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The recent decade has seen a huge impact of nanotechnology in different sciences. In analytical chemistry, nanomaterials have been utilized for various purposes from sample preparation to detection. The impact of nanotechnology in analytical science is not limited to the improvement of analytical methodologies. Nanomaterials have been utilized for nanomaterials analysis as nanotools. Nanotools are used to investigate and work with materials at the nanoscale. Nanotechnology has also enabled new applications such as nanoscale tips used for topological microscopy in atomic force microscopy, scanning tunneling microscopy, and magnetic force microscopy. These techniques utilize nanotechnology to improve their efficiency. Furthermore, nanotechnology has enabled the construction of tweezers and robots in the nanoscale. These nano-enabled tools (nanotools) have been successfully utilized for nanoanalysis and nanomanipulation. Atomic force microscopy, scanning tunneling microscope, and magnetic force microscopy are not only meant to image nanostructured surfaces but also they are utilized for the manipulation of materials at the atomic and nanoscale. Nanotweezers, nanorobots, and laser tweezers using nanoapertures are also able to manipulate nano and microscale materials. This paper reviews the principles and application of the mentioned nano-enabled techniques as nanotools in analytical chemistry with a focus on nanomaterials nanoanalysis and nanomanipulation as nanoanalytes. [ABSTRACT FROM AUTHOR]

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Nanotechnology has captured the information field on an impressive scale, which is in one way or another related to scientific topics. In the modern world, the term "nanotechnology" is heard by almost every layman, for marketing purposes there are abuses with reference to this area. A definition is given that restricts the scope of this term. At the same time, breakthrough opportunities with the use of this interdisciplinary field for science, the latest outstanding research both for the promotion of digitalization and for the knowledge of man himself are shown. Since 2022, North Kazakhstan University has been conducting classes in the discipline "Nanotechnology in Natural Science Research" using high-precision modern equipment. The goal is to reveal the features of teaching this discipline at the Department of Physics. The importance of training specialists of various educational programs of the natural sciences in this discipline, the need to apply practical research skills on advanced scientific equipment: atomic force microscope, scanning tunneling microscope are considered. The results of scanning by students obtained in laboratory classes are given. The aspects of teaching this discipline at the North Kazakhstan University at the Department of Physics are revealed, the importance of the knowledge and skills gained in the formation of a future competitive specialist in the labor market is shown. [ABSTRACT FROM AUTHOR]

Nanographenes with zigzag edges, for example, anthenes, exhibit a unique nonbonding π‐electron state, which can be described as a spin‐polarized edge state that yields specific magnetic ground state. However, prior researches on the magnetism of anthenes with varying lengths on a surface is lacking. This study systematically fabricated anthenes with inherent zigzag carbon atoms of different lengths ranging from bisanthene to hexanthene. Their magnetic evolution on the Au(111) surface was analyzed through bond‐resolved scanning probe techniques and density functional theory calculations. The analyses revealed a transition in magnetic properties associated with the length of the anthenes, arising from the imbalance between hybridization energy and the Coulomb repulsion between valence electrons. With the increasing length of the anthenes, the ground state transforms gradually from a closed‐shell to an antiferromagnetic open‐shell singlet, exhibiting a weak exchange coupling of 4 meV and a charge transfer‐induced doublet. Therefore, this study formulated a chemically tunable platform to explore size‐dependent π magnetism at the atomic scale, providing a framework for research in organic spintronics. [ABSTRACT FROM AUTHOR]

ABSTRACT: Investigation into the structural and magnetic properties of organic molecules at cryogenic temperature is beneficial for reducing molecular vibration and stabilizing magnetization, and is of great importance for constructing novel spintronics devices of better performance and scaling the device size down to nanoscale. In order to explore the possibility of fabricating molecule-based memory chips of ultrahigh density, two-dimensional close-packed molecular arrays with carboxylic acid molecules were constructed in the current work and the magnetic properties in a low-temperature scanning tunneling microscope were also investigated. The results demonstrated that each nonmagnetic molecule can be controllably and independently switched into a stable spin-carrying state at 4 K by applying a voltage pulse with atomic resolution. Benefiting from the small size of a single molecule as the basic storage bit, the two-dimensional molecular arrays allowing controllable electrical manipulations on each molecule can behave as a platform of memory chip with an ultrahigh storage density of ∼320 terabytes (Tb) (or ∼2500 terabits) per square inch. This work highlights the potential and advantage of employing organic molecules in developing future cryogenic information storage techniques and devices at nanoscale.

