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Use and performance criteria of photonic devices increase in various application areas such as information and communication, lighting, and photovoltaics. In many current and future photonic devices, surfaces of a semiconductor crystal are a weak part causing significant photo-electric losses and malfunctions in applications. These surface challenges, many of which arise from material defects at semiconductor surfaces, include signal attenuation in waveguides, light absorption in light emitting diodes, non-radiative recombination of carriers in solar cells, leakage (dark) current of photodiodes, and light reflection at solar cell interfaces for instance. To reduce harmful surface effects, the optical and electrical passivation of devices has been developed for several decades, especially with the methods of semiconductor technology. Because atomic scale control and knowledge of surface-related phenomena have become relevant to increase the performance of different devices, it might be useful to enhance the bridging of surface physics to photonics. Toward that target, we review some evolving research subjects with open questions and possible solutions, which hopefully provide example connecting points between photonic device passivation and surface physics. One question is related to the properties of the wet chemically cleaned semiconductor surfaces which are typically utilized in device manufacturing processes, but which appear to be different from crystalline surfaces studied in ultrahigh vacuum by physicists. In devices, a defective semiconductor surface often lies at an embedded interface formed by a thin metal or insulator film grown on the semiconductor crystal, which makes the measurements of its atomic and electronic structures difficult. To understand these interface properties, it is essential to combine quantum mechanical simulation methods. This review also covers metal-semiconductor interfaces which are included in most photonic devices to transmit electric carriers to the semiconductor structure. Low-resistive and passivated contacts with an ultrathin tunneling barrier are an emergent solution to control electrical losses in photonic devices. [ABSTRACT FROM AUTHOR]

Droplet impact dynamics is an interfacial phenomenon that is shown everywhere in nature and is the underlying of numerous technological applications including bio-printing, tissue engineering, pharmaceuticals, fight against COVID-19 pandemic, smart biomaterials, and flexible electronics. Over the last decade, expeditious advancement of novel functional interfacial surfaces, high-speed visualization, nanoscience, nanotechnology, machine learning, and computational power, as well as the connection of flow physics with interfacial science, have contributed to enhancing the understanding of relevant complex physical phenomena. Droplet, upon impacting onto substrates, can deposit, spread, bounce, and splash. Features of droplet impact physics and surface wettability necessitate elaborate solid–liquid interactions. Given the significance of droplet impact physics for healthcare and electronics, it is recommended for the scientific community to direct research studies to profound the understanding of such complex physics. Therefore, this Review initially focuses on liquid–solid interfacial science. Second, droplet impact physics on numerous solid surfaces was discussed. Substrates with various wettability and physical features were considered: hydrophilic, hydrophobic, superhydrophobic, smooth, rough, and flexible elastic surfaces. Furthermore, numerous advancements of droplet impact on solid surfaces related to advanced technologies and challenges including printed electronics, smart biomaterials, tissue engineering, machine learning, and COVID-19 pandemic were reviewed. Finally, this Review outlines future perspectives and research directions in complex droplet impact physics. [ABSTRACT FROM AUTHOR]

In fixed point theory, interpolation is acknowledged in numerous areas of research, for instance, earth sciences, metallurgy, surface physics, and so on because of its prospective applications in the estimation of signal sensation analysis. As a result, it is interesting to investigate the fixed point and fixed circle (disc) utilizing interpolative techniques via partial b‐metric spaces in which non‐trivial as well as real generalizations are feasible. We define some improved interpolative contractions to create an environment for the existence of a fixed point and fixed circle and solve a two‐point boundary value problem related to a differential equation of second order. The obtained conclusions are validated by providing illustrative examples. Determining the fixed point of a non‐self mapping, the uniqueness of the fixed point and fixed circle, and the study of fractal interpolants would also be a fascinating investigation in the time to come. [ABSTRACT FROM AUTHOR]

Pulsar electrodynamics could be relevant to the physics of stellar surface, which remains poorly understood for more than half a centenary and is difficult to probe due to the absence of direct and clear observational evidence. Nevertheless, highly sensitive telescopes (e.g., China's Five‐hundred‐meter Aperture Spherical radio Telescope, FAST) may play an essential role to solve the problem since the predicted surface condition would have quite different characteristics in some models of pulsar structure, especially after the establishment of the standard model of particle physics. For instance, small hills (or "zits") may exist on solid strangeon star surface with rigidity, preferential discharge, that is, gap sparking, may occur around the hills in the polar cap region. In this work, with the 110‐min polarization observation of PSR B0950+$$ + $$08 targeted by FAST, we report that the gap sparking is significantly non‐symmetrical to the meridian plane on which the rotational and magnetic axes lie. It is then speculated that this asymmetry could be the result of preferential sparking around zits which might rise randomly on pulsar surface. Some polarization features of both single pulses and the mean pulse, as well as the cross‐correlation function of different emission regions, have also been presented. [ABSTRACT FROM AUTHOR]

Piezoelectric nanobeams are important components in micro-nano electromechanical systems. They are often used as mechanical structures such as wireless sensors, biological probes and transistors. And their mechanical performance is a very important research topic. Based on the theory of surface elasticity and the "core–shell" model, post-buckling behavior of porous piezoelectric nanobeams is analyzed using the first-order shear deformation beam theory, where the surface effect is introduced by employing the surface energy model. The governing equations and boundary conditions of post-buckling of porous piezoelectric nanobeams under mechanical loading were derived by introducing the concept of median surface in physics and the principle of minimum potential energy. The influence of surface effect on post-buckling configuration, post-buckling path, amount of induced charge and critical load of porous piezoelectric nanobeams with different external constraints and porosities were discussed. The results show that considering surface effects, the effective elastic modulus and critical load of porous piezoelectric nanobeams will be increased, and the post-buckling configuration, post-buckling path and amount of induced charge will be reduced. Meanwhile, the mechanical properties of porous piezoelectric nanobeams can be effectively improved by appropriate pore distribution. These findings can be used as a theoretical basis for the accurate design and manufacture of micro-nano mechanical and electronic devices. [ABSTRACT FROM AUTHOR]

