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Based on the multiple scattering theory, reflection high-energy electron diffraction (RHEED) intensities are calculated from H-adsorbed Ni(111) surfaces by explicitly taking the scattering from H atoms into account. Systematic RHEED intensity changes in the rocking curves and the azimuthal plots are obtained by changing the H position both in the surface normal and parallel directions. In the rocking curves, the peak and dip positions as well as their intensities distinctly change under some diffraction conditions. In the azimuthal plots, the peak widths show systematic variations as a function of H height. Changes in RHEED intensities are also obtained from the surfaces with subsurface H as a function of the H depth. The intensity changes as a function of H position are different from those as a function of surface relaxation of the topmost Ni layer. The results show that RHEED should be a promising tool to extract the structural information of H on metal surfaces.

We fabricated Pt films on SrTiO 3 (STO)(100) using a DC-magnetron sputtering method to investigate the preferred orientation, surface structure, and electrochemical property. A film grown at 400 °C showed the two-dimensional polycrystalline features of Pt(111). Reflection high-energy electron diffraction (RHEED) showed diffraction patterns independent of the in-plane incident angle of the film. Films grown at 600 and 700 °C exhibited a preferred orientation of Pt(100) and (110). The films exhibited the morphology of faceted islands with roughness of several tens of nm, which consisted of two kinds of domains, namely a domain with preferred orientation of (100) and one with (110). The (100) and (110) domains had 45-degree twin boundaries, which were observed as V-shaped streaks by RHEED. The (100) domain was aligned in orientation of [011]Pt//[010]STO, which suggests that the binding strength of the (110) plane at the interface was larger than that of the (100). With a further increase in the growth temperature up to 750 °C, the film primarily showed a preferred orientation of (100) with an in-plane orientation of [010]Pt//[010]STO. The film also showed an island structure; however, atomic force microscopy revealed that the top was atomically flat.

Adsorption of formic acid and co-adsorption with oxygen have been investigated on the rutile TiO2(110) surface using p- and s-polarized infrared reflection-absorption spectroscopy (IRRAS) at O2 exposures between 45 L to 8100 L and at temperatures between 273 K and 343 K. On the clean surface formic acid dissociates into a formate ion (formate) and a proton. Formate binds to two five-fold coordinated Ti atoms in the troughs along the [001] direction, and the proton binds to neighboring bridging O atoms. Exposure of adsorbed formate to O2 leads to a decrease in the asymmetric νas(OCO) band at 1532 cm−1 and to the concomitant formation of a new vibration band at 1516 cm−1. From the s-and p-polarized IRRAS measurements performed at different O2 exposures, surface pre-treatments and substrate temperatures, and by comparisons with previous reports, we conclude that the new species is a bidentate surface hydrogen carbonate, which is formed by reaction between formate and oxygen adatoms on the surface. The σv reflection plane of the surface hydrogen carbonate molecule is oriented along the [001] direction, i.e. the same direction as the adsorbed formate molecule. On the clean TiO2(110) surface exposed to O2 prior to formic acid adsorption, similar results are obtained. The reaction rate to form surface hydrogen carbonate from formate is found to follow first-order kinetics, with an apparent activation energy of Er=0.25 eV.

The topography of a Si(001) vicinal surface is investigated using reflection electron microscopy (REM) during alternating current (AC) heating of the surface in ultra-high vacuum. The normal direction of the surface is slightly tilted from the [001] direction at θx or θy on the x or y axis (they are orthogonal 〈110〉 directions in the Si(001) surface), and the average widths of the terraces (a or b in x or y axis) are determined by θx or θy; the direction perpendicular to the incidence electron beam on the surface is selected as the x (horizontal) axis in each REM image. Alternating current heating changes each initial surface from stable to double-domain (DD), in which 2 × 1 and 1 × 2 terraces are arranged regularly with approximately equal width, at its transition temperature Tc; the dimer rows are parallel to the x or y axis in the 1 × 2 or 2 × 1 terraces. There are two types of stable surfaces in the vicinal surface. At temperatures below its Tc, the surface with horizontally (vertically) long terraces, where b a), changes to a 2 × 1 (1 × 2) surface with wide 2 × 1 (1 × 2) and narrow 1 × 2 (2 × 1) terraces. The terrace, the short side of which is parallel to its dimer row direction, grows to create a stable surface by thermal diffusion of Si atoms at temperatures below Tc. During AC heating, thermal diffusion plays a key role in analyzing the kinetics of the atoms on the surface because the thermal effect acts as the driving force for the atoms that have not yet evaporated from the surface. Then, by evaporating atoms from the vicinal surface, AC heating creates a DD surface at temperatures between its Tc and 1100 °C and a rugged surface consisting of small 2 × 1 and 1 × 2 terraces at temperatures above 1100 °C.

