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[Display omitted] • For both surfaces, the neutral fractions decrease as the incident energy increases. • Neutral fraction on H 2 O/Cu(1 1 0) is lower than that of Cu(1 1 0). • The work function of H 2 O/Cu(1 1 0) is lightly greater than that of clean Cu(1 1 0). keV-energy Na+ ions are scattered from clean and water covered Cu(1 1 0) surfaces in grazing incidence. For both surfaces the pronounced Na° fractions decrease with incident energy. In particular, the lower Na° fraction has been observed for the water covered Cu(1 1 0) surface. The simple calculations using rate equation are presented to compare with the experimental data. The calculation is in agreement with the experimental data. It indicates that the water covered Cu(1 1 0) surface has the slightly higher work function due to water molecules dissociation and forming hydroxyl groups, so that the neutral fraction on water covered Cu(1 1 0) is lower than that on the clean surface. [ABSTRACT FROM AUTHOR]

Jellium model is well known and used to understand the neutralization of alkali-metal ions on metal surfacesbut we find it cannot explain our experiments for the neutralization of 0.4 keV and 0.8 keV Na+ ions on Al(1 1 1) and Cu(1 1 0) surfaces in grazing incidence. As the exit angle increases neutral fractions on Cu(1 1 0) surface decreases first and then increases which is similar to our previous results at large scattering angles. While for the Al(1 1 1) surface we observe opposite characteristics. This anomalous bell-shaped feature cannot be explained by the Jellium model. One possible explanation is the inner 2p electron promotion at smaller exit angles this may cause the Na* excited states to be generated and produce excess Na+ ions while the similar electronic excitation process is inefficient for the Cu(1 1 0) surface in the present energy range. [ABSTRACT FROM AUTHOR]

[Display omitted] • Deposition rate affects roughness, activation barrier influences. • Unrestricted diffusion model leads to higher roughness. • Temperature smooth surfaces, alters growth mechanisms. • Higher temperatures increase layer occupancy, favor diffusion. • Steady state is not reached for any materials in unrestricted model. • Dynamic exponent Beta depends of the diffusion mechanism. The growth behavior of Cr and W surfaces using kinetic Monte Carlo (KMC) simulations based on Density-Functional Theory (DFT) is presented in this study. Three models, a growth model with random deposition and no diffusion, a growth model with restricted diffusion and a growth model with unrestricted diffusion model, were compared to understand their influence on the predicted surface roughness and layer density. The impact of deposition rate and temperature on surface growth for both metals were analyzed. For deposition rate studies, five different rates (0.01 ML/s, 0.1 ML/s, 1.0 ML/s, 10.0 ML/s, and 100 ML/s) were considered at 550 K for Cr and W respectively. The effect of temperature on roughness was also studied employing various temperatures from 300 K to 1100 K for both metals and under the two different evolution models. The results show that the unrestricted diffusion model exhibits higher roughness compared to the restricted model for both metals. The restricted model shows a stable region of roughness, whereas the unrestricted model shows a continuous increase in roughness throughout the simulation. Furthermore, layer density analysis revealed that temperature affects the filling of lower monolayers. Finally, dynamic exponents β and α for each studied model were calculated and discussed. The results highlight the influence of diffusion models, deposition rate and temperature on surface, roughness, and layer density. [ABSTRACT FROM AUTHOR]

Abstract We review our recent studies of photochemistry and plasmon chemistry of dimethyl disulfide, (CH 3 S) 2 , molecules adsorbed on metal surfaces using a scanning tunneling microscope (STM). The STM has been used not only for the observation of surface structures at atomic spatial resolution but also for local spectroscopies. The STM combined with optical excitation by light can be employed to investigate chemical reactions of single molecules induced by photons and localized surface plasmons. This technique allows us to gain insights into reaction mechanisms at a single molecule level. The experimental procedures to examine the chemical reactions using the STM are briefly described. The mechanism for the photodissociation reaction of (CH 3 S) 2 molecules adsorbed on metal surfaces is discussed based on both the experimental results obtained with the STM and the electronic structures calculated by density functional theory. The dissociation reaction of the (CH 3 S) 2 molecule induced by the optically excited plasmon in the STM junction between a Ag tip and metal substrate is also described. The reaction mechanism and pathway of this plasmon-induced chemical reaction are discussed by comparison with those proposed in plasmon chemistry. [ABSTRACT FROM AUTHOR]

Understanding the behavior of proteins at material interfaces has become increasingly important as the intersection between the biological and synthetic worlds continues to grow. By inducing changes in protein structure, interactions with materials may lead to a loss of function and/or biological activity, as well as undesirable cellular interactions in vivo , including the foreign body reaction to implantable materials. Despite extensive research, the understanding of the mechanisms that lead to protein conformational changes on surfaces remains incomplete. Here, we highlight recent advances in understanding and controlling protein conformation on the surface of synthetic materials, including nanomaterials, polymer films and brushes, metal coatings and particles, and graphitic materials. We also review developments in the use of biophysical and computational methods for characterizing the structure of proteins at solution–solid interfaces. These approaches have provided important new insights into the physico-chemical factors that control protein conformation in near-surface environments, which represents a critical step towards the rational design of biotic–abiotic interfaces in biomedical and biotechnological applications. Graphical abstract Image 1 Highlights • The mechanistic understanding of protein unfolding on surfaces remains incomplete. • Lack of understanding has hindered the use of materials in biological environments. • Review highlights advances in elucidating impact of materials on protein structure. • Recent findings show lack of consistent observations between different systems. • Protein unfolding on surfaces may be confounded by various types of heterogeneities. [ABSTRACT FROM AUTHOR]

