扫描隧道显微镜中的能谱分析

本文探讨了扫描隧道显微镜中的样品成分分析问题，提出了分析元素的方案，认为二极式结构的俄歇电子出现势谱具有很好的前景，本文对二极式结构的俄歇电子出现势谱的实验作了介绍，并提出了提高其性能的一些方法使它具有应用的可能。     

纳米材料的几种扫描探针显微表征方法

扫描探针显微镜（SPM）作为一种广泛应用的表面表征工具,不仅可以表征三维形貌,还能定量地研究表面的粗糙度、孔径大小和分布及颗粒尺寸,在许多学科均可发挥作用.以纳米材料为主要研究对象,综述了国外最新的几种扫描探针显微表征技术,包括扫描隧道显微镜（STM）、原子力显微镜（AFM）和近场扫描光学显微镜（SNOM）等方法,展示了这几种技术在纳米材料的结构和性能方面的应用.     

In Situ Atomic Force Microscopy of the Reconfiguration of On‐Surface Self‐Assembled DNA‐Nanoparticle Superlattices

The ability to dynamically reconfigure superlattices in response to external stimuli is an intriguing prospect for programmable DNA‐guided nanoparticle (NP) assemblies, which promises the realization of “smart” materials with dynamically adjustable interparticle spacing and real‐time tunable properties. Existing in situ probes of reconfiguration processes have been limited mostly to reciprocal space methods, which can follow larger ordered ensembles but do not provide access to real‐space pathways and dynamics. Here, in situ atomic force microscopy is used to investigate DNA‐linked NP assemblies and their response to external stimuli, specifically the contraction and expansion of on‐surface self‐assembled monolayer superlattices upon reversible DNA condensation induced by ethanol. In situ microscopy allows observation and quantification of key processes in solution, e.g., lattice parameter changes, defects, and monomer displacements in small groups of NPs. The analysis of imaging data uncovers important boundary conditions due to DNA bonding of NP superlattices to a substrate. Tension in the NP–substrate DNA bonds, which can elastically extend, break, and re‐form during contraction/expansion cycles, counteracts the changes in lattice parameter and causes hysteresis in the response of the system. The results provide insight into the behavior of supported DNA‐linked NP superlattices and establish a foundation for designing and probing tunable nanocrystal‐based materials in solution.     

Emerging In Situ and Operando Nanoscale X‐Ray Imaging Techniques for Energy Storage Materials

Electrical vehicles (EVs) are an attractive option for moving towards a CO₂ neutral transportation sector, but in order for widespread commercial use of EVs, the cost of electrical energy storage (i.e., batteries) must be reduced and the energy storage capacity must be increased. New, higher performing but Earth abundant electrodes are needed to accomplish this goal. To aid the development of these materials, in situ characterization to understand battery operation and failure is essential. Since electrodes are inherently heterogeneous, with a range of relevant length scales, imaging is a necessary component of the suite of characterization methods. In this Feature Article, the rapidly growing and developing field of X‐ray based microscopy (XM) techniques is described and reviewed focusing on in situ and operando adaptations. Further, in situ transmission electron microscopy (TEM) is briefly discussed in this context and its complement to XM is emphasized. Finally, a perspective is given on some emerging X‐ray based imaging approaches for energy storage materials.     

Photopicking: In Situ Approach for Site‐Specific Attachment of Single Multiprotein Nanoparticles to Atomic Force Microscopy Tips

Ligand–receptor interactions are fundamental in life sciences and include hormone–receptor, protein–protein, pathogen–host, and cell–cell interactions, among others. Atomic force microscopy (AFM) proved to be invaluable for scrutinizing ligand–receptor interactions at the single molecular level. Basically, a ligand is attached to the AFM tip while its cognate receptor is immobilized on a surface or vice versa, and interactions are studied following triggered ligand–receptor binding. However, with rising biological complexity it becomes increasingly challenging to attach a single intact biomolecule to the tip and ensure interaction‐specific orientation. This study presents a novel strategy of inducible in situ tip functionalization with complex multiprotein nanoparticles exemplified by viral capsids, termed photopicking. It ensures a firm attachment of single 125 nm large capsids to the tip. Specific orientation is attained by weak immunosorption of capsids to the substrate and strong photoinducible covalent cross‐linking to the tip. Validation of the tip functionalization success is immediate in situ. The versatility of the strategy is further demonstrated on 20–60 nm large amino‐modified nanoparticles. In conclusion, considering the size range of the tested biomolecules, the presented strategy is applicable to viruses, viral particles, cellular organelles, multiprotein ligands/receptors, and therapeutic nanoparticles, among others. It therefore opens up exciting new avenues in broad biomedical research fields.     

