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Controlling composition and plasmonic response of bimetallic nanoparticles (NPs) is of great relevance to tune their catalytic activity. Herein, we demonstrate reversible composition and plasmonic response transitions from a core/shell to a bimetallic alloyed palladium/gold NP triggered by CO adsorption and sample temperature. The use of self-organized growth on alumina template film allows scrutinizing the impact of core size and shell thickness onto NP geometry and plasmonic response. Topography, molecular adsorption, and plasmonic response are addressed by scanning tunneling microscopy, vibrational sum frequency generation (SFG) spectroscopy, and surface differential reflectance spectroscopy, respectively. Modeling CO dipolar interaction and optical reflectivity corroborate the experimental findings. We demonstrate that probing CO adsorption sites by SFG is a remarkably sensitive and relevant method to investigate shell composition and follow in real-time Pd atom migration between the core and the shell. Pd–Au alloying is limited to the first two monolayers of the shell and no plasmonic response is found, while for a thicker shell, a plasmonic response is observed, concomitant with a lower Pd concentration in the shell. Above 10−4 mbar, at room temperature, CO adsorption triggers the shell restructuration, forming a Pd–Au alloy that weakens the plasmonic response via Pd migration from the core to the shell. NP annealing at 550 K, after pumping CO, leads to the desorption of remaining CO and gives enough mobility for Pd to migrate back inside the core and recover a pure gold shell with its original plasmonic response. This work demonstrates that surface stoichiometry and plasmonic response can be tuned by using CO adsorption and NP annealing. [ABSTRACT FROM AUTHOR]

Structures formed by dense CO adsorption layers can provide information about the balance between molecule–surface and molecule–molecule interactions. However, in many cases, the structure models are not clear. Using density functional theory (DFT) and scanning tunneling microscopy (STM), we have investigated the high-coverage CO layer on the Ru(0001) surface. Previous investigations by low-energy electron diffraction (LEED) and vibrational spectroscopy led to conflicting results about the structure. In the present study, 88 models with coverages between 0.58 and 0.77 monolayers have been analyzed by DFT. The most stable structures consist of small, compact CO clusters with an internal pseudo 1 × 1 structure. The CO molecules in the cluster centers occupy on-top sites in an upright position, whereas the molecules farther outside are slightly shifted from these sites and tilted outward. STM data of the CO-saturated surface at low temperatures, corresponding to a coverage of 0.66 monolayers, show a quasi-hexagonal pattern of features with an internal hexagonal fine structure. Simulated images based on the cluster model agree with the experimental data. It is concluded that the high-coverage CO layer consists of the close-packed clusters predicted by DFT as the most stable structure elements. In the experiment, the sizes and shapes of the clusters vary. However, the arrangement is not random but follows defined tiling rules. The structure remains ordered, almost up to room temperature. The LEED data are re-interpreted on the basis of the Fourier transforms of the STM data, solving the long-standing conflict about the structure. [ABSTRACT FROM AUTHOR]

The interplay between orientation transition and chiral self-assemblies of para-terphenyl (P3P) molecules on the Cd(0001) surface has been investigated using low temperature scanning tunneling microscopy and density functional theory calculations. Three distinct molecular orientations have been discerned from the self-assembled thin films of P3P. At the low coverage, flat-lying molecules appear in the homochiral domains with the incommensurate registry to the substrate. With the coverage increasing, the incoming molecules are incorporated into the first layer with edge-on orientation and form the self-assembled zigzag chains. The alternative arrangement of zigzag chains with opposite chirality leads to the formation of a c(4 × 2) superstructure, in which the tilted molecules exhibit orientational frustration and fuzzy noises. The analysis of the tunneling spectra reveals that the electronic structure of P3P layers is contingent upon the hybridization between the electronic states of P3P molecules and the Cd(0001) surface. These results provide important insights into the interplay between orientational transition and chiral assembly of P3P molecules on metal substrates. [ABSTRACT FROM AUTHOR]

We observed a modification of transition pathways in polarized resonance Raman spectroscopy during tip-enhanced Raman spectroscopy (TERS) analysis of metallic carbon nanotubes (CNTs). At a spatial resolution reaching up to the sub-nanometer regime, the signal intensity of the typical D-band is observed to be even higher than the intensity of the G-band all over the probed CNTs in TERS imaging. The measured D-band is attributed to the non-vertical transitions of electrons in k-space that are facilitated by highly confined near-field light at the tip–sample junction of our scanning tunneling microscope based TERS system. The D-band signal was observed even when the CNTs were excited by light polarized perpendicular to the tube axis that corresponds to electronic excitations between different cutting line numbers of a CNT. By combining the electron pathways brought about by both the near-field light and its polarization, we found a unique optical transition of electrons of CNTs in near-field Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Transition metal catalysts supported on topological insulators are predicted to show improved catalytic properties due to the presence of topological surface states, which may float up to the catalysts and provide robust electron transfer. However, experimental studies of surface structures and corresponding catalytic properties of transition metal/topological insulator heterostructures have not been demonstrated so far. Here, we report the structures, chemical states, and adsorption behaviors of two conventional transition metal catalysts, Pt and Pd, on the surface of Bi2Se3, a common topological insulator material. We reveal that Pt forms nanoparticles on the Bi2Se3 surface. Moreover, the interaction between Pt and surface Se is observed. Furthermore, thermal dosing of O2 onto the Pt/Bi2Se3 heterostructure leads to no oxygen adsorption. Detailed scanning tunneling microscopy study indicates that Pt transforms into PtSe2 after the thermal process, thus preventing O2 from adsorption. For another transition metal Pd, it exhibits approximate layer-island growth on Bi2Se3, and Pd–Se interaction is also observed. Our work provides significant insights into the behaviors of transition metals on top of a common topological insulator material and will assist in the future design of catalysts built with topological materials. [ABSTRACT FROM AUTHOR]

Transition metal catalysts supported on topological insulators are predicted to show improved catalytic properties due to the presence of topological surface states, which may float up to the catalysts and provide robust electron transfer. However, experimental studies of surface structures and corresponding catalytic properties of transition metal/topological insulator heterostructures have not been demonstrated so far. Here, we report the structures, chemical states, and adsorption behaviors of two conventional transition metal catalysts, Pt and Pd, on the surface of Bi2Se3, a common topological insulator material. We reveal that Pt forms nanoparticles on the Bi2Se3 surface. Moreover, the interaction between Pt and surface Se is observed. Furthermore, thermal dosing of O2 onto the Pt/Bi2Se3 heterostructure leads to no oxygen adsorption. Detailed scanning tunneling microscopy study indicates that Pt transforms into PtSe2 after the thermal process, thus preventing O2 from adsorption. For another transition metal Pd, it exhibits approximate layer-island growth on Bi2Se3, and Pd–Se interaction is also observed. Our work provides significant insights into the behaviors of transition metals on top of a common topological insulator material and will assist in the future design of catalysts built with topological materials. [ABSTRACT FROM AUTHOR]