Most traditional techniques to recover latent fingermarks from metallic surfaces do not consider the metal surface properties and instead focus on the fingermark chemistry. The scanning Kelvin probe (SKP) technique is a non-contact, non-destructive method, used under ambient conditions, which can be utilised to recover latent prints from metallic surfaces and does not require any enhancement techniques or prevent subsequent forensic analysis. Where a fingermark ridge contacted the metal, the contact potential difference (CPD) contrast between the background surface and the fingermark contact area was 10-50mV. Measurements were performed on the untreated brass, nickel-coated brass and copper metal surfaces and compared to traditional forensic enhancement techniques such as Vacuum Metal Deposition (VMD) using Au-Zn and Au-Ag. Using VMD, the CPD change ranged from 0 to 150mV between the dissimilar metal surfaces affected by the fingermark. In general, SKP worked best without additional enhancement techniques. Scanning Electron Microscope (SEM) scans were used to identify the fingermark contact areas through a sodium, chlorine and oxygen electron probe micro-analyzer (EPMA). The fingermark was observed in the backscattered electron image as the carbon deposits scattered the electrons less than the surrounding metal surface. The fingermark is shown clearly in a Cathodoluminescence scan on the copper sample as it blocks the photon emission at band gap (2.17eV) from the underlying copper oxide (Cu2O) surface. For the first time, SEM, EPMA and Cathodoluminescence techniques were compared to SKP data. Visible and latent fingermarks were tested with latent, eccrinous fingermarks more easily imaged by SKP. Results obtained were very encouraging and suggest that the scanning Kelvin probe technique, which does not need vacuum, could have a place as a first stage analysis tool in serious crime investigation. [ABSTRACT FROM AUTHOR]

There is an increased interest in incorporating multi-wall carbon nanotubes (MWCNTs) into polymer matrices to control the adhesion of bacteria to surfaces and the subsequent formation of biofilm growth on the surface of water pipes, food packages, and medical devices. Microbial interactions with carbon nanotube-polymer composites in the environment are not well understood. The growth of Pseudomonas fluorescens (gram-negative) and Mycobacterium smegmatis (gram-positive) biofilms on copper, polyethylene (PE), polyvinyl chloride, and stainless steel was compared with growth on MWCNT-PE composites in order to gain insight into the effect of the surface properties of nanomaterials on the attachment and proliferation of microorganism which could result in the engineering of better, non-fouling materials. A statistical analysis of the biofilm growth showed a significant impact of materials for both P . fluorescens ( p  < 0.0001) and M . smegmatis ( p  = 0.00426). Biofilm growth after 56 days on PE compared to biofilm growth on copper surfaces decreased by 46.4% and 34.9% for P . fluorescens and M . smegmatis , respectively. Biofilm growth on PE-multiwall-carbon-nanotubes (MWCNTs)-composites surface compared to PE decreased by 89.3% and 29% for P . fluorescens and M . smegmatis , respectively. Bacterial species ( p  < 0.0006) and surface roughness ( p  < 0.0001) were important factors in determining the attachment and initial biofilm growth rate. The interactions between cells and material surface could be attributed to the complicated and collective effect of electrostatic forces, hydrophobic interactions, and hydrogen/covalent bonding. Further study is needed to determine whether or not there is a difference between the cell attachment in the exponential growth phase and the stationary, or decay, phase cells. [ABSTRACT FROM AUTHOR]

Abstract Atomic hydrogen is a highly reactive species of interest because of its role in a wide range of applications and technologies. Knowledge about the interactions of incident H atoms on metal surfaces is important for our understanding of many processes such as those occurring in plasma-enhanced catalysis and nuclear fusion in tokamak reactors. Herein we review some of the numerous experimental surface science studies that have focused on the interactions of H atoms that are incident on low-Miller index metal single-crystal surfaces. We briefly summarize the different incident H atom reaction mechanisms and several of the available methods to create H atoms in UHV environments before addressing the key thermodynamic and kinetic data available on metal and modified metal surfaces. Generally, H atoms are very reactive and exhibit high sticking coefficients even on metals where H 2 molecules do not dissociate under UHV conditions. This reactivity is often reduced by adsorbates on the surface, which also create new reaction pathways. Abstraction of surface-bound D(H) adatoms by incident H(D) atoms often occurs by an Eley-Rideal mechanism, while a hot atom mechanism produces structural effects in the abstraction rates and forms homonuclear products. Additionally, incident H atoms can often induce surface reconstructions and populate subsurface and bulk absorption sites. The absorbed H atoms recombine to desorb H 2 at lower temperature and can also exhibit higher subsequent reactivity with adsorbates than surface-bound H adatoms. Incident H atoms, either directly or via sorbed hydrogen species, hydrogenate adsorbed hydrocarbons, sulfur, alkali metals, oxygen, halogens, and other adatoms and small molecules. Thus, H atoms from the gas phase incident on surfaces and adsorbed layers create new reaction channels and products beyond those found from interactions of H 2 molecules. Detailed aspects of the dynamics and energy transfer associated with these interactions and the important applications of hydrogen in plasma processing of semiconductors are beyond the scope of this review. [ABSTRACT FROM AUTHOR]

This paper presents a review of the experimental and theoretical investigations of halogen interaction with metal surfaces. The emphasis was placed on the recent measurements performed with a scanning tunneling microscope in combination with density functional theory calculations. The surface structures formed on metal surface after halogen interaction are classified into three groups: chemisorbed monolayer, surface halide, bulk-like halide. Formation of monolayer structures is described in terms of surface phase transitions. Surface halide phases are considered to be intermediates between chemisorbed halogen and bulk halide. The modern theoretical approaches in studying the dynamics of metal halogenation reactions are also presented. [ABSTRACT FROM AUTHOR]