Scanning tunneling microscopy (STM) imaging has been routinely applied in studying surface nanostructures owing to its capability of acquiring high-resolution molecule-level images of surface nanostructures. However, the image analysis still heavily relies on manual analysis, which is often laborious and lacks uniform criteria. Recently, machine learning has emerged as a powerful tool in material science research for the automatic analysis and processing of image data. In this paper, we propose a method for analyzing molecular STM images using computer vision techniques. We develop a lightweight deep learning framework based on the YOLO algorithm by labeling molecules with its keypoints. Our framework achieves high efficiency while maintaining accuracy, enabling the recognitions of molecules and further statistical analysis. In addition, the usefulness of this model is exemplified by exploring the length of polyphenylene chains fabricated from on-surface synthesis. We foresee that computer vision methods will be frequently used in analyzing image data in the field of surface chemistry. [ABSTRACT FROM AUTHOR]

The interaction between a probing tip and an adsorbed molecule can significantly impact the molecular chemical structure and even induce its motion on the surface. In this study, the tip-induced bond weakening, tilting, and hopping processes of a single molecule were investigated by sub-nanometre resolved tip-enhanced Raman spectroscopy (TERS). We used single carbon monoxide (CO) molecules adsorbed on the Cu (100) surface as a model system for the investigation. The vibrational frequency of the C−O stretching mode is always redshifted as the tip approaches, revealing the weakening of the C−O bond owing to tip−molecule interactions. Further analyses of both the vibrational Stark effect and TERS imaging patterns suggest a delicate tilting phenomenon of the adsorbed CO molecule on Cu(100), which eventually leads to lateral hopping of the molecule. While a tilting orientation is found toward the hollow site along the [110] direction of the Cu(100) surface, the hopping event is more likely to proceed via the bridge site to the nearest Cu neighbour along the [100] or [010] direction. Our results provide deep insights into the microscopic mechanisms of tip−molecule interactions and tip-induced molecular motions on surfaces at the single-bond level.

We report on the chemical design of chiral molecular junctions with stress‐dependent conductance, whose helicity is maintained during the stretching of a single molecule junction due to the stapling of both ends of the inner helix. In the reported compounds, different conductive pathways are observed, with clearly different conductance values and plateau‐length distributions, attributed to different conformations of the helical structures. The large chiro‐optical responses and the potential use of these molecules as unimolecular spin filters have been theoretically proved using state‐of‐the‐art Density Functional Theory (DFT) calculations, including a fully ab‐initio estimation of the CISS‐originating spin polarization which is done, for the first time, for a realistic molecular system. [ABSTRACT FROM AUTHOR]

Azobenzene derivatives are a unique class of photo-switch molecules with promising potential for nanoscale optical applications. We have studied the self-assembly and photo-induced mechanical switching of azobenzene derivatives on Au(111) at the single-molecule level by using scanning tunneling microscope (STM). 4,4′-Dibromo-azobenzene (Br-AB) molecules are assembled into two types of well-ordered structures on Au(111) surfaces in the trans-isomer configuration. Br-AB molecules experienced configurational changes from trans-to-cis photo-isomerization upon the exposure to the UV light. This photo-isomerization of Br-AB molecules was observed to occur at random sites of ordered structure, evidenced by the appearance of bright protrusions with the height increment. Our results may open up new routes to engineer nanoscale photo-switch molecular devices. [ABSTRACT FROM AUTHOR]

We present a novel homebuilt scanning tunneling microscope (STM) with atomic resolution integrated into a cryogen-free superconducting magnet system with a variable temperature insert. The STM head is designed as a nested structure of double piezoelectric tubes (PTs), which are connected coaxially through a sapphire frame whose top has a sample stage. A single shaft made of tantalum, with the STM tip on top, is held firmly by a spring strip inside the internal PT. The external PT drives the shaft to the tip–sample junction based on the SpiderDrive principle, and the internal PT completes the subsequent scanning and imaging work. The STM head is simple, compact, and easy to assemble. The excellent performance of the device was demonstrated by obtaining atomic-resolution images of graphite and low drift rates of 30.2 pm/min and 41.4 pm/min in the X–Y plane and Z direction, respectively, at 300K. In addition, we cooled the sample to 1.6 K and took atomic-resolution images of graphite and NbSe2. Finally, we performed a magnetic field sweep test from 0 T to 9 T at 70 K, obtaining distinct graphite images with atomic resolution under varying magnetic fields. These experiments show our newly developed STM's high stability, vibration resistance, and immunity to high magnetic fields. [ABSTRACT FROM AUTHOR]

