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The structural and electronic properties of Bi nanolines on the InAs (001) surface are investigated via density functional theory. Thereby, three models, Miki (M) (Miki et al. Phys. Rev. B 59 (1999)14,868), Naitoh (N) (M. Naitoh et al. Surf. Sci 377 (1997) 899), and Two Ad-Dimer (TAD) (J.H.G. Owen et al. Phys. Rev. Lett 22 (2002) 226,104) are implemented to simulate the formation of Bi nanolines and study their physical properties. The structural analysis reveals some differences in atomic arrangements, bond lengths, and surface organization among the different models. The comparison of our results with Bi nanolines on Si(001) highlights the substrate role in Bi nanostructure formation. The surface stability examination demonstrates that the M model is energetically the most favorable one. On the other hand, the electronic properties analysis reveals that M, TAD models exhibit semiconductor behavior, whereas, the N model show a metallic character. Moreover, the calculations of the partial electronic charge density of surface states provide valuable information about the electronic structure of Bi nanolines on InAs(001). Finally, this study constitutes a theoretical support that can open the way to experimentally produce Bi nanostructures on the InAs(001) surface as a beneficial solution for several applications. [ABSTRACT FROM AUTHOR]

Abstract This work highlights the direct impact of selecting acceptor moiety for organic dyes on the electron dynamics at faster time scales, in which overlooked photo-physical properties are present on semiconductor surfaces with specific acceptor moieties. Four top-performing dyes of indoline family (D131, D102, D149, and D205) sharing the same donor moiety, but through different acceptor groups, were selected and compared with respect of electron injection process, using ultrafast transient-infrared probe. The presence of rhodanine moiety at the acceptor unit in D102, D149 and D205, shows an additional slow electron injection process, of picosecond time-scale, on the low band-gap semiconductor, TiO 2. This slow process is expected to be present due to a twisted intramolecular charge transfer/isomerized state of the excited dye prior to electron injection. This isomerized state reduces as well the detrimental electron recombination process rates, and results of high performance in solar cells based on these rhodanine dyes. Replacing the rhodanine moiety by a cyano-acrylic group in D131 dye shows faster electron injection and recombination processes, due to the lower dipole moment present in the excited state, hindering the formation of an isomerized state. These findings will aid to enhance the organic dyes design used in dye sensitized solar cells, in which designed photo-physical processes on semiconductor surfaces can increase the efficiencies of the solar cells. [ABSTRACT FROM AUTHOR]

The effect of the chemical modification of Ge(1 0 0) semiconductor surfaces on their electronic structure was studied using density functional theory calculations. We have considered various possible adsorption configurations of phenylthiol molecule on Ge(1 0 0) with different spatial orientations relative to the dimer row. The most favorable configuration is that the H-dissociated phenylthiol molecule is located at the inter-dimer site with the covalent bonding between sulfur atom of H-dissociated phenylthiol molecule and down-Ge atom. Simulated STM images of the adsorption configurations reflect the change of the electronic charge density and agree well with the adsorption features observed in the experiment. The projected density of states of the germanium and the phenylthiol molecule could explain the change in surface electronic structures upon chemical adsorption. Moreover, organic functionalization affects the electronic structure like band gap. Band structure analysis shows that the different adsorption configurations of phenylthiol molecules could modify the band gap of clean Ge(1 0 0) surfaces. [ABSTRACT FROM AUTHOR]

Electron gases (2DEG) confined in the quantum well (QW) of a semiconductor surface exhibit electronic properties with essentially two-dimensional (2D) character and quantized energies, directly observable by angle resolved photoemission spectroscopy (ARPES). Here, we present a simple formalism to extract the surface potential from the in-plane dispersion of the 2DEG and analytically derive the ARPES intensity in the damped free electron final state approximation. We find that the out-of-plane modulation of ARPES spectral weight explicitly encodes the shape and the bulk extent of the electronic wave function. Damping of the photoemission final state however leads to an underestimation of the wave function's bulk penetration. Our method provides a novel and universal way to deduce elusive information about the surface electronic structure from photon energy dependent ARPES measurements. [ABSTRACT FROM AUTHOR]

