewing the side- and facet-surfaces at the atomic scale by reflection high-energy electron diffraction (RHEED) and low-energy electron diffraction (LEED), can be used to determine process parameters in etching. This chapter introduces methods of evaluation by RHEED and LEED based on a reciprocal space map and methods of creating various atomically flat 111 and {100} side-surfaces of 3D Si nano-architectures and tilted 111 facet-surfaces fabricated by lithography dry and wet etching processes, followed by annealing treatment in vacuum.

The resistance modulation under various gate voltage (Vg) application conditions was systematically studied for a chemical field effect transistor (FET) composed of a SmNiO3 (SNO) film channel and ...

We investigated the epitaxial growth of Fe islands on clean and ammonia-saturated Si(111)7 × 7 surfaces by reflection high-energy electron diffraction for 0–10 monolayer Fe coverage. From the profi...

The realization of atomically flat side-surfaces, which are vertical planes on a substrate, would make an enormous contribution to a paradigm shift from two-dimensional planar film structures to three-dimensional (3D) nanostructures. In this paper, we demonstrate the successful creation of well-defined Si{111}7 × 7 side-surfaces on a 3D-architected Si(110) substrate by the combination of 3D Si patterning and surface preparation techniques, as confirmed by reflection high-energy electron diffraction (RHEED). The RHEED patterns consisted of 7 × 7 diffraction spots from the Si{111} side-surfaces and 2 × 16 diffraction spots from the Si(110) top/bottom surface. We also performed the deposition of metals (Au and Ag) onto the side-surfaces, leading to the formation of Si( 1 ¯ 11 ) √3 × √3R30°-Au and Si( 1 1 ¯ 1 ¯ ) √3 × √3R30°-Ag structures. This is the first demonstration indicating super-reconstructions of such well-defined side-surfaces.

Functional oxides with strongly correlated electron systems, such as vanadium dioxide, manganite, and so on, show a metal-insulator transition and an insulator-metal transition (MIT and IMT) with a change in conductivity of several orders of magnitude. Since the discovery of phase separation during transition processes, many researchers have been trying to capture a nanoscale electronic domain and investigate its exotic properties. To understand the exotic properties of the nanoscale electronic domain, we studied the MIT and IMT properties for the VO2 electronic domains confined into a 20 nm length scale. The confined domains in VO2 exhibited an intrinsic first-order MIT and IMT with an unusually steep single-step change in the temperature dependent resistivity (R-T) curve. The investigation of the temperature-sweep-rate dependent MIT and IMT properties revealed the statistical transition behavior among the domains. These results are the first demonstration approaching the transition dynamics: the competition between the phase-transition kinetics and experimental temperature-sweep-rate in a nano scale. We proposed a statistical transition model to describe the correlation between the domain behavior and the observable R-T curve, which connect the progression of the MIT and IMT from the macroscopic to microscopic viewpoints.

We have studied in situ structures and magnetic properties for several iron silicides grown on Si(111)7×7 clean surfaces by the solid phase epitaxy (SPE) method: deposition of Fe at 40 K and subsequently annealing, and summarized almost all silicide phases depending on the deposition thickness and the annealing temperature as a “schematic magnetic phase diagram”. In the SPE growth, bcc-Fe(111)1×1, c-FeSi(111)1×1, 2×2, and c(4×8), α-FeSi2(112)2×2, ϵ-FeSi(111)√3 × √ 3-R30°, β-FeSi2(101)/(110) and polycrystalline phases are formed on Si(111)7×7 surfaces depending on Fe coverage (0.15–10.0 nm) and annealing temperature (470–1070 K). The structures and magnetic properties of all the above Fe silicide phases have been characterized by using in situ reflection high-energy electron diffraction, scanning tunneling microscopy, and surface magneto-optical Kerr effect. Bulk-unstable c-FeSi phases showed ferromagnetic property at 40 K and this ferromagnetism remained even after air exposure. For the c-FeSi(111)/Si(111) system, the large spin polarization was proposed at the Fe interface atoms in the B5-type interface structure between the c-FeSi(111) ultra-thin film and the Si(111) substrate by first-principle calculations.