Quarteranthene is predicted to manifest nontrivial edge states as the competition from the hybridization of localized frontier states and the Coulomb repulsion between valence electrons, which hosts much research potential in memory, spintronic devices fabrication, and quantum computation. The fabrication of ribbon‐like structures with up‐mentioned edge states, such as chiral graphene nanoribbon, possesses a high significance in the topological phase transition investigation. However, the synthesis of chiral graphene nanoribbon is limited in reactive substrate or with the edge‐brominated precursor. Here, the fabrication of quarteranthene and its chiral graphene nanoribbon segment on Au(111) substrate is reported. A combined bond‐resolved scanning tunneling microscopy, noncontact atomic force microscopy characterization, and corresponding density functional theory calculations confirm the chemical structure of fabricated products on the Au(111) substrate. The detailed analysis of the laterally extended products reveals that the lateral‐extended structures are acquired via the linkage of the hydrocarbon quarter‐anthryl. In addition, several strategies are used to modulate the yield of quarteranthene and its lateral‐extended products. These findings provide a new insight into the lateral extension strategy on metal substrates and provide another possible fabrication strategy of chiral graphene nanoribbons on the relative inert Au(111) substrate. [ABSTRACT FROM AUTHOR]

The correlation of surface impurity states with the antiferromagnetic ground states is crucial for understanding the formation of the topological surface state in the antiferromagnetic topological insulators MnBi2Te4. By using low-temperature scanning tunneling microscopy and spectroscopy, we observed a localized bound state around the Mn-Bi antisite defect at the Te-terminated surface of the antiferromagnetic topological insulator MnBi2Te4. When applying a magnetic field perpendicular to the surface (Bz) from −1.5 to 3.0 T, the bound state shifts linearly to a lower energy with increasing Bz, which is attributed to the Zeeman effect. Remarkably, when applying a large range of Bz from −8.0 to 8.0 T, the magnetic field induced reorientation of surface magnetic moments results in an abrupt jump in the local density of states (LDOS), which is characterized by LDOS-change-ratio d σ ˜ / d B quantitatively. Interestingly, two asymmetric critical field, −2.0 and 4.0 T determined by the two peaks in d σ ˜ / d B are observed, which is consistent with simulated results according to a Mills-model, describing a surface spin flop transition (SSF). Our results provide a new flatform for studying the interplay between magnetic order and topological phases in magnetic topological materials. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: In recent years, the construction of stable multicomponent assembled structures on surfaces and the exploration of the assembled mechanism have become research hotspots. In this paper, the azobenzene‐carboxylic acid called (E)‐4',4"'‐(diazene‐1,2‐diyl) bis(([1,1'‐biphenyl]‐3,5‐dicarboxylic acid)) (H4DBBD) could self‐assemble into regular network structure at heptanoic acid/graphite via hydrogen bonding, and could be regulated into analogous kagomé network by coronene (COR) molecules. In addition, a series of bipyridine derivatives were further introduced to construct bi‐component systems with H4DBBD molecules, and successfully induced diversified structural transitions of H4DBBD on the graphite surface. Combined with scanning tunneling microscope (STM) and density functional theory (DFT) calculations, we have investigated the diversified structural transitions and analyzed the formation mechanism of the assembled systems. [ABSTRACT FROM AUTHOR]

Photocatalytic water oxidation over titanium dioxide (TiO2) was overviewed by surveying briefly the history of water photo-oxidation, followed by profiling the research for the molecular mechanism of oxygen evolution reaction (OER) at the TiO2 surface. As the experimental approach to investigate the reaction mechanism, ESR, NMR, and STM were described as well as FTIR spectroscopy. Detection of reactive oxygen species, which are the intermediate species in the OER, was also involved in discussing the mechanism. As the theoretical approach to the reaction mechanism, some research with density functional theory (DFT) for anatase (101) surface was illustrated. Since the OER activity of rutile TiO2 is higher than that of anatase, and the rutile (011) surface has been assigned to the oxidation facet, we performed a DFT calculation for a (011) surface model molecule. The results were successfully discussed with the reported mechanism. The first oxidation step occurs at the bridging OH site, which faces a Ti5C site. The water molecule which coordinates both sites is oxidized, and the resultant radical coordinates the Ti5C site to form a trapped hole Ti-O•. In the second step, a coordinated water molecule is oxidized at the Ti-O• site to form a Ti-OOH structure. [ABSTRACT FROM AUTHOR]