Tert-butyl functional groups can modulate the self-assembly behavior of organic molecules on surfaces. However, the precise construction of supramolecular architectures through their controlled thermal removal remains a challenge. Herein, we precisely controlled the removal amount of tert-butyl groups in tetraazaperopyrene derivatives by stepwise annealing on Ag(111). The evolution of 4tBu-TAPP supramolecular self-assembly from the grid-like structure composed of 3tBu-TAPP through the honeycomb network formed by 2tBu-TAPP to the one-dimensional chain co-assembled by tBu-TAPP and TAPP was successfully realized. This series of supramolecular nanostructures were directly visualized by high resolution scanning tunneling microscopy. Tip manipulation and density functional theory calculations show that the formation of honeycomb network structure can be attributed to the van der Waals interactions, N–Ag–N coordination bonds, and weak C–H⋯N hydrogen bonds. Further addition of two tert-butyl groups (6tBu-TAPP) leads to a completely different assembly evolution, due to the fact that the additional tert-butyl groups affect the molecular adsorption behavior and ultimately induce desorption. This work can possibly be exploited in constructing stable and long-range ordered nanostructures in surface-assisted systems, which can also promote the development of nanostructures in functional molecular devices. [ABSTRACT FROM AUTHOR]

Polymorph engineering involves the manipulation of material properties through controlled structural modification and is a candidate technique for creating unique two-dimensional transition metal dichalcogenide (TMDC) nanodevices. Despite its promise, polymorph engineering of magnetic TMDC monolayers has not yet been demonstrated. Here we grow FeSe2 monolayers via molecular beam epitaxy and find that they have great promise for magnetic polymorph engineering. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we find that FeSe2 monolayers predominantly display a 1T' structural polymorph at 5 K. Application of voltage pulses from an STM tip causes a local, reversible transition from the 1T' phase to the 1T phase. Density functional theory calculations suggest that this single-layer structural phase transition is accompanied by a magnetic transition from an antiferromagnetic to a ferromagnetic configuration. These results open new possibilities for creating functional magnetic devices with TMDC monolayers via polymorph engineering.

For the most precise incorporation of single impurities in silicon, which is utilized to create quantum devices, a monolayer of adatoms on the Si(100) surface and a dopant-containing molecule are used. Here, we studied the interaction of phosphorus tribromide with a chlorine monolayer with mono- and bivacancies using a scanning tunneling microscope (STM) at 77 K. The combination of different halogens in the molecule and the adsorbate layer enabled unambiguous identification of the structures after PBr3 dissociation on Si(100)-Cl. A Cl monolayer was exposed to PBr3 in the STM chamber, which allows us to compare the same surface areas before and after PBr3 adsorption. As a result of this comparison, we detected small changes in the chlorine layer and unraveled the molecular fragments filling mono- and bivacancies. Using density functional theory, we found that the phosphorus atom occupies a bridge position after dissociation of the PBr3 molecule, which primarily bonds with silicon in Cl bivacancies. These findings provide insight into the interaction of a dopant-containing molecule with an adsorbate monolayer on Si(100) and can be applied to improve the process of single impurity incorporation into silicon. [ABSTRACT FROM AUTHOR]

Hydration, as a ubiquitous and vital phenomenon in nature, has attracted great attention in the field of surface science concerning the fundamental interactions between water and organic molecules. However, the role of functional group derivatization is still elusive in terms of its potential impact on hydration. By the combination of high-resolution scanning tunneling microscopy imaging and density functional theory calculations, the hydration of 9mA molecules was realized on Au(111) in real space, forming 9mA–H2O–9mA structures. In comparison with the hydration of adenine molecules, methyl derivatization is experimentally found to remotely regulate the hydration sites from the imidazole ring to the pyrimidine ring and is further theoretically revealed to allow intramolecular electron redistribution and, therefore, steer the priority of the hydration sites. These results provide sub-molecular understandings of the relationship between derivatization and hydration, which would shed light on the regulation of hydration processes in chemically and biologically related systems. [ABSTRACT FROM AUTHOR]

We have studied the epitaxial growth of Si thin films on the Cd(0001) surface using low-temperature scanning tunneling microscopy. When deposited at low temperatures (100 K), Si atoms form dendritic islands with triangular shapes, indicating the existence of anisotropic edge diffusion in the process of Si film growth. After annealing to elevated temperatures, the triangular dendritic Si islands become hexagonal compact islands. Moreover, the 2D Si islands located on two different substrate terraces exhibit different heights due to the influence of quantum-well states in Cd(0001) films. Based on high-resolution scanning tunneling microscopy images, it is observed that the first, second, and third Si layers show the pseudomorphic 1 × 1 structure. In particular, the first and second layer islands reveal the opposite triangles, indicating the hexagonal close-packed stacking of Si atoms. These results provide important information for the growth of pristine Si films on metal substrates and the understanding of Si–metal interaction. [ABSTRACT FROM AUTHOR]

The interaction of the PBr3 molecule with Si dangling bonds (DBs) on a chlorinated Si(100) surface was studied. The DBs were charged in a scanning tunneling microscope (STM) and then exposed to PBr3 directly in the STM chamber. Uncharged DBs rarely react with molecules. On the contrary, almost all positively charged DBs were filled with molecule fragments. As a result of the PBr3 interaction with the positively charged DB, the molecule dissociated into PBr2 and Br with the formation of a Si–Br bond and PBr2 desorption. These findings show that charged DBs significantly modify the reactivity of the surface toward PBr3. Additionally, we calculated PH3 adsorption on a Si(100)–2 × 1–H surface with DBs and found that the DB charge also has a significant impact. As a result, we demonstrated that the positively charged DB with a doubly unoccupied state enhances the adsorption of molecules with a lone pair of electrons. [ABSTRACT FROM AUTHOR]

Dimensional modifications play a crucial role in various applications, especially in the context of device miniaturization, giving rise to novel quantum phenomena. The many-body dynamics induced by dimensional modifications, including electron-electron, electron-phonon, electron-magnon and electron-plasmon coupling, are known to significantly affect the atomic and electronic properties of the materials. By reducing the dimensionality of orthorhombic CoSe2 and forming heterostructure with bilayer graphene using molecular beam epitaxy, we unveil the emergence of two types of phase transitions through angle-resolved photoemission spectroscopy and scanning tunneling microscopy measurements. We disclose that the 2 × 1 superstructure is associated with charge density wave induced by Fermi surface nesting, characterized by a transition temperature of 340 K. Additionally, another phase transition at temperature of 160 K based on temperature dependent gap evolution are observed with renormalized electronic structure induced by electron-boson coupling. These discoveries of the electronic and atomic modifications, influenced by electron-electron and electron-boson interactions, underscore that many-body physics play significant roles in understanding low-dimensional properties of non-van der Waals Co-chalcogenides and related heterostructures.