The electrical characteristics of the Ni/Cd 1 − x Zn x Te/In structures with a metal–semiconductor rectifying contact are investigated. The diodes, fabricated on the base of In-doped n -type Cd 1 − x Zn x Te (CZT) crystals with resistivity of ∼ 10 10 Ω ⋅ cm, have low leakage current and can be used as X/ γ -ray detectors. The rectifying contact was obtained by vacuum deposition of Ni on the semiconductor surface pretreated with argon plasma. The high barrier rectifying contact allowed us to increase applied reverse bias voltage up to 2500 V at the CZT crystal thickness of 1 mm. Dark (leakage) currents of the diodes with the rectifying contact area of 4 mm 2 did not exceed 3–5 nA at bias voltage of 2000 V and room temperature. The charge transport mechanisms in the Ni/CZT/In structures have been interpreted as generation–recombination in the space charge region within the range of reverse bias of 5–100 V and as currents limited by space charge at both forward and reverse bias at V >100 V. [ABSTRACT FROM AUTHOR]

The temperature-dependent energetics of self-assembled Au nanowires on Ge(001) surfaces is studied with the help of density-functional theory (DFT) calculations: By calculating the surface phonon modes within harmonic approximation the surface vibrational free energy is obtained to complement the zero-temperature DFT total energies. We consider several previously suggested structural models for a Au coverage between 0.75 and 1.75 monolayer and investigate a temperature range between 0 and 900 K. The stability of the investigated surface models is found to depend clearly on temperature. We find that the extended Ge bridge dimer model previously predicted to be most stable for a large range of preparation conditions is less prominent in the phase diagrams for finite temperatures. On the other hand, a model derived previously from the giant missing row structure with a higher Au coverage gets stabilized by temperature. These findings explain, at least partially, the discrepancies between experimental data and previous theoretical investigations neglecting temperature effects. [ABSTRACT FROM AUTHOR]

Hydrogen titanate (H 2 Ti 3 O 7 ) and TiO 2 -B polymorph are potential surfaces identified experimentally in the last years, which need to be analyzed. To study their performance as surfaces for dye sensitized solar cells (DSSC), a set of dye adsorption configurations were evaluated on them, as model dye the small and organic catechol molecule was used. We have calculated adsorption geometry, energy, electronic transfer from dye to semiconductor adsorbent and frontier orbitals by means of density functional theory (DFT). Results show that vacancy-like defected H 2 Ti 3 O 7 (100) and TiO 2 -B (100) surfaces present favorable adsorption energies. Finally, an adequate energy level alignment make both surfaces prone to be adequate for direct electron transfer upon excitation, from catechol to the conduction band of the semiconductors, with bands located in the Visible region of the electromagnetic spectrum. Additionally, the band structure alignment indicates an increase in the open circuit voltage, in reference to I 2 /I 3 − redox pair potential. All these characteristics make hydrogen titanate (H 2 Ti 3 O 7 ) and TiO 2 -B polymorph promising for DSSC applications. [ABSTRACT FROM AUTHOR]

Understanding the physical and chemical processes in which local interactions lead to ordered structures is of particular relevance to the realization of supramolecular architectures on surfaces. While spectacular patterns have been demonstrated on metal surfaces, there have been fewer studies of the spontaneous organization of supramolecular networks on semiconductor surfaces, where the formation of covalent bonds between organics and adatoms usually hamper the diffusion of molecules and their subsequent interactions with each other. However, the saturation of the dangling bonds at a semiconductor surface is known to make them inert and offers a unique way for the engineering of molecular patterns on these surfaces. This review describes the physicochemical properties of the passivated B-Si(111)-(√3x√3) R30° surface, that enable the self-assembly of molecules into a rich variety of extended and regular structures on silicon. Particular attention is given to computational methods based on multi-scale simulations that allow to rationalize the relative contribution of the dispersion forces involved in the self-assembled networks observed with scanning tunneling microscopy. A summary of state of the art studies, where a fine tuning of the molecular network topology has been achieved, sheds light on new frontiers for exploiting the construction of supramolecular structures on semiconductor surfaces. [ABSTRACT FROM AUTHOR]