Atomic‐Scale CoOx Species in Metal–Organic Frameworks for Oxygen Evolution Reaction

The activity of electrocatalysts strongly depends on the number of active sites, which can be increased by downsizing electrocatalysts. Single‐atom catalysts have attracted special attention due to atomic‐scale active sites. However, it is a huge challenge to obtain atomic‐scale CoO_x catalysts. The Co‐based metal–organic frameworks (MOFs) own atomically dispersed Co ions, which motivates to design a possible pathway to partially on‐site transform these Co ions to active atomic‐scale CoO_x species, while reserving the highly porous features of MOFs. In this work, for the first time, the targeted on‐site formation of atomic‐scale CoO_x species is realized in ZIF‐67 by O₂ plasma. The abundant pores in ZIF‐67 provide channels for O₂ plasma to activate the Co ions in MOFs to on‐site produce atomic‐scale CoO_x species, which act as the active sites to catalyze the oxygen evolution reaction with an even better activity than RuO₂.     

激光共聚焦显微镜在磨损表面粗糙度表征中的应用

磨损是材料常见的表面失效现象,粗糙度是数字化描述材料磨损表面形貌特征的最常用参数.采用激光共聚焦显微镜(LSCM),通过调节物镜倍率、测量视场和过滤参数等,能够得到材料磨损表面的真实形貌,同时能够对磨损表面三维(3D)形貌特征进行精确数字化描述.对常见的粗糙度值0.5～2.0μm磨损表面采用20×物镜扫描测量比较合适;粗糙度小于0.5μm的磨损表面宜采用50×物镜;粗糙度大于2.5μm宜采用10×物镜.对比较规则的磨损表面,采用1～3个物镜视场叠加扫描即可得到比较精确的粗糙度值;对于不太规则的磨损表面,则需要3～5个物镜视场叠加扫描.借助这一手段,采用上述优化参数对Cr5冷轧辊材料磨损各阶段试样表面形貌及粗糙度轮廓曲线进行表征、分析,效果较好.     

Wear‐Resistant Nanoscale Silicon Carbide Tips for Scanning Probe Applications

The search for hard materials to extend the working life of sharp tools is an age‐old problem. In recent history, sharp tools must also often withstand high temperatures and harsh chemical environments. Nanotechnology extends this quest to tools such as scanning probe tips that must be sharp on the nanoscale, but still very physically robust. Unfortunately, this combination is inherently contradictory, as mechanically strong, chemically inert materials tend to be difficult to fabricate with nanoscale fidelity. Here a novel process is described, whereby the surfaces of pre‐existing, nanoscale Si tips are exposed to carbon ions and then annealed, to form a strong silicon carbide (SiC) layer. The nanoscale sharpness is largely preserved and the tips exhibit a wear resistance that is orders of magnitude greater than that of conventional silicon tips and at least 100‐fold higher than that of monolithic, SiO‐doped diamond‐like‐carbon (DLC) tips. The wear is well‐described by an atom‐by‐atom wear model, from which kinetic parameters are extracted that enable the prediction of the long‐time scale reliability of the tips.     

In Situ Study of Size and Temperature Dependent Brittle‐to‐Ductile Transition in Single Crystal Silicon

Silicon based micro‐ and nanometer scale devices operating at various temperatures are ubiquitous today. However, thermo‐mechanical properties of silicon at the small scale and their underlying mechanisms remain elusive. The brittle‐to‐ductile transition (BDT) is one such property relevant to these devises. Materials can be brittle or ductile depending on temperature. The BDT occurs over a small temperature range. For bulk silicon, the BDT is about 545 °C. It is speculated that the BDT temperature of silicon may decrease with size at the nanoscale. However, recent experimental and computational studies have provided inconclusive evidence, and are often contradictory. Potential reasons for the controversy might originate from the lack of an in situ methodology that allows variation of both temperature and sample size. This controversy is resolved in the present study by carrying out in situ thermo‐mechanical bending tests on single crystal silicon samples with concurrent control of these two key parameters. It is unambiguously shown that the BDT temperature reduces with sample size. For example, the BDT temperature decreases to 293 °C for a sample size 720 nm. A mechanism‐based model is proposed to interpret the experimental observations.     