Transition metal dichalcogenide (TMD) moiré superlattices have emerged as a significant area of study in condensed matter physics. Thanks to their superior optical properties, tunable electronic band structure, strong Coulomb interactions, and quenched electron kinetic energy, they offer exciting avenues to explore correlated quantum phenomena, topological properties, and light-matter interactions. In recent years, scanning tunneling microscopy (STM) has made significant impacts on the study of these fields by enabling intrinsic surface visualization and spectroscopic measurements with unprecedented atomic scale detail. Here, we spotlight the key findings and innovative developments in imaging and characterization of TMD heterostructures via STM, from its initial implementation on the in situ grown sample to the latest photocurrent tunneling microscopy. The evolution in sample design, progressing from a conductive to an insulating substrate, has not only expanded our control over TMD moiré superlattices but also promoted an understanding of their structures and strongly correlated properties, such as the structural reconstruction and formation of generalized two-dimensional Wigner crystal states. In addition to highlighting recent advancements, we outline upcoming challenges, suggest the direction of future research, and advocate for the versatile use of STM to further comprehend and manipulate the quantum dynamics in TMD moiré superlattices.

Selective activation of the C–H bond of aromatic hydrocarbons is significant in synthetic chemistry. However, achieving oriented C–H activation remains challenging due to the poor selectivity of aromatic C–H bonds. Herein, we successfully constructed alternately arranged Au–C4 and Au–O4 organometallic coordination networks through selective aromatic C–H bond activation on Au(111) substrate. The stepwise reaction process of the 5, 12-dibromopyrene 3,4,9, 10-tetracarboxylic dianhydride precursor is monitored by high-resolution scanning tunneling microscopy. Our results show that the gold atoms in C–Au–C organometallic chains play a crucial role in promoting the selective ortho C–H bonds activation and forming Au–C4 coordination structure, which is further demonstrated by a comparative experiment of PTCDA precursor on Au(111). Furthermore, our experiment of 2Br-PTCDA precursor on Cu(111) substrate confirms that copper atoms in C–Cu–C organometallic chains can also assist the formation of Cu–C4 coordination structure. Our results reveal the vital effect of organometallic coordination on selective C–H bond activation of reactants, which holds promising implications for controllable on-surface synthesis. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) that can be simultaneously performed with scanning tunneling microscopy (STM) using metallic tips attached to self-sensing quartz cantilevers (qPlus sensors) has advanced the field of surface science by allowing for unprecedented spatial resolution under ultrahigh vacuum conditions. Performing simultaneous AFM and STM with atomic resolution in an electrochemical cell offers new possibilities to locally image both the vertical layering of the interfacial water and the lateral structure of the electrochemical interfaces. Here, a combined AFM/STM instrument realized with a qPlus sensor and a home-built potentiostat for electrochemical applications is presented. We demonstrate its potential by simultaneously imaging graphite with atomic resolution in acidic electrolytes. Additionally, we show its capability to precisely measure the interfacial solvent layering along the surface normal as a function of the applied potential. [ABSTRACT FROM AUTHOR]

We demonstrate a high electron conductivity (>102 S/cm and up to 103 S/cm) of tungsten suboxide W18O52.4−52.9 (or equivalently WO2.91−2.94) nanotubes (2–3 nm in diameter, ∼μm long). The conductivity is measured in the temperature range of 120–300 K by a four-probe scanning tunneling microscope in ultrahigh vacuum. The nanotubes are synthesized by a low-temperature and low-cost solvothermal method. They self-assemble in bundles of hundreds of nanotubes forming nanowires (∼μm long, few tens nm wide). We observe a large anisotropy of the conductivity with a ratio (longitudinal conductivity/perpendicular conductivity) of ∼105. A large fraction of them (∼65%–95%) shows a metallic-like, thermal activation-less electron transport behavior. Few of them, with a lower conductivity from 10 to 102 S/cm, display a variable range hopping behavior. In this latter case, a hopping barrier energy of ∼0.24 eV is inferred in agreement with the calculated energy level of the oxygen vacancy below the conduction band. This result is in agreement with a relative average concentration of oxygen vacancies of ∼3%, for which a semiconductor-to-metal transition was theoretically predicted. These tungsten suboxide nanostructures are prone to a wide range of applications in nanoelectronics. [ABSTRACT FROM AUTHOR]

Mastering the manipulation of the electron spin plays a crucial role in comprehending the behavior of organic materials in several applications, such as asymmetric catalysis, chiroptical switches, and electronic devices. A promising avenue for achieving such precise control lies in the Chiral Induced Spin Selectivity (CISS) effect, where electrons with a favored spin exhibit preferential transport through chiral assemblies of specific handedness. Chiral supramolecular polymers emerge as excellent candidates for exploring the CISS effect due to their ability to modulate their helical structure through noncovalent interactions. In this context, systems capable of responding to external stimuli are particularly intriguing, sometimes even displaying chirality inversion. This study unveils spin selectivity in chiral supramolecular polymers, derived from single enantiomers, through scanning tunneling microscopy conducted in scanning tunneling spectroscopy mode. Following two distinct sample preparation protocols for each enantiomer, we generate supramolecular polymers with opposite handedness and specific spin transport characteristics. Our primary focus centers on chiral π-conjugated building blocks, with the aim of advancing novel systems that can inspire the organic spintronics community from a supramolecular chemistry level. [ABSTRACT FROM AUTHOR]

Tunability of interfacial effects between two-dimensional (2D) crystals is crucial not only for understanding the intrinsic properties of each system, but also for designing electronic devices based on ultra-thin heterostructures. A prerequisite of such heterostructure engineering is the availability of 2D crystals with different degrees of interfacial interactions. In this work, we report a controlled epitaxial growth of monolayer TaSe2 with different structural phases, 1H and 1 T, on a bilayer graphene (BLG) substrate using molecular beam epitaxy, and its impact on the electronic properties of the heterostructures using angle-resolved photoemission spectroscopy. 1H-TaSe2 exhibits significant charge transfer and band hybridization at the interface, whereas 1 T-TaSe2 shows weak interactions with the substrate. The distinct interfacial interactions are attributed to the dual effects from the differences of the work functions as well as the relative interlayer distance between TaSe2 films and BLG substrate. The method demonstrated here provides a viable route towards interface engineering in a variety of transition-metal dichalcogenides that can be applied to future nano-devices with designed electronic properties.