Horizontal convective rolls (HCR) are sub-mesoscale motions that influence the transport of heat, momentum, and pollutants within the boundary layer. In this work, a high-resolution (0.666 km) Weather Research and Forecasting (WRF) model is employed to simulate the structure of the HCRs over Kalpakkam along the southeast coast of India. The sensitivity of HCR simulation to model land surface physics is studied with two land surface models (LSM), (i) Noah and (ii) Noah multi-parameterization (NMP), for three selected days (15 April 2013, 07 May 2015, 28 March 2018) during summer synoptic conditions. On all three selected days, the boundary layer rolls formed over a period of about 2–3 h in the morning under moderate winds (4–5.0 m/s), moderate vertical wind shear (2.4–3.5 m/s) in the lower atmosphere, and slightly unstable conditions [gradient Richardson number (RiG) −4.5 to −5.0] in both simulations and observations, indicating that thermal instability is the chief mechanism in their development. Simulated mean surface meteorological parameters by NMP were found to be in better agreement with observations than Noah. Results suggest that the LSMs mainly affected the simulated turbulent roll structure in terms of updraft cores and their horizontal and vertical extent by variation in simulated surface energy fluxes, boundary layer structure, wind shear, and stability. The structure of simulated HCRs is better represented by NMP due to the improvements in the flux distribution and surface properties. Simulations using the FLEXPART dispersion model for a hypothetical case of tracer release indicated an uneven spatial concentration pattern due to upward and downward motions in the region of HCRs. The stronger winds and stronger flow convergence in Noah and higher heat flux and more unstable conditions in NMP led to differences in the simulated tracer concentrations in the two cases. [ABSTRACT FROM AUTHOR]

Grain boundary grooving significantly affects the grain growth behavior in a polycrystalline thin film with columnar grain structure by partial or complete pinning of moving grain boundaries. Theoretically, it can be shown that the stagnation of grain growth can occur for certain combinations of grain size and film thickness, for which grain boundaries cannot escape from the groove root. However, in real systems, grooves attached with the grain boundaries can migrate along with the moving grain boundaries. The possibility for stagnation arises when a groove behaves like a notch fixed at the surface. Such a condition can arise if the surface diffusivity is sufficiently reduced after stable groove formation using surface treatment. In the present study, grain growth in a solid-state thin film is investigated using a three-dimensional phase-field method that allows grains of a solid phase to be in equilibrium with a vapor phase at a constant temperature. The model captures the essential physics of surface diffusion-controlled thermal grooving and its interaction with a moving grain boundary. From the phase-field simulations, three possible interactions between the grain boundary and the groove are identified: stagnation of grain boundary, grain boundary-groove detachment, and coupled movement of the groove and the grain boundary. [ABSTRACT FROM AUTHOR]

The phenomenon of a water droplet impact on a free surface is studied to understand the physics of free surface bubble entrainment. Particle image velocimetry (PIV) and high-speed image system are used to analyse the flow structure evolutions in the droplet impact cavity period and bubble entrainment cavity period, respectively. The photographic results show that the entrapped surface of the impact cavity remains intact and continuous, and individual bubble entrainment occurs during the secondary entrainment cavity evolution. The instantaneous distributions of velocity fields in the longitudinal and lateral directions are uniform and independent of the approaching impact velocity. For the entrainment cavity evolution, the transverse diffusion intensity is higher than that for the impact cavity period. An individual bubble forms during the transverse velocity penetration across the droplet impact area. Consequently, for the droplet impact on a water surface, the present study implies the presence of a mechanism by which the interior flow field plays a key role in the bubble entrainment. [ABSTRACT FROM AUTHOR]

We study the growth of entanglement entropy in a doubly holographic model of gravity for a spherical AdS black hole. Compared to previous work, which was limited to the case of planar black holes, this introduces an extra scale to the problem. This allows us to analyze the interplay between the reorganization of entanglement entropy due to island formation and the onset of the Hawking-Page phase transition and to find the appearance of a new critical black hole radius unrelated to the thermodynamics. We also find that the geometry of the Ryu-Takayanagi surface capturing the physics of islands exhibits drastically different behavior than in the planar case. [ABSTRACT FROM AUTHOR]

The most fundamental response of a solid to a plasma and vice versa is electric. An electric double layer forms with a solid-bound electron-rich region—the wall charge—and a plasma-bound electron-depleted region—the plasma sheath. However, it is only the plasma sheath that has been studied extensively ever since the beginning of plasma physics. The wall charge received much less attention. Particularly, little is known about the operando electronic structure of plasma-facing solids and how it affects the spatiotemporal scales of the wall charge. The purpose of this Perspective is to encourage investigations of this terra incognita by techniques of modern surface physics. Using our own theoretical explorations of the electron microphysics at plasma–solid interfaces and a proposal for measuring the wall charge by infrared reflectivity to couch the discussion, we hope to put together enough convincing reasons for getting such efforts started. They would open up—at the intersection of plasma and surface physics—a new arena for applied as well as fundamental research. [ABSTRACT FROM AUTHOR]

Surface plasmons have shown increasingly widespread applications in the last decade, especially in the field of solar energy conversion, recently leading to the use of metal nanoparticles as plasmonic photocatalysts. The latter offers great potential in overcoming traditional catalysts by providing localized heating and unconventional reaction pathways leading to improved product selectivity. A complete understanding of the underlying mechanisms remains, however, elusive due to the close resemblance between thermal and non-thermal effects, both leading to enhanced reaction rates. In this tutorial, we will introduce the basic physics of surface plasmons and the interaction mechanisms with surrounding molecules. We will then discuss the main strategies to evaluate photothermal effects and the main signatures of hot electron-driven processes. These aspects will be covered in specific examples of plasmonic photocatalysis for energy-relevant chemical reactions in the case of colloidal suspensions and at the solid/gas interphase in solid pellets, which involve different thermal constraints and thus different experimental strategies to reveal the effects of localized heating and hot electrons. [ABSTRACT FROM AUTHOR]

We explore stochastic–fractional Drinfel'd–Sokolov–Wilson (SFDSW) equations for some wave solutions such as the cross-kink rational wave solution, periodic cross-rational wave solution and homoclinic breather wave solution. We also examine some M-shaped solutions such as the M-shaped rational solution, M-shaped rational solution with one and two kink waves. We also derive the M-shaped interaction with rogue and kink waves and the M-shaped interaction with periodic and kink waves. This model is used in mathematical physics, surface physics, plasma physics, population dynamics and applied sciences. Moreover, we also show our results graphically in different dimensions. We obtain these solutions under some constraint conditions. [ABSTRACT FROM AUTHOR]

