Surface Science Reports最新文献

The synthesis and characterization of two dimensional materials are in the focus of nanomaterial and surface science, heterogeneous catalytic and nanoelectronic research laying the basis for various technological applications. Hexagonal boron nitride (h-BN) is an important member of 3D and reduced dimensional materials. Atomically clean sp²-hybridized 2D nano-layers can be grown on various metal supports by different chemical and physical vapor deposition techniques. In case of a significant lattice mismatch and a strong interaction at the h-BN/metal interface, a periodically undulating monolayer - a so-called “moirè structure” - is formed. In the present review, we address some important characteristics of h-BN prepared on several metal surfaces, and we focus on its application as a template for individual atoms, metal clusters and molecules. Moreover, several experimental findings are collected about the features and applications of monolayer h-BN nanosheets as supporting materials. We highlight the results of recent surface science studies, which emphasize the unique role of h-BN including nanomeshes in characteristic adsorption properties, stability and catalytic activity. The characterization of few layer and defective h-BN involving their catalytic applications are also the subject of the present review. We present a comprehensive overview on the electronic and vibrational states of nanoparticles (covered by adsorbates, as well) monitored by surface spectroscopy tools, e.g. XPS, ARPES, UPS, LEIS, AES, STS and HREELS. We also elaborate on the structural and morphological information of h-BN nanoobjects obtained by scanning probe microscopy (SPM). It is also highlighted that density functional theory (DFT) is considered as a very important complementary technique contributing to the better understanding of experimental results. Beside updated recollection of key findings, we outline the present and future research directions of 2D materials and their heterostructures including h-BN-based systems.

X-ray photoelectron spectroscopy is a powerful experimental technique that yields invaluable information on a range of phenomena that occur in solids, liquids, and gasses. The binding energy and shape of a photoemission peak is sensitive not only to the atomic number, valence and orbital from which the electron is ejected, but also to complex many-body effects that accompany photoemission. Provided the influences of these different drivers of spectral line shapes can be disentangled, a great deal can be learned about the electronic structure of materials of interest. In addition to these largely local effects, the long-range electrostatic environment and resulting electric potential at the emitting atom also have a direct effect on the measured binding energies. This fact opens the door to extracting information about the dependence of the valence and conduction band minima on depth below the surface, which in turn allows both vertical and lateral electrical transport data to be better understood. One purpose of this Report is to summarize how the different physical forces described above impact the spectral properties of complex oxide epitaxial films. This class of materials typically incorporates transition metal cations in different valences and such ions exhibit the most complex core-level spectra of any on the periodic chart. A second purpose is to show how a comprehensive understanding of local physical effects in x-ray photoemission allows one to model spectra and extract from core-level line shapes and binding energies detailed information on built-in potentials and band edge discontinuities in heterostructures involving complex oxides.

Wires having a width of one or two atoms are the smallest possible physical objects that may exhibit one-dimensional properties. In order to be experimentally accessible at finite temperatures, such wires must stabilized by interactions in two and even three dimensions. These interactions modify and partly destroy their one-dimensional properties, but introduce new phenomena of coupling and correlation that entangle both charge and spin. We explore this fascinating field by first giving an overview of the present status of theoretical knowledge on 1D physics, including coupling between chains and to the substrate, before we set out for experimental results on ordered arrays of atomic wires on both flat and vicinal Si(111) surfaces comprising Si(111)-In, Si(hhk)-Au, Si(557)-Pb, Si(557)-Ag, on Ge(001)-Au and of rare earth silicide wires. While for these systems structural, spectroscopic and (magneto-)conductive properties are in the focus, including temperature- and concentration-induced phase transitions, explicit dynamics on the femto- and picosecond time scales were explored for the modified Peierls transition in indium chains on Si(111). All these systems are characterized by strong correlations, including spin, that are extended over whole terraces and partly beyond, so that small geometric changes lead to large modifications of their electronic properties. Thus this coupling in one (1D), two (2D) (and even three) dimensions results in a wealth of phase transitions and transient quasi-1D conductance. As extremes, modified quasi-1D properties survive, as in the Si(111)-In system, whereas strong Fermi nesting results in entanglement of spin and charge between terraces for Si(557)-Pb, so that spin orbit density waves across the steps are formed.