Self organized nano-structure array on the surfaces of semiconductors have potential applications in photonics, magnetic devices, photovoltaics, and surface-wetting tailoring etc. Therefore, the control over their dimensions is gaining scientific interest in last couple of decades. In this work, fabrication of pits of nano-dimensions is carried out on the GaAs (1 0 0) surface using 50 keV Ar + at normal incidence. Variation in fluence from 3 × 10 17 ions/cm 2 to 5 × 10 18 ions/cm 2 does not make a remarkable variation in the dimension of pits such as size and depth, which is confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). However the simultaneous dots formation is observed along with the pits at higher fluences. Average size of pits is found to be of 22 nm with depth of 1–5 nm for the used fluences. The importance of preferential sputtering of ‘As’ as compared to ‘Ga’ is estimated using energy dispersive X-ray analysis (EDX). The observed alteration in near surface composition shows the Ga enrichment of surface, which is not being much affected by variation in fluence. The growth evolution of pits and dots for the used experimental conditions is explained on the basis of ion beam induced preferential sputtering and surface diffusion. [ABSTRACT FROM AUTHOR]

We have developed a simple cubic solid-on-solid (SOS) model of growth that captures many of the features of 2 × 1 reconstructed surfaces. Energetics in the model is based on bond-counting and the tendency to form dimer rows is controlled by a reconstruction energy parameter δ . We examine the dependence of the shapes and sizes of islands formed at submonolayer coverage on the parameter δ . The aspect ratio distribution of islands indicates a transition from two-dimensional to one-dimensional growth as δ is increased. At coverages below 0.2 ML, the islands are mostly made of dimer chains with aspect ratios as large as 14. On annealing the system, the islands coalesce into larger islands with a much smaller aspect ratio of approximately 3. Through extensive simulations, we have found a set of parameters that reproduces the known experimental results on submonolayer growth on Si(001) in Molecular Beam Epitaxy(MBE). These results include island size and shape distribution and their dependence on temperature. This model can be used to study heteroepitaxial thin film growth on reconstructed surfaces. [ABSTRACT FROM AUTHOR]

Abstract: Structural changes on cleaved (110) surfaces of InP, induced by tunneling carriers from the tip of a scanning tunneling microscope, were studied. Bond rupture takes place at intrinsic P-sites only at negative sample voltages (i.e., under hole-injection conditions), resulting in the formation of P-vacancies, while injected electrons induce no structural change. The rate of bond rupture, showing a prominent threshold sample voltage at −2.2V, is a quadratic function of the tunneling current. Nonlinear localization of two holes injected into surface bands is crucial as the primary step in the electronic bond rupture on semiconductor surfaces. [Copyright &y& Elsevier]

Abstract: A copper film was coated using a high-power impulse magnetron sputtering (HIPIMS) source with a target diameter of 25.4mm. This process is a coating process for a half-inch-scaled semiconductor manufacturing system. To realize the stable plasma production, the following issues were considered: (1) a water-cooled plasma generation system, (2) plasma generation using an external magnet near the plasma source, and (3) facilitation of the expansion of the sputtered metallic species (atoms and ions) to the substrate. A high magnetic flux density of 0.3T at the target surface is used to produce plasma at a source voltage less than 600V with negative polarity, where the glow is not transited to an arc discharge during the pulse. To enhance the deposition rate of the prepared films, a long pulse duration of 600μs at a repetition frequency of 120Hz is used. The argon and sputtered copper ions are in a glow plasma region, and a high deposition rate of 2.5μm/min is realized on a 0.5-inch silicon-wafer. [Copyright &y& Elsevier]

Abstract: We have used scanning tunneling microscopy to probe the effect of oxygen exposure on an ensemble of Ag islands separated by a Ag wetting layer on Si(111)-7×7. Starting from a distribution dominated by islands that are 1 layer high (measured with respect to the wetting layer), coarsening in ultrahigh vacuum at room temperature leads to growth of 2-layer islands at the expense of 1-layer islands, which is expected. If the sample is exposed to oxygen, 3-layer islands are favored, which is unexpected. There is no evidence for oxygen adsorption on top of Ag islands, but there is clear evidence for adsorption in the wetting layer. Several possible explanations are considered. [Copyright &y& Elsevier]