Lithiation and delithiation of porous silicon were studied using reflection high energy electron diffraction (RHEED), two-dimensional photoelectron diffraction, and a stereo atom-scope, which is realized by the combination of a display-type spherical mirror analyzer and circularly polarized soft X-ray. A nanosized porous silicon layer was prepared by electrochemical etching of p-type silicon (001) wafer in ethanolic solutions containing hydrofluoric acid. The morphology of the as-grown porous silicon as observed using SEM was filled with about 9 nm holes. This porous silicon also retains the crystallographic orientation of the wafer from which it was etched and is optically active with visible photoluminescence. The measured RHEED pattern and 2π steradian Si 2p photoelectron diffraction pattern from Si (001) surface showed an increase in lattice constant by lithiation, and that change in lattice constant was restored to its original values by delithiation.

Monolayer and bilayer graphene films with a few hundred nm domain size were grown on ultraprecision figured 4H-SiC(0001) on-axis and 8 degrees -off surfaces by annealing in ultra-high vacuum. Using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, reflection high-energy electron diffraction, low-energy electron diffraction (LEED), Raman spectroscopy, and scanning tunneling microscopy, we investigated the structure, number of graphene layers, and chemical bonding of the graphene surfaces. Moreover, the magnetic property of the monolayer graphene was studied using in-situ surface magneto-optic Kerr effect at 40 K. LEED spots intensity distribution and XPS spectra for monolayer and bilayer graphene films could become an obvious and accurate fingerprint for the determination of graphene film thickness on SiC surface.

Damaged layers and polishing haze exist on substrate surfaces owing to abrasion during figuring processes, which deteriorate surface integrity. We have developed a novel damage-free ultraprecision figuring technique and obtained atomically flat and damage-free SiC(0001) surfaces with a domain size of 300–500 nm. Using ultraprecision-figured 0°-off 4H-SiC(0001) surfaces as substrates, we demonstrated the formation of graphene layers upon them and successfully produced atomically flat monolayer graphene with a domain size of over 300 nm on entire ultraprecision-figured SiC surfaces by annealing in ultra high vacuum without any Si flux. The quality of the graphene layers on the ultraprecision-figured SiC surfaces was markedly higher than that of layers on non-figured SiC surfaces. This indicates that the damaged surface layers with scratches, defects, and so on, enhance roughness on SiC surfaces, and reduce the quality of graphene films. In addition, we found a new phenomenon:step terraces of 500 nm width exhibited erosion at step edges, leading to the creation of hexagonal pits at terraces, while step terraces of 300 nm width exhibited hardly any erosion. A graphitization mechanism was discussed.

The creation of atomically-ordered Si{111}7 × 7 facet structures on a Si(110) substrate is realized for the first time. Au was deposited on atomically-flat {111} facet surfaces. The resistance of Au wires crossing over three-dimensional (3D) facet edges with an angular shape is intrinsically sensitive to the edge alignments in electric path: the resistance in crossing the facet edges was 3–10 times larger than that along the facet edges. We suggest the enlargement of the resistance originated from conduction electron scattering along the angular path. This work pioneers the fundamental understanding of electron transport in 3D angular metal-interconnects.

We studied the procedure of cleaning GaN(0001) substrate surfaces by wet etching and subsequent annealing in ultrahigh vacuum for two different types of freestanding GaN wafers: hydride vapor phase epitaxy (HVPE) crystal and Na flux liquid phase epitaxy (LPE) crystal wafers. A flat surface containing GaN(0001)2 × 2 reconstruction was successfully achieved on both HVPE and LPE surfaces by etching in HF and subsequent annealing at ∼ 550 °C but was not achieved by etching in HCl, NaOH, and HNO 3 .