Comprehensive Summary: Kagome lattices have garnered significant attention due to their promising applications in catalysis, electronics, and magnetics. Although many efforts have been paid to the design and synthesis of Kagome lattices, there is a limited focus on constructing this lattice by multiple interaction forces. In this work, we employ 2,7‐dibromo‐carbazole as precursors to successfully fabricate the two‐dimensional self‐assembly Kagome lattices stabled by multiple interaction forces on Au(111) substrate. Using low‐temperature scanning tunneling microscopy, non‐contact atomic force microscopy and density functional theory calculation, we visualize and identify the four interaction forces within Kagome lattices: Au—N coordination bonds, Au—H hydrogen bonds, Br—Br halogen bonds, and Br—H hydrogen bonds, respectively. This study provides a basic understanding for designing and constructing more complex Kagome lattices. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Carbohelicenes have garnered considerable attention for their inherent chirality and structural flexibility. Increasing multi‐helicity and incorporating non‐six‐membered rings to substitute benzenoid rings within helicenes are effective strategies for introducing unique photoelectric properties. Despite the disclosure of numerous helicenes, the inaccessible precursors and the lack of synthetic routes pose a challenge in achieving desired helicene structures fused with non‐benzenoid rings. Herein, we report the synthesis of multiple non‐benzenoid carbohelicenes fused with fluorene unit(s) through intramolecular cyclodehydrogenation of 9,10‐di(naphthalen‐1‐ yl)anthracene on Au(111) surface. Two potential cyclodehydrogenation manners between naphthyl and anthracene lead to the formation of fluorene‐fused [5]helicene and [4]helicene moiety. Consequently, a total of four stable products were observed. The atomic topographies of products are characterized by bond‐resolving scanning tunneling microscopy. The chiral helicity of targeted products can be switched by tip manipulation. Density‐functional‐theory calculations unveils the reaction pathway of four products. The comparative analysis of their respective energy barriers exhibits a correlation with the experimentally determined yields. Furthermore, we synthesize the polymer chains incorporating non‐benzenoid carbohelicenes via the Ullmann reaction of 2,6‐dibromo‐9,10‐di(1‐naphthyl)anthracene precursors. Our work proposes a synthetic methodology for several novel helicene‐like structures fused with fluorene units and the polymer bearing helicene subunits, thus highlighting the immense potential of these compounds in the application fields of luminescent electronic devices. [ABSTRACT FROM AUTHOR]

With rational designability, versatile tunability, and quantum coherence, molecular electron spin qubits could offer new opportunities for quantum information science, enabling simplified implementation of quantum algorithms and chemical‐specific quantum sensing. The development of these transformative technologies relies on coherent addressing of single molecular electron spin qubits with high initialization, manipulation, and readout fidelities. This is unfeasible to conventional electron spin resonance spectroscopy, which is widely used for coherent addressing of ensemble electron spins, due to its low initialization efficiency and readout sensitivity. Taking advantage of single spin detectability of single‐molecule spectroscopy, scanning tunneling microscopy, atomic force microscopy, and quantum metrology, several strategies have been developed to empower electron spin resonance spectroscopy with single qubit addressability. In this Emerging Topic, we introduce principles and technical implementation of strategies for coherent addressing of single molecular electron spin qubits, discuss their potential applicability in quantum technologies, and point out their challenges in terms of scalability, molecular design, and/or decoherence suppression. We discuss future directions to overcome these challenges and to improve single qubit addressing technologies, which will facilitate the advancement of molecular quantum information science. [ABSTRACT FROM AUTHOR]

A lateral expansion of molecular spoked wheels (MSWs) based on an all‐phenylene backbone is described. The MSWs contain a central hub, six spokes, and a rim that is formed by a sixfold Yamamoto coupling of the respective non‐cyclized dodecabromo precursor yielding MSWs with up to 30 phenylene rings in the perimeter. Attempts to prepare compounds of such size without flexible side groups at the spokes were unsuccessful, most probably due to an aggregation and accompanying oligomerization of the precursors during the cyclization. To overcome these problems, fluorene units are inserted into the spokes. These contain additional alkyl chains and lead to a curvature of the wheels. Quantum chemical calculations on the mechanism of the Yamamoto coupling lead to geometry and strain‐related criteria for the successful rim closure to the respective MSW. Subsequently, MSWs are prepared with four and even six phenylene units at each edge of the hexagonal wheels. The resulting MSWs are characterized by spectroscopic methods, and additionally some of them are visualized via scanning tunneling microscopy (STM). [ABSTRACT FROM AUTHOR]

Triangulenes as neutral radicals are becoming promising candidates for future applications such as spintronics and quantum technologies. To extend the potential of the advanced materials, it is of importance to control their electronic and magnetic properties by multiple graphitic nitrogen doping. Here, we synthesize triaza[5]triangulene on Au(111) by cyclodehydrogenation, and its derivatives by cleaving C−N bonds. Bond‐resolved scanning tunneling microscopy and scanning tunneling spectroscopy provided detailed structural information and evidence for open‐shell singlet ground state. The antiferromagnetic arrangement of the spins in positively doped triaza[5]triangulene was further confirmed by density function theory calculations. The key aspect of triangulenes with multiple graphitic nitrogen is the extra pz electrons composing the π orbitals, favoring charge transfer to the substrate and changing their low‐energy excitations. Our findings pave the way for the exploration of exotic low‐dimensional quantum phases of matter in heteroatom doped organic systems. [ABSTRACT FROM AUTHOR]