To improve the ensemble prediction system of the tropical regional atmosphere model for the South China Sea (TREPS) in predicting landfalling tropical cyclones (TCs), the impacts of three new implementing strategies for surface and model physics perturbations in TREPS were evaluated for 19 TCs making landfall in China during 2014–16. For sea surface temperature (SST) perturbations, spatially uncorrelated random perturbations were replaced with spatially correlated ones. The multiplier f, which is used to form perturbed tendency in the Stochastically Perturbed Parameterization Tendency (SPPT) scheme, was inflated in regions with evident convective activity (f-inflated SPPT). Lastly, the Stochastically Perturbed Parameterization (SPP) scheme with 14 perturbed parameters selected from the planetary boundary layer, surface layer, microphysics, and cumulus convection parameterizations was added. Overall, all these methods improved forecasts more significantly for non-intensifying than intensifying TCs. Compared with f-inflated SPPT, the spatially correlated SST perturbations generally showed comparable performance but were more (less) skillful for intensifying (non-intensifying) TCs. The advantages of the spatially correlated SST perturbations and f-inflated SPPT were mainly present in the deterministic guidance for both TC track and wind and in the probabilistic guidance for reliability of wind. For intensifying TCs, adding SPP led to mixed impacts with significant improvements in probability-matched mean of modest winds and in probabilistic forecasts of rainfall; while for non-intensifying TCs, adding SPP frequently led to positive impacts on the deterministic guidance for track, intensity, strong winds, and moderate rainfall and on the probabilistic guidance for wind and discrimination of rainfall. [ABSTRACT FROM AUTHOR]

Fractional–stochastic Drinfel'd–Sokolov–Wilson equations (FSDSWEs) forced by multiplicative Brownian motion are assumed. This equation is employed in mathematical physics, plasma physics, surface physics, applied sciences, and population dynamics. The (G ′ / G) -expansion method is utilized to find rational, hyperbolic, and trigonometric stochastic solutions for FSDSWEs. Because of the priority of FSDSWEs, the derived solutions are more useful and effective in understanding various important physical phenomena. Furthermore, we used the MATLAB package to create 3D graphs for specific solutions in order to investigate the effect of fractional-order and Brownian motions on the solutions of FSDSWEs. [ABSTRACT FROM AUTHOR]

Silicon (Si) has been scaled below 10 nm in multigate and silicon-on-insulator (SOI) device technologies, but clearly Si thickness cannot be reduced indefinitely, as we will run out of atoms eventually. As thickness approaches 5 nm, surfaces and interfaces will significantly impact the electrical behavior of Si, and surface physics cannot be discounted. Below that, bulk material properties will be altered considerably in the few-monolayer limit. One of the most basic defining properties of a semiconductor is its conductivity. To improve conductivity, while inducing a channel by appropriate biasing, it is necessary to define an accurate impurity doping strategy to reduce parasitic resistance. In this paper, we investigated the changing electrical conductivity of SOI films as a function of the Si thickness, in the range of 3–66 nm. SOI films were ex situ doped using three different approaches: liquid/vapor phase monolayer doping of phosphorus using allyldiphenylphosphine, gas-phase doping of arsenic using arsine (AsH3), and room-temperature beam-line ion implantation of phosphorus. The circular transfer length method and micro-four-point probe measurements were used to determine the resistivity of the Si films, mitigating the contribution from contact resistance. The resistivity of the Si films was observed to increase with decreasing Si film thickness below 20 nm, with a dramatic increase observed for a Si thickness at 4.5 nm. This may drastically impact the number of parallel conduction paths (i.e., nanowires) required in gate-all-around devices. Density functional theory modeling indicates that the surface of the Si film with a thickness of 4.5 nm is energetically more favorable for the dopant atom compared to the core of the film. [ABSTRACT FROM AUTHOR]

In this study, we carried out molecular dynamics simulations of a cylindrical Lennard-Jones droplet on a flat and smooth solid surface and showed that Young's equation as the relation among solid-liquid, solid-vapor, and liquid-vapor interfacial tensions γSL, γSV, and γLV, respectively, was applicable only under a very restricted condition. Using the fluid stress-tensor distribution, we examined the force balance in the surface-lateral direction exerted on a rectangular control volume set around the contact line. As the mechanical route, the fluid stress integrals along the two control surfaces normal to the solid-fluid interface were theoretically connected with γSL and γSV relative to the solid-vacuum interfacial tension γS0 by Bakker's equation extended to solid-related interfaces via a thought experiment, for which the position of the solid-fluid interface plane was defined at the limit that the fluid molecules could reach. On the other hand, the fluid stress integral along the control surface lateral to the solid-fluid interface was connected with γLV by the Young-Laplace equation. Through this connection, we showed that Young's equation was valid for a system in which the net lateral force exerted on the fluid molecules from the solid surface was zero around the contact line. Furthermore, we compared γSL − γS0 and γSV − γS0 obtained by the mechanical route with the solid-liquid and solid-vapor works of adhesion obtained by the dry-surface method as one of the thermodynamic routes and showed that both routes resulted in a good agreement. In addition, the contact angle predicted by Young's equation with these interfacial tensions corresponded well to the apparent droplet contact angle determined by using the previously defined position of the solid-fluid interface plane; however, our theoretical derivation indicated that this correspondence was achieved because the zero-lateral force condition was satisfied in the present system with a flat and smooth solid surface. These results indicated that the contact angle should be predicted not only by the interfacial tensions but also by the pinning force exerted around the contact line. [ABSTRACT FROM AUTHOR]

