Group V element analogues of graphene have attracted a lot attention recently due to their semiconducting band structures, which make them promising for next generation electronic and optoelectronic devices based on two-dimensional materials. Theoretical investigations predict high electron mobility, large band gaps, band gap tuning by strain, formation of topological phases, quantum spin Hall effect at room temperature, and superconductivity amongst others. Here, we report a successful formation of freestanding like monolayer arsenene on Ag(111). This was concluded from our experimental atomic and electronic structure data by comparing to results of our theoretical calculations. Arsenene forms a buckled honeycomb layer on Ag(111) with a lattice constant of 3.6 Å showing an indirect band gap of ~1.4 eV as deduced from the position of the Fermi level pinning.The isolation of two-dimensional (2D) carbon in the form of a single layer honeycomb structure (graphene) 1 was the starting point of today's intensive research on various 2D materials. In particular, the electronic properties, i.e., the high conductivity in combination with the linear dispersion of the -band, forming a Dirac cone, are highly interesting for applications in nanoelectronics 2 . However, this utilization of graphene is severely hampered by the lack of an intrinsic band gap, which it shares with graphene like structures of other group IV atoms, i.e., Si, Ge, and Sn 3 .

Engineering tunable graphene–semiconductor interfaces while simultaneously preserving the superior properties of graphene is critical to graphene-based devices for electronic, optoelectronic, biomedical, and photoelectrochemical applications. Here, we demonstrate this challenge can be surmounted by constructing an interesting atomic Schottky junction via epitaxial growth of high-quality and uniform graphene on cubic SiC (3C-SiC). By tailoring the graphene layers, the junction structure described herein exhibits an atomic-scale tunable Schottky junction with an inherent built-in electric field, making it a perfect prototype to systematically comprehend interfacial electronic properties and transport mechanisms. As a proof-of-concept study, the atomic-scale-tuned Schottky junction is demonstrated to promote both the separation and transport of charge carriers in a typical photoelectrochemical system for solar-to-fuel conversion under low bias. Simultaneously, the as-grown monolayer graphene with an extremely high conductivity protects the surface of 3C-SiC from photocorrosion and energetically delivers charge carriers to the loaded cocatalyst, achieving a synergetic enhancement of the catalytic stability and efficiency.

We report a study of structural and electronic properties of a germanium layer on Al(111) using scanning tunneling microscopy (STM), low energy electron diffraction and core-level photoelectron spectroscopy. Experimental results show that a germanium layer can be formed at a relatively high substrate temperature showing either (3×3) or (√7×√7)R±19.1° reconstructions. First-principles calculations based on density functional theory suggest an atomic model consisting of a strongly buckled (2×2) germanene layer, which is stable in two different orientations on Al(111). Simulated STM of both orientations fit nicely with experimental STM images and the Ge 3d core-level data decomposed into four components is consistent with the suggested model.

We have performed angle-and spin-resolved photoemission measurements on Fe 3 O 4 (0 0 1)/MgO(0 0 1). Despite intrinsic electron-lattice (polaron) interaction a Fe t 2g band dispersion is observed, as well as a Fermi surface. The states close to the Fermi level show a spin polarization up to −72% as measured with a 4.65 eV laser light. All the data can be simulated starting from GGA + U bulk band-structure calculations and taking into account the polaron and initial-state lifetime broadening involved in the photoemission process. This conciliates the electronic structure of Fe 3 O 4 with a band model and confirms the half-metallic nature of Fe 3 O 4 .

We report a study of the atomic and electronic structures of the ordered Ag 2 Ge surface alloy containing ⅓ monolayer of Ge. Low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and angle-resolved photoelectron spectroscopy (ARPES) data reveal a symmetry breaking of the expected Ý3 × Ý3 periodicity, which is established for other Ag 2 M alloys (M = Bi, Sb, Pb, and Sn). The deviation from a simple Ý3 × Ý3 structure manifests itself as a splitting of diffraction spots in LEED, as a striped structure with a 6× periodicity including a distortion of the local hexagonal structure in STM, and as a complex surface band structure in ARPES that is quite different from those of the other Ag 2 M alloys. These results are interesting in view of the differences in the atomic and electronic structures exhibited by different group IV elements interacting with Ag(111). Pb and Sn form Ý3 × Ý3 surface alloys on Ag(111), of which Ag 2 Pb shows a surface band structure with a clear spin-orbit split. Si and C form silicene and graphene structures, respectively, with linear band dispersions and the formation of Dirac cones as reported for graphene. The finding that Ag 2 Ge deviates from the ideal (Ý3 × Ý3) Ag 2 Sn and Ag 2 Pb surface alloys makes Ge an interesting "link" between the heavy group IV elements (Sn, Pb) and the light group IV elements (Si, C).

FinEstBeAMS (Finnish–Estonian Beamline for Atmospheric and Materials Sciences) is a multidisciplinary beamline constructed at the 1.5 GeV storage ring of the MAX IV synchrotron facility in Lund, Sweden. The beamline covers an extremely wide photon energy range, 4.5–1300 eV, by utilizing a single elliptically polarizing undulator as a radiation source and a single grazing-incidence plane grating monochromator to disperse the radiation. At photon energies below 70 eV the beamline operation relies on the use of optical and thin-film filters to remove higher-order components from the monochromated radiation. This paper discusses the performance of the beamline, examining such characteristics as the quality of the gratings, photon energy calibration, photon energy resolution, available photon flux, polarization quality and focal spot size.

The stacking order of multilayer graphene significantly influences its electronic properties. The rhombohedral stacking sequence is predicted to introduce a flat band, which has high density of states and the enhanced Coulomb interaction between charge carriers, thus possibly resulting in superconductivity, fractional quantum Hall effect, and many other exotic phases of matter. In this work, we comprehensively study the effect of the stacking sequence and interlayer spacing on the electronic structure of four-layer graphene, which was grown on a high crystalline quality 3C-SiC(111) crystal. The number of graphene layers and coverage were determined by low energy electron microscopy. First-principles density functional theory calculations show distinctively different band structures for ABAB (Bernal), ABCA (rhombohedral), and ABCB (turbostratic) stacking sequences. By comparing with angle-resolved photoelectron spectroscopy data, we can verify the existence of a rhombohedral stacking sequence and a nearly dispersionless electronic band (flat band) near the Fermi level. Moreover, we find that the momentum width, bandgap, and curvature of the flat-band region can be tuned by the interlayer spacing, which plays an important role in superconductivity and many other exotic phases of matter.

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