Emerging Scanning Probe–Based Setups for Advanced Nanoelectronic Research

Scanning probe microscopy (SPM) refers to a family of techniques that have become essential to study many different properties of materials and devices at the nanoscale. All of them have in common that they use an ultrasharp probe tip to scan the surface of a sample. However, although many of these techniques are interrelated, some of them have become very sophisticated and require specific and deep study. While there are plenty of review articles available for most of these techniques, newer developments need to be carefully analyzed in a critical manner in order to promote their development. In this progress report, some of the newest SPM‐based developments that are expected to generate a larger impact in the field of nanoelectronics are discussed, and critical advice on how to improve each of them is provided. In particular, the combination of wear and electrical tests; scanning gate microscopy; the integration of conductive atomic force microscopy into scanning electron microscopy; and the integration of a scanning probe into transmission electron microscopy, multiprobe scanning tunneling microscopy, multiprobe atomic force microscopy, and fountain‐pen nanolithography are focused on.     

A Natural Silk Fibroin Protein‐Based Transparent Bio‐Memristor

The recent discovery of nanoelectronics memristor devices has opened up a new wave of enthusiasm and optimism in revolutionizing electronic circuit design, marking the beginning of new era for the advancement of neuromorphic, high‐density logic and memory applications. Here a highly non‐linear dynamic response of a bio‐memristor is demonstrated using natural silk cocoon fibroin protein of silkworm, Bombyx mori. A film that is transparent across most of the visible spectrum is obtained with the electronic‐grade silk fibroin aqueous solution of ca. 2% (wt/v). Bipolar memristive switching is demonstrated; the switching mechanism is confirmed to be the filamentary switching as observed by probing local conduction behavior at nanoscale using scanning tunneling microscopy. The memristive transition is elucidated by a physical model based on the carrier trapping or detrapping in silk fibroin films and this appears to be due to oxidation and reduction procedures, as evidenced from cyclic voltammetry measurements. Hence, silk fibroin protein could be used as a biomaterial for bio‐memristor devices for applications in advanced bio‐inspired very large scale integration circuit design as well as in biologically inspired synapse links for energy‐efficient neuromorphic computing.     

In Situ Scanning Electron Microscopy Observation of Growth Kinetics and Catalyst Splitting in Vapor–Liquid–Solid Growth of Nanowires

In situ observations during vapor–liquid–solid (VLS) growth of semiconductor nanowires in the chamber of an environmental scanning electron microscope (ESEM) are reported. For nanowire growth, a powder mixture of CdS and ZnS is used as a source material and silver nanoparticles as a metal catalyst. Through tracing growth kinetics of nanowires, it is found that nanowires with a relatively bigger catalyst droplet on the tip grow faster. Intriguingly, it is also found that the growth of nanowires can involve catalyst splitting: while the majority of catalyst remains at the nanowire tip and continues facilitating the growth, a portion of it is removed from the tip due to the splitting. It remains attached to the nanowire at the position where the splitting occurred and subsequently induces the growth of a nanowire branch. As far as it is known, this is the first time that catalyst splitting is revealed experimentally in situ. It is proposed that the instability of catalyst droplet caused by the volume increase is the main reason for the splitting. It is believed that in situ growth inside the ESEM can largely enrich our understanding on the metal‐catalyzed VLS growth kinetics, which may open up more opportunities for morphology‐controlled synthesis of 1D semiconductor nanowires in future study.     

Atomic‐Scale Spectroscopic Imaging of the Extreme‐UV Optical Response of B‐ and N‐Doped Graphene

Substitutional doping of graphene by impurity atoms such as boron and nitrogen, followed by atom‐by‐atom manipulation via scanning transmission electron microscopy, can allow for accurate tailoring of its electronic structure, plasmonic response, and even the creation of single atom devices. Beyond the identification of individual dopant atoms by means of “Z contrast” imaging, spectroscopic characterization is needed to understand the modifications induced in the electronic structure and plasmonic response. Here, atomic scale spectroscopic imaging in the extreme UV‐frequency band is demonstrated. Characteristic and energy‐loss‐dependent contrast changes centered on individual dopant atoms are highlighted. These effects are attributed to local dopant‐induced modifications of the electronic structure and are shown to be in excellent agreement with calculations of the associated densities of states.     

