The interaction of water with solid surfaces: Fundamental aspects

The purpose of this review is to compare and discuss recent experimental and theoretical results in the field of H₂O-solid interactions. We emphasize studies of low (submonolayer) coverages of water on well-characterized, single-crystal surfaces of metals, semiconductors and oxides. We discuss the factors which influence dissociative versus associative adsorption pathways. When H₂O adsorbs molecularly, it tends to form three-dimensional hydrogen-bonded clusters, even at fractional monolayer coverages, because the strength of the attractive interaction between two molecules is comparable to that of the substrate-H₂O bond. The template effect of the substrate is important in determining both the local orientation and long-range order of H₂O molecules in these clusters. The influence of surface additive atoms (e.g., O, Br, Na, K) and also surface imperfections (e.g. steps and defects) on the surface structure and chemistry of H₂O is examined in detail. Some results on single-crystal substrates are compared with earlier measurements of H₂O adsorption on high-area materials.     

A comprehensive model for simulating the interaction of water with solid surfaces in fire suppression environments

A novel framework for sprinkler-based fire suppression modeling has been developed that includes detailed interaction of water with solid surfaces. This model builds on the fire growth model (FireFOAM) previously developed at FM Global. The fundamental film-transport equations for mass continuity, momentum, and energy have been formulated and implemented in an open-source CFD code (OpenFOAM®) and subsequently coupled with FireFOAM. Water transport, as would occur in a fire suppression environment, is tracked along solid surfaces. Interaction of the water with the solid surfaces in the form of cooling and pre-wetting is represented. Coupling between the film-transport model and the gas-phase and condensed-phase regions has been specified through interfacial transport models. Model validation for vaporization and conjugate heat transfer is shown for a surrogate fire environment. Radiation heat transfer is applied to a vertical panel with water flowing down the surface. Heat fluxes range from 5 to 33 kW/m² and water flow rates range from 2 to 52 g/m/s.     

Electronic properties of SiC surfaces and interfaces: some fundamental and technological aspects

The wide band gap semiconductor silicon carbide (SiC) is the first-choice material for power electronic devices operating at high voltages, high temperatures, and high switching frequencies. Due to their importance for crystal growth, processing, and device fabrication, the electronic properties of SiC surfaces and interfaces to other materials such as metals and dielectrics are of particular interest. Unreconstructed, H-terminated SiC surfaces which are passivated in a chemical as well as an electronic sense are obtained in a thermal hydrogenation process. It is demonstrated that deposition of Al₂O₃ on H-terminated SiC(0001) leads to an interface which is lower in defects than the thermally grown SiO₂/SiC interface. Furthermore, starting from hydrogenated SiC{0001} surfaces it is possible to prepare unreconstructed (1×1) surfaces with one dangling bond per unit cell. These surfaces show indications for strong electron correlation effects. PACS 68.47.Fg; 73.20.At; 79.60.Bm; 68.35.Bs; 68.35.Dv     

The interaction of neutral molecules with dielectric surfaces

The energy of interaction between a neutral atom or molecule with a dielectric surface is calculated; radiative corrections are included. The interaction energy is expressed in terms of the frequency dependent polarizability of the atom and the dielectric permeability of the surface. Approximate expressions for the energy of interaction with metals are developed and their numerical values are compared with those derived from experiment.     

Atomic control of water interaction with biocompatible surfaces: the case of SiC(001)

The interaction of water with Si- and C- terminated beta-SiC(001) surfaces was investigated by means of ab initio molecular dynamics simulations. Irrespective of coverage, varied from 1/4 to 1 monolayer, we found that water dissociates on the Si-terminated surface, substantially modifying the clean surface reconstruction, while the C-terminated surface is nonreactive and hydrophobic. Based on our results, we propose that STM images and photoemission experiments may detect specific changes induced by water on both the structural and electronic properties of SiC(001) surfaces.     