Depth profiling using surface sensitive analysis methods in combination with sputter ion etching is a common procedure for thorough material investigations, where clean surfaces free of any contamination are essential. Hence, surface analytic studies are mostly performed under ultra-high vacuum (UHV) conditions, but the cleanness of such UHV environments is usually overrated. Consequently, the current study highlights the in principle known impact of the residual gas on metal surfaces (Fe, Mg, Al, Cr and Zn) for various surface analytics methods, like X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and low-energy ion scattering (LEIS). The investigations with modern, state-of-the-art equipment showed different behaviors for the metal surfaces in UHV during acquisition: (i) no impact for Zn, even after long time, (ii) solely adsorption of oxygen for Fe, slight and slow changes for Cr and (iii) adsorption accompanied by oxide formation for Al and Mg. The efficiency of different counter measures was tested and the acquired knowledge was finally used for ZnMgAl coated steel to obtain accurate depth profiles, which exhibited before serious artifacts when data acquisition was performed in an inconsiderate way. [ABSTRACT FROM AUTHOR]

• Dopant atoms enhanced the adsorption behavior of benzene. • The highest adsorption energy was found in Pt 2 Pd 2 -Ag configuration AB. • A remarkable change from physisorption to chemisorption binding for benzene molecule. Heterogeneous catalysis, molecular sensors, and photovoltaics all rely on the interfaces between organic molecules and metal surfaces. Here, we study the adsorption of benzene on Ag(100) surface doped by Au n , Pd n , Pt n (n = 1–4), Au 2 Pd 2 , Au 2 Pt 2 and Pd 2 Pt 2 using density-functional theory (DFT), with the inclusion of van der Waals interactions, and compare with available computational and experimental result. The calculated quantities reveal that the interaction strength of Benzene with the surface gradually increases when it is doped by Pd or Pt atoms, showing a change in the nature of the interaction, from physisorption to chemisorption. We found that with surface allowing, one can tune the interaction strength. The charge transfer was found to occur from the molecule to the clean and doped surfaces with Au atoms and from the doped surface with Pd to the molecule. The redistribution of charge density indicates modifications in the features of the interface between the doped Ag(100) surfaces and benzene. In addition, alloying the Ag(100) surface with reactive TM changes substantially its electronic properties, which impacts its interactions with benzene. Finally, mixing two dopants or more can tune the electronic structure in designing more effective interfaces for various applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Charge transfer interactions between C 60 and the metal surfaces of Ag(111), Cu(111), Au(111) and Pt(111) have been studied using synchrotron-based photoemission, resonant photoemission and X-ray absorption spectroscopies. By placing the X-ray absorption and valence band spectra on a common binding energy scale, the energetic overlap of the unoccupied molecular orbitals with the density of states of the underlying metal surface have been assessed in the context of possible charge transfer pathways. Resonant photoemission and resonant Auger data, measuring the valence region as a function of photon energy for C 60 adsorbed on Au(111) reveals three constant high kinetic energy features associated with Auger-like core-hole decay involving an electron transferred from the surface to the LUMO of the molecule and electrons from the three highest occupied molecular orbitals, respectively and in the presence of ultra-fast charge transfer of the originally photoexcited molecule to the surface. Data for the C 60 /Ag(111) surface reveals an additional Auger-like feature arising from a core-hole decay process involving more than one electron transferred from the surface into the LUMO. An analysis of the relative abundance of these core-hole decay channels estimates that on average 2.4 ± 0.3 electrons are transferred from the Ag(111) surface into the LUMO. A core-hole clock analysis has also been applied to assess the charge transfer coupling in the other direction, from the molecule to the Au(111) and Ag(111) surfaces. Resonant photoemission and resonant Auger data for C 60 molecules adsorbed on the Pt(111) and Cu(111) surfaces are shown to exhibit no super-Auger features, which is attributed to the strong modification of the unoccupied molecular orbitals arising from stronger chemical coupling of the molecule to the surface. [ABSTRACT FROM AUTHOR]

We study the effect of electron and phonon degrees of freedom on the relaxation dynamics of adsorption processes in gas-surface systems by using ab initio molecular dynamics that incorporates an electronic friction force (AIMDEF). As representative cases we have chosen three systems with different adsorption energies and adsorbate-to-surface atom mass ratios: H on Pd(1 0 0), N on Ag(1 1 1), and N 2 on Fe(1 1 0). We show, through inspection of the total energies and trajectories of the hot adsorbates on the surface, that electron–hole (e–h) pair excitations dominate relaxation of the light gas species, while the phonon channel is dominant for the heavy species. In the latter case e–h pairs become more important at the final thermalization stages. [ABSTRACT FROM AUTHOR]

Bacterial adhesion can be dictated by different surface characteristics. In this study we concentrate on the surface roughness of a stainless steel material. We prepared the stainless steel surfaces by 3D polishing, brushing, grinding and electropolishing. Untreated stainless steel surfaces were also considered. The corresponding surface roughness was assessed by profilometry and atomic force microscopy. In experiments we have used different types of bacteria. The rate of adhered bacteria on metal surfaces was determined spectrophotometrically. The results showed that the rate of adhered bacteria increases with increasing surface roughness. Scanning electron microscopy was used to image surfaces in order to determine locations of adhered bacteria. The increased adhesion of bacteria on more rough surfaces results from an increased interplay between the increasing effective surface area and increasing numbers of cracks, voids and gaps. [ABSTRACT FROM AUTHOR]

Possible adsorbate induced reconstruction effects of methanethiolate (MeS) and methaneselenolate (MeSe) on Au(111) are studied employing density functional theory (DFT). For the purposes of this study these simple alkanechalcogenates prove to be representative models for chalcogenate molecules with larger rest groups. MeS and MeSe show very similar properties regarding the adsorption at the unreconstructed and reconstructed surfaces. The latter are constructed by systematically introducing defects at various adsorbate coverages. It turns out that only if the defect site is occupied by at least two molecules the costs of creating the defect can be counterbalanced by the energetic gain and thus adsorbate induced reconstruction gets energetically feasible. Furthermore, for various molecular coverages the adatom-dichalcogenate model, as found by Maksymovych et al. (Phys. Rev. Lett. 97 (2006) 146103), is indeed the most stable reconstruction motif among the simple models studied herein. In order to mimic the impact of the environment, e.g. solvent effects, temperature or electric potentials, the stability of the reconstruction motifs was studied as a function of both the chemical potential of the adsorbate and the energy needed to create the defect substrate structure following the ansatz of ab initio atomistic thermodynamics. This approach hints at the fact that different reconstruction motifs can be realized in different chemical environments. [ABSTRACT FROM AUTHOR]