Process Pathway Controlled Evolution of Phase and Van‐der‐Waals Epitaxy in In/In2O3 on Graphene Heterostructures

Many applications of 2D materials require deposition of non‐2D metals and metal‐oxides onto the 2D materials. Little is however known about the mechanisms of such non‐2D/2D interfacing, particularly at the atomic scale. Here, atomically resolved scanning transmission electron microscopy (STEM) is used to follow the entire physical vapor deposition (PVD) cycle of application‐relevant non‐2D In/In₂O₃ nanostructures on graphene. First, a “quasi‐in‐situ” approach with indium being in situ evaporated onto graphene in oxygen‐/water‐free ultra‐high‐vacuum (UHV) is employed, followed by STEM imaging without vacuum break and then repeated controlled ambient air exposures and reloading into STEM. This allows stepwise monitoring of the oxidation of specific In particles toward In₂O₃ on graphene. This is then compared with conventional, scalable ex situ In PVD onto graphene in high vacuum (HV) with significant residual oxygen/water traces. The data shows that the process pathway difference of oxygen/water feeding between UHV/ambient and HV fabrication drastically impacts not only non‐2D In/In₂O₃ phase evolution but also In₂O₃/graphene out‐of‐plane texture and in‐plane rotational van‐der‐Waals epitaxy. Since non‐2D/2D heterostructures' properties are intimately linked to their structure and since influences like oxygen/water traces are often hard to control in scalable fabrication, this is a key finding for non‐2D/2D integration process design.     

Highly Ordered Self‐Assembled Architectures of Modified Terpyridines on Highly Ordered Pyrolitic Graphite Imaged by Scanning Tunneling Microscopy

Scanning tunneling microscopy has been used to study the adsorbed phases of functionalized terpyridines at the solid–liquid interface of highly ordered pyrolitic graphite (HOPG). Terpyridines are well‐known for their complexing behavior to transition metal ions, making them widely used ligands in organometallic and supramolecular chemistry. We found that solutions of 2,2′:6′,2″‐terpyridine‐4′‐oxydodecane (tpy‐O‐C12) and 2,2′:6′,2″‐4′‐oxyoctadecane (tpy‐O‐C18) form highly ordered two‐ dimensional (2D) arrays on HOPG in phenyloctane. For both compounds, large, well‐defined lamellar domains have been observed with domain sizes larger than 500 nm. Sequential scans of an area with two grain boundaries indicate that desorption–resorption is taking place along the domain edges. High‐resolution images of the lamella have been obtained, and the 2D packing within the lamella was determined in detail. The terpyridines align in long uniform double rows with their alkyl chains packing in an alternating, zipper‐like fashion. The terpyridines pack with the polar head‐groups head to head, and the observed size and shape of the molecules fit exactly to their modeled geometries.     

Hierarchical Spiky Microstraws‐Integrated Microfluidic Device for Efficient Capture and In Situ Manipulation of Cancer Cells

Techniques for capturing circulating tumor cells (CTCs) play an important role in cancer diagnosis. Recently, various 3D micro/nanostructures have been applied for effective CTC detection, yet in situ manipulation of the captured cancer cells on micro/nano‐structural substrates is rarely achieved. In this work, a hierarchical spiky microstraw array (HS‐MSA)‐integrated microfluidic device is demonstrated that possessed dual functions of cancer cell capture and in situ chemical manipulations of the captured cells. The 3D micro/nanostructure of HS‐MSA could capture cancer cells with high efficiency (≈84%) and strong specificity. Based on the HS‐MSA‐integrated microfluidic device, extracellular drug delivery to the captured cancer cells is achieved in situ with excellent spatial, dose, and temporal controls. In addition, a drug‐screening assay on the captured cancer cells is implemented to investigate the cell apoptosis behavior under the microstraw‐mediated delivery of staurosporine (STS). This microfluidic system not only presents tremendous potential for CTCs detection technology, but also opens up new opportunities for high‐throughput drug screening on cancer cells and understanding the cellular activity.     