Abstract: Photoelectron diffraction in the layer-resolved mode brings more detailed information about local atomic arrangement than is obtained in the standard mode. This is demonstrated in crystals with diamond and zinc-blende structures, both for unpolarized photon excitation as well as for circularly polarized excitation. The full angular distributions of photoemission intensities are evaluated for large atomic clusters representing ideally truncated surfaces of Si(001) and GaAs(001). Highly structured layer-resolved patterns enable a more detailed understanding of the standard mode outcomes. Photoelectron intensities from atomic layers placed at different depths under the crystal surface provide direct evidence about electron attenuation and its anisotropy in crystals. [Copyright &y& Elsevier]

Abstract: The atomic structure of the GaN (1×1) reconstruction was investigated by quantitative low-energy electron diffraction (LEED). The GaN surface was annealed in an NH3 atmosphere and cooled down without any NH3 flux. LEED patterns with 6-fold symmetry were measured after annealing. The diffraction symmetry was explained by the presence of two domains on the GaN surface. LEED intensity–voltage (I–V) curves were acquired up to 500eV and calculated in the framework of the dynamical theory of electron scattering. Good agreement between the experimental and theoretical curves was achieved for the bare GaN (1×1) surface. Relaxation of the surface atomic layers decreased Pendry''s R-factor to 0.21±0.03. The plane relaxations derived from the LEED analysis were found to be in qualitative agreement with ab initio calculations. By using previously suggested models with adlayers on the bare GaN (1×1) surface, much worse R-factors were obtained. It was concluded that the measured LEED I–V curves could be used to determine the bare GaN polarity. [Copyright &y& Elsevier]

Abstract: The atomic structures of the Bi/Si(111)-() reconstructed surfaces obtained at different adsorbate coverages were studied by dynamical low-energy electron diffraction (LEED) I–V analysis. The experimentally obtained I–V curves of the β-Bi/Si(111)-() surface, which is formed by a Bi coverage of 1ML, showed good agreement with the curves calculated for the milk stool model, a model proposed in the literature. In contrast to this result, the I–V curves of the α-phase obtained at a coverage of 1/3ML do not agree with those reported in early LEED studies. We found that the I–V curves reported in the former LEED studies resemble closely to the results obtained for the surface on which the β and α-phases coexist. Based on the obtained I–V curves, we propose a more reliable structural model for the α-phase, and present the way to determine the presence of a high quality α-phase by using LEED. [Copyright &y& Elsevier]

Abstract: We present first-principles results obtained within the framework of density functional theory referring to Mg adsorption and its incorporation in two distinct InN surfaces ((0001), ) under various adsorption coverage conditions. In all deposition cases we deducted the bonding characteristics and the electronic character of the structures. It is found that in In rich conditions N-polarity facilitates the diffusion of In and Mg adatoms while In-polarity facilitated the Mg-induced weakening of adatom (In, Mg)–surface interactions for small doses of Mg. This implies that the Mg dopant decreases In and Mg diffusion barrier leading to smoother surfaces. Interestingly, we found significant differences of Mg incorporation in In- and N-polar surfaces: Mg incorporation is easier in bare N-polar than in the In-polar surface, except when an In contracted bilayer is formed on top of the InN. In the case of In-polarity, Mg impurities start to penetrate in the subsurface region as the Mg coverage increases. In the contracted In bilayer case, Mg incorporation in the InN is significantly enhanced. Furthermore, we found that the presence of Mg close to the InN surface does not alter significantly the local structure, contrary to the In-polarity case in which a flattening of the bilayers is observed at the highest Mg coverage that may lead to the formation of basal inversion domain boundaries. [Copyright &y& Elsevier]