We review several representative experimental results of action spectroscopy (AS) of single molecules on metal surfaces using a scanning tunneling microscope (STM) by M. Kawai’s group over last decade. The experimental procedures to observe STM-AS are described. A brief description of a low-temperature STM and experimental setup are followed by key experimental techniques of how to determine an onset bias voltage of a reaction and how to measure a current change associated with reactions and finally how to observe AS for single molecule reactions. The experimental results are presented for vibrationally mediated chemical transformation of trans -2-butene to 1.3-butadiene molecule and rotational motion of a single cis -2-butene molecule among four equivalent orientations on Pd(1 1 0). The AS obtained from the motion clearly detects more vibrational modes than inelastic electron tunneling spectroscopy with an STM. AS is demonstrated as a useful and novel single molecule vibrational spectroscopy. The AS for a lateral hopping of water dimer on Pt(1 1 1) is presented as an example of novelty. Several distinct vibrational modes are detected as the thresholds in the AS. The assignment of the vibrational modes determined from the analysis of the AS is made from a view of the adsorption geometry of hydrogen-bond donor or acceptor molecules in water dimer. A generic theory of STM-AS, i.e., a reaction rate or yield as a function of bias voltage, is presented using a single adsorbate resonance model for single molecule reactions induced by the inelastic tunneling current. Formulas for the reaction rate R ( V ) and Y ( V ) , i.e., reaction yield per electron Y ( V ) = eR ( V ) / I are derived. It provides a versatile framework to analyze any vibrationally mediated reactions of single adsorbates on metal surfaces. Numerical examples are presented to demonstrate generic features of the vibrational generation rate and Y ( V ) at different levels of approximations and to show how the effective broadening of the vibrational density of states (as described by Gaussian or Lorentzian functions) manifest themselves in Y ( V ) near the threshold bias voltage corresponding to a vibrational excitation responsible for reactions. A prefactor of Y ( V ) is explicitly derived for various types of elementary processes. Our generic formula of Y ( V ) also underlines the need to observe Y ( V ) at both bias voltage polarities, which can provide additional insight into the adsorbate projected density of states near the Fermi level within a span of the vibrational energy. The theory is applied to analysis of some highlights of the experimental results: Xe transfer, hopping of a single CO molecule on Pd(1 1 0), a dissociation of a single dimethyl disulfide (CH 3 S) 2 and a hopping of a dissociated product, i.e., single methyl thiolate CH 3 S on Cu(1 1 1). It underlines that an observation of Y ( V ) at both bias polarities permits us to certain insight into the molecular alignment with respect to the Fermi level. [ABSTRACT FROM AUTHOR]

Silicene is emerging as a two-dimensional material with very attractive electronic properties for a wide range of applications; it is a particularly promising material for nano-electronics in silicon-based technology. Over the last decade, the existence and stability of silicene has been the subject of much debate. Theoretical studies were the first to predict a puckered honeycomb structure with electronic properties resembling those of graphene. Though these studies were for free-standing silicene, experimental fabrication of silicene has been achieved so far only through epitaxial growth on crystalline surfaces. Indeed, it was only in 2010 that researchers presented the first experimental evidence of the formation of silicene on Ag(1 1 0) and Ag(1 1 1), which has launched silicene in a similar way to graphene. This very active field has naturally led to the recent growth of silicene on Ir(1 1 1), ZrB 2 (0 0 0 1) and Au(1 1 0) substrates. However, the electronic properties of epitaxially grown silicene on metal surfaces are influenced by the strong silicene–metal interactions. This has prompted experimental studies of the growth of multi-layer silicene, though the nature of its “silicene” structure remains questionable. Of course, like graphene, synthesizing free-standing silicene represents the ultimate challenge. A first step towards this has been reported recently through chemical exfoliation from calcium disilicide (CaSi 2 ). In this review, we discuss the experimental and theoretical studies of silicene performed to date. Special attention is given to different experimental studies of the electronic properties of silicene on metal substrates. New avenues for the growth of silicene on other substrates with different chemical characteristics are presented along with foreseeable applications such as nano-devices and novel batteries. [ABSTRACT FROM AUTHOR]

Enhanced colors can be formed when white light is irradiated on the surface ripples induced by femtosecond laser. In this paper, we have demonstrated the ability to display the diverse colors by simultaneously adjusting the incident white light angle and the ripples orientation. Furthermore, our investigation revealed that multi-patterns constituted by ripples with different orientations could be designed on metal surfaces. The diverse display for the desired ones can be realized by exquisitely varying the incident light angle and rotating sample angle. More interestingly, it is found that, although the same patterns could be displayed under different conditions, the colors might be different. These findings can provide a novel method to carry and identify high quantity of information, which may find potential applications in the fields of information storage, identifying codes and anti-counterfeiting patterns. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we have investigated the surface structure of Cu3Au(001) using low energy electron diffraction analysis and ab initio calculations by density functional theory. Our results indicate a different structure from that usually reported in the literature, where we have observed a stacking fault between the first and third layers of the surface. The rippling effect and the interlayer distances belonging to the first six layers of the surface were calculated and compared with other works too. Specifically, a rippling with gold atoms moving towards the vacuum in the first layer of 0.09Å was observed and of 0.02Å in the third layer. A small expansion of the first interlayer distance of 1.3% and a contraction of 0.8% at the second also were observed. Finally, ab initio calculations performed in this work are in good agreement with the experimental results. [Copyright &y& Elsevier]