Nanomanipulation of Ligand‐Stabilized Au55 Clusters by Means of Scanning Tunneling Microscopy

We have investigated ligand‐stabilized Au₅₅ clusters by means of scanning tunneling microscopy (STM) at room temperature on highly oriented pyrolytic graphite (HOPG) and other substrates. Single clusters or groups of several clusters were transferred between sample and STM tip using conventional voltage pulses. With a new variant of voltage pulses called “field‐emission pulses”, cluster shells were partly destroyed by heating with the field‐emission current, resulting in a “hardening” of the cluster layer. HOPG substrate surfaces with most of the clusters removed exhibit “pearl chains” of clusters attached to step edges.     

Deciphering Unexplored Reversible Potassium Storage and Small Volume Change in a CaV4O9 Anode with In Situ Transmission Electron Microscopy

Vanadium-based compounds are explored as promising electrode materials in lithium/sodium-ion batteries exhibiting superior energy storage properties. However, similar attempts are rarely reported for potassium-ion batteries (PIBs), in which the fundamental reaction mechanisms remain inexplicit. Herein, porous CaV₄O₉ nanobelts (NBs) are selected as a PIB anode to systematically investigate potassium storage mechanisms through in situ transmission electron microscopy. In situ measurements track overall electrochemical potassiation reactions of CaV₄O₉ and identify a polyphase state of V₄O₇, CaO, and K₂O phases after potassiation. Unexpectedly, the potassiated products can be partially converted back to the original CaV₄O₉ phase with residual VO₂ and CaO phases, which is different from the irreversible phase transformations in lithium/sodium storages of CaV₄O₉. Impressively, the cavities in NBs alternately disappear and appear with (de)potassiation, avoiding the drastic volume change and structural degradation of anodes. The reversible potassium storage and stable cycling are evaluated by electrochemical measurements and in situ X-ray diffraction analysis. This work provides a paradigm by revisiting the existing anode materials in lithium/sodium-ion batteries to seek out viable anodes for next-generation PIBs.     

Selective Vertical and Horizontal Growth of 2D WS2 Revealed by In Situ Thermolysis using Transmission Electron Microscopy

Direct observation of the growth dynamics of 2D transition metal dichalcogenides (TMDs) is of key importance for understanding and controlling the growth modes and for tailoring these intriguing materials to desired orientations and layer thicknesses. Here, various stages and multiple growth modes in the formation of WS₂ layers on different substrates through thermolysis of a single solid-state (NH₄)₂WS₄ precursor are revealed using in situ transmission electron microscopy. Control over vertical and horizontal growth is achieved by varying the thickness of the drop-casted precursor from which WS₂ is grown during heating. First depositing platinum (Pt) and gold (Au) on the heating chips much enhance the growth process of WS₂ resulting in an increased length of vertical layers and in a self-limited thickness of horizontal layers. Interference patterns are formed by the mutual rotation of two WS₂ layers by various angles on metal deposited heating chips. This shows detailed insights into the growth dynamics of 2D WS₂ as a function of temperature, thereby establishing control over orientation and size. These findings also unveil the important role of metal substrates in the evolution of WS₂ structures, offering general and effective pathways for nano-engineering of 2D TMDs for a variety of applications.     

Atomic Insight into Thermolysis‐Driven Growth of 2D MoS2

Understanding and controlling the transformations of transition metal dichalcogenides (TMDs) from amorphous precursors into two‐dimensional (2D) materials is important for guiding synthesis, directing fabrication, and tailoring functional properties. Here, the combined effects of thermal energy and electron beam irradiation are explored on the structural evolution of 2D MoS₂ flakes through the thermal decomposition of a (NH₄)₂MoS₄ precursor inside an ultrahigh vacuum (10^?9 Torr) scanning transmission electron microscope (STEM). The influence of reaction temperature, growth substrate, and the initial precursor morphology on the resulting 2D MoS₂ flake morphology, edge structures, and point defects are explored. Although thermal decomposition occurs extremely fast at elevated temperatures and is difficult to capture using current STEM techniques, electron beam irradiation can induce local transformations at lower temperatures, enabling direct observation and interpretation of critical growth steps including oriented attachment and transition from single‐ to multilayer structures at atomic resolution. An increase in the number of layers of the MoS₂ flakes from island growth is investigated using electron beam irradiation. These findings provide insight into the growth mechanisms and factors that control the synthesis of few‐layer MoS₂ flakes through thermolysis and toward the prospect of atomically precise control and growth of 2D TMDs.