We studied processes of cleaning GaN(0 0 0 1) surfaces on four different types of wafers: two types were hydride vapor phase epitaxy (HVPE) free-standing substrates and two types were metal-organic chemical vapor deposition (MOCVD) films grown on these HVPE substrates and prepared by annealing and/or Ar ion sputtering in ultra high vacuum. We observed the surfaces through treatments using in situ low-energy electron diffraction (LEED), reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and Auger electron spectroscopy, and also using ex situ temperature programmed desorption, X-ray photoelectron spectroscopy, X-ray diffraction, and secondary ion mass spectrometry. For HVPE samples, we obtained relatively clean surfaces under optimized three-step annealing conditions (200 ° C for 12 h + 400 ° C for 1 h + 500 ° C for 5 min) without sputtering, after which the surface contamination of oxide and carbide was reduced to ∼ 20 % of that before annealing. Clear GaN(0 0 0 1) 1 × 1 patterns were obtained by LEED and RHEED. STM images showed flat terraces of ∼ 10 nm size and steps of ∼ 0.5 nm height. Upon annealing the HVPE-GaN samples at a much higher temperature ( > 550 ° C), three-dimensional (3D) islands with facets were formed and the surface stoichiometry was broken down with the desorption of nitrogen in the form of ammonia, since the samples include hydrogen as an impurity. Ar+ sputtering was effective for removing surface contamination, however, postannealing could not recover the surface roughness but promoted the formation of 3D islands on the surface. For MOCVD/HVPE homoepitaxial samples, the surfaces are terminated by hydrogen and the as-introduced samples showed a clear 1 × 1 structure. Upon annealing at 500–600 ° C, the surface hydrogen was removed and a 3 × 3 reconstruction structure partially appeared, although a 1 × 1 structure was dominant. We summarize the structure differences among the samples under the same treatment and clarify the effect of crystal quality, such as dislocations, the concentration of hydrogen impurities, and the residual reactant molecules in GaN films, on the surface structure.

We studied the initial stage of iron deposition on an ethanol-saturated Si(111)7 × 7 surface at room temperature using scanning tunneling microscopy (STM). The statistical analysis of the Si adatom height at empty states for Si(111)-C2H5OH before and after the Fe deposition showed different types of adatoms: type B (before the deposition) and type B′ (after the deposition) assigned to bare adatoms, type D and type D′ to C2H5O-terminated adatoms, and type E′ to adatoms with Fe. The analysis of the height distribution revealed the protection of the molecule termination for the Fe capture at the initial stage. The analysis also indicated the preferential capture of a single Fe atom to a bare center-adatom rather than a bare corner-adatom which remain after the C2H5OH saturation, but no selectivity was observed in faulted and unfaulted half unit-cells. This is the first STM-based report proving that a remaining bare adatom, but not a molecule-terminated adatom, captures a metal.

Various iron-silicides are grown on clean Si(0 0 1) surfaces by solid phase epitaxy, a process which involves the deposition of iron and subsequent annealing [6] . Among them, we studied the structure of three-dimensional (3D) elongated islands, which are the major silicide type produced at lower Fe coverage (∼1 monolayer) and ⩾500–600 °C annealing. We applied a newly developed method of azimuth-scan reflection high-energy electron diffraction (RHEED) to obtain 3D reciprocal-lattice mapping. We succeeded in discriminating an α - FeSi 2 phase from controversial bulk phases of the islands, and we were also able to determine the orientation relation as α - FeSi 2 ( 1 1 0 ) ∥ Si ( 0 0 1 ) and α - FeSi 2 [ 1 ¯ 1 0 ] ∥ Si 〈 1 1 0 〉 , where the lattice mismatches are −1% in α - FeSi 2 [ 1 ¯ 1 0 ] direction and +34% in α - FeSi 2 [ 0 0 1 ] direction. The attenuation of the incident electron beam along the length direction of the islands leads to extremely weak spots in the RHEED pattern. We emphasize that such an analysis of the reciprocal-lattice mapping is also useful in studying other 3D island structures. Using scanning tunneling microscopy, we showed that the island’s elongated directions are perpendicular to the dimer rows of the substrate located under the islands. The islands are located near the S B step edges. The elongation lengths of the islands are almost the same as the widths of the Si substrate terraces. We discussed the formation mechanism of the 3D-elongated islands. From an atomic image of the facet and edge of a 3D-elongated island, we proposed an atomic-structure model of the island facet and edge: a Si adatom on the hollow site of four Si atoms of an α - FeSi 2 ( 1 1 0 ) unit, with [ 1 ¯ 1 0 ] ordering in the direction of the elongation, forming an α - FeSi 2 ( 1 1 1 ) facet locally.