The structure of the Fe3O4(110)-(1x3) surface was studied with scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and reflection high energy electron diffraction (RHEED). The so-called one-dimensional reconstruction is characterised by bright rows that extend hundreds of nanometers in the [1-10] direction and have a periodicity of 2.52 nm in [001] in STM. It is concluded that this reconstruction is the result of a periodic faceting to expose {111}-type planes with a lower surface energy., 6 pages, 3 figures

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.

We have used in situ ultrahigh vacuum reflection electron microscopy to investigate the process of two-dimensional negative islands (etching pits) nucleation on extremely wide (up to 120 μm in diameter) terraces at Si(111) surface during thermal etching with molecular oxygen at temperatures above 1000 °C. By analyzing nucleation kinetics at different temperatures and comparing the results with theoretical model, we determined the dominant surface mass transport mechanism. The squared critical terrace size D crit 2 for nucleation of new island is found to follow power law form with scaling exponent χ changing from 0.95 to 1.15 as the temperature increased T crit = 1180 °C. At temperatures above T crit we estimated the energy of the vacancy–step interaction E AD as 1.5 ± 0.15 eV. We conclude that observed changes of the D crit in high temperature region (above T crit ) can occur through detachment–attachment kinetics of vacancy–step exchange process rather than via surface diffusion.

We have investigated the Si(111)-√21 × √21-(Ag, Cs) superstructure using reflection high-energy positron diffraction. Rocking curve analysis based on the dynamical diffraction theory reveals that Cs atoms are located at a height of 3.04 A above the underlying √3 × √3-Ag structure and that they form a triangular structure with a side length of 10.12 A. The structure of the Si(111)-√21 × √21-(Ag, Cs) surface is significantly different from those of the Si(111)-√21 × √21-Ag and Si(111)-√21 × √21-(Ag, Au) surfaces, probably because of the different electronic structures of the alkali and noble metal atoms.

The InSb(111)A surface is prepared by molecular beam epitaxy and investigated by reflection high-energy electron diffraction (RHEED). The complete two dimensional diffraction pattern is mapped out by azimuthal RHEED (ARHEED). Two reconstructions are identified and additionally a set of new symmetries is observed. At low temperature a 2 3 × 2 3 pattern is observed which changes to the (2 × 2) pattern at high temperature. In contrast to the GaSb(111)A surface the observed 2 3 × 2 3 structure is not stabilized by configurational entropy.

The atomic structures of Au and Ag co-adsorption-induced √21 × √21 superstructure on a Si(111) surface, i.e., (Si(111)-√21 × √21-(Au, Ag)), where the Si(111)-5 × 2-Au surface is used as a substrate, have been investigated using reflection high-energy positron diffraction (RHEPD) and photoemission spectroscopy. From core-level spectra, we determined the chemical environments of Ag and Au atoms present in the Si(111)-√21 × √21-(Au, Ag) surface. From the rocking curve and pattern analyses of RHEPD, we found that the atomic coordinates of the Au and Ag atoms were approximately the same as those of the Au and Ag atoms in other Si(111)-√21 × √21 surfaces with different stoichiometries. On the basis of the core-level and RHEPD results, we revealed the atomic structure of the Si(111)-√21 × √21-(Au, Ag) surface.

The structure of the 3 × 3 -R30° reconstruction on the (0001) surface of silicon carbide before and after initial oxidation at room temperature was determined with reflection high-energy electron diffraction (RHEED) rocking curves in the one-beam condition and density-functional theory calculations. The structural parameters of the clean surface are in good agreement with previous reports. For the oxidized surface, good agreement between experimental and calculated RHEED rocking curves was obtained for a model with oxygen atoms in the backbonds of the Si adatom and on its top (ad-ins × 3). The atomic positions of the oxidized surface determined from the density-functional theory calculations agree reasonably well with the RHEED results.

The adsorption of carbon monoxide on Pt(111) was studied using polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and sum frequency generation (SFG) spectroscopy. Two CO on-top signals at 2110 cm − 1 and 2097 cm − 1 have been detected under continuous CO exposure in a pressure range from 10 − 7 to 100 mbar and at temperatures between 200 K and 300 K. The formation of the higher wavenumber signal is found to be kinetically limited below 200 K and by the presence of a stable c (4 × 2) adlayer in UHV. On the basis of the results presented in this study and previous experimental findings the two on-top signals are related to different CO compression layers on Pt(111) with θ > 0.5, hexagonal Moire lattices and rectangular coincident site lattices.