• The STM construction employs a minimal number of components, and the shaft itself makes a piezoelectric material to make this structure compact and simple. • The step size curves for upward and downward movements closely align, and successfully obtained atomic-resolution images of a highly oriented pyrolytic graphite (HOPG) sample, low drift rates in X - Y plane and Z directions and high eigenfrequency under ambient conditions. • This simple, compact STM unit shows the potential for the development of a rotatable STM for use in narrow space environments such as cryogen-free magnets, superconducting magnets, and low- temperature systems. Scanning tunneling microscope (STM) is a renowned scientific tool for obtaining high-resolution atomic images of materials. Herein, we present an innovative design of the scanning unit with a compact yet powerful inertial piezoelectric motor inspired by the Spider Drive motor principle. The scanning unit mainly consists of a small 9 mm long piezoelectric tube scanner (PTS), one end of which is coaxially connected to the main sapphire body of the STM. Of particular emphasis in this design is the piezoelectric shaft (PS), constructed from piezoelectric material instead of conventional metallic or zirconium materials. The PS is a rectangular piezoelectric stack composed of two piezoelectric plates, which are elastically clamped on the inner wall of the PTS via a spring strip. The PTS and PS expand and contract independently with each other to improve the inertial force and reduce the threshold voltage. To ensure the stability of the PS and balance the stepping performance of the inertial motor, a counterweight, and a matching conical spring are fixed at the tail of the PS. This innovative design allows for the assessment of scanning unit performance by applying a driving signal, threshold voltage is 50 V at room temperature. Step sizes vary from 0.1 to 1 µm by changing the driving signal at room temperature. Furthermore, we successfully obtained atomic-resolution images of a highly oriented pyrolytic graphite (HOPG) sample and low drift rates of 23.4 pm/min and 34.6 pm/min in X-Y plane and Z direction, respectively, under ambient conditions. This small, compact STM unit has the potential for the development of a rotatable STM for use in cryogen-free magnets, and superconducting magnets. [ABSTRACT FROM AUTHOR]

Abstract Quarteranthene is predicted to manifest nontrivial edge states as the competition from the hybridization of localized frontier states and the Coulomb repulsion between valence electrons, which hosts much research potential in memory, spintronic devices fabrication, and quantum computation. The fabrication of ribbon‐like structures with up‐mentioned edge states, such as chiral graphene nanoribbon, possesses a high significance in the topological phase transition investigation. However, the synthesis of chiral graphene nanoribbon is limited in reactive substrate or with the edge‐brominated precursor. Here, the fabrication of quarteranthene and its chiral graphene nanoribbon segment on Au(111) substrate is reported. A combined bond‐resolved scanning tunneling microscopy, noncontact atomic force microscopy characterization, and corresponding density functional theory calculations confirm the chemical structure of fabricated products on the Au(111) substrate. The detailed analysis of the laterally extended products reveals that the lateral‐extended structures are acquired via the linkage of the hydrocarbon quarter‐anthryl. In addition, several strategies are used to modulate the yield of quarteranthene and its lateral‐extended products. These findings provide a new insight into the lateral extension strategy on metal substrates and provide another possible fabrication strategy of chiral graphene nanoribbons on the relative inert Au(111) substrate.

Abstract Alkali atom doping is an efficient way to induce charge transfer and Fermi level tuning in layered materials through intercalation. However, there is a general lack of microscopic understanding of the effect of doping inhomogeneity in geometric and electronic aspects. Here, we report surface doping of a bulk VSe2 crystal by sodium. Na atoms form intercalated subsurface islands that modify the electronic phase of the top layer of VSe2. In addition to n‐doping, the charge density wave of the intercalated VSe2 surface layer changes from the (4 × 4) bulk phase to the (3×7) known in monolayer phase of VSe2. Surprisingly, an electronic state at the edges of Na‐intercalated area shift anomalously upward in energy as detected by scanning tunneling spectroscopy. This is explained by a local gating effect resulting from local dipoles at the edges. The study illustrates a clear example of intercalation effect that should be general in alkali‐intercalated bulk layered materials.

Recently, log-periodic quantum oscillations have been detected in the topological materials zirconium pentatelluride (ZrTe5) and hafnium pentatelluride (HfTe5), displaying an intriguing discrete scale invariance (DSI) characteristic. In condensed materials, the DSI is considered to be related to the quasi-bound states formed by massless Dirac fermions with strong Coulomb attraction, offering a feasible platform to study the longpursued atomic-collapse phenomenon. Here, we demonstrate that a variety of atomic vacancies in the topological material HfTe5 can host the geometric quasi-bound states with a DSI feature, resembling an artificial supercritical atom collapse. The density of states of these quasi-bound states is enhanced, and the quasi-bound states are spatially distributed in the “orbitals” surrounding the vacancy sites, which are detected and visualized by low-temperature scanning tunneling microscope/spectroscopy. By applying the perpendicular magnetic fields, the quasi-bound states at lower energies become wider and eventually invisible; meanwhile, the energies of quasi-bound states move gradually toward the Fermi energy (EF). These features are consistent with the theoretical prediction of a magnetic field–induced transition from supercritical to subcritical states. The direct observation of geometric quasi-bound states sheds light on the deep understanding of the DSI in quantum materials. [ABSTRACT FROM AUTHOR]

Scanning tunneling microscopy (STM) imaging has been routinely applied in studying surface nanostructures owing to its capability of acquiring high-resolution molecule-level images of surface nanostructures. However, the image analysis still heavily relies on manual analysis, which is often laborious and lacks uniform criteria. Recently, machine learning has emerged as a powerful tool in material science research for the automatic analysis and processing of image data. In this paper, we propose a method for analyzing molecular STM images using computer vision techniques. We develop a lightweight deep learning framework based on the YOLO algorithm by labeling molecules with its keypoints. Our framework achieves high efficiency while maintaining accuracy, enabling the recognitions of molecules and further statistical analysis. In addition, the usefulness of this model is exemplified by exploring the length of polyphenylene chains fabricated from on-surface synthesis. We foresee that computer vision methods will be frequently used in analyzing image data in the field of surface chemistry.

