Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, ðNi þ AlÞ∕NiAlð110Þ, which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems.S elf-assembly involves the autonomous organization of components into structures (1). This process requires mobility of aggregating components, and usually occurs on smooth surfaces or in fluids. Some degree of relaxation in the aggregated state is typically also operative. Self-assembly can be manifested in either complex equilibrium structures, e.g., reflecting competing interactions, or in far-from-equilibrium growth structures (1). The latter can be very different and more diverse than the equilibrium forms (2). Significantly, self-assembly provides a practical strategy for creating ensembles of nanostructures with unique size and shape dependent properties, a central goal of nanotechnology.A broad range of systems self-assemble, spanning hard and soft matter, with a wide variety of interactions and component sizes. We consider the formation of metal nanostructures motivated by applications ranging from catalysis to plasmonics (3-5). Our specific focus is vapor deposition of metal atoms on single-crystal metal surfaces under the well controlled conditions of ultrahigh vacuum (UHV). This process leads to the self-assembly of metal nanostructures and growth of epitaxial metal films. Here, the nonaggregated components are rapidly diffusing adsorbed atoms (adatoms) which assemble into islands. Relaxation in the aggregated state can be achieved via diffusion of adatoms along island edges or via detachment-reattachment. Understanding these processes on the atomic scale facilitates guided formation of functional nanostructures with tailored morphologies and (for alloys) compositions. Ideally, control over formation allows tuning of desired properties, e.g., for heterogeneous catalysis (6).Despite the complexity of self-assembly processes, significant advances are being made in the development of predictive models even in soft material systems (7). Our focus on epitaxial growth on perfect single-crystal surfaces (hard materials) under UHV has a special advantage in facilitating extremely detailed and realistic atomistic-level modeling. Localization of adatoms to a periodic array of adsorption sites enables the use of lattice-gas (LG) models for which nonequilibrium evolution can be efficiently analyzed on the appropriate time-and length-scales via kinetic Monte Carlo (KMC)...

We present a detailed study of the ͑110͒ surface of the ␥-Al 4 Cu 9 crystal using both experimental methods and first-principles calculations based on density-functional theory. Our experimental approach, using lowenergy electron diffraction, scanning tunneling microscopy ͑STM͒ images, and x-ray photoelectron spectroscopy highlights the presence of two types of surface terminations. Combining experimental results and simulations provides many arguments to match the two observed surfaces with the two puckered terminations built from bulk truncation: ͑i͒ calculations show that these two puckered terminations present lower surface energies compared to another conceivable flat termination obtained also from bulk truncation, ͑ii͒ step height measurements are consistent with calculated interlayer spacings and ͑iii͒ simulated STM images are in reasonable agreement with the experimental ones and mirror the experimental voltage dependence.

Experiments and computations are performed to assess the interfacial bonding between Cu and a poly-epoxy surface relevant to many applications. The surface of the poly-epoxy is characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy before and after ultrahigh vacuum Cu deposition. Modifications of the XPS spectra are observed, suggesting a strong interaction between specific C and O atoms of the surface with Cu. Density functional theory (DFT) calculations are then performed to simulate XPS spectra and to better understand bonding. DFT computations are performed in the framework of the uGTS methodology, which takes initial and final state effects into account, and allows to calculate chemical shifts between the different C 1s and O 1s molecular orbitals with good accuracy, for the pristine surface. DFT calculations are then set to determine the preferential adsorption sites of Cu on different sites of the polymer surface. Finally, XPS simulation of the C 1s and O 1s spectra with Cu adsorbed at these sites matches very well with the experimental spectra, indicating that Cu atoms interact preferentially with hydroxyls to form Cu−O−C bonds, stabilized by a transfer of 0.5 electrons from Cu to O; hence, Cu is partially oxidized.