We report a novel approach to control the wavefronts of shear vertical (SV) waves in solids using metasurfaces constituted by a stacked array of composite plates, which are composed of two connecting parts made of different materials. The metasurfaces are connected at two ends to the half-space solids where the elastic SV waves propagate. The incident SV waves in the left half-space solid induce flexural waves in the composite plates and subsequently are converted back to SV waves in the right half-space solid. The time delay of flexural waves in each composite plate of the metasurfaces is tuned through the varying length of the two connecting components. To quantitatively evaluate the time delay in each composite plate, a theoretical model for analyzing the phase of the transmitted SV waves is developed based on the Mindlin plate theory. To control the SV waves at will, each composite plate in the metasurface is delicately designed according to the proposed theoretical model. For illustrative purposes, two metasurfaces are designed and numerically validated. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are carried out for a single component, monatomic Lennard-Jones fluid confined between two mica surfaces to investigate the structure and relaxation dynamics of the confined fluid as a function of surface separation. Due to the underlying symmetry of the potassium ions on the mica surface, the contact layers prefer to adopt an incommensurate square or rhombic symmetry. The inner layers adopt a symmetry varying between rhombic, triangular, and square, depending on the density and surface separation. When the surface separation is an integral multiple of the particle diameter, distinct layering is observed, whereas jammed layers are formed at intermediate surface separations. This leads to the formation of both commensurate and incommensurate layering with varying intralayer symmetry. The self-intermediate scattering function exhibits a gamut of rich dynamics ranging from a distinct two-step relaxation indicative of glassy dynamics to slow relaxation processes where the correlations do not relax to zero over a microsecond for specific surface separations. An extended β relaxation is observed for both commensurate and incommensurate layering. Stretched exponential fits are used to obtain the relaxation times for the late α-relaxation regime of the self-intermediate scattering function. In some cases, we also observed dynamic and structural heterogeneities within individual layers. Although a single-component Lennard-Jones fluid does not exhibit a glass transition in the bulk, this study reveals that such a fluid can display, without supercooling, complex relaxation dynamics with signatures of a fluid approaching a glass transition upon confinement at constant temperature. [ABSTRACT FROM AUTHOR]

A method is developed for rough surface reconstruction using fields scattered at grazing angles in a medium with a linearly varying refractive index and Neumann boundary condition. This regime represents a ducting medium, bounded by a perfectly conducting surface with a TM incident field or an acoustically hard surface. This significantly extends the iterated marching method, based upon the parabolic integral equation for forward-scattered field components [Chen and Spivack, J. Opt. Soc. Am. A 35, 504–513 (2018)]. The approach, which uses a fixed frequency, is able to accurately recover multiscale surfaces and is found to be robust with respect to measurement noise and localized perturbations. [ABSTRACT FROM AUTHOR]

The article discusses the results of a study which synthesized a trilayer-type van der Waals heterostructure of manganese telluride/bismuth telluride/Iron (Tellurium, Selenium), which combined s-wave superconductivity, thickness-dependent magnetism and strong spin-orbital coupling. Topics covered include growth and scanning tunneling microscopy (STM) characterization of the heterostructure, the spatial distributions of superconducting states and STM measurement.

Using 3D sonic crystals as acoustic higher‐order topological insulators (HOTIs), 2D surface states described by spin‐1 Dirac equations at the interfaces between the two sonic crystals with distinct topology but the same crystalline symmetry are discovered. It is found that the Dirac mass can be tuned by the geometry of the two sonic crystals. The sign reversal of the Dirac mass reveals a surface topological transition where the surface states exhibit zero refractive index behavior. When the surface states are gapped, 1D hinge states emerge due to the topology of the gapped surface states. The zero refractive index behavior and the emergent topological hinge states are confirmed experimentally. This study reveals a multidimensional Wannier orbital control that leads to extraordinary properties of surface states and unveils an interesting topological mechanism for the control of surface waves. [ABSTRACT FROM AUTHOR]

• A formulated correlation between vibration characteristics and surface topography. • Time-varying vibration and texture features along the cutting path are extracted. • An interpretation of the mechanism behind machining chatter mode shift phenomenon. • A hybrid physics and data-driven method for the surface topography reconstruction. Machining thin-walled cylindrical workpieces is frequently subjected to vibration due to their low rigidity, resulting in complicated surface topography. This paper investigates the vibration characteristics of thin-walled cylinder turning as well as its effect on the machined surface topography comprehensively by means of numerical simulations and experimental measurements. It is seen that the circumferential shell mode of vibration exhibits higher sensitivity to the variation of the wall thickness than the axial beam mode. The features of the vibration characteristics as well as the machined surface textures of thin-walled workpieces are shifting in a cutting pass. The underlying physical mechanism behind this phenomenon was interpreted. By extracting the critical vibration frequency and surface waviness measurement along the cutting path, a hybrid physics and data-driven surface topography was reconstructed, which showed consistency with the real surface topography. The formulated correlation between the vibration characteristics and the surface topography contributes to a holistic understanding of dynamic behaviors of thin-walled cylinder machining, and a tool that utilizes vibration to produce functional microstructures on cylindrical surfaces. [ABSTRACT FROM AUTHOR]

Density function theory calculations have been performed to study the stability of small helium-vacancy (He-V) complexes near tungsten (W) surfaces of different orientations. The results show that the stability of vacancies and He-V complexes near W surfaces depends on surface orientation. However, as the depth below the surface increased beyond about 0.65–0.8 nm, the stability of He-V complexes is similar to the bulk. The formation energies of single vacancies and di-vacancies at depths less than 0.2 nm below the W(110) surface are higher than for W(100) or W(111) surfaces, but have lower energies at depths between 0.2 and 0.65 nm. The formation energies of He-V complexes below W surfaces are sensitive to the geometric orientation of the He and vacancy, especially below the W(111) surface. Within about 0.2 nm of the top layer of the three W surfaces, neither a vacancy nor a di-vacancy can trap He. Because of the lower formation energy of He-V complexes and higher He binding energy to vacancies below the W(110) surface, the He desorption from the W(110) surface is less likely to occur than from the W(100) and W(111) surfaces. Our results provide fundamental insight into the differences in surface morphology changes observed in single W crystals with different surface orientations under He plasma exposure. [ABSTRACT FROM AUTHOR]