Abstract: We present a theoretical study of the geometrical and electronic properties of the C- and Si-terminated -SiC(0 0 1) surfaces in the vicinity of the missing dimer defect. The experimental results suggest that the atomic structures of these two surfaces may be considerably modified by external stress. In our present study we have considered the possible influence of this factor on the surface geometry of both systems. We have shown that the structural differences between the C- and Si-terminated surfaces lead to their different behaviour in the presence of a missing dimer and applied stress. In the case of the C-terminated c() surface, the missing dimer defect causes the buckling of the adjacent carbon dimers lying in the line of the defect (dimer atoms adjacent to the defect have vertical positions lower by 0.18 Å). This effect becomes more pronounced in the presence of compressive stress — the stress of 8% leads to the buckling of these two dimers of around 0.5 Å. The vertical positions of silicon atoms located directly below the defect were increased by 0.2 Å. We have also found that the missing dimer influences the structure of the carbon dimers on the neighbouring lines of dimers. Contrary to the C-terminated surface, the missing dimer defect on the Si-terminated SiC(0 0 1)-p() surface remains neutral for silicon dimers located in the line of defect, i.e. the dimers do not change their geometrical properties in unstrained structure nor in the presence of a tensile stress. On the other hand, this defect modifies considerably the geometry of the dimers from the two neighbouring lines of dimers by reducing their bond lengths and vertical positions. Changes in the geometrical properties of the second neighbour dimers (with respect to the defect) in these two lines are also noticeable. Moreover, we have found that the presence of a missing dimer modifies significantly the positions of the adjacent subsurface carbon atoms. [Copyright &y& Elsevier]

Abstract: The growth of silicon carbide nanocrystals on Si(100) is studied by synchrotron surface X-ray diffraction (SXRD) during annealing at high temperature. A chemisorbed methanol monolayer is used as carbon source, allowing to have a fixed amount of carbon atoms to feed the growth. At room temperature, minor changes in the 2×1 reconstruction of silicon are observed due to the formation of Si–O–CH3 and Si–H bonds from methanol molecules. When annealed at 500°C, carbon incorporation into the silicon leads only to local modifications of the surface structure. Above 600°C, tri-dimensional silicon carbide nanocrystals growth takes place, together with surface roughening and sharp decrease of domain sizes of the 2×1 reconstruction. The different processes taking place at each temperature are clearly distinguished and identified during the real time SXRD measurements. [Copyright &y& Elsevier]

Abstract: The deposition of metals on semiconductors encompasses a broad range of technologically important processes, with applications ranging from electronic devices to chemical sensors. Recent years have witnessed a surge of research activities in galvanic displacement processes on semiconductor substrates. After a brief review of the fundamental aspects underlying galvanic displacement processes on semiconductor surfaces, this paper discusses applications to micro- and nanoscale devices, including schemes developed for the metallization and nanopatterning of semiconductor substrates with high selectivity and with optimal interfacial properties. [Copyright &y& Elsevier]

Abstract: We review the morphologic changes of Si(111)-(7×7) and InP(110)-(1×1) surfaces under repeated irradiation with laser pulses of intensities well below thresholds of melting and ablation. Direct imaging of the irradiated surfaces by means of scanning tunneling microscopy (STM) has revealed the excitation-induced electronic bond breaking, with efficiencies strongly site-dependent and highly superlinear with respect to the excitation intensity, resulting in formation of monovacancies and clustering of pre-existing vacancies. On Si(111)-(7×7), formation of monovacancies is predominantly induced under repeated irradiation, and the rate is constant up to the vacancy concentration of 10% relative to the total adatom sites. On the other hand, STM images of irradiated InP(110)-(1×1) have shown the preferential removal of the surface P atoms and prominent Fermi-level effects on the morphology of laser-induced vacancies: vacancy clusters are efficiently formed on n-type surface, while monovacancies are exclusively formed on p-type surface. The surface-dependent morphology of laser-induced vacancies can be explained by non-linear localization of surface holes at vacancy-sites based on the structural and electronic properties of the two surfaces. [Copyright &y& Elsevier]

Abstract: The adsorption of hydrogen on semiconductors strongly modifies the electronic and chemical properties of the surfaces, whether on the surface or in the sub-surface region. This has been the starting point, in recent years, of many new areas of research and technology. This paper will discuss the properties, at the atomic scale, of hydrogenated semiconductor surfaces studied with scanning tunnelling microscopy (STM) and synchrotron radiation. Four semiconductor surfaces will be described – germanium(111), silicon(100), silicon carbide(100) and diamond(100). Each surface has its particularities in terms of the physical and electronic structure and in regard to the adsorption of hydrogen. The manipulation of hydrogen on these surfaces by electronic excitation using electrons from the STM tip will be discussed in detail highlighting the excitation mechanisms. The reactivity of these surfaces towards various molecules and semiconductor nanocrystals will be illustrated. [Copyright &y& Elsevier]