Abstract: In this paper we present a combined low-energy electron diffraction (LEED) and a DFT study of the Au(110)c(2×2)–Sb surface in order to determine its atomic structure. The DFT calculations, using both LDA and GGA approaches, have indicated that the adsorption of antimony atoms on the Au(110) surface hollow sites is energetically more favored as compared with other possible adsorption sites. The LEED analysis also showed a Sb-overlayer termination with the Sb atoms segregating to the hollow sites instead of forming an Au–Sb surface alloy. This overlayer results to be contracted of about 0.16Å with the first gold layer presenting a small expansion (0.04Å) with respect to the Au bulk interlayers distance. The agreement between the LEED and DFT results is very good. [Copyright &y& Elsevier]

Abstract: Silicene–the silicon-based counterpart of graphene–has a two dimensional structure that is responsible for the variety of potentially useful chemical and physical properties. The existence of silicene has been achieved recently owing to experiments involving epitaxial growth of silicon as stripes on Ag(001), ribbons on Ag(110), and sheets on Ag(111). The nano-ribbons observed on Ag(110) were found–by both high definition experimental scanning tunneling microscopy images and density functional theory calculations–to consist of an arched honeycomb structure. Angle resolved photo-emission experiments on these silicene nano-ribbons on Ag(110), along the direction of the ribbons, showed a band structure which is analogous to the Dirac cones of graphene. Unlike silicon surfaces, which are highly reactive to oxygen, the silicene nano-ribbons were found to be resistant to oxygen reactivity. On the theoretical side, recent extensive efforts have been deployed to understand the properties of standalone silicene sheets and nano-ribbons using both tight-binding and density functional theory calculations. Unlike graphene it is demonstrated that silicene sheets are stable only if a small buckling (0.44 Å) is present. The electronic properties of silicene nano-ribbons and silicene sheets were found to resemble those of graphene. Although this is a fairly new avenue, the already obtained outcome from these important first steps in understanding silicene showed promising features that could give a new future to silicon in the electronics industry, thus opening a promising route toward wide-range applications. In this review, we plan to introduce silicene by presenting the available experimental and theoretical studies performed to date, and suggest future directions to be explored to make the synthesis of silicene a viable one. [Copyright &y& Elsevier]

Abstract: In this work we report on a very accurate low-energy electron diffraction (LEED) and a DFT study of Au(110)-(1×2) in order to determine its surface geometry. The LEED results indicate a surface missing row reconstruction with a large contraction of , a pairing in the second layer and in the fourth layer , and a buckling in the third layer of 0.30Å and in the fifth layer of 0.01Å. These LEED results are in very good agreement with those found by the DFT calculations. [Copyright &y& Elsevier]

Abstract: We present vibrational dynamics and thermodynamics for the (100) surfaces of Cu, Ag, Pd, Pt and Au using a real space approach. The force field for these systems is described by density functional theory. The changes in the vibrational dynamics and thermodynamics from those in bulk are confined mostly to the first-layer. A substantial enhancement of the low-frequency end of the acoustic branch was found and is related to a loosening of the bond at the surface. The thermodynamics of the first-layer also show significant differences (higher heat capacity, lower free energy and higher mean vibrational square amplitudes) from what obtains in bulk. Comparing these results with those calculated using embedded-atom method potentials, we discovered that for Ag(100) and Cu(100), the two methods yield very similar results while for Pd(100), Pt(100) and Au(100) there are substantial differences. [Copyright &y& Elsevier]

Abstract: Water adsorption at metal surfaces is governed by a subtle balance between water–water hydrogen bonding and water–metal interactions, which together determine the stability of the water structures formed. This review describes recent experimental and theoretical studies of water and OH/water coadsorption on well-defined single crystal metal surfaces, systems that have seen an upsurge in interest as new results modify our picture of how water adsorbs on metal surfaces. These results reveal that the simple, conventional ice ‘bilayer’ description of water adsorption, in which water is only marginally distorted from its bulk ice arrangement, is inadequate to describe wetting. Instead, optimisation of the water–metal interaction distorts the local hydrogen bonding geometry of water monolayers significantly from that of bulk ice, with consequent effects on the lateral size and geometry of ice clusters, on the structure of water monolayers and on the wetting of first layer water and growth of ice multilayers. Here we compare adsorption across different metal surfaces, review evidence for the formation of mixed OH/H2O co-adsorption structures and highlight issues that remain uncertain. [Copyright &y& Elsevier]

Abstract: Nanoscience and nanotechnology are tremendously increasing fields of research that aim at producing, characterizing and understanding nanoobjects and assemblies of nanoobjects. Their new physical or chemical properties, which arise from confinement effects, intimately depend on their morphological properties, i.e. their shapes, their sizes and their spatial organization. This calls for dedicated morphological characterization tools, among which is the Grazing Incidence Small Angle X-Ray Scattering (GISAXS). This reciprocal space technique has emerged in the last two decades as a powerful tool that allows investigating in a non-destructive way the morphological properties from one to billions of nanoparticles, either on a surface, or embedded in a matrix, with sizes ranging from 1 nm to several microns. The advantages of the technique are that it is non-destructive; it yields statistical information averaged on a large number of nanoparticles; it allows probing both the surface or deep below it, by changing the incident angle of the X-ray beam; it can be used in very different sample environments, in particular in situ in the course of a given process such as growth, annealing, gas exposure; and it may be given chemical sensitivity by use of anomalous scattering. This report presents a review of the GISAXS technique, from experimental issues to the theories underlying the data analysis, with a wealth of examples. The physical morphological information contained in GISAXS data and its analysis are presented in simple terms, introducing the notions of particle form factor and interference function, together with the different cases encountered according to the size/shape dispersion. The theoretical background of X-ray diffuse scattering under grazing incidence is presented in a general way, and then applied to the particular case of grazing incidence small angle X-ray scattering from assemblies of particles either on a substrate, or buried below it. Most of the GISAXS measurements published to date are reported, covering the fields of ex situ studies of embedded metallic nanoparticles, granular multilayered systems, implanted systems, embedded or stacked or deposited semi-conductor nanostructures, porous materials and copolymer thin films. A special emphasis is brought on in situ experiments, performed either in ultra-high vacuum during nanoparticle growth by molecular beam epitaxy, or in gas-reactors during catalytic reactions. This covers a very broad field, from (i) the 3D island (Volmer–Weber) growth of metals on oxides surfaces to (ii) the organized growth of metals on surfaces that are nanopatterned either by surface reconstruction or by underlying dislocation networks or by deposit-induced nanofacetting, to (iii) the in situ investigation of the self-organized Stranski–Krastanow hetero-epitaxial growth of semi-conductor quantum dots on semi-conductor surfaces, or (iv) the in situ surface nanopatterning by ion bombardment. Many examples are discussed in detail, to illustrate the large diversity of systems and morphologies that can be addressed as well as the different analysis issues and the conclusions of the technique in terms of growth mode. [Copyright &y& Elsevier]