Thermally‐induced dehydrogenative coupling of polyphenylenes on metal surfaces is an important technique to synthesize π ${\pi }$ ‐conjugated carbon nanostructures with atomic precision. However, this protocol has rarely been utilized to fabricate structurally defined carbon nanosheets composed of sp‐ and sp2‐hybridized carbon atoms. Here, we present the synthesis of butadiyne‐linked hexabenzocoronenes (HBCs) on Au(111) surfaces as core‐expanded graphdiynes. The reaction started from hexa(4‐ethylphenyl)benzene, which undergoes dehydrogenation toward hexa(4‐vinylphenyl)benzene, followed by planarization to hexabenzocoronene, coupling between the vinyl groups, and further dehydrogenation. In addition to butadiyne linkages, benzene groups were also found as another type of linker. The reaction sequences were monitored by scanning tunneling microscopy and bond‐resolved non‐contact atomic force microscopy, which disclose the structures of intermediates and final products. In combination with density functional theory simulations, the key steps from ethyl substituents to butadiyne and benzene linkers were elucidated. This is a new on‐surface synthesis of core‐expanded graphdiynes with unprecedented electronic properties. [ABSTRACT FROM AUTHOR]

Enhanced electronic coupling gives rise to many intriguing properties in π–d conjugated metal–organic frameworks (CMOFs). By low-temperature scanning tunneling microscopy and density functional theory calculation, we investigate the electronic coupling in one-dimensional (1D) π–d conjugated FeQDI polymers. Our experiments have resolved the bulk and end states stemming from Fe atoms in different coordination environments and their spatial extension due to π–d conjugation. By fitting the band structure by Wannier functions in an energy range of −0.5 eV to 0 eV, the Fe–Fe, QDI–QDI and Fe–QDI hopping integrals are determined to be 15 meV, 121 meV and 24 meV, respectively. Our work provides experimental and theoretical insights into the electronic coupling in 1D CMOFs. [ABSTRACT FROM AUTHOR]

N‐Heterocyclic olefins (NHOs), possessing highly polarizable and remarkably electron‐rich double bonds, have been effectively utilized as exceptional anchors for surface modifications. Herein, the adsorption, orientation, and electronic properties of NHOs on a metal surface are investigated. On Cu(111), the sterically low‐demanding IMe‐NHO is compared to its analogous IMe‐NHC counterpart. High‐resolution electron energy‐loss spectroscopy (HREELS) measurements show for both molecules a flat‐lying ring adsorption configuration. While the NHC adopts a dimer configuration including a Cu adatom, the NHO chemisorbs over a C–Cu bond perpendicular to the surface. This distinct difference leads for the IMe‐NHOs to have a higher thermal stability on the surface. Moreover, IMe‐NHOs introduce a higher net electron transfer to the surface compared to the IMe‐NHCs, which results in a stronger effect on the work function. These results highlight the role of NHOs in surface science as they extend the functionalization capabilities of NHCs into stronger electronic modification. [ABSTRACT FROM AUTHOR]

This article explores the surface architecture formation on layered A3B6 semiconductors, such as In4Se3, InSe, and InTe, focusing on kinetics of surface roughness parameters, such as RMS, skewness and kurtosis, and power spectral density (PSD) under indium deposition studied through large-scale 1 × 1 µm2 and 150 × 150 nm2 scanning tunneling microscopy (STM) images analysis. Our findings reveal common kinetics of surface parameters across different crystals, suggesting fundamental similarities in their interface kinetics. Particularly, PSD analysis elucidates the role of low-frequency spatial structures, underscoring their significance in surface roughness kinetics to some extent independent of the specific layered crystal surface structure. [ABSTRACT FROM AUTHOR]

Multicentre redox metalloproteins undergo conformational changes on electrochemical surfaces, or on enzyme substrate binding. The two‐centre copper enzymes, laccase (Type I and TypeII/III Cu) and nitrite reductase (CuNIR) (Type I and Type II Cu) are examples. With some exceptions, these enzymes show no non‐turnover voltammetry on Au(111)‐surfaces modified by thiol based self‐assembled molecular monolayers, but dioxygen or nitrite substrate triggers strong electrocatalytic signals. Scanning tunnelling microscopy also shows high conductivity only when dioxygen or nitrite is present. Atomic force microscopy shows constant CuNIR height but pronounced structural expansion in the electrocatalytic range on nitrite binding. We have recently offered a rationale, based on ab initio quantum chemical studies of water/nitrite substitution in a 740‐atom CuNIR fragment. Presently we provide much more detailed structural assignment mapped to single‐residue resolution. NO2−‐binding induces both a 2 Å Cu−Cu distance increase, and pronounced frontier orbital delocalization strongly facilitating ET between the Cu regions. The conformational changes transmit from the catalytic Type II centre to the electron inlet Type I centre, via the His129‐Cys130 ligands, and via Type I–Cys130 or Type I‐His129 ending at Type II Asp92. The ET patterns are reflected in different atomic Mulliken charges in the water and nitrite CuNIR fragment. [ABSTRACT FROM AUTHOR]

Topological defects are ubiquitous, they manifest in a wide variety of systems such as liquid crystals, magnets or superconductors. The recent quest for non‐abelian anyons in condensed matter physics stimulates the interest for topological defects since they can be hosted in vortices in quantum magnets or topological superconductors. In addition to these vortex defects, this study proposes to investigate edge dislocations in 2D magnets as new building blocks for topological physics since they can be described as vortices in the structural phase field. It demonstrates the existence of higher order topological dislocations within the higher order moiré pattern of the van der Waals 2D magnet CrCl3 deposited on Au(111). Surprisingly, these higher order dislocations arise from ordinary simple edge dislocations in the atomic lattice of CrCl3. This study provide a theoretical framework explaining the higher order dislocations as vortices with a winding Chern number of 2. It is expected that these original defects can stabilize some anyons either in a 2D quantum magnet or within a 2D superconductor coupled to it. [ABSTRACT FROM AUTHOR]

Structural imperfections can be a promising testbed to engineer the symmetries and topological states of solid-state platforms. Here, we present direct evidence of hierarchical transitions of zero- (0D) and one-dimensional (1D) topological states in symmetry-enforced grain boundaries (GB) in 1T′–MoTe2. Using a scanning tunneling microscope tip press-and-pulse procedure, we construct two distinct types of GBs, which are differentiated by the underlying symmorphic and nonsymmorphic symmetries. The GBs with the nonsymmorphic rotation symmetry harbor first-order topological edge states protected by a nonsymmorphic band degeneracy. On the other hand, the edge state of the symmorphic GBs attains a band gap. More interestingly, the gapped edge state realizes a hierarchical topological phase, evidenced by the additional 0D boundary states at the GB ends. We anticipate our experiments will pioneer the material platform for the hierarchical realization of first-order and higher-order topology. Engineering topological states at defect sites in quantum materials is of great interest in condensed matter physics. Here, the authors demonstrate 0D and 1D topological states at symmetry-engineered grain boundaries in a 2D material. [ABSTRACT FROM AUTHOR]