Ultrathin films of iron silicides were grown on Si(111) surfaces by solid phase epitaxy (SPE); iron deposition and subsequent annealing, and analyzed using in situ high energy-resolution X-ray photoelectron spectroscopy (XPS). We analyzed peaks using Lorentzian and Donaich-SunjiC curves and estimated the validity of both fittings. Under the sequence from bcc-Fe to polycrystal phase (the mixture of Fe 3 Si and β-FeSi 2 ), and then β-FeSi 2 phase with annealing process, the slight chemical shifts of Fe 2p 3 / 2 toward higher binding energy (BE) and the reduction of peak asymmetry for Fe 2p 3/2 and Fe 2p 1/2 were observed. We attributed this behavior to the reduction of the metallicity in iron silicide films.

We have developed an ultrahigh-vacuum (UHV) complex sample preparation and analysis system, which realizes a reliable surface science analyzing various characters on an identical surface. The system contains three sample-preparation-and-characterization chambers and five analysis chambers. They are (1) an electronic-properties-characterization chamber, (2) a magnetic-properties-characterization chamber, (3) an organic-molecule chamber, (4) UHV SEM, (5) a high-energy-resolution angle-resolved photoelectron spectrometer, (6) a high-energy-resolution display-type spherical mirror analyzer, (7) a room-temperature (RT) STM, and (8) an optical-properties characterization chamber. A special sample holder is used with six electrodes on it, which enables accurate temperature measurement of a sample by connecting a thermocouple directly to the sample even if it is transferred. Four other electrodes can be used for construction of various circuits including evaporators. Some examples are shown.

We systematically studied the formation of various iron–silicide phases, grown on Si(0 0 1) surfaces by solid phase epitaxy, with scanning tunneling microscopy, low-energy electron diffraction and reflection high-energy electron diffraction. We found and studied the phases of c(2 × 2) islands, rectangle-like islands, elongated islands, layered islands, dome-like islands, eddy and cracked structures, and small clusters. A schematic phase diagram of these phases is successfully summarized against iron coverage at room temperature and subsequent annealing temperature.

Thin iron silicide films were grown by solid phase epitaxy method on Si(111) surface. Silicide structure and magnetic properties at 40 K were observed with reflection high-energy electron diffraction and surface magneto-optic Kerr effect in-situ. The bcc-Fe film was grown at 40 K and transformed to polycrystals at 670 K annealing. The SMOKE revealed ferromagnetic property of the polycrystals at 40 K. After 820 K annealing, a β-FeSi2 film was formed. This sample was ferromagnetic at 40 K. We suggest a multilayer structure including a ferromagnetic interface between the β-FeSi2 film and the Si(111) substrate.

Three-dimensional atomic arrangements of ultra thin Fe silicide films were directly revealed. By using circularly polarized light with opposite helicities, forward focusing peaks with their positions shifted in photoelectron angular distribution (PEAD) patterns can be obtained. We successfully observed the PEAD patterns of ultra thin Fe silicide films from different core levels of Fe and Si atoms by display-type spherical mirror analyzer (DIANA). The element selective stereo photographs indicate similar hexagonal atomic arrangement with three-fold symmetry for Si and Fe atoms, which is consistent with a model based on a CsCl -type structure with B-type stacking. This is the first observation of stereoscopic atomic arrangements for ultra thin compound films, which implies that the stereo atomscope is very powerful structure analysis tool also for complex structures on surface.

The phase transition of glycine phosphite (GPI) and partially deuterated glycine phosphite (DGPI) single crystals has been characterized by applying the effective mean field theory. Temperature dependence of the spontaneous polarization P s(T) has been analyzed from hysteresis loops for these crystals. With the increment of deuteration ratio, saturated spontaneous polarization P s 0 is also increased. As a result, the quantitative phase transition indicator g according to the mean field theory is being increased but the maximum increment is underlying the decisive tricritical point g = 1/3. The phase transition character of GPI crystal is proved to be second order but very near to the tricritical point.