Reflection electron energy loss spectra (REELS) of Al(111) single crystal and of the aluminum polycrystalline (poly Al) film were measured at 200 eV and 1000 eV electron energies for a variety of experimental geometries and were mutually compared. No anisotropy was found for the poly Al, as expected. Polar intensity plots evaluated from the elastic (no loss) and inelastic first surface plasmon- and first bulk plasmon-loss intensities of the Al(111) surface show clearly discernable peaks for both considered electron energies. Their positions on the angular axis are the same for the elastic as well as for the inelastic, surface and bulk plasmon-loss peaks. The polar plots of intensities of the elastically and inelastically reflected electrons were compared to calculated intensities of photoelectrons emitted from the Al 2s core level to the same kinetic energy. Peak positions in the theoretically determined polar plots of electron intensities agree with those obtained experimentally in REELS.

A detailed comparison of two different physical approaches for quantitative analysis of reflection electron energy loss spectra (REELS) is presented. The Tougaard–Chorkendorff (TC) algorithm [S. Tougaard, I. Chorkendorff, Phys. Rev. B35 (1987) 6570] is analyzed theoretically and applied to experimental spectra of four elemental solids (Si, Cu, Ag, and Au). A closed expression is derived for the quantity retrieved by the TC-algorithm, the so-called “effective” cross section, which was originally only given as a recursive procedure. Single scattering loss distributions are derived from the experimental spectra using the bivariate reversal method [W.S.M. Werner, Phys. Rev. B74 (2006) 075421]. The latter agree satisfactorily with density functional theory (DFT) calculations and other data found in the literature. Using these single scattering loss distributions, the TC “effective” cross section can be perfectly reproduced if the fact is taken into account that the effective cross section is not a single scattering loss distribution and is governed to a significant extent by elastic scattering. On the basis of the above results, a dramatically simplified deconvolution scheme for quantitative analysis of REELS is developed.

Reflection high-energy electron diffraction (RHEED), reflectance difference spectroscopy (RDS), and scanning tunneling microscopy (STM) have been used to study the anisotropic kinetics on the growing Ge(0 0 1) surface. While switching of dimer direction in alternate (2 × 1)/(1 × 2) layers causes the bilayer-period oscillations in RD response, RHEED oscillations are governed by variations in surface step densities. We show that the RHEED oscillations are strongly affected by the growth front morphology: when the growth front becomes distributed over several layers, the transition from bilayer- to monolayer-period occurs in RHEED oscillations.

In this letter we report on the formation of long-range surface disorder features during the growth by molecular beam epitaxy (MBE) of homoepitaxial GaAs (0 0 1) films having the β2(2 × 4) reconstruction. Observations were made in real-time at the growth temperature using reflection high energy electron diffraction (RHEED) and analyzed kinematically. We show that kinks (cooperative shifts of whole columns of 2 × 4 units along the [1 1 0] direction) form rapidly as growth commences and that the antiphase domain structure present on the substrate prior to growth as a result of the arrangement of As–As dimers persists. This produces a surface with two types of long-range disorder. We speculate on the role of incident Ga atoms on this process.

By using reflection high-energy positron diffraction (RHEPD) and first-principles calculations, we investigated an In/Si(1 1 1) surface on which the quasi-one-dimensional In atomic chains that exhibit the metal–insulator transition were formed. From the analyses of rocking curves, we found the transformation of the zigzag chain structure of In atomic chains to hexagon structures below 130 K along with the phase transition from the 4 × 1 to the 8 × 2 periodicities. The band structure calculated with the optimum hexagon structure displays the gap opening of 60 meV, which indicates the semiconducting character. This confirms the recent theoretical prediction that the hexagon structure is energetically favored at low temperatures [C. Gonzalez, F. Flores, J. Ortega, Phys. Rev. Lett. 96 (2006) 136101].

Reflection electron energy loss spectra have been measured for silver using incoming electrons with energies between 5 and 40 keV, in a surface and volume-sensitive geometry. Bulk and surface loss functions are extracted from these data and various consistency checks are applied to the obtained loss functions. Depositing minute amounts of Al onto the Ag surface causes a severe reduction in surface features. The intensity of the surface feature seems now to increase as the probe energy is increased. A mechanism by which this can occur is discussed. The relation between the bulk loss function and the dielectric function is discussed, and a comparison with the results of transmission electron energy loss spectra and optical data is made.