This paper proposes a method for simulating liquids in large bodies of water by coupling together a water surface wave simulator with a 3D Navier‐Stokes simulator. The surface wave simulation uses the equivalent sources method (ESM) to efficiently animate large bodies of water with precisely controllable wave propagation behavior. The 3D liquid simulator animates complex non‐linear fluid behaviors like splashes and breaking waves using off‐the‐shelf simulators using FLIP or the level set method with semi‐Lagrangian advection. We combine the two approaches by using the 3D solver to animate localized non‐linear behaviors, and the 2D wave solver to animate larger regions with linear surface physics. We use the surface motion from the 3D solver as boundary conditions for 2D surface wave simulator, and we use the velocity and surface heights from the 2D surface wave simulator as boundary conditions for the 3D fluid simulation. We also introduce a novel technique for removing visual artifacts caused by numerical errors in 3D fluid solvers: we use experimental data to estimate the artificial dispersion caused by the 3D solver and we then carefully tune the wave speeds of the 2D solver to match it, effectively eliminating any differences in wave behavior across the boundary. To the best of our knowledge, this is the first time such a empirically driven error compensation approach has been used to remove coupling errors from a physics simulator. Our coupled simulation approach leverages the strengths of each simulation technique, animating large environments with seamless transitions between 2D and 3D physics. [ABSTRACT FROM AUTHOR]

Molecular level interactions that take place at the interface of different materials determine their local electrical, chemical, and mechanical properties. In the case of solid interfaces, this information has traditionally been obtained with experimental techniques that require ultra-high vacuum conditions. However, these methods are not suitable for studying surface chemistry of aqueous interfaces. Recently, an approach emerged for probing such interfaces using interfacial water as a contrast agent. This approach is based on second harmonic generation from water molecules next to a charged interface and can be utilized in both scattering and microscopy geometries. In this Perspective, we explain this approach in more detail and provide examples and comparisons for a diverse set of applications: colloid science and solid state physics, illustrated by silica–water surface chemistry, and biophysics, illustrated by membrane–water–ion channel interactions. Those two diverse applications show that by following the structure of interfacial water, it is possible to extract and quantify important chemical parameters such as surface potential values, structure of the electric double layer, and local dissociation constants that are useful in many different contexts. [ABSTRACT FROM AUTHOR]

For a gas at thermal equilibrium, it is usually assumed that the velocity distribution follows an isotropic 3-dimensional Maxwell-Boltzmann (M-B) law. This assumption classically implies the assumption of a "cos θ" law for the flux of atoms leaving the surface. Actually, such a law has no grounds in surface physics, and experimental tests of this assumption have remained very few. In a variety of recently developed sub-Doppler laser spectroscopy techniques for gases one-dimensionally confined in a thin cell, the specific contribution of atoms moving nearly parallel to the boundary of the vapor container becomes essential. We report here on the implementation of an experiment to probe effectively the distribution of atomic velocities parallel to the windows for a thin (60 μm) Cs vapor cell. The principle of the setup relies on a spatially separated pump-probe experiment, where the variations of the signal amplitude with the pump-probe separation provide the information on the velocity distribution. The experiment is performed in a sapphire cell on the Cs resonance line, which benefits from a long-lived hyperfine optical pumping. Presently, we can analyze specifically the density of atoms with slow normal velocities ∼5-20 m/s, already corresponding to unusual grazing flight--at ∼85°-88.5° from the normal to the surface--and no deviation from the M-B law is found within the limits of our elementary setup. Finally we suggest tracks to explore more parallel velocities, when surface details--roughness or structure--and the atom-surface interaction should play a key role to restrict the applicability of an M-B-type distribution. [ABSTRACT FROM AUTHOR]

An ultra-wideband polarization conversion metasurface based on S-shaped metallic structure is designed and prepared. The simulation results show that the polarization conversion bandwidth is 14GHz for linearly polarized normally incident electromagnetic waves and the cross-polarized reflectance is more than 99% in the range of 10.3GHz--20.5GHz. On the premise of high reflection efficiency, the reflective phase can be regulated by changing the geometrical parameter of the S-shaped metallic structure. A phase gradient metasurface composed of six periodically arrayed S-shaped unit cells is proposed and further demonstrated both numerically and experimentally. The specular cross-polarization reflection of the phase gradient metasurface is below -10 dB, which shows a good performance on manipulating the direction of the reflected electromagnetic waves. [ABSTRACT FROM AUTHOR]

Full phase manipulation with equal amplitude is critical for optical wavefront engineering in various systems. Here we theoretically explore a general approach for optical wavefront manipulation using dipolar metasurfaces under the coherent control. From the microscopic perspective, we theoretically show that the dispersion of a dipolar metasurface under the coherent control can provide the phase manipulation within a full range of [0, 2π] and retain an equal amplitude simultaneously. As an example, such a dipolar metasurface can be constructed by compensatory H-shaped unit resonators to avoid polarization conversion. Specifically, we confirm the feasibility of designed metasurfaces for achieving the beam bending and the vortex-phase beam by the full-wave simulation. The proposed approach enriches the well-established wavefront engineering for extending the functionality of metasurface under the coherent control. [ABSTRACT FROM AUTHOR]

Three dimensional topological insulators are insulators with topologically protected surface states that can have a high band velocity and high mobility at room temperature. This suggests electronic applications that exploit these surface states, but the lack of a band gap poses a fundamental difficulty. We report a first principles study based on density functional theory for thin Bi2Se3 films in the context of a field effect transistor. It is known that a gap is induced in thin layers due to hybridization between the top and bottom surfaces, but it is not known whether it is possible to use the topological states in this type of configuration. In particular, it is unclear whether the benefits of topological protection can be retained to a sufficient degree. We show that there is a thickness regime in which the small gap induced by hybridization between the two surfaces is sufficient to obtain transistor operation at room temperature, and furthermore, that the band velocity and spin texture that are important for the mobility are preserved for Fermi levels of relevance to device application. [ABSTRACT FROM AUTHOR]

We derive simple analytical expressions to model the electromagnetic response of an electrically large printed cavity. The analytical model is then used to develop printed cavities for microwave imaging purposes. The proposed cavity is excited by a cylindrical source and has boundaries formed by subwavelength metallic cylinders (vias) placed at subwavelength distances apart. Given their small size, the electric currents induced on the vias are assumed to have no angular dependence. Applying this approximation simplifies the electromagnetic problem to a matrix equation which can be solved to directly compute the electric current induced on each via. Once the induced currents are known, the electromagnetic field inside the cavity can be computed for every location. We verify the analytical model by comparing its prediction to full-wave simulations. To utilize this cavity in imaging settings, we perforate one side of the printed cavity with radiative slots such that they act as the physical layer of a computational imaging system. An analytical approximation for the slots is also developed, enabling us to obtain estimates of the cavity performance in imaging scenarios. This ability allows us to make informed decisions on the design of the printed metasurface cavity. The utility of the proposed model is further highlighted by demonstrating high-quality experimental imaging; performance metrics, which are consistent between theory and experiment, are also estimated. [ABSTRACT FROM AUTHOR]