Abstract: Using high resolution electron energy loss spectroscopy (HREELS), we have characterized the fingerprint spectra of clean, hydrogenated, methanol-dosed and air-exposed n-doped Ge(100). On clean Ge(100) 2×1, we report the observation of a surface phonon peak between ∼28–35meV. The position and shape of this peak is sensitive to the presence of low surface coverage of hydrogen and oxygen. By adsorbing molecular hydrogen on the n-doped Ge, this peak shifts towards the elastic peak, and becomes attenuated. The HREELS fingerprint spectrum of air-exposed Ge is similar to that created by dosing Ge with methanol. Methanol undergoes dissociation into methyl radicals and hydroxyl species on Ge surfaces at room temperature and oxidizes the Ge surface readily. [Copyright &y& Elsevier]

For β-FeSi2 formation, interdiffusion and silicidation are key processes in order to achieve better crystallinity, orientation and material properties. Transmission electron microscope (TEM) for the structural analysis and synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) for the diffusion process analysis are reviewed for the nanoscopic observation through the β-FeSi2 formation. The TEM analysis provides nanostructure of interface region (β-FeSi2/Si) obtained by ion beam sputter deposition (IBSD) method at 600–800 °C. The substrates were prepared by several methods, such as ordinary chemical etching of Si or ion beam sputtering, etc. Cross-sectional TEM images and electron diffraction patterns were obtained for the interface of silicide and Si substrate. The images showed that “damaged” surface produced by ion sputtering and subsequent thermal annealing provides quite smooth interface and epitaxially grown films compared with the chemically etched Si, which has atomically flat surface. The SR-XPS results provide compositional changes in the nm region non-destructively. Vapor deposited iron on Si substrate was measured after various annealing temperatures. The gradual changes of the composition from the topmost surface to the deeper region were clearly observed from the obtained results. [Copyright &y& Elsevier]

In the last couple of years there has been much methodological and computational progress in the modeling of optical properties from first principles. While the calculation of non-linear optical coefficients is still hampered by numerical limitations—demonstrated here for the case of bulk GaAs—linear optical spectra can now be calculated accurately and with true predictive power, even for large and complex surface structures. This allows on one hand for a much better understanding of the origin of specific features such as surface optical anisotropies. We find that in particular microscopic electric fields at the surface induce slight deformations of bulk-like wavefunctions and thus give rise to optical anisotropies even from sub-surface layers. On the other hand, from the comparison of measured and calculated spectra, one can now confidently reach conclusions on the surface geometry. This short review focuses on the simulation of reflectance anisotropy spectroscopy. The clean, hydrogenated and uracil-covered Si(001) surface is used to illustrate the microscopic origin of surface optical anisotropies and the present state-of-the-art in computational modeling of optical spectra. [Copyright &y& Elsevier]

With the availability of first principles methods to simulate the operation of a scanning tunneling microscope (STM) theory has moved from the qualitative and topographic to the quantitative and dynamic. Simulations in effect predict the influence of a model-tip or chemical interactions between tip and sample in the actual imaging process. By comparing experiments and simulations, the information about the analyzed system can be substantially extended. We give an overview of recent work, where the combination of first principles simulations with high resolution measurements was decisive to arrive at consistent results. This concerns the resolution of single wavefunctions by STM, force effects in high resolution scans, contrast reversal due to the field of the tip, the imaging of magnetic properties by spin-polarized STM, and the analysis of dynamic processes on surfaces. [Copyright &y& Elsevier]

[Display omitted] • Diffusion mechanism of Si, C, and H adatoms of 3C-SiC(111) surfaces is studied. • Detailed diffusion pathways for each adatom are identified. • Si adatoms have a lower diffusion barrier than C and H adatoms on the terrace. • Ehrlich-Schwoebel effect is prominent for Si adatoms. We report first-principles total-energy calculations based on real-space density-functional theory that unveil the atom-scale mechanisms of surface diffusion of adatoms on the Si-faced 3C-SiC(111) stepped surface. The quality of the epitaxial layer of SiC affects the device performance. Therefore, fundamental knowledge of the microscopic mechanisms of epitaxial growth is crucial for the improvement of the quality of SiC power devices. However, adatom diffusion on the growing stepped SiC surfaces is still unknown. We identify diffusion pathways for three important adatom species of SiC chemical vapor deposition (CVD), Si, C, and H, and obtain the corresponding energy profiles for both on the surface terraces and near the surface steps, providing a complete picture of the adatom diffusion. We find that the Si adatom is most mobile on the terrace and shows prominent Ehrlich-Schwoebel (ES) effect in the inter-terrace diffusion, whereas the C and H adatoms show less ES effect and in an ascending diffusion even the inverse ES effect appears for the C adatom. The results obtained are fundamentals to explore the microscopic mechanism of the epitaxial growth on 3C-SiC(111) surfaces and equivalently hexagonal SiC(0001) surfaces. [ABSTRACT FROM AUTHOR]