The interaction of KCl with tungsten single crystal surfaces

The interaction of KCl vapor with W single crystal surfaces is studied with the aim of obtaining information on the adsorption of ionically bonded molecules. The atomically smoothest and roughest surfaces, (110) and (111), are used. The adsorbate is characterized by LEED, thermal desorption spectroscopy (TDS) and by photoemission experiments which can be related to known work function data. It is found that the adsorbate is undissociated on W(110) and to a large extent also on W(111) at room temperature and that no ordered structures are formed. Electron bombardment causes KCl dissociation and Cl desorption which is complete with sufficiently high electron doses. Close-packed K monolayers can be formed this way.     

The interaction of naphthalene and adamantane with gold surfaces

Isotherms, isosteric heats, and entropies of adsorption of naphthalene and adamantane on optically flat gold films are reported.     

All-solid-state lithium batteries with inorganic solid electrolytes:Review of fundamental science

The scientific basis of all-solid-state lithium batteries with inorganic solid electrolytes is reviewed briefly, touching upon solid electrolytes, electrode materials, electrolyte/electrode interface phenomena, fabrication, and evaluation. The challenges and prospects are outlined as well.     

The interaction of hydrogen with stepped surfaces of copper: A pairwise-additive model

A pairwise-additive model, with Morse functions as the two-body potentials, has been employed to study stepped surfaces of copper. In general, the hydrogen-atom-copper bond energy is increased when one or more copper atoms are added to the surface at sites different from that which the hydrogen atom is approaching. Approaches of the hydrogen atom to a step face produced hydrogen-copper binding energies larger than those found in the absence of the step. Variations in these general observations are noted for alterations of the approach site environment.     

The interaction of hydrogen with copper-ruthenium surfaces: Application of a pairwise-additive model

A pairwise-additive model, with Morse functions as the two-body potentials, is applied to the interaction of a hydrogen atom with a two-element system: copper-ruthenium. The results show that such a simple model can be applied to two-element systems where no ligand effect is operative.     

Organic molecule adsorption on solid surfaces: chemical bonding, mutual polarisation and dispersion interaction

We discuss some of the most relevant bonding scenarios for the adsorption of organic molecules on solid surfaces from the perspective of first-principles calculations. The adsorption of uracil and phenanthrenequinone on Si(001) and the adsorption of adenine on Cu(110) and graphite(0001) surfaces serve as prototypical examples to highlight relevant molecule–substrate interactions and their consequences for the properties of the adsystem. Covalent bonds formed during organic reactions with semiconductor surfaces significantly modify the structural and electronic properties of both the adsorbed molecules and the substrate. Organic molecule adsorption on metals may be driven by mutual polarisation that leads to substantial charge transfer and rehybridisation, despite small adsorption energies. Subtle effects related to the lowering of the kinetic energy of the valence electrons as well as dispersion forces, finally, govern the interaction between the organic molecules and chemically inert substrates such as graphite. PACS 68.35.Md; 68.43.Bc; 68.43.-h; 73.20.-r; 82.39.Pj     

Water droplets interaction with super-hydrophobic surfaces

Static and dynamic behavior of water droplets on various super-hydrophobic (SH) surfaces were investigated. First, SH plant leaves were used as samples and we found out that surface nanostructure has a great influence on the droplets dynamic behavior. Then, we made biomimetic structures by depositing SH films through microwave-plasma enhanced chemical vapor deposition (MPECVD). Next, SH surfaces were fabricated by covering previously roughened SiOx films with self-assembled monolayers (SAMs). The substrates were then charged with static electricity, and water droplets falling on tilted charged surfaces leaped up or run uphill at high speeds, proving that not only the surface nanostructure but also its chemical endgroups have a great effect on the water droplets motion on SH surfaces.     