The Au adsorption induced √21 × √21 super-lattice structure on the Si(1 1 1)-√3 × √3-Ag structure has been investigated using reflection high-energy positron diffraction. The height of the Au adatom was determined to be 0.59 A from the underlying Ag layer from the rocking curve analysis with the dynamical diffraction theory. The adatoms were preferentially situated at the center of the large Ag triangle of the inequivalent triangle structure of the Si(1 1 1)-√3 × √3-Ag substrate. From the intensity distribution in the fractional-order Laue zone, the in-plane coordinate of the Au adatoms was obtained.

A simple procedure is developed to simultaneously eliminate multiple scattering contributions from two reflection electron energy loss spectra (REELS) measured at different energies or for different experimental geometrical configurations. The procedure provides the differential inverse inelastic mean free path (DIIMFP) and the differential surface excitation probability (DSEP). The only required input parameters are the differential cross section for elastic scattering and a reasonable estimate for the inelastic mean free path (IMFP). No prior information on surface excitations is required for the deconvolution. The retrieved DIIMFP and DSEP can be used to determine the dielectric function of a solid by fitting the DSEP and DIIMFP to theory. Eventually, the optical data can be used to calculate the (differential and total) inelastic mean free path and the surface excitation probability. The procedure is applied to Fe, Co and Ni and the retrieved optical data as well as the inelastic mean free paths and surface excitation parameters derived from it are compared to values reported earlier in the literature. In all cases, reasonable agreement is found between the present data and the earlier results, supporting the validity of the procedure., 27 pages 9 figs

Growth behavior of thin Ag films on Si substrates at room temperature has been investigated by scanning tunneling microscopy and reflection high energy electron diffraction. In the layer-plus-island growth Ag islands show strongly preferred atomic scale heights and flat top. At low coverage (1 ML), islands containing two atomic layers of Ag are overwhelmingly formed. At higher coverages island height distribution shows strong peaks at relative heights corresponding to an even number (2, 4, 6, .. .) of Ag atomic layers. Beyond some coverage the height preference vanishes due to the appearance of screw dislocations and spiral growth. � 2006 Elsevier B.V. All rights reserved.

We observed four kinds of adsorbed NO molecules on Pt(9 9 7) at 11 K using infrared reflection absorption spectroscopy (IRAS). The peaks at 1690, 1484 and 1615 cm−1 are assigned to the N–O stretching modes of the on-top site and the hollow site on the terrace and the bridge site at the step, respectively. The 1385 cm−1 peak is observed below ∼70 K. We assign the 1385 cm−1 peak to the hollow site of the (1 1 1) microfacet at the step or the lower-terrace hollow site nearest to the step. By heating, site-to-site hopping to the more stable site occurs and the relative stability of four adsorption sites can be determined.

We study the nucleation phase of molecular beam epitaxy of (hexagonal) MnAs on (cubic) GaAs (0 0 1) using reflection high-energy electron diffraction (RHEED) azimuthal scans. The nucleation proceeds from a non-reconstructed initial stage through randomly oriented small nuclei and two orientation stages to the final single-phase epitaxial orientation. The fascinatingly complex nucleation process contains elements of both Volmer–Weber and Stranski–Krastanov growth. The measurement demonstrates the potential of high-resolution RHEED techniques to assess details of the surface structure during epitaxy.

Crystal orientation of poly(ethylene 2, 6-naphthalate) (PEN) ultrathin films was investigated by the combination of reflection–absorption infrared spectroscopy (RAIR) and grazing incidence X-ray diffraction (GIXD) techniques. It is concluded that the main-chain of PEN molecule in ultrathin film is prone to alignment parallel to the substrate when compared with thicker films. During the formation of α form crystalline, the naphthalene ring, the CO group in molecular chain of PEN as well as the b axis in crystalline tend to take orientation more parallel to the substrate due to the surface-induced effect. However, such an anisotropic structure could not be observed in the bulk PEN.

Owing to its surface sensitivity, reflection electron microscopy (REM) is widely used to study surface structure and surface dynamic processes. However, because of the glancing conditions, REM images are severely foreshortened in one direction by a factor varying between 1/40 and 1/70. If this foreshortening does not really affect the study of roughly one-dimensional objects as monoatomic steps on a surface, it is dramatic when considering the shape of two-dimensional objects (as 2D islands) or even 3D objects (as growth or evaporation spirals) at the surface. In these cases, the distorted images may be numerically corrected, but the finite size of the pixels limits the final resolution. In this paper we show that a simple modification inside the column of the microscope (based on a controlled tilt of the screen, on the use of an intensity magnification and on the large depth of focus available in electron microscopes) allows a true correction of the distortion. We thus are able to obtain low distorted REM images. The results are illustrated by some images of the Si(0 0 1) and Si(1 1 1) surfaces.

