Magnetic anisotropy is essential for permanent magnets to maintain their magnetization along specific directions. Understanding and controlling the magnetic anisotropy on a single-molecule scale are challenging but of fundamental importance for the future's spintronic technology. Here, by using scanning tunneling microscopy (STM), we demonstrated the ability to control the magnetic anisotropy by tuning the ligand field at the single-molecule level.
View Article and Find Full Text PDFThe polymorphism of borophene makes it a promising system to realize tunable physical or chemical properties. Various pure borophene phases consisting of quasi-1D boron chains with different widths have been commonly obtained in experimental studies. Here, it is shown that, due to a substrate mediation effect, artificial long-range ordered phases of borophene consisting of different combinations of boron chains seamlessly joined together can be achieved on Ag(100).
View Article and Find Full Text PDFCreating and controlling the topological properties of two-dimensional topological insulators is essential for spintronic device applications. Here, we report the successful growth of bismuth homostructure consisting of monolayer bismuthene and single-layer black phosphorus-like Bi (BP-Bi) on the HOPG surface. Combining scanning tunneling microscopy/spectroscopy with noncontact atomic force microscopy, moiré superstructures with twist angles in the bismuth homostructure and the modulation of topological edge states of bismuthene were observed and studied.
View Article and Find Full Text PDFBreaking bonds selectively in molecules is vital in many chemistry reactions and custom nanoscale device fabrications. The scanning tunneling microscope (STM) has proved to be an ideal tool to initiate and view bond-selective chemistry at the single-molecule level, offering opportunities for the further study of the dynamics in single molecules on metal surfaces. We demonstrate H─HS and H─S bond breaking on Au(111) induced by tunneling electrons using low-temperature STM.
View Article and Find Full Text PDFTwo-dimensional boron (borophene) features structural polymorphs and distinct in-plane anisotropy, opening opportunities to achieve tailored electronic properties by intermixing different phases. Here, using scanning tunneling spectroscopy combined with first-principles calculations, delocalized one-dimensional nearly free electron states (NFE) in the (2,3) or β borophene sheet on the Ag(111) surface were observed. The NFE states emerge from a line defect in borophene, manifested as a structural unit of the (2,2) or χ sheet, which creates an in-plane potential well that shifts the states toward the Fermi level.
View Article and Find Full Text PDFTwo-dimensional (2D) materials consisting of heavy atoms with particular arrangements may host exotic quantum properties. Here, we report a unique 2D semiconducting binary compound, a Sn_{2}Bi atomic layer on Si(111), in which hexagons are formed by bonding Bi with a triangular network of Sn. Because of the unique honeycomb configuration, the heavy elements, and the energy-dependent hybridization between Sn and Bi, 2D Sn_{2}Bi not only shows strong spin-orbit coupling effects but also exhibits high electron-hole asymmetry: Nearly free hole bands and dispersionless flat electron bands coexist in the same system.
View Article and Find Full Text PDFTwo-dimensional surface structures often host a surface state in the bulk gap, which plays a crucial role in the surface electron transport. The diversity of in-gap surface states extends the category of two-dimensional systems and gives us more choices in material applications. In this article, we investigated the surface states of β-√3 × √3-Bi/Si(111) surface by scanning tunneling microscopy.
View Article and Find Full Text PDFThe atomic structures of self-assembled silicon nanoribbons and magic clusters on Ag(110) substrate have been studied by high-resolution noncontact atomic force microscopy (nc-AFM) and tip-enhanced Raman spectroscopy (TERS). Pentagon-ring structures in Si nanoribbons and clusters have been directly visualized. Moreover, the vibrational fingerprints of individual Si nanoribbon and cluster retrieved by subnanometer resolution TERS confirm the pentagonal nature of both Si nanoribbons and clusters.
View Article and Find Full Text PDFWe report the successful preparation of a purely honeycomb, graphene-like borophene, by using an Al(1 1 1) surface as the substrate and molecular beam epitaxy (MBE) growth in ultrahigh vacuum. Scanning tunneling microscopy (STM) images reveal perfect monolayer borophene with planar, non-buckled honeycomb lattice similar as graphene. Theoretical calculations show that the honeycomb borophene on Al(1 1 1) is energetically stable.
View Article and Find Full Text PDFSome two-dimensional liquid systems are theoretically predicted to have an anomalous phase transition due to unique intermolecular interactions, for example the first-order transition between two-dimensional high-density water and low-density amorphous ice. However, it has never been experimentally observed, to the best of our knowledge. Here we report an entropy-driven phase transition between a high-density liquid crystal and low-density crystalline solid, directly observed by scanning tunneling microscope in carbon monoxide adsorbed on Cu(111).
View Article and Find Full Text PDF