Surface Science Reports最新文献

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.

The property of a variable charge state makes ions unique to other types of radiation a material surface can be exposed to. As a consequence of charge exchange between ions and surfaces, energy is transferred to the surface and material damage may be triggered. Furthermore, a changing charge state of the ion alters its slowing down process in solids and has important implications when back-scattered ions are to be measured for material analysis purposes. Over the last decades extensive research was devoted to the understanding of ion charge exchange with solids. Here I review recent progress in this field with special emphasize on slow ions in high charge states. This class of ions allows a detailed analysis of charge exchange in experiments, which employ also ultra-thin solid targets and therefore give experimental access to electronic processes on the femtosecond timescale. In this review I will discuss general properties of charge exchange and present typical experimental techniques. I will also discuss current developments in the modelling and simulation of ion-surface interaction. Recent findings using freestanding 2D materials are discussed as well as results from spectroscopy of emitted secondary particles. The paper concludes with a unified picture of ion charge exchange at surfaces and presents possible applications based on the understanding of the underlying physics.

The interest in graphene (a carbon monolayer) adsorbed on metal surfaces goes back to the 60's, long before isolated graphene was produced in the laboratory. Owing to the carbon-metal interaction and the lattice mismatch between the carbon monolayer and the metal surface, graphene usually adopts a rippled structure, known as moiré, that confers it interesting electronic properties not present in isolated graphene. These moiré structures can be used as versatile templates where to adsorb, isolate and assemble organic-molecule structures with some desired geometric and electronic properties. In this review, we first describe the main experimental techniques and the theoretical methods currently available to produce and characterize these complex systems. Then, we review the diversity of moiré structures that have been reported in the literature and the consequences for the electronic properties of graphene, attending to the magnitude of the lattice mismatch and the type of interaction, chemical or physical, between graphene and the metal surface. Subsequently, we address the problem of the adsorption of single organic molecules and then of several ones, from dimers to complete monolayers, describing both the different arrangements that these molecules can adopt as well as their physical and chemical properties. We pay a special attention to graphene/Ru(0001) due to its exceptional electronic properties, which have been used to induce long-range magnetic order in tetracyanoquinodimethane (TCNQ) monolayers, to catalyze the (reversible) reaction between acetonitrile and TCNQ molecules and to efficiently photogenerate large acenes.

Molybdenum Disulfide (MoS₂) is a well-known transition metal dichalcogenide with a hexagonal structure arrangement analogous to graphene. Two dimensional (2D) MoS₂ has attracted wide attention in various applications such as energy storage, catalysis, sensing, energy conversion and optoelectronics due to its unique properties including tunable bandgap, substantial carrier mobility, outstanding mechanical strength and dangling-bond free basal surface. Moreover, MoS₂ has shown an excellent capability to be a host for foreign atoms which tune its physicochemical properties. Herein, currently known structural changes in the MoS₂ crystals introduced by various single atom dopants coming from all over the chemical table of elements are reviewed. Accompanying electrical, optical and magnetic properties of such structures are discussed in detail. Potential applications of the doped MoS₂ are introduced briefly as well. The review concentrates on the recent state-of-the-art results obtained mostly by the high resolution scanning transmission electron microscopy (STEM), such as high angle annular dark field (HAADF) imaging as well as scanning probe microscopy (SPM) such as scanning tunneling microscopy (STM). These techniques have been used to decipher dopant positions and other sub-atomic structural changes introduced to the MoS₂ structure by isolated dopants.