Nanoclusters consisting of a few atoms have attracted a lot of research interests due to their exotic size-dependent properties. Here, well-ordered two-dimensional Sb cluster superlattice was fabricated on Si substrate by a two-step method and characterized by scanning tunneling microscopy. High resolution scanning tunneling microscope measurements revealed the fine structures of the Sb clusters, which consist of several Sb atoms ranging from 2 to 7. Furthermore, the electronic structure of the nanocluster displays the quantized energy-level which is due to the single-electron tunneling effects. We believe that the fabrication of Sb cluster superlattice broadens the species of the cluster superlattice and provides a promising candidate to further explore the novel physical and chemical properties of the semimetal nanocluster. [ABSTRACT FROM AUTHOR]

Functionalized two-dimensional (2D) materials play an important role in both fundamental sciences and practical applications. The construction and precise control of patterns at the atomic-scale are necessary for selective and multiple functionalization. Here we report the fabrication of monolayer pentasilver diselenide (Ag5Se2), a new type of intrinsically patterned 2D material, by direct selenization of a Ag(111) surface. The atomic arrangement is determined by a combination of scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and density-functional-theory (DFT) calculations. Large-scale STM images exhibit a quasi-periodic pattern of stoichiometric triangular domains with a side length of ~ 15 nm and apical offsets. The boundaries between triangular domains are sub-stoichiometric. Deposition of different molecules on the patterned Ag5Se2 exhibits selective adsorption behavior. Pentacene molecules preferentially adsorb on the boundaries, while tetracyanoquinodimethane (TCNQ) molecules adsorb both on the boundaries and the triangular domains. By co-depositing pentacene and TCNQ molecules, we successfully construct molecular corrals with pentacene on the boundaries encircling TCNQ molecules on the triangular domains. The realization of epitaxial large-scale and high-quality, monolayer Ag5Se2 extends the family of intrinsically patterned 2D materials and provides a paradigm for dual functionalization of 2D materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A range of potassium fullerides, K x C 60 (x = 1, 4/3 and 2) monolayers, are newly fabricated on Si(111)-√3×√3-Ag. • All the fulleride monolayers show an energy gap at the Fermi level due to electronic interactions and structural distortion. • The energy gap in K 2 C 60 is significantly softened by partial electron doping from the Si(111)-√3×√3-Ag surface. Metal-terminated silicon surfaces are a specific class of templates for growth of fulleride ultrathin films. Using scanning tunneling microscope and spectroscope, we investigate the geometric and electronic structures of K x C 60 monolayers on Si(111)-√3×√3-Ag with x gradually increased to 2. Besides long-range ordered KC 60 and K 2 C 60 monolayers, a fraction-stoichiometric fulleride, K 4/3 C 60 monolayer, is newly discovered. All these fulleride monolayers open an energy gap at the Fermi level owing to electronic correlations and Jahn-Teller distortion. The gap of the even-stoichiometric fulleride, K 2 C 60 , is prominently softened by partial electron doping from the Si(111)-√3×√3-Ag surface. [ABSTRACT FROM AUTHOR]

The thin films of c -plane dominated hexagonal ζ - phase Mn 2 N were successfully grown on a cubic MgO (001) substrate directly using plasma-assisted molecular beam epitaxy. The surface was comprehensively studied through experimental and theoretical approaches. Reflection high energy electron diffraction revealed two pseudo-cubic domains along [100] MgO and [110] MgO , and one hexagonal domain, which is 30° apart from the [100] MgO direction. Scanning tunneling microscopy was used to image and resolve the high quality surface, revealing a distorted hexagonal surface structure. Furthermore, atomic resolution of the hexagonal domain with a 2 × 2 reconstructed surface is presented. For the c -plane surface, theoretical investigations were carried out using first-principle studies to determine the surface formation energy for various reconstructed surfaces. The theoretical study shows that the nitrogen terminated 2 × 2 structure with a manganese adatom on the surface is the most stable reconstruction that reproduces the experimental results. A corresponding simulated scanning tunneling microscopy model is also presented, providing strong support for the experimentally observed in-plane lattice structures. The manganese:nitrogen stoichiometry within the bulk and surface is in good agreement with the expected ratio of 2:1. [Display omitted] • Heteroepitaxial growth of Mn 2 N on cubic substrate. • Film grown on cubic substrate isn't always constrained to maintain cubic symmetry. • Crystal structure accommodated on symmetry mismatched substrate in various ways. • STM images reveal 2 × 2 reconstructed pseudo-cubic and hexagonal domains. • N-terminated Mn ad-atom model corresponds to the most stable Mn 2 N surface. [ABSTRACT FROM AUTHOR]