Structural and optical properties of MBE-grown GaAs(0 0 1) and GaAs(1 1 1)B surfaces have been studied by reflection high-energy electron diffraction and single-wavelength ellipsometry under dynamic conditions of ramp heating after desorption of passivating As-cap-layer with and without As4 beam applied to the surface. For a number metastable reconstruction transitions a clear correlation is established between diffraction and optical data. Boundary lines for transitional superstructures on GaAs(0 0 1) are determined as a function of As flux and corresponding activation energies are estimated. For the first time it is shown ellipsometrically that optical response of the surface is drastically different for transitions of the order ⇒ order and order ⇒ disorder type.

We first summarise previous work on long-range disorder effects occurring on the GaAs(0 0 1) β2(2 × 4) surface, as determined by reflection high energy electron diffraction (RHEED), grazing incidence X-ray diffraction and scanning tunnelling microscopy (STM). Models which have been deduced are related to the assembly of β2(2 × 4) and c(2 × 8) unit cells and involve the presence of antiphase domains and one-dimensional disorder boundaries. We ignore kinks produced by cooperative shifts of whole (2 × 4) units in the [1 1 0] direction, since they are only present in significant numbers on surfaces formed in the presence of a large excess of arsenic. We show from a combination of multi-azimuthal RHEED data and structure factor calculations that none of the existing models is consistent with all of the diffraction information. In particular, STM images show that the surface has a non-ideal c(2 × 8) structure made up of a distribution of β2(2 × 4) cells having equal but irregular occupancy of the two possible phase positions. The equal occupancy means that certain reflections should be forbidden, but in practice some of these appear strongly. We have suggested possible structural effects which might produce these results, such as a change in atom positions in the boundary region where two cells conjoin, so that they are no longer identical entities. We have been unable to obtain confirmation, however, since the precise atom locations are not known.

Simulations of multilayer reflection–absorption infrared spectra (RAIRS) are commonly based upon the application of Greenler equations which treat each layer as being optically isotropic. Extensions of the theory to include anisotropic adsorbate layers are also available but discussion of anisotropy in subsequent substrate layers have largely been ignored. In this paper, based on known principles, we develop a general theory for the simulation of RAIR spectra taking into account optical anisotropy in any or all layers of a many-layered system. The effect of considering optical anisotropy is illustrated by a four-layer system (typical when using the so called buried metal layer BML method) where adsorbate-induced substrate-derived bands may be observed. We show that in such cases, the effect of optical anisotropy may significantly alter the appearance of the spectrum.

The edge-on orientation of alkyl chains, in which the carbon zigzag plane is perpendicular but the chain direction is parallel to the substrate surface, has been detected for specially designed 9,9-dioctadecylfluorene (DOF) molecules on an iodine-covered Au(1 1 1) surface by infrared reflection absorption spectroscopy (IRAS). Using p-polarized light, the methylene symmetric stretching vibrational mode with transition dipole moment μ parallel to the carbon plane has been observed predominantly at 2852 cm −1 compared to the methylene antisymmetric stretching mode with μ perpendicular to the plane.

We studied the atomic structure of the As-stabilized GaAs(0 0 1)- c (4×4) surface using scanning tunneling microscopy, reflection high-energy electron diffraction, reflectance difference spectroscopy, and first-principles calculations. The structure model consisting of three Ga–As dimers per c (4×4) unit cell explains well the experimental data. The three Ga–As dimers in the c (4×4) unit cells are usually aligned in the same orientation, which was found to be energetically stable. We also discuss the possible change to the symmetric As–As dimer structure under more As-rich condition.

Using our Monte-Carlo (MC) code, we calculated the ratio of the coefficients of elastic reflection of electrons from Si, SiO2 and Au to those of Cu and Al in the electron energy range 0.2–1.0 and 1.5 keV (Au–Cu), respectively. The electron scattering was simulated by a single scattering model. For the MC calculations, we compared the elastic differential cross-sections calculated using a static field approximation with relativistic partial wave analysis on either the Thomas–Fermi–Dirac potential of free atoms (TFD model) or the Hartree–Fock–Wigner–Seitz (muffin-tin) potential of atoms in the solid state (HFWS model). The MC data were compared with the experimental values. For both models, reasonably good agreement for Si–Cu and SiO2–Cu systems was found. In the Au–Cu system, better agreement was achieved using the TFD model. The addition of C in a surface interaction layer of 2–5 nm improves the agreement between simulated and experimental values for the Si–Al and Si–SiO2 systems.