Point defects in two-dimensional materials are of key interest for quantum information science. However, the parameter space of possible defects is immense, making the identification of high-performance quantum defects very challenging. Here, we perform high-throughput (HT) first-principles computational screening to search for promising quantum defects within WS2, which present localized levels in the band gap that can lead to bright optical transitions in the visible or telecom regime. Our computed database spans more than 700 charged defects formed through substitution on the tungsten or sulfur site. We found that sulfur substitutions enable the most promising quantum defects. We computationally identify the neutral cobalt substitution to sulfur ( Co S 0 ) and fabricate it with scanning tunneling microscopy (STM). The Co S 0 electronic structure measured by STM agrees with first principles and showcases an attractive quantum defect. Our work shows how HT computational screening and nanoscale synthesis routes can be combined to design promising quantum defects. Point defects in 2D semiconductors have potential for quantum computing applications, but their controlled design and synthesis remains challenging. Here, the authors identify and fabricate a promising quantum defect in 2D WS2 via high-throughput computational screening and scanning tunnelling microscopy. [ABSTRACT FROM AUTHOR]

Silicon surface alloys and silicide nanolayers are highly important as contact materials in integrated circuit devices. Here we demonstrate that the submonolayer Si/Ag(001) surface reconstruction, reported to exhibit interesting topological properties, comprises a quasi-one-dimensional Si-Ag surface alloy based on chains of planar double-pentagon Si moieties. This geometry is determined using a combination of density functional theory calculations, scanning tunnelling microscopy, and grazing incidence x-ray diffraction simulations, and yields an electronic structure in excellent agreement with photoemission measurements. This work provides further evidence of pentagonal geometries in 2D materials and heterostructures and elucidates the importance of surface alloying in stabilizing their formation. Using DFT simulations and STM measurements, the Si/Ag(001) surface reconstruction is revealed to be a Si-Ag surface alloy. Its atomic structure is composed of quasi-1D double-pentagon chains of silicon, electronically isolated by surface Ag atoms. [ABSTRACT FROM AUTHOR]

Nickel nanoparticles (Ni NPs) combined with carbon nanomaterials are of significant interest due to their wide range of applications, including catalysis, hydrogen storage, and sensor technologies. However, it is challenging to develop an efficient process to produce small and stable Ni NPs ideal for functionalizing graphene or substrates with complex geometries. For this purpose, a rapid, simple, and cost‐effective method is presented for synthesizing uniformly small Ni NPs. The process involves cooling aqueous solutions of Ni(OAc)2 and cetyltrimethylammonium bromide (CTAB) to ≈1 °C, followed by the rapid addition of NaBH4. Crucial parameters, such as temperature and stirring rate, are precisely controlled to ensure uniform particle growth, with the reaction completing in just a few minutes. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) characterizations reveal spherical NPs with an average diameter of ≈11 nm and a narrow size distribution. Additionally, epitaxial graphene (EG) samples are functionalized with the synthesized NPs and their arrangement on the surface and their stability upon thermal annealing are investigated. X‐ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) measurements demonstrate the degradation of CTAB, along with the recovery of Ni(0) under mild conditions (below 350 °C), with the NPs maintaining structural stability up to approximately 550 °C. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) systems have received a lot of attention due to their exotic physical phenomena such as quantization of conductance, Peierls instability, and Luttinger liquid behavior. Here, we present the synthesis of self-assembled quasi-1D bismuth (Bi) chains on an Au(111) substrate, highlighting their topological properties. Scanning tunneling microscopy and spectroscopy measurements reveal that the high-quality large area array is composed of Bi atomic chains with a bandgap of 0.5 eV. Density functional theory (DFT) calculations confirm the experimental observation and reveal the topological properties of the system, providing evidence of the spin texture of the Bi atomic chains. Our DFT results predict that a single Bi chain hosts exotic topological properties. The atomically precise synthesis of Bi atomic chains overcomes the limitation of the top-down approach toward integration of devices. The work sheds light on the realization of 1D system, providing a platform for further investigation into the intriguing physics in 1D systems. [ABSTRACT FROM AUTHOR]

Nearly four decades have passed since IBM scientists pioneered atomic force microscopy (AFM) by merging the principles of a scanning tunneling microscope with the features of a stylus profilometer. Today, electrical AFM modes are an indispensable asset within the semiconductor and nanotechnology industries, enabling the characterization and manipulation of electrical properties at the nanoscale. However, electrical AFM measurements suffer from reproducibility issues caused, for example, by surface contaminations, Joule heating, and hard‐to‐minimize tip drift and tilt. Using as experimental system nanoscale Schottky diodes assembled on oxide‐free silicon crystals of precisely defined surface chemistry, it is revealed that voltage‐dependent adhesion forces lead to significant rotation of the AFM platinum tip. The electrostatics‐driven tip rotation causes a strain gradient on the silicon surface, which induces a flexoelectric reverse bias term. This directional flexoelectric internal‐bias term adds to the external (instrumental) bias, causing both an increased diode leakage as well as a shift of the diode knee voltage to larger forward biases. These findings will aid the design and characterization of silicon‐based devices, especially those that are deliberately operated under large strain or shear, such as in emerging energy harvesting technologies including Schottky‐based triboelectric nanogenerators (TENGs). [ABSTRACT FROM AUTHOR]

Scanning tunneling spectroscopy (STS) and scanning tunneling microscopy (STM) are perhaps the most promising ways to detect the superconducting gap size and structure in the canonical unconventional superconductor Sr2RuO4 directly. However, in many cases, researchers have reported being unable to detect the gap at all in STM conductance measurements. Recently, an investigation of this issue on various local topographic structures on a Sr-terminated surface found that superconducting spectra appeared only in the region of small nanoscale canyons, corresponding to the removal of one RuO surface layer. Here, we analyze the electronic structure of various possible surface structures using first principles methods, and argue that bulk conditions favorable for superconductivity can be achieved when removal of the RuO layer suppresses the RuO4 octahedral rotation locally. We further propose alternative terminations to the most frequently reported Sr termination where superconductivity surfaces should be observed. [ABSTRACT FROM AUTHOR]