We studied adsorption and reaction of nitric oxide on Si(111)7 × 7, 5 × 2-Au, $\alpha-\sqrt{3},\times \sqrt{3}-{\rm Au}$, $\beta-\sqrt{3} \times \sqrt{3}-{\rm Au}$, and 6 × 6-Au surfaces with low-energy electron diffraction, Auger electron spectroscopy, and scanning tunneling microscopy (STM). We found that NO gas reacts most strongly with the 7 × 7 surface, strongly with the 5 × 2-Au surface, and little with the other Si(111)-Au surfaces. STM results indicated that the NO exposure removes adatoms and erodes the row structure on the 5 × 2-Au surface at room temperature.

The atomic structure of thin iron silicide film, grown epitaxially on the Si(111) surface, has been analyzed by means of the three-dimensional RHEED Patterson function analysis. The iron-silicide-terminated surface with (2 × 2) periodicity has been prepared by a solid-phase epitaxy method. 2 ML of Fe were deposited on the Si(111)-(7 × 7) surface and annealed at 500°C. Three-dimensional Patterson function was calculated from series of φ-scanned RHEED intensity distributions converted to the k-space. The resulting model of γ-FeSi2 structure consists of two silicide layers faulted to each other with three relaxed Si adatoms above the H3 site.

The complex magnetic properties of Fe films epitaxially grown on Cu(0 0 1) have been discussed in relation to their atomic structure. We have studied the Fe films on Cu(0 0 1) by a new direct method for three-dimensional (3D) atomic structure analysis, so-called “stereoscopic photography”. The forward-focusing peaks in the photoelectron angular distribution pattern excited by the circularly polarized light rotate around the light axis in either clockwise or counterclockwise direction depending on the light helicity. By using a display-type spherical mirror analyzer for this phenomenon, we can obtain stereoscopic photographs of atomic structure. The photographs revealed that the iron structure changes from bcc to fcc and almost bcc structure with increasing iron film thickness.

We have studied a Si(111)2×2-Fe surface exposed to nitric oxide at room temperature with Auger electron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy (STM). The surface local structure of Si(111)2×2-Fe has been modeled to be similar to that of Si(111)7×7; both structures have Si adatom and Si first-layer restatom, but the restatom in the former surface bonds to Fe atoms. It is known that NO molecules dissociatively adsorb on Si(111)7×7 surface, especially atop adatoms. Before the exposure to the Si(111)2×2-Fe surface, STM images showed 2×2 islands on the 2×2 terrace. After the exposure, the 2×2 islands were eroded at the island edge while the 2×2 terrace was stable against nitric oxide. We ascribed the inert property of the 2×2 terrace, and the reactive property of the 2×2 island edges and the 7×7 terrace, primarily to the Si restatom with different neighbor atoms.

A combined system of the Auger electron analysis and the scanning tunneling microscope (STM) has been developed for both topographical observation and elemental analysis of surface. An STM tip works as a field-emission electron source inducing the Auger process. Conventionally used STM tip has a problem for the Auger measurements; Auger electrons from the sample surface are accelerated toward the sample in the strong electric field between the cathode tip and the sample. We constructed a new special tip with a shield electrode around the cathode tip to prevent the bending of the trajectories of Auger electrons. The field-emission electron was ejected from the cathode tip, and the special tip played a role of primary electron source for the Auger electron analysis. We detected silicon Auger electrons successfully from a clean Si(111) surface using a cylindrical mirror analyzer that located behind the special tip. This system works for both STM observation and Auger element analysis by exchanging the tip in vacuum.

We have studied GaP ( 1 1 1 ) reconstructed clean surface with scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED). We found that the surface consists of six equivalent mirror-symmetric domains and each domain has stripe structure. The stripe directions tilt from three 〈 1 1 2〉 directions clockwise and counterclockwise at the same angle, resulting in six domains. The stripe period and the tilt angle are 1.30 nm and 6.8°, respectively. Magnified STM images revealed that all stripes in one domain have the same protrusion unit along the stripe direction, and that the origin of the protrusion unit is arranged by two vectors for the inter-stripe direction. The same unit-vector in the stripe direction and the two unit-vectors in the inter-stripe direction constitute two different surface-reconstruction units, namely units 1 and 2. We assigned the reconstruction matrices of units 1 and 2 in one domain to 3 −1 2 5 and 4 1 2 5 , respectively. A trial structure model assuming the same elements located at the protrusions well explains observed LEED patterns.