Experiments and computations are performed for the metalorganic chemical vapor deposition (MOCVD) of aluminum (Al) from dimethylethylamine alane (DMEAA). The deposition rate as a function of the substrate temperature and the evolution of the deposition rate along the radius of the susceptor are experimentally determined, in a vertical, warm wall MOCVD reactor operating at 10 Torr, in the temperature range 139 °C‐240 °C. Following previously published mechanism for the decomposition of DMEAA, a predictive 3D model of the process is built, based on the mass, momentum, energy and species transport equations with the aim to simulate the process. Taking into account experimental results it is demonstrated that a volumetric and a surface reaction are responsible for the deposition of Al from DMEAA. For both reactions, first order Arrhenius kinetics are implemented and the kinetic parameters are determined through fitting to the experimental data. The results show satisfactory agreement between experiments and computations for almost the whole temperature range examined. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

To cite this version: T. Duguet, Emilie Gaudry, Th. Deniozou, J. Ledieu, M.-C. de Weerd, et al.. Complex metallic surface phases in the Al/Cu(111) system: An experimental and computational study. Physical Review B:The growth of complex intermetallics as surface alloys is investigated by annealing Al thin films deposited on Cu͑111͒ substrate in ultrahigh vacuum. Already at room temperature, the large lattice mismatch between Al and Cu results in interfacial intermixing. Upon annealing, various phases are formed by diffusion depending on the thickness of the Al films and the annealing temperature. The surface structures are characterized by scanning tunneling microscopy, low-energy electron diffraction, and x-ray photoelectron spectroscopy. Three different superlattice phases are identified as well as the complex Hume-Rothery ␥-Al 4 Cu 9 phase. The epitaxial relationships between the surface phases and the Cu͑111͒ substrate are determined. We further investigate the electronic structure of the ␥ phase by density functional calculations. Experimental valence bands are compared to calculated density of states and simulated STM images are used to identify possible bulk planes appearing as surface termination.

Whereas poly-epoxy polymers represent a class of materials with a wide range of applications, the structural disorder makes them difficult to model. In the present work, we use good experimental model samples in the sense that they are pure, fully polymerized, flat and smooth, defect-free, and suitable for ultrahigh vacuum x-ray photoelectron spectroscopy, XPS, experiments. In parallel, we perform Hartree-Fock, HF, calculations of the binding energies, BEs, of the C1s electrons in a model molecule composed of the two constituents of the poly-epoxy sample. These C1s BEs were determined using the HF ΔSCF method, which is known to yield accurate values, especially for the shifts of the BEs, ΔBEs. We demonstrate the benefits of combining rigorous theory with careful XPS measurements in order to obtain correct assignments of the C1s XPS spectra of the polymer sample. Both the relative binding energies-by the ΔSCF method-and relative intensities-in the sudden approximation, SA, are calculated. It results in an excellent match with the experimental spectra. We are able to identify 9 different chemical environments under the C1s peak, where an exclusively experimental work would have found only 3 contributions. In addition, we observe that some contributions are localized at discrete binding energies, whereas others allow a much wider range because of the variation of their second neighbor bound polarization. Therefore, HF-ΔSCF simulations significantly increase the spectral resolution of XPS and thus offer a new avenue for the exploration of the surface of polymers.

Direct comparison to experimental data with good agreement. Effective sticking coefficient including chemical information. Prediction of electrical resistivity through roughness simulations.

Low adhesion with normal metals is an intrinsic property of many quasicrystalline surfaces. Although this property could be useful to develop low friction or non-stick coatings, it is also responsible for the poor adhesion of quasicrystalline coatings on metal substrates. Here we investigate the possibility of using complex metallic surface alloys as interface layers to enhance the adhesion between quasicrystals and simple metal substrates. We first review some examples where such complex phases are formed as an overlayer. Then we study the formation of such surface alloys in a controlled way by annealing a thin film deposited on a quasicrystalline substrate. We demonstrate that a coherent buffer layer consisting of the γ-Al4Cu9 approximant can be grown between pure Al and the i-Al–Cu–Fe quasicrystal. The interfacial relationships between the different layers are defined by .