1D grain boundaries in transition metal dichalcogenides (TMDs) are ideal for investigating the collective electron behavior in confined systems. However, clear identification of atomic structures at the grain boundaries, as well as precise characterization of the electronic ground states, have largely been elusive. Here, direct evidence for the confined electronic states and the charge density modulations at mirror twin boundaries (MTBs) of monolayer NbSe2, a representative charge‐density‐wave (CDW) metal, is provided. The scanning tunneling microscopy (STM) measurements, accompanied by the first‐principles calculations, reveal that there are two types of MTBs in monolayer NbSe2, both of which exhibit band bending effect and 1D boundary states. Moreover, the intrinsic CDW signatures of monolayer NbSe2 are dramatically suppressed as approaching an isolated MTB but can be either enhanced or suppressed in the MTB‐constituted confined wedges. Such a phenomenon can be well explained by the MTB‐CDW interference interactions. The results reveal the underlying physics of the confined electrons at MTBs of CDW metals, paving the way for the grain boundary engineering of the functionality. [ABSTRACT FROM AUTHOR]

Dispersionless flat bands (FBs) in momentum space, given rise to electron destructive interference in frustrated lattices, offer opportunities to enhance electronic correlations and host exotic many‐body phenomena, such as Wigner crystal, fractional quantum hall state, and superconductivity. Despite successes in theory, great challenges remain in experimentally realizing FBs in frustrated lattices due to thermodynamically structural instability. Here, the observation of electronic FB in a potassium distorted colouring triangle (DCT) lattice is reported, which is supported on a blue phosphorene‐gold network. It is verified that the interaction between potassium and the underlayer dominates and stabilizes the frustrated structures. Two‐dimensional electron gas is modulated by the DCT lattice, and in turn results in a FB dispersion due to destructive quantum interferences. The FB exhibits suppressed bandwidth with high density of states, which is directly observed by scanning tunneling microscopy and confirmed by the first‐principles calculation. This work demonstrates that DCT lattice is a promising platform to study FB physics and explore exotic phenomena of correlation and topological matters. [ABSTRACT FROM AUTHOR]

Engineering Kondo lattice with tailored functionality is desirable for elucidating the heavy fermion physics. We realize the construction of an artificial Kondo lattice/superconductor heterojunction by growing monolayer VSe2 on bulk 2H-NbSe2 with molecular beam epitaxy. Spectroscopic imaging scanning tunneling microscopy measurements show the emergence of a new charge density wave (CDW) phase with 3 × 3 periodicity on the monolayer VSe2. Unexpectedly, a pronounced Kondo resonance appears around the Fermi level, and distributes uniformly over the entire film, evidencing the formation of Kondo lattice. Density functional theory calculations suggest the existence of magnetic interstitial V atoms in VSe2/NbSe2, which play a key role in forming the CDW phase along with the Kondo lattice observed in VSe2. The Kondo origin is verified from both the magnetic field and temperature dependences of the resonance peak, yielding a Kondo temperature of ~ 44 K. Moreover, a superconducting proximity gap opens on monolayer VSe2, whose shape deviates from the function of one-band BCS superconductor, but is reproduced by model calculations with heavy electrons participating the pairing condensate. Our work lays the experimental foundation for studying interactions between the heavy fermion liquids and the superconducting condensate. The authors observe a coherent Kondo lattice in a monolayer of VSe2 grown on a superconducting 2H-NbSe2 substrate. Superconductivity is established in the Kondo lattice through proximity effect from the substrate. [ABSTRACT FROM AUTHOR]

In a molecule formed by two atoms, energy difference between bonding and antibonding orbitals depends on distance between the two atoms. However, exploring molecular orbitals of two natural atoms with tunable distance has remained an outstanding experimental challenge. Graphene quantum dots can be viewed as relativistic artificial atoms, thus offering a unique platform to study molecular physics. Here, through scanning tunneling microscope, we create and directly visualize the formation process of relativistic artificial molecules based on two coupled graphene quantum dots with tunable distance. Our study indicates that energy difference between the bonding and antibonding orbitals of the lowest quasibound state increases linearly with inverse distance between the two graphene quantum dots due to the relativistic nature of the artificial molecule. For quasibound states with higher orbital momenta, the coupling between these states leads to half-energy spacing of the confined states because the length of the molecular-like orbit is approximately twice that of the atomic-like orbit. Evolution from ring-like whispering-gallery modes in the artificial atoms to figure-eight orbitals in the artificial molecules is directly imaged. The ability to resolve the coupling and orbitals of the relativistic artificial molecule at the nanoscale level yields insights into the behavior of quantum-relativistic matter. Graphene quantum dots have electronic structures resembling these of atoms. Here, the authors use two of these compounds to construct artificial molecules and study their electronic properties at tunable distances. [ABSTRACT FROM AUTHOR]

Monolayer MoTe2 exhibits a variety of derivative structural phases and associated intriguing electronic properties that enable a wealth of potential applications in future electronic and optoelectronic devices. However, a comprehensive study focusing on the complexities of the controllable phase evolution in this atomically thin film has yet to be performed. This work aims to address this issue by systematically investigating molecular beam epitaxial growth of monolayer Mo–Te compounds on bilayer graphene substrates. By utilizing scanning tunneling microscopy, we explored a series of thermally driven structural phase evolutions, including distinct T′-MoTe2, H-MoTe2, Mo6Te6 nanowires, and multistoichiometric MoTe2−x. Furthermore, we carefully investigated the critical effects of the growth parameters—annealing temperature and time and tellurium concentration—on the controllable and reversible phase transformation within monolayer MoTe2−x. The findings have significant implications for understanding the thin film synthesis and phase transformation engineering inherent to two-dimensional crystals, which can foster further development of high-performance devices. [ABSTRACT FROM AUTHOR]

Comprehensive Summary In on‐surface synthesis, dimers are typically utilized to explore reaction mechanisms or as intermediates in the formation of final products. However, constructing the innovative nanostructures with dimers as building blocks remains challenging. Here, using non‐planar 2,2′,7,7′‐tetrabromo‐9,9′‐biflurenyliden molecules, we have successfully synthesized dimeric covalent organic frameworks (COFs) on the Au(111) surface through a temperature‐controlled cascade reaction. Notably, the H‐H steric hindrance within precursors caused by double bonds leads to selective stepwise debromination during the thermal annealing, which promotes the dimerization through intermolecular Ullmann coupling and cyclodehydrogenation reaction to form COFs primarily constituted by dimer building blocks. Combining scanning tunneling microscopy/spectroscopy and density functional theory calculations, we have precisely confirmed the structural evolution and reaction mechanism. Furthermore, by introducing Ag adatoms to form C−Ag−C intermediates, we have successfully regulated the reaction path and synthesized one‐dimensional nanoribbons with dimers as building blocks. This work not only validates the strategy of synthesizing dimeric nanostructures on different surfaces through cascade reactions induced by precursor design, but also enriches the research field of surface synthesis of COFs and nanoribbons. [ABSTRACT FROM AUTHOR]