Stability of metal vicinal surfaces revisited

The stability of metal vicinal surfaces with respect to faceting is investigated using empirical potentials as well as electronic structure calculations. It is proven that for a wide class of empirical potentials all vicinal surfaces between (100) and (111) are unstable at 0 K when the role of third and farther nearest neighbors is negligible. However, electronic structure calculations reveal that the answer concerning the stability of vicinal surfaces is not so clear-cut. Finally, it is shown that surface vibrations at finite temperatures have little effect on the stability of vicinal surfaces.     

Molecular dynamics studies of the interaction between water and oxide surfaces

The water-surface interaction is a research target of great importance for a broad spectrum of technological applications and fundamental scientific disciplines. In the present study, a comparative analysis is performed to clarify the structural and diffusion properties of water on a number of oxide surfaces. Based on the molecular dynamics (MD) simulation method, the water-surface interaction mechanism was investigated for the oxide materials TiO₂ (anatase), Al₂O₃ (corundum), and Fe₂O₃ (hematite). A comparison of the water-TiO₂ interaction with the water-Al₂O₃ and water-Fe₂O₃ systems demonstrates the specificity of the adsorption and layer formation on the atomic/molecular level scale. The obtained MD analysis data point to a considerable enhancement of water-TiO₂ surface adsorption and a relatively high density distribution profile near the surface. The novel data on water structure and diffusion on oxide surfaces are discussed from the point of view of possible material innovation and design.     

Deconvolution in electron spectroscopy revisited: computational aspects

The most common methods of deconvolution for electron spectroscopy are reviewed. An account is given of their disadvantages, for example the production of artifacts. Five new methods which combine the basic methods are described. These new methods do not produce artifacts, are fast because they incorporate a FFT algorithm, and can be run on personal computers.     

The interaction of a laser-generated cavity with a solid boundary

In this paper new observations of a laser-generated cavitation bubble interacting with an inertial boundary are presented. Employing schlieren photography techniques and a thin film transducer placed on the surface of the boundary, the pressure stresses induced in the solid boundary and the surrounding fluid by collapsing bubbles, created very close to the solid surface, are experimentally measured. Liquid jet development, shock wave emission, and "splash" phenomena are identified. For different creation sites close to the boundary, the relevance of each of these phenomena with respect to potentially damaging pressure stresses in the boundary is speculated on.     

Thermodynamics of solid surfaces

In contrast to the thermodynamics of fluid surfaces, the thermodynamics of solid surfaces was not elaborated in detail by Gibbs and other founders of surface thermodynamics. During recent decades, significant progress in this field has been achieved in both the understanding of old notions, like chemical potentials, and in formulating new areas. Applying to solid surfaces, basic relationships of classical theory of capillarity, such as the Laplace equation, the Young equation, the Gibbs adsorption equation, the Gibbs-Curie principle, the Wulff theorem and the Dupré rule, were reformulated and generalized. The thermodynamics of self-dispersion of solids and the thermodynamics of contact line phenomena were developed as well. This review provides a fresh insight into the modern state of the thermodynamics of solid surfaces. Not only a solid surface itself, both in a macroscopic body and in the system of fine particles, but also the interaction of solid surfaces with fluid phases, such as wetting phenomenon, will be analyzed. As the development of surface thermodynamics has given a powerful impetus to the creation of new experimental methods, some of these will be described as examples.     

The study of solid surfaces by electrochemical methods

The basic concepts of electrochemistry at the solid-electrolyte interface are discussed in this article with special emphasis on surface physical aspects. The electrochemical environment is shown to provide several unique experimental possibilities for the study of metal and semiconductor surfaces. Chemisorption processes, which are associated with charge transfer across the interface, can be studied with great accuracy, even when only submonolayer amounts are adsorbed. Semiconductor electrodes have recently received increasing attention and their fundamental properties, as well as selected experimental results, are described here. The optical reflectance of metal electrodes measures sensitively overlayers and the electric charge on the surface, both of which can easily be controlled by the voltage applied to the electrochemical cell. The final topic is photo-emission, which is usually associated with ultra high vacuum conditions but which, when studied at a metal-electrolyte contact, can be used to obtain complementary information, particularly at low excitation energies.