In the spirit of the fewest switches surface hopping, the frozen Gaussian approximation with surface hopping (FGA-SH) method samples a path integral representation of the non-adiabatic dynamics in the semiclassical regime. An improved sampling scheme is developed in this work for FGA-SH based on birth and death branching processes. The algorithm is validated for the standard test examples of non-adiabatic dynamics. [ABSTRACT FROM AUTHOR]

A theory of the effect that ion implantation has on the patterns produced by ion bombardment of solid surfaces is introduced. For simplicity, the case of self-sputtering of an elemental material is studied. We find that implantation of self-ions has a destabilizing effect along the projected beam direction for angles of incidence θ that exceed a critical value. In the transverse direction, ion implantation has a stabilizing influence for all θ. [ABSTRACT FROM AUTHOR]

Shoe outsole design strongly influences slip and fall risk. Certain tread features that can be readily measured have been shown to predict friction performance. This research aimed to replicate those findings and quantify their ability to predict slipping. Participants (n = 34) were exposed to a low friction oil-coated floor surface, while wearing slip-resistant shoes. The coefficient of friction (COF) of each shoe were predicted based on tread surface area, the presence of a bevel, and hardness. The COF was measured, and the slip outcome was determined. Predicted and measured COF were correlated, and measured COF was a sensitive predictor of slip outcome. The relationship of predicted COF on slip outcome was weaker than anticipated and was not statistically significant. This study partially confirmed the ability of previous regression equations to predict COF. However, the effect size was weaker than previously reported and predicted COF was not sensitive for predicting slips. • Validity of a coefficient of friction (COF) regression model was tested. • Slip outcomes, predicted COF, and measured COF was assessed for 34 shoes. • Weak relationships were reported between predicted COF and slip outcomes. • Predicted COF was correlated with measured COF, which correlated with slipping. • The study provided mixed prospective validation evidence for the model. [ABSTRACT FROM AUTHOR]

Recent work has highlighted roles for thermodynamic phase behavior in diverse cellular processes. Proteins and nucleic acids can phase separate into three-dimensional liquid droplets in the cytoplasm and nucleus and the plasma membrane of animal cells appears tuned close to a two-dimensional liquid–liquid critical point. In some examples, cytoplasmic proteins aggregate at plasma membrane domains, forming structures such as the postsynaptic density and diverse signaling clusters. Here we examine the physics of these surface densities, employing minimal simulations of polymers prone to phase separation coupled to an Ising membrane surface in conjunction with a complementary Landau theory. We argue that these surface densities are a phase reminiscent of prewetting, in which a molecularly thin three-dimensional liquid forms on a usually solid surface. However, in surface densities the solid surface is replaced by a membrane with an independent propensity to phase separate. We show that proximity to criticality in the membrane dramatically increases the parameter regime in which a prewetting-like transition occurs, leading to a broad region where coexisting surface phases can form even when a bulk phase is unstable. Our simulations naturally exhibit three-surface phase coexistence even though both the membrane and the polymer bulk only display two-phase coexistence on their own. We argue that the physics of these surface densities may be shared with diverse functional structures seen in eukaryotic cells. [ABSTRACT FROM AUTHOR]

Summary: Over the last few years, fractal structure has been used in several engineering fields such as surface physics, telecommunication, fluid mechanics, and so forth. In telecommunication, often there is a demand for miniaturized patch antennas with fractal structures because it is capable of handling very high frequencies with its diminutive structure. The space filling capability of the fractal structures is used to effectively distribute the surface current all over the radiating material. Fractal structures have a better size reduction capability which aids a miniaturized antenna design. This article provides a generalized and detailed survey on fractal structures in a Euclidean space using iterated function system (IFS) in patch antennas. There are various techniques to design a fractal structure, namely, IFSs, escape‐time fractals, strange attractors, L‐systems, random fractals, and so forth. IFSs are widely used technique to construct a finite set of construction mapping on a complete metric space. The fractal geometries designed using the technique are Sierpinski carpet and gasket, Koch snowflake, deterministic tree/binary tree, Gosper island, Minkowski island, Cantor set, T‐square, and some space filling fractals. This paper deals with the above given fractal structures with their design expressions and shapes in recent developments and applications mentioned. The fractal geometries are used in MIMO antennas to abridge the mutually coupled radiators and improve the gain and efficiency of the antenna. This paper also analyzes the effects of fractal structures on MIMO antennas and discusses the ascendancy fractal structures by cross‐referencing the significant antenna parameters. [ABSTRACT FROM AUTHOR]

The introduction of engineered resonance phenomena on surfaces has opened a new frontier in surface science and technology. Pillared phononic crystals, metamaterials, and metasurfaces are an emerging class of artificial structured media, featuring surfaces that consist of pillars—or branching substructures—standing on a plate or a substrate. A pillared phononic crystal exhibits Bragg band gaps, while a pillared metamaterial may feature both Bragg band gaps and local resonance hybridization band gaps. These two band-gap phenomena, along with other unique wave dispersion characteristics, have been exploited for a variety of applications spanning a range of length scales and covering multiple disciplines in applied physics and engineering, particularly in elastodynamics and acoustics. The intrinsic placement of pillars on a semi-infinite surface—yielding a metasurface—has similarly provided new avenues for the control and manipulation of wave propagation. Classical waves are admitted in pillared media, including Lamb waves in plates and Rayleigh and Love waves along the surfaces of substrates, ranging in frequency from hertz to several gigahertz. With the presence of the pillars, these waves couple with surface resonances richly creating new phenomena and properties in the subwavelength regime and in some applications at higher frequencies as well. At the nanoscale, it was shown that atomic-scale resonances—stemming from nanopillars—alter the fundamental nature of conductive thermal transport by reducing the group velocities and generating mode localizations across the entire spectrum of the constituent material well into the terahertz regime. In this article, we first overview the history and development of pillared materials, then provide a detailed synopsis of a selection of key research topics that involve the utilization of pillars or similar branching substructures in different contexts. Finally, we conclude by providing a short summary and some perspectives on the state of the field and its promise for further future development. [ABSTRACT FROM AUTHOR]