We have developed a scanning tunneling microscope (STM) combined with an Auger electron energy analyzer for both topography observation and element analysis on surfaces. A special STM tip was designed for a field-emission source that induces the Auger process. We found that a simple STM tip is not effective, since the trajectories of Auger electrons ejected from the surface are bent considerably by the high electric field between the surface and the tip. Instead, the shield electrode around the tip reduces the bending, and carbon Auger electrons (KLL) ejected from the highly oriented pyrolytic graphite were detected. In future, such an Auger-STM will enable both types of observation conveniently on the same region by changing modes between topography and Auger measurements.

A three-dimensional Si{111} vertical side-surface structure on a Si(110) wafer was fabricated by reactive ion etching (RIE) followed by wet-etching and flash-annealing treatments. The side-surface was studied with scanning tunneling microscopy (STM) in atomic scale for the first time, in addition to atomic force microscopy (AFM), scanning electron microscopy (SEM), and low-energy electron diffraction (LEED). AFM and SEM showed flat and smooth vertical side-surfaces without scallops, and STM proved the realization of an atomically-flat 7 × 7-reconstructed structure, under optimized RIE and wet-etching conditions. STM also showed that a step-bunching occurred on the produced {111} side-surface corresponding to a reversely taped side-surface with a tilt angle of a few degrees, but did not show disordered structures. Characteristic LEED patterns from both side- and top-reconstructed surfaces were also demonstrated.

The surface structure of epitaxial $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2}$(100) thin film grown on Si(001) was analyzed using the quantitative low-energy electron diffraction intensity-voltage (LEED I-V) method, ab initio density functional theory (DFT) calculations, and scanning tunneling microscopy (STM). LEED patterns measured on the $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2}$(100) surface reveal two domains of a $p(2\ifmmode\times\else\texttimes\fi{}2)$ reconstruction with $p2gg$ diffraction symmetry. The iron-silicide film truncation and atomic surface structure were determined by LEED I-V method: The smallest Pendry's reliability factor ${R}_{P}=0.22\ifmmode\pm\else\textpm\fi{}0.02$ was achieved for the bare $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2}$ film truncated by an Si layer, whereas Si and Fe ad-atom structures were excluded. Significant atomic relaxations within the topmost surface layers were revealed by the LEED I-V method and confirmed by DFT. The simulated STM patterns from the best-fit model agree well with the measured STM images on the $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2}(100)/\mathrm{Si}(001)\text{\ensuremath{-}}p(2\ifmmode\times\else\texttimes\fi{}2)$ surface: Four Si atoms on a surface form one bright protrusion on STM patterns. Electronic band structure analysis of the bulk and epitaxial $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2}$(100) was carried out. A bare truncated epitaxial film was found to be metallic. Surface electronic states were identified by a partial $k$-resolved atomic-orbital based local density-of-state analysis.

Circular dichroism has been measured in the photoelectron diffraction of W 4f photoelectrons from W(1 1 0)1×1 clean surface. The forward-focusing peaks along symmetric axes in diffraction pattern rotate azimuthally in either counterclockwise or clockwise direction depending on light helicity around the incident light axis. Using the formula suggested by Daimon et al. [Jpn. J. Appl. Phys. 32 (1993) L1480] substituting measured rotation angles for the [1 0 0] and [1 1 1] peaks, we evaluated effective atomic distance between an emitter and a scatterer, after calculating effective magnetic quantum number as a function of the polar angle between directions of the incident light and the photoelectron. The results of the effective atomic distance longer than the nearest-neighbor distance for each forward-focusing direction suggest partial contribution to the forward-focusing peak by the scatterers behind the nearest neighbor, within a single scattering theory.

The photoelectron angular distribution (PEAD) from single-crystalline graphite is measured by using a two-dimensional display-type spherical mirror analyzer and a linearly polarized synchrotron radiation by varying the photon and photoelectron kinetic energies. From the study of the photon energy (hν) dependence of umklapp processes, it is found that their intensities are reduced considerably at hν = 50–60 eV. The mechanism of the umklapp process is discussed. The atomic orbitals composing the valence band is shown to be specified from the PEAD pattern by considering a transition matrix as well as umklapp processes. Furthermore, the band structure of graphite over the entire Brillouin zone is measured. The three-dimensional [EB-kx-ky] dispersion of the π and σ bands are extracted and presented for the first time.