Volcano plots and scaling relations are commonly used to design catalysts and understand catalytic behavior. These plots are a useful tool due to their robust and simple analysis of catalysis; however, catalysts that follow the volcano plot paradigm have an inherent limit to their performance. Scaling and Brønsted-Evans-Polanyi (BEP) relations, which are linear correlations in reaction energetics, force tradeoffs when optimizing catalysts, which leads to this limit on performance. Therefore, materials and design strategies that are not limited by volcano plots and scaling relations are of high interest, and this is the focus of this Report. We first give an overview of volcano plots and scaling relations. Deviations from scaling relations and the volcano plot and their causes are discussed in more detail. Finally, design strategies that do not rely on the volcano plot paradigm are reviewed.

Recently there has been an explosion of research related to the Dzyaloshinskii-Moriya interaction (DMI) in magnetic and multiferroic materials. This article reviews the key themes in this research and provides insight into the consequences of the DMI through simple theoretical models. The topics covered include new magnetic structures such as skyrmions and changes in domain wall structures along with their motion under a variety of driving fields. In addition, the influence of DMI on linear and nonlinear spin wave behavior is discussed. Multiferroic materials and new two-dimensional materials with DMI are briefly discussed. Finally, we also present an overview of different DMI materials and their characteristic parameters and potential applications.

Molecular switching has established itself as a key functionality of building blocks developed for addressable materials and surfaces over the last two decades. Many challenges in their use and characterisation have been presented by the wide variation in interfaces studied, these ranging from truly single-molecule devices to two-dimensional self-assembled monolayers and thin films that bridge the gap between surface and macroscopically bulk materials (polymers, MOFs, COFs), and further still to other interfaces (solid–liquid, liquid–air, etc.). The low number density of molecules on monolayer-coated interfaces as well as in thin films, for example, presents substantial challenges in the characterisation of the composition of modified interfaces. The switching of molecular structure with external stimuli such as light and electrode potential adds a further layer of complexity in the characterisation of function. Such characterisation “in action” is necessary to correlate macroscopic phenomena with changes in molecular structure. In this review, key classes of molecular switches that have been applied frequently to interfaces will be discussed in the context of the techniques and approaches used for their operando characterisation. In particular, we will address issues surrounding the non-innocence of otherwise information-rich techniques and show how model – non-switching – compounds are often helpful in confirming and understanding the limitations and quirks of specific techniques.

The interest in understanding and controlling the properties of two-dimensional materials (2DMs) has fostered in the last years a significant and multidisciplinary research effort involving condensed matter physics and materials science. Although 2DMs have been investigated with a wide set of different experimental and theoretical methodologies, experiments carried out with surface-science based techniques were essential to elucidate many aspects of the properties of this family of materials. In particular, synchrotron-based X-ray photoelectron spectroscopy (XPS) has been playing a central role in casting light on the properties of 2DMs, providing an in-depth and precise characterization of these materials and helping to elucidate many elusive and intricate aspects related to them. XPS was crucial, for example, in understanding the mechanism of growth of several 2DMs at surfaces and in identifying the parameters governing it. Moreover, the chemical sensitivity of this technique is crucial in obtaining knowledge about functionalized 2DMs and in testing their behavior in several model chemical reactions. The achievements accomplished so far in this field have reached a maturity point for which a recap of the milestones is desirable. In this review, we will showcase relevant examples of studies on 2DMs for which synchrotron-based XPS, in combination with other techniques and state-of-the-art theoretical modeling of the electronic structure and of the growth mechanisms, was essential to unravel many aspects connected to the synthesis and properties of 2DMs at surfaces. The results highlighted herein and the methodologies followed to achieve them will serve as a guidance to researchers in testing and comparing their research outcomes and in stimulating further investigations to expand the knowledge of the broad and versatile 2DMs family.

The review describes electrochemical applications of tip-enhanced Raman spectroscopy (TERS). These applications combine the merits of both scanning probe microscopy (SPM) and Raman spectroscopy, which enables us to simultaneously obtain high-resolution images of surface morphology and chemical information under the electrochemical environment. This review, first summarizes the pioneering work done on the TERS systems that operate in liquid and electrochemical environments, and then gives an overview of the typical instrumentation of electrochemical TERS (EC-TERS) based on electrochemical scanning tunneling microscopy (EC-STM). Furthermore, this review summarizes the advancements in EC-TERS studies of events that occur at the interfaces. These include potential dependent structural changes and electrochemical reactions. Finally, we discuss the current issues and future prospects of EC-TERS for microscopic studies of electrochemical interfaces.