We provide a road towards obtaining gravitational waveforms from inspiraling material binaries with an accuracy viable for third-generation gravitational wave detectors, without necessarily advancing computational hardware or massively-parallel software infrastructure. We demonstrate a proof-of-principle 1 + 1-dimensional numerical implementation that exhibits up to 7th-order convergence for highly dynamic barotropic stars in curved spacetime, and numerical errors up to 6 orders of magnitude smaller than a standard method. Aside from errors associated with overshoot in high-order extrapolation from the interior of the star to the surface, there are no obvious fundamental obstacles to obtaining convergence of even higher order. The implementation uses a novel surface-tracking method, where the surface is evolved and high-order accurate boundary conditions are imposed there. Computational memory does not need to be allocated to fluid variables in the vacuum region of spacetime. We anticipate the application of this new method to full 3 + 1-dimensional simulations of the inspiral phase of compact binary systems with at least one material body. The additional challenge of a deformable surface must be addressed in multiple spatial dimensions, but it is also an opportunity to input more precise surface tension physics. [ABSTRACT FROM AUTHOR]

The interface between a carbon nanotube (CNT) and its environment can dramatically affect the electrical properties of CNT-based field-effect transistors (FETs). For such devices, the channel environment plays a significant role inducing doping or charge traps giving rise to hysteresis in the transistor characteristics. Thereby the fabrication process strongly determines the extent of those effects and the final device performance. In CNT-based devices obtained from dispersions, a proper individualization of the nanotubes is mandatory. This is generally realized by an ultrasonic treatment combined with surfactant molecules, which enwrap nanotubes forming micelle aggregates. To minimize impact on device performance, it is of vital importance to consider post-deposition treatments for removal of surfactant molecules and other impurities. In this context, we investigated the effect of several wet chemical cleaning and thermal post treatments on the electrical characteristics as well as physical properties of more than 600 devices fabricated only by wafer-level compatible technologies. We observed that nitric acid and water treatments improved the maximum-current of devices. Additionally, we found that the ethanol treatment successfully lowered hysteresis in the transfer characteristics. The effect of the chemical cleaning procedures was found to be more significant on CNT-metal contacts than for the FET channels. Moreover, we investigated the effect of an additional thermal cleaning step under vacuum after the chemical cleaning, which had an exceptional impact on the hysteresis behavior including hysteresis reversal. The presence of surfactant molecules on CNT was evidenced by X-ray photoelectron and Raman spectroscopies. By identifying the role of surfactant molecules and assessing the enhancement of device performance as a direct consequence of several cleaning procedures, these results are important for the development of CNT-based electronics at the wafer-level. [ABSTRACT FROM AUTHOR]

The elementary surface processes occurring on chromium targets exposed to reactive plasmas have been mimicked in beam experiments by using quantified fluxes of Ar ions (400-800 eV) and oxygen atoms and molecules. For this, quartz crystal microbalances were previously coated with Cr thin films by means of high-power pulsed magnetron sputtering. The measured growth and etching rates were fitted by flux balance equations, which provided sputter yields of around 0.05 for the compound phase and a sticking coefficient of O2 of 0.38 on the bare Cr surface. Further fitted parameters were the oxygen implantation efficiency and the density of oxidation sites at the surface. The increase in site density with a factor 4 at early phases of reactive sputtering is identified as a relevant mechanism of Cr oxidation. This ion-enhanced oxygen uptake can be attributed to Cr surface roughening and knock-on implantation of oxygen atoms deeper into the target. This work, besides providing fundamental data to control oxidation state of Cr targets, shows that the extended Berg's model constitutes a robust set of rate equations suitable to describe reactive magnetron sputtering of metals. [ABSTRACT FROM AUTHOR]

We generalize the inverse patchy colloid model that was originally developed for heterogeneously charged particles with two identical polar patches and an oppositely charged equator to a model that can have a considerably richer surface pattern. Based on a Debye-Hückel framework, we propose a coarse-grained description of the effective pair interactions that is applicable to particles with an arbitrary patch decoration. We demonstrate the versatility of this approach by applying it to models with (i) two differently charged and/or sized patches, and (ii) three, possibly different patches. [ABSTRACT FROM AUTHOR]

Interfaces are ubiquitous objects, whose thermodynamic behavior we only recently started to understand at the microscopic detail. Here, we borrow concepts from the techniques of surface identification and intrinsic analysis, to provide a complementary point of view on the density, stress, energy, and free energy distribution across liquid ("soft") interfaces by analyzing the respective contributions coming from successive layers. [ABSTRACT FROM AUTHOR]

In this review, we mention about the theoretical achievement of physics of surface Andreev bound state (SABS) and odd-frequency pairing during this quarter century based on our research. Currently, topological superconductors with Majorana edge state have become a central issue in condensed matter physics. It is noted that Majorana edge state is nothing but a zero energy surface Andreev bound state (ZESABS) and the study of ZESABS has started in the context of the pairing symmetry of high Tc cuprate. We mention our obtained conductance formula of quasiparticle tunneling and Josephson current in unconventional superconductor junctions through ZESABS have already captured the essence of the charge transport profile via the Majorana fermion. We also mention that in the presence of ZESABS, odd-frequency pairing like spin-triplet s-wave or spin-singlet p-wave is hugely enhanced near the surface or interface. We further analyze the spectroscopy of the induced odd-frequency pairings by extending bulk-boundary correspondence in ZESABS. If we consider a semi-infinite superconductor with ZESABS, the induced odd-frequency pair amplitude can be expressed by a c-number defined in bulk, which we call spectral bulk-boundary correspondence. The odd-frequency pair amplitude is classified into singular part and regular one, the former part is proportional to ∼ 1 / z (z is a complex frequency) reflecting the presence of ZESABS, and the latter one is proportional to ∼ z . The coefficient of the latter one diverges at the topological phase transition point. Analyzing the spectral behavior of the odd-frequency pairing is useful to understand the critical phenomena near topological transition points. [ABSTRACT FROM AUTHOR]