In this paper we report a theoretical investigation of the reflection absorption infrared spectroscopy (RAIRS) experiment applied to non-metallic substrates incorporating a buried metal layer (BML). In particular we concentrate on the low wavenumber region (280-480 cm(-1)) typically studied using synchrotron based RAIRS experiments. To illustrate this study, an example system consisting of a hypothetical isotropic layer adsorbed on thin-films of tin(IV) oxide on tungsten has been used. Using a four-layer model, systematic wavenumber-dependent Greenlet type calculations of DeltaR/R (often taken as a measure of the sensitivity of the experiment) have been performed. The calculated spectra show the absorption band associated with the adsorbate but also reproduce an "inverse absorption" feature, which has been observed experimentally. The results show that the factors which influence the intensity of these adsorbate-induced inverse absorption bands are different from those that influence adsorbate bands and may therefore be used to discriminate between these two types of feature. A partial first order approximation of the full Greenler-type formula has then been used to rationalise the calculated dependences of the intensities of both absorption and inverse absorption bands and system parameters like layer thicknesses, incidence angles and optical characteristics of the adsorbate. (C) 2004 Elsevier B.V. All rights reserved.

Using molecular-dynamics simulation, we study sputtering and defect formation induced by 5 keV Xe + ion impact on a Pt(1 1 1) surface at oblique and glancing incidence angles. Impact on a terrace produces yield maxima at ϑ =60–65° incidence angle towards the surface normal. Beyond 75–80°, no damage is produced due to projectile ion reflection. Impact on a dense-packed step, however, produces defects in sizeable numbers up to glancing incidence, ϑ =85°. The dependence of the yields on the incidence angle and distance of the impact point of the projectile to the step are discussed.

We construct a 3D representation of the N/W(1 0 0) potential energy surface using the “corrugation-reducing procedure” to interpolate between ab initio data. We study the absorption and reflection dynamics on the frozen surface using classical trajectory methods. Our results show the importance of “dynamic trapping” which causes a decrease of the absorption probability with increasing impact energy. The strong corrugation of the surface induces a diffusion-like evolution of the atom degrees of freedom parallel to the surface.

The vicinal Au(1 1 0) surface morphology throughout the (2 × 1) to (1 × 1) phase transition is studied by quantitative reflection high-energy electron diffraction. As the surface is heated from 300 K, the average terrace width remains unchanged up to 635 ± 10 K. Above that temperature, the average terrace width increases and at 683 K has a value (34 ± 10)% more than at 300 K. At higher temperatures, the average terrace width decreases. The average string length at step terraces on Au(1 1 0) remains basically unchanged up to ∼650 K and decreases sharply at higher temperatures indicative of a step-induced roughening transition. Thermal-induced adatom/vacancy generation on terraces is shown to increase significantly above ∼680 K. At room temperature, the spacing between the topmost two layers of the Au(1 1 0) surface is contracted by 0.31 ± 0.03 A or ∼22% of the bulk-terminated structure.

Reflection anisotropy spectroscopy (RAS) achieves surface specificity by sensing optical anisotropy. While surface specificity is prized, it is often rather difficult to relate optical anisotropy to properties of more direct interest. This fact, together with its inability to study isotropic surfaces, can be considered weaknesses of RAS. Here, on the contrary, the application of studying liquid crystal (LC) alignment layers is presented. In this, RAS directly probes the key characteristic and suppression of the isotropic optical response is essential. In the commercial fabrication of LC displays, defects in alignment layers cannot be detected until the construction of the device has been completed. The potential of RAS to detect improperly processed regions and therefore predict the quality of displays during the fabrication process is demonstrated.

Density functional calculations show that the electric field effect on Si ad-dimer diffusion on Si(0 0 1) is largely a reflection of the position dependence of the ad-dimer’s dipole moment. Surface diffusion barriers’ dependence on perpendicular electric fields can be used to discriminate between diffusion mechanisms. Since the previously accepted mechanism for ad-dimer diffusion on Si(0 0 1) has the opposite field dependence to what is observed, it cannot be the one that dominates mass-transport. We identify an alternate process, with a similar barrier at zero electric field and field dependence in agreement with measurements. For rotation, calculations to date show linear field dependence, in contrast to experiments.

In order to investigate dynamic change in surface structure, we tried to measure the rocking curve of reflection high-energy electron diffraction (RHEED) by using a quasi-1D convergent beam method, which means a superposition of a hundred RHEED patterns at different glancing angles on one image. After we have checked the experimental accuracy, it is confirmed that the measurement time is shortened to 0.3 s by using this method. We also show an application of this method to a real time observation of surface segregation of B atoms while a highly B-doped Si is annealed.