We present the design, fabrication and discuss the performance of a new combined high-resolution Scanning Tunneling and Thermopower Microscope (STM/SThEM). We also describe the development of the electronic control, the user interface, the vacuum system, and arrangements to reduce acoustical noise and vibrations. We demonstrate the microscope's performance with atomic-resolution topographic images of highly oriented pyrolytic graphite (HOPG) and local thermopower measurements in the semimetal Bi 2 Te 3 . Our system offers a tool to investigate the relationship between electronic structure and thermoelectric properties at the nanoscale. • Novel thermopower microscope for thermoelectric property measurements. • Comprehensive description of the electronic control system and user interface. • Insights for researchers to replicate or build upon this technology. • High-quality measurements are provided, showcasing the new technique's capabilities. • Successful demonstration of the combined microscopes for material characterization. [ABSTRACT FROM AUTHOR]

• We present a novel scan unit that featuring standalone structure, non-magnetic design and ultra-high stability, as well as bidirectional movement capability. • Different types of piezoelectric motors can be incorporated into the scan unit to create a highly stable STM. • The novel scan unit and STM exhibit exceptional stability at varying temperature ranging from 300 K to 2 K, as well as in varying magnetic fields ranging from 0 T to 23 T. • High-quality atomic images and high-resolution dI/dV spectrums of NbSe 2 demonstrate the new device's excellent application ability. The high resolution of a scanning tunneling microscope (STM) relies on the stability of its scan unit. In this study, we present an isolated scan unit featuring non-magnetic design and ultra-high stability, as well as bidirectional movement capability. Different types of piezoelectric motors can be incorporated into the scan unit to create a highly stable STM. The standalone structure of scan unit ensures a stable atomic imaging process by decreasing noise generated by motor. The non-magnetic design makes the scan unit work stable in high magnetic field conditions. Moreover, we have successfully constructed a novel STM based on the isolated scan unit, in which two inertial piezoelectric motors act as the coarse approach actuators. The exceptional performance of homebuilt STM is proved by the high-resolution atomic images and dI/dV spectrums on NbSe 2 surface at varying temperatures, as well as the raw-data images of graphite obtained at ultra-high magnetic fields of 23 T. According to the literature research, no STM has previously reported the atomic image at extreme conditions of 2 K low temperature and 23 T ultra-high magnetic field. Additionally, we present the ultra-low drift rates between the tip and sample at varying temperatures, as well as when raising the magnetic fields from 0 T to 23 T, indicating the ultra-high stability of the STM in high magnetic field conditions. The outstanding performance of our stable STM hold great potential for investigating the materials in ultra-high magnetic fields. [ABSTRACT FROM AUTHOR]

The study of processes concerning adsorption, diffusion and reaction of atoms and molecules on surfaces is one of the core areas of surface science research. Resolving these dynamic processes with atomic resolution in real space and at real time is of great significance for the understanding of catalytic reaction mechanism and the development of new materials. A scanning tunneling microscope with fast imaging function, a so-called "high-speed scanning tunneling microscope" combining both high temporal and high spatial resolution, is an ideal instrument to characterize processes within this area. This review aims to highlight some recent developments of high-speed scanning tunneling microscope technique and its application to study the structural dynamics on surfaces. Firstly, factors that limit the time resolution of scanning tunneling microscope are analyzed from the aspects of both hardware and software. Secondly, strategies and instrument designs enabling imaging rate up to 100 frames per second are introduced. Then, recent breakthroughs on resolving surface structural dynamics, such as atom diffusion, on-surface synthesis of low-dimensional materials and chemical reaction, by high-speed scanning tunneling microscope are highlighted. Finally, the challenges and opportunities of high-speed scanning tunneling microscope technique are outlined and a perspective is provided. [ABSTRACT FROM AUTHOR]

We present a novel homebuilt scanning tunneling microscope (STM) with atomic resolution integrated into a cryogen-free superconducting magnet system with a variable temperature insert. The STM head is designed as a nested structure of double piezoelectric tubes (PTs), which are connected coaxially through a sapphire frame whose top has a sample stage. A single shaft made of tantalum, with the STM tip on top, is held firmly by a spring strip inside the internal PT. The external PT drives the shaft to the tip–sample junction based on the SpiderDrive principle, and the internal PT completes the subsequent scanning and imaging work. The STM head is simple, compact, and easy to assemble. The excellent performance of the device was demonstrated by obtaining atomic-resolution images of graphite and low drift rates of 30.2 pm/min and 41.4 pm/min in the X–Y plane and Z direction, respectively, at 300K. In addition, we cooled the sample to 1.6 K and took atomic-resolution images of graphite and NbSe2. Finally, we performed a magnetic field sweep test from 0 T to 9 T at 70 K, obtaining distinct graphite images with atomic resolution under varying magnetic fields. These experiments show our newly developed STM’s high stability, vibration resistance, and immunity to high magnetic fields.