Abstract: The article reviews work on graphene monolayers adsorbed on metal surfaces. Graphene layers on metals have been prepared by surface segregation of carbon and by decomposition of hydrocarbons. The films are often not rotationally aligned to the metal surface. However, for a number of hexagonally close-packed surfaces perfectly ordered epitaxial overlayers have been obtained, with domains larger than the terraces of the metal substrate. In most cases the well-ordered overlayers display moiré structures with large periodicities, resulting from the lattice mismatch between graphene and the underlying metal. These structures are connected with a buckling of the graphene layer indicating local variations of the binding to the metal. For the metal–graphene spacings values between approximately 2.1 and 3.8Å have been found, depending on the metal. Reasons for these strong variations are not yet clear, but there are indications that the systems fall into two classes that differ qualitatively with respect to the metal/graphene interaction. These variations are also reflected by the electronic structure. There are metal–graphene systems in which the π band is significantly downshifted in energy compared to the free-standing graphene, and a band gap of order eV has opened at the point of the Brillouin zone. In other systems, the electronic structure of free-standing graphene is almost intact. The perfectness of the epitaxial moiré phases offers promising applications, e.g., as templates for nanostructures. [Copyright &y& Elsevier]

Abstract: A quantitative analysis of infrared absorption spectra to determine coadsorbate induced relative changes of the vibrational polarizability α v of an adsorbate mode and of the dielectric screening ϵ due to this extra species is presented. Four (ternary) coadsorption systems consisting of the Ru(0001)-(2×2)-(X+CO+O) layer with additional coadsorbates X=H, NO, CO, or O (all of them occupying the remaining empty fcc site) have been studied with FT-IRAS, TDS, LEED and work function change measurements. On-top CO is thereby used as a probe molecule to monitor coadsorbate effects on the dielectric properties of the layer. The vibrational polarizability α v associated with the internal C–O stretch mode (ν C–O) of on-top CO is lowered by all coadsorbates. The dielectric screening ϵ within the adsorbate layer is reduced in the presence of the atomic coadsorbates O and H whereas an increase of ϵ is found for the molecular coadsorbates, threefold coordinated CO and NO. The derived changes of α v and dielectric screening ϵ, as well as the involved line shifts of ν C–O and ν Ru–CO can be understood in terms of the standard Blyholder backbonding model, i.e. CO 5σ charge donation to the metal combined with a backdonation to electronic states with 2π∗ character. [Copyright &y& Elsevier]

Abstract: Self-assembly represents a promising strategy for surface functionalisation as well as creating nanostructures with well-controlled, tailor-made properties and functionality. Molecular self-assembly at solid surfaces is governed by the subtle interplay between molecule–molecule and molecule–substrate interactions that can be tuned by varying molecular building blocks, surface chemistry and structure as well as substrate temperature. In this review, basic principles behind molecular self-assembly of organic molecules on metal surfaces will be discussed. Controlling these formation principles allows for creating a wide variety of different molecular surface structures ranging from well-defined clusters, quasi one-dimensional rows to ordered, two-dimensional overlayers. An impressive number of studies exist, demonstrating the ability of molecular self-assembly to create these different structural motifs in a predictable manner by tuning the molecular building blocks as well as the metallic substrate. Here, the multitude of different surface structures of the natural amino acid cysteine on two different gold surfaces observed with scanning tunnelling microscopy will be reviewed. Cysteine on Au(110)-(1×2) represents a model system illustrating the formation of all the above mentioned structural motifs without changing the molecular building blocks or the substrate surface. The only parameters in this system are substrate temperature and molecular coverage, controlling both the molecular adsorption state (physisorption versus chemisorption) and molecular surface mobility. By tuning the adsorption state and the molecular mobility, distinctly different molecular structures are formed, exemplifying the variety of structural motifs that can be achieved by molecular self-assembly. [Copyright &y& Elsevier]

Abstract: We present ab initio calculation results for electron–phonon (e–ph) contribution to hole lifetime broadening of the surface state on Al(001). We show that e–ph coupling in this state is significantly stronger than in bulk Al at the Fermi level. It makes the e–ph decay channel very important in the formation of the hole decay in the surface state at . We also present the results for e–e lifetime broadening in a quantum-well state in 1ML K/Cu(111). We show that this contribution is not negligible and is much larger than that in a surface state on Ag(111). [Copyright &y& Elsevier]

Abstract: We present calculation results for electron–phonon (e–ph) coupling in one monolayer (ML) of Na on the Cu(111) surface. We show that the e–p coupling parameter λ decreases compared to that for clean Cu(111) due to the significant decrease of the Na vertical vibrational mode contribution to the Eliashberg function in the 1ML Na/Cu(111) system. The corresponding phonon induced lifetime broadening Γ e–ph of a quantum-well state at low temperature decreases by 30% compared to that on clean Cu(111). [Copyright &y& Elsevier]