• The 04BM beamline is operational and very effective for the soft x-ray absorption spectroscopy. • The examples for PEEM and XAS end stations show good surface sensitivity down to submonolayer material thickness. • The transition metal sensitivity using XAS is down to submonolayer material thickness. • The nanocomposite films were decomposed to different iron oxide phases. The spectroscopy using synchrotron radiation is the advanced tool for materials characterization. In the current work we are reporting recent activity in this research field implemented at the 04BM (PEEM/XAS) beamline of the National Synchrotron Radiation Centre SOLARIS in Krakow, Poland. The beamline is designed to cover wide energy range of soft X-rays, which is well suited for a broad range of applications, including surface physics, material science and magnetism. The comparison of the experimental parameters and selected examples of the results achieved on the PEEM and XAS end stations is demonstrated. [ABSTRACT FROM AUTHOR]

The physics of spoof surface plasmon polaritons (SSPPs) is widely studied for their intrinsic confinement of electromagnetic wave, leading to the useful applications of device miniaturization and signal integrity. As another imitation of surface plasmon polaritons (SPPs) in microwave, effective SPPs (ESPPs) are excited inside the waveguide based on structural dispersion. Without using lossy plasmonic materials, slow wave property is achieved inside the waveguide for the interface confinement. In this work, for further enhancing the field confinement of SSPPs, the waveguide dispersion method is utilized on the structure of SSPPs. In this way, the techniques of ESPPs and SSPPs are feasibly combined for the first time, coining the name of “effective SSPPs (ESSPPs).” The dispersion relation of the ESSPPs is analyzed theoretically and numerically with the obvious field confinement. The structural dispersion makes the wavelength of ESSPPs reach 1/18 of the wavelength of SSPPs, which has potential applications for device miniaturization and signal integrity. Finally, two prototypes of the ESSPPs waveguide are fabricated on the substrate integrated waveguide (SIW) platform. The experimental results of the prototypes verify the stronger field confinement, indicating new possibilities to slow down the wave propagation with controllable confinement. [ABSTRACT FROM AUTHOR]

Dust grains play a central role in the physics and chemistry of cosmic environments. They influence the optical and thermal properties of the medium due to their interaction with stellar radiation; provide surfaces for the chemical reactions that are responsible for the synthesis of a significant fraction of key astronomical molecules; and they are building blocks of pebbles, comets, asteroids, planetesimals, and planets. In this paper, we review experimental studies of physical and chemical processes, such as adsorption, desorption, diffusion and reactions forming molecules, on the surface of reliable cosmic dust grain analogues as related to processes in diffuse, translucent, and dense interstellar clouds, protostellar envelopes, planet-forming disks, and planetary atmospheres. The information that such experiments reveal should be flexible enough to be used in many different environments. In addition, we provide a forward look discussing new ideas, experimental approaches, and research directions. [ABSTRACT FROM AUTHOR]

Size-selected Mon-, Wn-, and Fen - cluster anions are deposited on a weakly interacting substrate (highly oriented pyrolytic graphite) and studied ex-situ using atomic force microscopy. Depending on size, three growth modes can be distinguished. Very small clusters consisting of less than 10-30 atoms behave similar to atoms and coalesce into 3-dimensional bulk-like islands. Medium sized clusters consisting of hundreds of atoms do not coalesce and follow a Stanski-Krastanov growth pattern. At low coverage, an almost perfect monolayer is formed. This is a new finding different from all previous studies on deposited metal clusters. For clusters with several thousands of atoms, the growth pattern again changes. At low coverage, the substrate is dotted with individual clusters, while at high coverage, the surface becomes extremely rough. [ABSTRACT FROM AUTHOR]

It was found first that macromolecules made of amphiphilic monomer units could form spontaneously an ultra-thin layer on the surface which the macromolecules are grafted to. The width of such layer is about double size of monomer unit consisting of hydrophilic A (repulsive) and hydrophobic (attractive) B beads. The hydrophilic A beads are connected in a polymer chain while hydrophobic B beads are attached to A beads of the backbone as side groups. Three characteristic regimes are distinguished. At low grafting density, the macromolecules form ultra-thin micelles of the shape changing with decrease of distance d between grafting points as following: circular micelles-- prolonged micelles--inverse micelles--homogeneous bilayer. Those micelles have approximately constant height and specific top-down A-BB-A structure. At higher grafting density, the micelles start to appear above the single bilayer of amphiphilic macromolecules. The thickness of grafted layer in these cases is different in different regions of grafting surface. Only at rather high density of grafting, the height of macromolecular layer becomes uniform over the whole grafting surface. The study was performed by computer modeling experiments and confirmed in framework of analytical theory. [ABSTRACT FROM AUTHOR]

Understanding electronic dynamics on material surfaces is fundamentally important for applications including nanoelectronics, inhomogeneous catalysis, and photovoltaics. Practical approaches based on time-dependent density functional theory for open systems have been developed to characterize the dissipative dynamics of electrons in bulk materials. The accuracy and reliability of such approaches depend critically on how the electronic structure and memory effects of surrounding material environment are accounted for. In this work, we develop a novel squared-Lorentzian decomposition scheme, which preserves the positive semi-definiteness of the environment spectral matrix. The resulting electronic dynamics is guaranteed to be both accurate and convergent even in the long-time limit. The long-time stability of electronic dynamics simulation is thus greatly improved within the current decomposition scheme. The validity and usefulness of our new approach are exemplified via two prototypical model systems: quasi-one-dimensional atomic chains and two-dimensional bilayer graphene. [ABSTRACT FROM AUTHOR]

We present a new trajectory surface hopping study of the rotational energy transfer and collisional quenching of electronically excited OH(A) radicals by Kr. The trajectory surface hopping calculations include both electronic coupling between the excited 2²A' and ground 1²A' electronic states, as well as Renner-Teller and Coriolis roto-electronic couplings between the 1²A' and 1²A'', and the 2²A' and 1²A'' electronic states, respectively. The new calculations are shown to lead to a noticeable improvement in the agreement between theory and experiment in this system, particularly with respect to the OH(X) rotational and Λ-doublet quantum state populations, compared with a simpler two-state treatment, which only included the electronic coupling between the 2²A' and 1²A' states. Discrepancies between the predictions of theory and experiment do however remain, and could arise either due to errors in the potential energy surfaces and couplings employed, or due to the limitations in the classical treatment of non-adiabatic effects. [ABSTRACT FROM AUTHOR]