Circular dichroism has been measured in the photoelectron diffraction of bulk W 4f photoelectrons from the W(110)(1×1) clean surface. The forward focusing peaks along the symmetric axis in the diffraction pattern showed an azimuthal rotation similar to those reported in a prior experiment on Si(001) and chemically shifted W 4f photoelectrons from the W(110)(1×1)-O surface. The emission angle dependence of the rotation angles has been measured and analyzed for the first time and the angles observed are in good agreement with those calculated using the formula Δ ϕ=m/kR sin 2θ derived previously by Daimon et al. [Jpn. J. Phys.32, L1480 (1993)] considering the angular dependence of m. This property gives a basis for the analysis of structure or various magnetic and electronic properties on surfaces.

Using scanning tunneling microscopy, we studied Ge(001) surfaces covered with an average of approximately 0.8 monolayers of silver. In the deposition at room temperature, we observed that Ag predominantly grew in a three-dimensional (3D) mode on bare Ge substrates, corresponding to Volmer–Weber growth. At the same time, we found two-dimensional (2D) Ag islands elongated in the dimer-row direction with one monolayer height, though the density of the 2D islands was smaller than one-fifth of that of the 3D islands. Images with atomic resolution showed stripe patterns on the 2D islands and enhancement of asymmetry of the Ge dimers on both sides of the islands at high positive bias voltages.

Germanium(001) surfaces deposited with less than 0.3 nm thick Ag on average were studied by scanning tunneling microscopy. After the small amount of Ag deposition at 100 K, thin two-dimensional (2D) islands with 0.18 nm height are predominantly found to elongate to the dimer-row direction on clean Ge(001)-2×1 surfaces. With increasing temperature during the deposition, the density of three dimensional (3D) islands with more than 0.6 nm height increases, although few 2D islands are still formed at room temperature. With increasing average thickness of deposited Ag, the density of 3D islands increases at any temperature between 100 K and 300 K. These features are explained in terms of the diffusion of Ag atoms on the surface during deposition.

Tunneling spectra are measured at various positions on iron-deposited surfaces of superconducting 2H-NbSe 2 crystals using scanning tunneling microscopy at 4.2 K. Iron islands are formed on the surface at the initial deposition stage at room temperature. For isolated iron islands, the spectra around the islands are slightly modified from the original for the superconductor and depend on the distance from the islands. The spectra change significantly and have spatial dependence on the surface where iron islands are randomly and densely distributed. The spatial changes are discussed with inhomogeneous magnetic scatterings of substrate superconducting electrons by the iron islands.

The atomic structure and tunneling spectra of a cleaved surface of a 2H-NbSe 2 single crystal were studied by scanning tunneling microscopy at 4.2 K. Small domains with \(\sqrt{13} \times \sqrt{13}\) modulation were found adjacent to the flat surface with a 3 ×3 intrinsic charge density wave (CDW). The surface atom arrangement in the domains is the same as that in the 2H-type surface. The density of states around the Fermi energy was measured at the domains by tunneling spectroscopy, and found to be lower than that at the 2H-type surface. The \(\sqrt{13} \times \sqrt{13}\) modulation is considered to originate from another CDW, which can be expected to occur in 4H-NbSe 2 clusters buried in a 2H-type crystal. The change of the tunneling spectrum across the boundary between the 2H-type surface and a \(\sqrt{13} \times \sqrt{13}\) modulated domain was also measured, and the proximity of superconductivity of 2H type to the modulated domain is discussed.

Surface structure changes of hydrogen- or chlorine-adsorbed Si(111)-(7 × 7) caused by ultra-violet laser light have been studied with a scanning tunneling microscope. Experiments were performed in ultra-high vacuum conditions with a small fluence of laser light in order to avoid gas-phase excitation and strong thermal effects. Polyhydrides are found to decompose slowly to monohydrides, and polychlorides are desorbed by electronic excitation with the light. On the other hand, monohydride and monochloride Si atoms on the surface are stable against irradiation. The results are discussed in terms of hot carriers excited by light in the substrate, and their relaxation to the vibration of the adsorbates at surfaces.