Two-dimensional (2D) materials with defects are desired for catalysis after the adsorption of monodispersed noble metal atoms. High-performance catalysts with the absolute value of Gibbs free energy (∣∆GH∣) close to zero, is one of the ultimate goals in the catalytic field. Here, we report the formation of monolayer titanium selenide (TiSe2) with line defects. The low-temperature scanning tunneling microscopy/spectroscopy (STM/S) measurements revealed the structure and electronic states of the line defect. Density functional theory (DFT) calculation results confirmed that the line defects were induced by selenium vacancies and the STM simulation was in good agreement with the experimental results. Further, DFT calculations show that monolayer TiSe2 with line defects have good catalytic activity for hydrogen evolution reaction (HER). If the defects are decorated with single Pt atom, the HER catalytic activity will be enhanced dramatically (∣∆GH∣ = 0.006 eV), which is much better than Pt metal (∣∆GH∣ = 0.09 eV). Line defects in monolayer TiSe2/Au(111) provide a wonderful platform for the design of high-performance catalysts. [ABSTRACT FROM AUTHOR]

Direct coupling or transformation of inert alkanes based on the selective C-H activation is of great importance for both chemistry and chemical engineering. Here, we report the coupling of polyenes that are transformed from n-dotriacontane (n-C32H66) through on-surface cascade dehydrogenation on Cu (110) surface, leading to the formation of polyacetylene (PA). Three distinct linkages have been resolved by scanning tunneling microscope (STM) and noncontact atomic force microscope (nc-AFM). Apart from the α-type linkage which is the stemless coupling of the terminal C-C double bond in trans-configuration, β- and γ-type linkages appear as knots or defects which are, in fact, the C-C couplings in cis-configurations. Interestingly, the "defects" can be effectively suppressed by adjusting the surface coverage, thus making it of general interest for uniform structure modulation. [ABSTRACT FROM AUTHOR]

Scanning Tunneling Microscope (STM) is used to generate the surface image of any conducting sample surface with an atomic-scale resolution. A multi-axis 3D piezoelectric actuator is attached with the STM tip to move it in horizontal (x and y) and vertical (z) directions. The purpose of control design is to achieve precise reference tracking for horizontal 2D scanning system and to keep the tunneling current constant in the vertical direction in the presence of all possible disturbances. A usual practice is to design independent single-input-single-output (SISO) controllers for individual x, y and z axes by neglecting the cross-coupling dynamics of the multi-axis 3D piezoelectric actuator. In this paper, a complete 3D STM system, without neglecting the cross-coupling dynamics as well as the hysteresis nonlinearity of the actuator, is first mathematically modeled. The parameters of the hysteresis model are identified from the real-time experimental data by using the nonlinear least-squares curve fitting problem. A feedforward compensator is then designed without finding an inverse hysteresis model to avoid any inverse modeling complexity. Then, two control strategies (SISO and multi-input-multi-output (MIMO) $\text{H}_\infty $ feedback controllers cascaded in series with the feedforward compensator) are investigated for an overall 3D system. Three different scanning trajectories (raster, spiral and Lissajous) are considered to analyze and compare the performance of SISO and MIMO control schemes. In the presence of cross-couplings, an average improvement of 83% in reducing the variations of the tunneling current is achieved with the suggested MIMO control scheme as compared to the generally used SISO control scheme for STM.

The control of the Kondo effect is of great interest in single-molecule junction due to its potential applications in spin based electronics. Here, we demonstrate that the Kondo effect is reversibly switched on and off in an iron phthalocyanine (FePc) single-molecule junction by using a superconducting Nb tip. In a scanning tunneling microscope-based Nb-insulator-FePc-Au junction, we achieve a reversible switching between the Kondo dip and inelastic electronic tunneling spectra by simply adjusting the tip-sample distance to tune the tunnel coupling at low temperature. Further approaching the tip leads to the picking up of the molecule to the tip apex, which transfers the geometry of the single-molecule junction into a Nb-FePc-insulator-Au type. As the molecule forms an effective magnetic impurity embedded into the superconducting ground states of the Nb tip, the out-gap Kondo dip switched to an in-gap Yu-Shiba-Rusinov state. Our results open up a new route for manipulating the Kondo effect within a single-molecule junction. [ABSTRACT FROM AUTHOR]