Abstract: The formation energies of isolated vacancy and adatom–vacancy pair (where the two are separated by a large distance) at low-index surfaces of fcc metals calculated by using the modifies analytical embedded atom method (MAEAM). The results predict the prevailing formation of vacancies on the surfaces (111), (100) (but Pd), Cu and Ni on the (110) surfaces at low temperature, and the defect formation energies consistently create in the sequence (110)→(100)→(111). With good accuracy, the calculated energy values coincide with those obtained by the embedded atom methods (EAM) and from experiments. The correctness of the method by which calculated the formation energies of point defects on the surface was proved. [Copyright &y& Elsevier]

Abstract: We present a brief survey of the contemporary state of theoretical study of quasiparticles (excited electrons and holes) dynamics in bulk metals and at metal surfaces. Quasiparticle decay mechanisms are discussed in terms of electron–electron (e–e) and electron–phonon (e–ph) interactions. The e–ph decay channel is shown to be important for all materials considered. It is especially important for systems with the thickness of one monolayer. In the e–e decay channel the quasiparticle decay can be realized via one-electron transfer processes, via creation of electron–hole pairs, and via plasmon excitation. In ferromagnetic systems the electron (hole) decay via the Stoner pair excitation or/and magnon excitation is made possible. [Copyright &y& Elsevier]

Abstract: We investigate the quantum mechanical behavior of adsorbed hydrogen (H, D, T) on Cu(100) and (110) surfaces. We construct potential energy surfaces (PESs) for the motion of the hydrogen H atom on Cu(100) and (110) surfaces within the framework of density functional theory. The potential energy takes a minimum value on the hollow site of Cu(100) and on the short bridge site of Cu(110). Moreover, we calculate the quantum states of hydrogen atom motion on these calculated PESs. The ground state wave function of the hydrogen atom motion is strongly localized around the hollow site on the Cu(100) surface. On the other hand, the ground state wave function of the hydrogen atom motion on Cu(110) is distributed from the short bridge site to two neighboring pseudo-threefold sites. We finally show isotope effects on the quantum states of the motion of hydrogen on both surfaces. [Copyright &y& Elsevier]

Abstract: We describe stepped metal surfaces by the stabilized-jellium model, and calculate the step formation energy within the local density approximation of the density-functional theory. Using fourth-order gradient expansion for the kinetic energy, we determine the electron density variationally from a parameterized trial density. We compare our numerical results for a monatomic step on the Al(111) surface with other theoretical calculations and estimates. [Copyright &y& Elsevier]

Abstract: The progress in applications of density functional methods to problems of materials for heterogeneous catalysis as well as to their adsorption properties and reactivity is overviewed. Transition metal surfaces (Cu, Ru, Pd, Pt, Pd/Zn, Pd/Pt), metal oxide surfaces (MgO, NiO) and supported d-metal particles (atoms, Pd nanosize clusters) are taken as examples of catalytic substrates. Reactants/adsorbates considered range from single atoms, diatomic molecules, ammonia and small unsaturated hydrocarbons to more complex such as carbonate and urea molecules. Results of cluster- and slab-model density functional calculations chosen from various theoretical and experimental groups illustrate impressive achievements of the past decade in selected aspects of theory in heterogeneous catalysis. Also, some problems and limitations of the density functional description are alluded. [Copyright &y& Elsevier]

Abstract: Electron emission from surfaces due to interaction with charged particles and electromagnetic fields is a topic of research for over 100 years. In the past decade new developments in the production of ultrashort laser pulses (τ &#60;10fs at a wavelength of λ ≈750nm) and of slow highly charged ions (HCI) have rendered these interactions to be remarkably similar. The description of electron emission in HCI-surface interactions can therefore be transcribed to model and understand photoemission from surfaces interacting with ultrashort laser pulses. Examples will be presented for two model systems. [Copyright &y& Elsevier]

Abstract: Experimental and theoretical studies on the quantum delocalization of hydrogen atoms, in particular in vibrationally excited states, on transition-metal surfaces are reviewed. The present status and remaining problems are discussed. The quantum delocalization of hydrogen atoms in the ground state is briefly reviewed. [Copyright &y& Elsevier]

Abstract: The adsorption of S-histidine on gold and copper well-defined surfaces has been characterised by reflection absorption infrared spectroscopy (RAIRS), a surface technique that gives chemical as well as orientational information. Analyses were carried out in a UHV chamber. The RAIRS data are in agreement with the following conclusions. Under low pressure of histidine, 10-8mbar, histidine molecules form an adsorbed molecular layer on Au (111) and Cu (110) surfaces. On gold, histidine mainly adsorbs through the depronated carboxylate group in a quasi-upright geometry that maintains the imidazole ring far from the surface. On copper, the histidine NH2 and COO- groups are involved in the interaction with the surface, with the cycle closer to the surface. [Copyright &y& Elsevier]

Dynamical properties of atoms on surfaces depend sensitively on their bonding environment and thus provide valuable insight into the local geometry and chemical binding at the boundary of a solid. Density-functional theory provides a unified approach to the calculation of structural and dynamical properties from first principles. Its high accuracy and predictive power for lattice dynamical properties of semiconductor surfaces has been demonstrated in a previous article by Fritsch and Schro¨der (Phys. Rep. 309 (1999) 209). In this report, we review the state-of-the-art of these ab initio approaches to surface dynamical properties of metal surfaces. We give a brief introduction to the conceptual framework with focus on recent advances in computational procedures for the ab initio linear-response approach, which have been a prerequisite for an efficient treatment of surface dynamics of noble and transition metals. The discussed applications to clean and adsorbate-covered surfaces demonstrate the high accuracy and reliability of this approach in predicting detailed microscopic properties of the phonon dynamics for a wide range of metallic surfaces. [Copyright &y& Elsevier]