Reflection electron energy loss spectra have been measured for a semiconductor and some metals (Si, Cu, Ag and Au). A novel procedure is presented to rigorously decompose the spectra into contributions corresponding to surface and volume excitations. The resulting distributions of energy losses in an individual surface loss are in good agreement with theory. In particular, the begrenzungs effect occurring at the boundary of a solid state plasma, i.e. the reduction of the intensity of bulk modes due to the coupling with surface modes, can be clearly observed in the retrieved energy loss distribution.

Angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) of a Si(1 1 1) surface regularly terminated by methyl groups is reported. The electrochemical methylation was performed in inert atmosphere. The cleanliness and 1×1 ordering of the surface were confirmed by Auger electron spectroscopy and reflection high-energy electron diffraction, respectively. The energy band diagram has been obtained from ARUPS and each energy level was assigned from the comparison with the results of hydrogen-terminated Si(1 1 1) and quantum chemical cluster calculation.

By using scanning tunneling microscopy and reflection high-energy electron diffraction (RHEED), kinetics during the low temperature (LT) growth of GaAs as well as anomaly in RHEED intensity oscillation (RO) has been studied. At the intermediate temperature in the range of 300–500 °C, the growing surface roughens, while at the still LT, with decreasing the island size, the surface roughening settles down to some extent, which renders reentrant behavior of the RO. In the reentrant LT region, the RO shows temporal frequency shift. Dynamical calculations reproduce the observed features qualitatively, confirming that the anomaly is largely concerned with the multilayered morphology evolved during the growth.

In this work, we compare the (2×4) reconstructions of GaP and InP(0 0 1) surfaces. Two different (2×4) reconstructions are detected by reflection high energy electron diffraction for both materials. Photoemission experiments reveal that the high temperature one is cation-rich whereas the low temperature one is anion-rich. High resolution spectra on the high temperature (2×4) reconstructions exhibit surface components which are in agreement with what is expected from the mixed-dimer model in both cases. As regards the low temperature (2×4) GaP, a second surface component on the P 2p core level line reveals that two different atomic sites exist for the P-atoms at the surface which is different from the β2 (2×4) geometry. The low temperature (2×4) InP is more phosphorus-rich and turns to be a mixture between the (2×1) and the high temperature (2×4) reconstructions.

We studied the infrared absorption lines for the stretching mode of CO on ultrathin Fe(1 0 0) prepared as smooth as possible on MgO(0 0 1) by various methods. For films that gave different atomic force microscopic pictures but similar LEED patterns, the signal strength and the CO-line shapes were investigated in normal transmission and also in reflection at grazing incidence of p-polarized light. The comparison of both types of spectra for various degrees of film smoothness made obvious that asymmetric absorption lines may occur only in the susceptibility component parallel to the surface. The oscillator strength of these asymmetric lines is correlated to the number of holes in the film. The usual reflectance change that arises due to CO vibrations perpendicular to the film may be considerably modified by the adsorbate induced changes in the parallel susceptibility.

The dependence of the line width of the coupled monohydride symmetric stretching vibration of the H-terminated Si(1 0 0)-(2×1) surface on the exposure temperature and the hydrogen exposure has been investigated with infrared reflection absorption spectroscopy (IRRAS) using CoSi 2 buried metal layer substrate. Even for nearly ideally H-terminated Si(1 0 0) surface, the line width significantly changes depending on the exposure temperature and the hydrogen exposure. The reason of the line width broadening is discussed, and it is strongly suggested that hydrogen diffusion into the subsurface of Si has a significant influence on the line width broadening. Evidence of hydrogen (deuterium) diffusion into the subsurface is investigated for the first time using an IRRAS measurement.

The topography of a Si(0 0 1) vicinal surface is investigated by using reflection electron microscopy after alternating current (AC) heating at temperatures up to about 1140 °C. At temperatures below 850 °C, AC heating produces 1×2 surfaces that consist of wide 1×2 and narrow 2×1 terraces. The 1×2 terraces grow with a 1/2 power-law of time dependence, and the activation energy of the growth is about 1.1 eV. At temperatures between 850 and 1100 °C, AC heating produces double-domain surfaces, where 2×1 and 1×2 terraces are arranged regularly with approximately equal widths. During AC heating, the driving force for growth changes from thermal effect to evaporation effect at about 850 °C.