Monolayer MoTe2 exhibits a variety of derivative structural phases and associated intriguing electronic properties that enable a wealth of potential applications in future electronic and optoelectronic devices. However, a comprehensive study focusing on the complexities of the controllable phase evolution in this atomically thin film has yet to be performed. This work aims to address this issue by systematically investigating molecular beam epitaxial growth of monolayer Mo–Te compounds on bilayer graphene substrates. By utilizing scanning tunneling microscopy, we explored a series of thermally driven structural phase evolutions, including distinct T′-MoTe2, H-MoTe2, Mo6Te6 nanowires, and multistoichiometric MoTe2−x. Furthermore, we carefully investigated the critical effects of the growth parameters—annealing temperature and time and tellurium concentration—on the controllable and reversible phase transformation within monolayer MoTe2−x. The findings have significant implications for understanding the thin film synthesis and phase transformation engineering inherent to two-dimensional crystals, which can foster further development of high-performance devices. [ABSTRACT FROM AUTHOR]

Combinations of phosphorus with main group III, IV, and V elements are theoretically predicted to generate 2D binary phosphides with extraordinary properties and promising applications. However, experimental synthesis is significantly lacking. Here, a general approach for preparing 2D binary phosphides is reported using single crystalline surfaces containing the constituent element of target 2D materials as the substrate. To validate this, SnP3 and BiP, representing typical 2D binary phosphides, are successfully synthesized on Cu2Sn and bismuthene, respectively. Scanning tunneling microscopy imaging reveals a hexagonal pattern of SnP3 on Cu2Sn, while α‐BiP can be epitaxially grown on the α‐bismuthene domain on Cu2Sb. First‐principles calculations reveal that the formation of SnP3 on Cu2Sn is associated with strong interface bonding and significant charge transfer, while α‐BiP interacts weakly with α‐bismuthene so that its semiconducting property is preserved. The study demonstrates an attractive avenue for the atomic‐scale growth of binary 2D materials via substrate phase engineering. [ABSTRACT FROM AUTHOR]

The on‐surface synthesis of an isomer of undecacene, bearing two four‐membered rings and two para‐quinodimethane moieties, starting from a tetramethyl‐substituted diepoxy precursor, is presented. The transformation implies a thermal double deoxygenation followed by a stepwise double dehydrogenation reaction on the Au(111) surface, locally induced by inelastic tunneling electrons. This results in the transformation of para‐dimethylbenzene moieties into non‐aromatic para‐quinodimethanes. The structures and electronic properties of the intermediate and final products are investigated at the single molecule level with high spatial resolution, using both scanning tunneling microscopy/spectroscopy and non‐contact atomic force microscopy. The experimental results are supported by density functional theory calculations. [ABSTRACT FROM AUTHOR]

Tin‐based halide perovskite solar cells can be efficient and environmentally friendly substitutions to lead‐based halide perovskite solar cells, but they have a drawback due to oxidation from Sn2+ to Sn4+. Using vacuum deposition, epitaxially aligned CsSnBr3 ultrathin films are prepared on Au(111) and Au(100) and characterized with scanning tunneling microscopy (STM), low‐energy electron diffraction (LEED), and X‐ray photoelectron spectroscopy (XPS). By co‐evaporation of the precursor molecules CsBr and SnBr2, few monolayers of perovskite are obtained. On Au(111), CsSnBr3 grows in three differently oriented domains due to the hexagonal symmetry of the substrate. On Au(100), which has square symmetry, identical to CsSnBr3, but with about half the lattice constant of the perovskite, a (2×2) superstructure is observed. The perovskite is terminated with the (001) facet showing a square surface structure in agreement with density functional theory (DFT) calculations. Chemical analysis is performed in ultra‐high vacuum (UHV) conditions and no indication of a tin oxidation state higher than Sn2+ is found in the films. However, after exposure to air, rapid and severe changes in the films are observed, highlighting the importance of preparing tin perovskites in a controlled environment to maintain their stability and avoid oxidation‐related issues. [ABSTRACT FROM AUTHOR]

Advancements in the on-surface synthesis of atomically precise graphene nanostructures are propelled by the introduction of innovative precursor designs and reaction types. Until now, the latter has been confined to cross-coupling and cyclization reactions that involve the cleavage of specific atoms or groups. In this article, we elucidate how the migration of phenyl substituents attached to graphene nanoribbons can be harnessed to generate arrays of [18]-annulene pores at the edges of the nanostructures. This sequential pathway is revealed through a comprehensive study employing bond-resolved scanning tunneling microscopy and ab-initio computational techniques. The yield of pore formation is maximized by anchoring the graphene nanoribbons at steps of vicinal surfaces, underscoring the potential of these substrates to guide reaction paths. Our study introduces a new reaction to the on-surface synthesis toolbox along with a sequential route, altogether enabling the extension of this strategy towards the formation of other porous nanostructures. The on-surface synthesis of graphene nanoribbons typically relies on Ullmann polymerization followed by an internal cyclodehydrogenation. Here, following these two steps, the authors expand the synthetic protocol by adding controlled phenyl migration and intraribbon aryl-aryl dehydrogenative coupling to afford graphene nanoribbons with periodic arrays of [18]annulene pores at the edges. [ABSTRACT FROM AUTHOR]

The metal‐electrode interface is key to unlocking emergent behaviour in all organic electrified systems, from battery technology to molecular electronics. In the latter, interfacial engineering has enabled efficient transport, higher device stability, and novel functionality. Mechanoresistivity – the change in electrical behaviour in response to a mechanical stimulus and a pathway to extremely sensitive force sensors – is amongst the most studied phenomena in molecular electronics, and the molecule‐electrode interface plays a pivotal role in its emergence, reproducibility, and magnitude. In this contribution, we show that organometallic molecular wires incorporating a Pt(II) cation show mechanoresistive behaviour of exceptional magnitude, with conductance modulations of more than three orders of magnitude upon compression by as little as 1 nm. We synthesised series of cyclometalated Pt(II) molecular wires, and used scanning tunnelling microscopy – break junction techniques to characterise their electromechanical behaviour. Mechanoresistivity arises from an interaction between the Pt(II) cation and the Au electrode triggered by mechanical compression of the single‐molecule device, and theoretical modelling confirms this hypothesis. Our study provides a new tool for the design of functional molecular wires by exploiting previously unreported ion‐metal interactions in single‐molecule devices, and develops a new framework for the development of mechanoresistive molecular junctions. [ABSTRACT FROM AUTHOR]