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Unraveling the Structural and Electronic Properties of Graphene/Ge(110)
摘要： The direct growth of graphene on a semiconducting substrate opens a new avenue for future graphene-based applications. Understanding the structural and electronic properties of the graphene on a semiconducting surface is key for realizing such structures; however, these properties are poorly understood thus far. Here, we provide an insight into the structural and electronic properties of graphene grown directly on a Ge(110) substrate. Our scanning tunneling microscopy (STM) study reveals that overlaying graphene on Ge(110) promotes the formation of a new Ge surface reconstruction, i.e., a (6 × 2) superstructure, which has been never observed for a bare Ge(110) surface. The electronic properties of the system exhibit the characteristics of both graphene and Ge. The differential conductance (dI/dV) spectrum from a scanning tunneling spectroscopy (STS) study bears a parabolic structure, corresponding to a reduction in the graphene Fermi velocity, with exhibiting additional peaks stemming from the p-orbitals of Ge. The density functional theory (DFT) calculations confirm the existence of surface states due to the p-orbitals of Ge.
关键词： density functional theory calculations,scanning tunneling microscopy,Ge(110),scanning tunneling spectroscopy,Graphene,Ge surface reconstruction
更新于2025-09-10 09:29:36
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Transport properties of Cu-AlF3-W and Cu-AlF3-Cu heterojunctions using STS measurements and a DFT-NEGF approach
摘要： To understand and to analyze the transport properties of different metal-insulator systems, we developed an experimental study of the electronic transport properties of AlF3 thin films deposited over a Cu(1 0 0) substrate, and a theoretical study to model systems composed by an AlF3 molecule between two metallic Cu(1 0 0)-W(1 0 0) and Cu(1 0 0)-Cu(1 0 0) electrodes with different geometries. The left common electrode is always a Cu(1 0 0) layer, meanwhile the right changing electrode, W(1 0 0) or Cu(1 0 0), in some cases is represented as a layer and in others as having a tip ending. Tunnelling current against voltage (I-V) characteristic curves have been obtained by Scanning Tunneling Spectroscopy (STS) measurements and computed using density functional theory (DFT) with the non equilibrium Green function method (NEGF) within a bias voltage range from ?2.5 to 5.0 V. The theoretical curves show low current values, in the order of 10?12 to 10?9, in good agreement with the I-V experimental curves in the same range. This reveals that breakdown response currents begin at higher voltages than 5.0 V. The transmission spectrum, total (DOS) and partial (PDOS) density of states are also presented being the transmission variations addressed in terms of the DOS.
关键词： Scanning Tunneling Spectroscopy (STS),Non Equilibrium Green Functions (NEGF),Scanning Tunneling Microscopy (STM),Electronic transport,AlF3 thin films
更新于2025-09-04 15:30:14
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Two distinct surface terminations of SrVO <sub/>3</sub> (001) ultrathin films as an influential factor on metallicity
摘要： Pulsed laser deposition-grown SrVO3 (001) ultrathin films on SrTiO3 (001) substrates were investigated by in situ low-temperature scanning tunneling microscopy and spectroscopy. SrVO3 (001) ultrathin films showed two distinct surface terminations. One termination was a ((√2 × √2)-R45° reconstruction as was previously observed for SrVO3 (001) thick films, while the other was a ((√5 × √5)-R26.6° reconstruction. Scanning tunneling spectroscopy revealed that the ((√2 × √2)-R45° surface shows a metallic electronic structure, whereas the ((√5 × √5)-R26.6° surface exhibits a significantly reduced density of states at the Fermi level. These results suggest that the surface reconstruction may be an important factor to influence metallicity in epitaxial ultrathin films of transition metal oxides.
关键词： ultrathin films,scanning tunneling microscopy,scanning tunneling spectroscopy,SrVO3,metallicity,surface terminations
更新于2025-09-04 15:30:14
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Atomic scale depletion region at one dimensional MoSe <sub/>2</sub> -WSe <sub/>2</sub> heterointerface
摘要： Lateral heterojunctions based on two dimensional (2D) transition metal dichalcogenides (TMDCs) potentially realize monolayer devices exploiting 2D electronic structures and the functions introduced by the presence of 1D heterointerfaces. Electronic structures of a lateral MoSe2-WSe2 junction have been unveiled using scanning tunneling microscopy and spectroscopy. A smooth and narrow depletion region exists despite a defect-rich heterointerface deviating from the preferred zigzag orientations of the TMDC lattice. From the characteristics of the depletion region, a high carrier concentration and high internal electric fields are inferred, offering to benefit designs of lateral TMDC devices.
关键词： depletion region,MoSe2-WSe2,heterointerface,scanning tunneling microscopy,scanning tunneling spectroscopy,TMDCs
更新于2025-09-04 15:30:14
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Heterodimer on MgO
摘要： We report on the magnetic properties of HoCo dimers as a model system for the smallest intermetallic compound of a lanthanide and a transition metal atom. The dimers are adsorbed on ultrathin MgO(100) films grown on Ag(100). New for 4f elements, we detect inelastic excitations with scanning tunneling spectroscopy and prove their magnetic origin by applying an external magnetic field. In combination with density functional theory and spin Hamiltonian analysis, we determine the magnetic level distribution, as well as sign and magnitude of the exchange interaction between the two atoms. In contrast to typical 4f ? 3d bulk compounds, we find ferromagnetic coupling in the dimer.
关键词： ferromagnetic coupling,heterodimer,density functional theory,spin excitations,scanning tunneling spectroscopy
更新于2025-09-04 15:30:14