Cyclic-conjugated linkages between planar-macrocydic molecules contribute to the robustness of the two-dimensional (2D) polymerization and extension of π-interactions. The fabrication of such linkages in 2D polymers remains challenging. Combining scanning tunneling microscope (STM) measurements and density functional theory (DFT) calculations, we demonstrate a linear polymerization of metal-free naphthalocyanine (NPc) molecules with [4]-radialene-like linkages on silver surfaces. Experimentally, by depositing NPc molecules on the Ag(110) surface and subsequent annealing up to 750 K, one-dimensional polymers are constructed along the [ 1 1 ¯ 0 ] direction. High-resolution STM images show a stem-leaf-like feature. STM simulations based on a linear polymer of NPc molecules linked by four-membered carbon rings, [4]-radialene-like structure, agree well with the experimental observations. DFT calculations reveal that the polymerization process includes detaching two-terminal H atoms of NPc molecules along [ 1 1 ¯ 0 ] direction, then bonding with a neighboring dehydrogenated NPc molecule by forming a four-membered ring. The dehydrogenation process can be promoted by on-surface impurities such as additional H atoms. Similar polymerizations have been achieved on Ag(111) surfaces in an amorphous way. Moreover, the energy gap of the NPc molecule decreases after linear polymerization, suggesting a red-shift for its optical absorption/scattering spectrum. Our study offers a new route to polymerize conjugated molecules with extended planar π-interactions. [ABSTRACT FROM AUTHOR]

Azobenzene derivatives are a unique class of photo-switch molecules with promising potential for nanoscale optical applications. We have studied the self-assembly and photo-induced mechanical switching of azobenzene derivatives on Au(111) at the single-molecule level by using scanning tunneling microscope (STM). 4,4′-Dibromo-azobenzene (Br-AB) molecules are assembled into two types of well-ordered structures on Au(111) surfaces in the trans-isomer configuration. Br-AB molecules experienced configurational changes from trans-to-cis photo-isomerization upon the exposure to the UV light. This photo-isomerization of Br-AB molecules was observed to occur at random sites of ordered structure, evidenced by the appearance of bright protrusions with the height increment. Our results may open up new routes to engineer nanoscale photo-switch molecular devices.

The electrostatic environment around nanoscale molecular junctions modulates charge transport; solvents alter this environment. Methods to directly probe solvent effects require correlating measurements of the local electrostatic environment with charge transport across the metal-molecule-metal junction. Here, we measure the conductance and current-voltage characteristics of molecular wires using a scanning tunneling microscope-break junction (STM-BJ) setup in two commonly used solvents. Our results show that the solvent environment induces shifts in molecular conductance, which we quantify, but more importantly we find that the solvent also impacts the magnitude of current rectification in molecular junctions. By incorporating electrochemical impedance spectroscopy into the STM-BJ setup, we measure the capacitance of the dipole layer formed at the metal-solvent interface and show that rectification can be correlated with solvent capacitance. These results provide a method of quantifying the impact of the solvent environment and a path toward improved environmental control of molecular devices.

We demonstrate and verify the in-situ addition of a collecting lens for electroluminescence experiments to an existing scanning tunneling microscope. We fabricate a simple clip-on lens that we reversibly attach at the sample plate via regular sample transfer tools to collimate the light emitted from a plasmonic tunneling junction to the viewport ordinarily used for optical access. The proximity of the lens to the tunneling junction allows us achieve good collection efficiencies, demonstrating the quick turnaround of converting an existing setup with optical access into a practical scanning luminescence microscope. We verify the function of the clip-on lens by measuring the bias dependent plasmon of Au, Ag, and spatial luminescence maps.•Reversible clip-on lens.•In-situ transfer.•Luminescence., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Using inelastic electron tunneling spectroscopy with the scanning tunneling microscope (STM-IETS) and density functional theory calculations (DFT), we investigated properties of a single H2 molecule trapped in nanocavities with controlled shape and separation between the STM tip and the Au (110) surface. The STM tip not only serves for the purpose of characterization, but also is directly involved in modification of chemical environment of molecule. The bond length of H2 expands in the atop cavity, with a tendency of dissociation when the gap closes, whereas it remains unchanged in the trough cavity. The availability of two substantially different cavities in the same setup allows understanding of H2 adsorption on noble metal surfaces and sets a path for manipulating a single chemical bond by design.

The paper studies the structure and microhardness of the heat-affected zone, welding area in low carbon and low alloy steel 09G2S (AISI A516 grade 55), and the coating created by two-pass manual metal arc welding with the addition of titanium carbonitride nanoparticles. It is shown that the microhardness dependence on the distance to the coating surface is divided into four zones. The microstructure of each zone is studied by using the optical and scanning tunneling microscopies. It is found that the formation of highly dispersed acicular ferrite and globular bainite structures in the deposition superheat zone of surfacing is favorable for the improvement of the coating–base metal composition impact toughness. [ABSTRACT FROM AUTHOR]