The strain fields near three different reconstructed Si surfaces, Si(1 1 1)7×7, Si(1 1 1) 3 × 3 -Ag, and Si(1 1 1) 3 × 3 -Al, were measured by using a strain-sensitive X-ray diffraction technique. The rocking curves of Si 1 1 3 reflection for these surfaces differed in peak intensity and peak width. The strain fields near these surfaces were quantitatively evaluated by fitting the measured curves with curves calculated by assuming a distorted atomic layer under the reconstructed surfaces. The results show that all three reconstructed surfaces induce compressive strain in the substrates and that this strain penetrates to a depth of 10–30 nm beneath the surface. Among these three reconstructed surfaces, the 3 × 3 -Ag surface induces the largest strain to the substrate.

Adsorption processes of Au on a high index Si(5 5 12) surface were studied in situ by high resolution reflection electron microscopy with subunit cell resolution. Growth of new phases is quite anisotropic and rapid along the [1 1 0] direction reflecting quite anisotropic substrate surface structure. At around 715°C, successive changes from (5 5 12) to two-fold (3 3 7), (5 5 11) and (2 2 5) facet were noted as an increase of Au deposit. (7 7 17) surface units are locally formed before formation of the two-fold (3 3 7) surfaces. At higher temperature 780°C (above roughening temperature 750°C of (5 5 11)-Au surface), a disordered surface is formed after formation of the two-fold (3 3 7) facet. The disordered surface is a higher temperature phase of the (5 5 11) surface. Above changes are discussed in terms of characteristics of these high index surface structures.

We used a novel technique for reflection electron microscopy observation of Si surfaces during crystal growth to determine how the rate ν of step motion depends on the interstep distance l . Our measurements manifest a linear dependence of ν on l in a wide interval of values of the interstep distance ( 0.2⩽l⩽8 μ m at 1335 K, 1⩽l⩽10 μ m at 1480 and 1560 K). Confrontation of the experimental data with the expression for the step rate (when l ≪ λ s ) ν =2 abKτ s ( R − R e )( l / Kτ s )/(2+( l /2 λ s ) 2 + l / Kτ s ) (derived in the BCF model) provides a ground to conclude that the condition l / Kτ s ≪1 is fulfilled in our experiments (here R and R e are the deposition rate and its equilibrium value, the product ab is the atomic area, K is the step kinetic coefficient, λ s is the mean diffusion distance and τ s is the life time of an adatom). In other words, our results provide a ground to estimate the characteristic length d = D s / K by rewriting l / Kτ s ≪1 in the form D s / K ≪ λ s 2 / l . In our experiments the interstep distance l reaches a value l=10 μ m and λ s is definitely larger (that is why we observe ν ∼ l ), so that a reasonable value of the right-hand side of this inequality is 100 μ m, i.e., d=D s /K≪100 μ m.

In this paper, the single-crystalline (0 0 1) V surface is studied by electron diffraction, Auger spectroscopy, and scanning tunnelling microscopy (STM). (1×1), (5×5) (and sometimes 6×6) surface atomic arrangement are observed in correlation with the oxygen surface concentration. For less than 0.15 ml of oxygen, no reconstruction is detected. The (5×5) surface structure is observed for an oxygen coverage in the range 0.15–1.2 ml. However, a pseudo-(1×1) surface structure can also be observed near 1 ml of oxygen. The STM analysis demonstrates that the (5×5) reconstruction results in fact from a mixing of (5×1) and (1×5) domains. At the atomic scale, the images show that the electronic density is modified over two parallel atomic lines every five but also six atomic distances. For the pseudo-(1×1) reconstructed surface, these lines are still present, but, depending on the density of vacancies, (6×1) up to (12×1) periodicities can be observed locally. We find that the periodicity linearly increases with the number of vacancies. The extension of this linear dependence up to the lack of vacancies leads to the (5×1) periodicity. These surface reconstructions lead to unusual reflection high-energy electron diffraction (RHEED) patterns, that are perfectly explained by the surface morphology. Finally, RHEED measurement of the in-plane lattice parameter allows us to demonstrate that the (5×5) reconstructed surface is compressed. This behaviour allows us to propose a model for the (0 0 1) V surface reconstructions induced by oxygen.

Reflection high-energy electron diffraction (RHEED) intensity oscillations recorded along high-symmetry azimuths during the homoepitaxial growth of GaAs(111)A thin films by molecular-beam epitaxy show reentrant behaviour, with oscillations occurring at high and low temperatures but disappearing at intermediate values over a ∼10°C temperature window. In off-symmetry azimuths, however, the oscillations persist at all temperatures. Scanning tunnelling microscopy images indicate growth-mode changes with temperature consistent with the RHEED results. RHEED patterns and rocking curves provide further evidence for a model based on a transition between two-dimensional layer-by-layer growth and step propagation.