Low-dimensional self-organized surface structures, induced by (sub)monolayer metal adsorbates on semiconductor surfaces may give rise not only to a variety of emergent electronic properties, but also to a multitude of specific localized vibronic features. The focus of this review is on the analysis of these novel surface vibration eigenmodes. The application of in situ surface Raman spectroscopy under UHV conditions on clean semiconductor surfaces and those with self-ordered adsorbates, in close conjunction with the calculations of Raman spectra, based on the first-principles determination of the structural, electronic and vibronic properties, allows a consistent determination of the vibration eigenfrequencies, symmetry properties, and elongation patterns of the systems of interest. The localized nature of the surface eigenmodes determines the surface sensitivity, independent of the large penetration depth of light. The surface contribution can be selectively enhanced by employing resonance conditions to surface electronic transitions. Moreover, surface and bulk contributions can be separated by taking difference spectra between various stages of surface preparation. The relevant surfaces are Ge and especially Si with different orientations ((111) and vicinal (hhk)), on which the adsorption of various metals (Au, Sn, Pb, or In) gives rise to two- and quasi-one-dimensional structures (e.g. Au-(5 × 2)/Si(111)) with a variety of vibration modes. The Raman analysis of these modes not only enables the distinction between different proposed structural models (e.g. for Au-(3 × 3)/Si(111)), but also gives access to the role of electron-phonon coupling in structural phase transitions (e.g. for In-(8 × 2)–(4 × 1)/Si(111)). [ABSTRACT FROM AUTHOR]

Reflectance anisotropy (RA) spectroscopy is applied to study indium nanocluster arrays formed on InAs(001) crystal surface by electrochemical treating. The measured RA spectra exhibit a resonant feature of negative sign whose scale ~ 10 − 1 exceeds by two orders of magnitude the scale of the related spectra conventionally observed for semiconductor surfaces. Plasmonic origin of the resonant feature is unambiguously established both experimentally and theoretically. The RA spectra of In nanoclusters covering InAs(001) surface are interpreted in terms of coupled dipole plasmons belonging to ellipsoidal metal nanoparticles. From the experimental RA spectra, an effective plasmonic anisotropy is estimated within a lattice model of indium nanoparticle coverage. It is concluded that the in-surface semi-axes of ellipsoids can differ by a few percent, as well as the periods of rectangular lattice occupied by nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the formation of Ge(001) c(8×2)–Au surfaces on vicinal samples by scanning tunneling microscopy. The vicinal samples are tilted 1° toward [110]. The c(8×2)–Au surface is prepared by depositing 0.75±0.05 ML of Au onto a germanium surface held at 800K. The anisotropy introduced by the atomic steps of the vicinal surface and the preferential etching of SB steps during Au deposition is sufficient to introduce a preferred growth direction for the c(8×2)–Au phase. The result is a sample on which 78% of the surface is populated by Au-induced chains oriented parallel to the step direction. These parallel Ge(001) c(8×2)–Au domains are separated by single or multiple height DA steps (0.28nm high). [Copyright &y& Elsevier]

Nanolines of Bi 1.5 nm wide and more than 400 nm long way be grown on Si(0 0 1). Although they are not conducting themselves, they may be used as templates for nanowires of other metals, such as Al or Ga. To this end, we have found that these nanolines are stable against exposure to both atomic hydrogen and ozone. Hydrogen will passivate the silicon dimers, acting as an atomic-scale mask. Oxidation of the silicon surrounding the nanoline would allow for electrical isolation of the wire from the substrate, reducing or eliminating leakage currents into the substrate. [Copyright &y& Elsevier]