We have treated the surfaces of Al, SUS and Cu metals using an atmospheric-pressure plasma jet generated by nitrogen and oxygen gases under the atmospheric pressure at room temperature. The plasma ignition occurred by flowing mixed gases between two coaxial metal electrodes, and the voltage was applied with impulse type and 16–20 kHz frequencies. The treated surfaces were basically characterized by means of a contact angle analyzer for the activation property on their surfaces. From the results of XPS, FE-SEM, OES and AFM, we could confirm that the main phenomena such as the reactive etching and oxidation were observed on their surfaces as well as even the aggregation of particles by the activated atoms, radicals and metastable species in the plasma space. However, all treated surfaces contained only oxygen and carbon without nitrogen, even though the excited nitrogen species were generated in the plasma due to its higher reactivity than oxygen ones observed in the OES data. The aging effect on the duration time of the surface energy, moreover, was also studied because of the production cost on the industrial applications in addition. [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]

The results of low-energy ion spectroscopy can be compromised by the damage that the ions cause in surface layers of target single crystals, so it is important to characterize the impact of the probe ion on the target. In this investigation Al(1 0 0) single crystal surfaces have been irradiated at room temperature with 1 keV He+ and Ar+ ions typical of low-energy ion scattering spectroscopy (LEIS) and sample sputter cleaning, respectively, and the effects have been studied as a function of ion dose and annealing. Rutherford backscattering and channeling measurements were used to probe the depth distribution and annealing characteristics of the dechanneling yield induced by low-energy ion bombardment. Analysis of the Al surface peak area for channeled MeV He ions, as well as the dechanneling yield from well below the surface, indicated an unusual increase in the depth distribution of the backscattered ion yield from Al with increasing low-energy He+ ion dose. Thermal annealing of the crystal following irradiation with the highest He+ dose of 4×1017 ions/cm2 restored the dechanneled ion yield to its lower starting value, with the relatively low activation energy of 0.05 eV. The increase in backscattered ions is attributed to implanted He atoms located in the [1 0 0] channels. The Ar+ ion induced effects in the channeling spectrum are not as significant as those for He+ ions, even at the highest Ar+ dose of ∼1017 ions/cm2. [Copyright &y& Elsevier]

The manifestation of chirality at surfaces has attracted much attention in recent years. In this review, some of main features of chiral endowments by complex organic molecules at defined metal surfaces are reviewed. Detailed surface spectroscopic data have enabled a hierarchy of chiral expressions to be delineated, from point group chirality expressed by local chiral motifs, to space group chirality in which these motifs act as building blocks which self-assemble into organised chiral structures, to deeper propagation of chirality into the metal leading to chiral reconstructions. Chiral endowments by both chiral and achiral molecules is discussed alongside the implications for progressing chirality from the local to the global level. [Copyright &y& Elsevier]

Among fundamental diatomic molecules, the adsorption of carbon monoxide (CO) and nitric oxide (NO) on metal surfaces has been a subject of intensive research in the surface science community, partly owing to its relevance to heterogeneous catalysis used for environmental control. Compared to the rather well-defined adsorption mechanism of CO, that of NO is less understood because the adsorption results in much more complex reactions. The complexity is ascribed to the open-shell structure of valence electrons, making the molecule readily interact with the metal surface itself as well as with co-adsorbed molecules. Furthermore, the interaction crucially depends on the local structure of the surface. Therefore, to elucidate the interaction at the molecular scale, it is essential to study the valence state as well as the bonding geometry for individual NO molecules placed in a well-defined environment on the surface. Scanning tunneling microscopy (STM) is suitable for this purpose. In this review, we summarize the knowledge about the interaction of NO with metal surfaces, mainly focused on the valence electronic states, followed by recent studies using STM and atomic force microscopy (AFM) at the level of individual molecules. [ABSTRACT FROM AUTHOR]

• Arginine is deposited on copper surface via electrospray device in the UHV chamber. • XPS results highlight the presence of anionic and zwitterionic ARG molecules at the Cu(1 1 0) surface. • STM data show complex 2D arrays formed from dimers of ARG molecules. • A complex adsorption geometry is deciphered through DFT calculations. In this work we present a detailed surface science characterization of L-arginine adsorption on the Cu(1 1 0) surface in a submonolayer regime. Arginine (ARG) is one of the main components of the tripeptide RGD (arginine-glycine-aspartic acid) commonly used as a linker/binder when engineering biomedical devices such as integrin receptors. We replaced the traditional Knusden cell sublimation method to obtain molecular films by dosing arginine directly from an aqueous solution through an electrospray ionization device (ESI). X-ray Photoelectron Spectroscopy (XPS) evidenced the co-existence of different adsorbed molecular species. In addition, Scanning Tunneling Microscopy (STM) data show that the arginine molecules form short and well-separated lines, constituted of dimers of molecules on the surface. Density Functional Theory (DFT) calculations helped clarifying these experimental findings, bringing strong evidences that ARG molecules adsorb in an ionic and a neutral form, with varied binding modes between N atoms and Cu atoms from the surface. These different N Cu bonds lead to the establishment of intermolecular H-bonds, responsible for the dimerization process. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we present the results of a comparative study of vibrational and structural properties of the ordered and c(2×2) phases formed by Na adatoms at room temperature on the Al(111) and Al(100) surfaces, respectively. The surface relaxation, surface phonon dispersion, and polarization of vibrational modes are calculated using the embedded-atom method. Our calculated structural parameters are in agreement with experimental and ab initio results. The obtained vibrational frequencies compare fairly well with available experimental data. [Copyright &y& Elsevier]

Abstract: We report an ab initio study of electron–phonon interactions on the Be(0001) surface. The calculations based on density-functional theory were carried out using a linear response approach in the plane-wave pseudopotential representation. The phonon-induced contribution to excited hole (electron) lifetime broadening is calculated for the zone center surface state. The obtained results show a rather strong momentum dependence. [Copyright &y& Elsevier]

Abstract: This paper provides a perspective on the article "Hydrogen adsorption, absorption and diffusion on and in transition metal surfaces: A DFT study" by Ferrin et al. in this issue. [Copyright &y& Elsevier]