Silicene, a honeycomb lattice of silicon, presents a particular case of allotropism on Ag(111). Silicene forms multiple structures with alike in-plane geometry but different out-of-plane atomic ...buckling and registry to the substrate. Angle-resolved photoemission and first-principles calculations show that these silicene structures, with (4×4), (√13×√13)R13.9°, and (2√3×2√3)R30° lattice periodicity, display similar electronic bands despite the structural differences. In all cases the interaction with the substrate modifies the electronic states, which significantly differ from those of free-standing silicene. Complex photoemission patterns arise from surface umklapp processes, varying according to the periodicity of the silicene allotropes.
By means of angle-resolved photoemission spectroscopy (ARPES) measurements, we unveil the electronic band structure of three-dimensional PbBi6Te10 topological insulator. ARPES investigations evidence ...multiple coexisting Dirac surface states at the zone-center of the reciprocal space, displaying distinct electronic band dispersion, different constant energy contours, and Dirac point energies. We also provide evidence of Rashba-like split states close to the Fermi level, and deeper M- and V-shaped bands coexisting with the topological surface states. The experimental findings are in agreement with scanning tunneling microscopy measurements revealing different surface terminations according to the crystal structure of PbBi6Te10. Our experimental results are supported by density functional theory calculations predicting multiple topological surface states according to different surface cleavage planes.
The composition of 75V2O5-(25 – x)MgO-(x)Na2O with x = 0, 1.5, 3.0, 4.5, 6.0, 9.0, and 12 is synthesized by the melt quench technique. The prepared samples were characterized by the X-ray ...diffraction (XRD) method. XRD pattern of 75V2O5-25MgO confirmed the glass formation. The addition of Na2O converted glass into a glass ceramic/ceramics. The density shows no trend with the Na2O content in the glass compositions. Differential thermal analysis confirmed the glassy nature of the x = 0 sample. For all samples, the conductivity variation as a function of the temperature follows an Arrhenius relationship. The highest conductivity is found for the x = 12 sample, i.e., 10–2 S/cm at 250 °C with better thermal stability. The developed samples can find applications as cathode materials in Mg- or Na-based batteries due to good conductivity with better thermal and structural stability.
The disorder can exert a dominant impact on correlated and quantum materials, resulting in unique behaviors that lack clear analogies in pristine conditions. In high entropy materials, the presence ...of multiple elements introduces a high atomic level disorder and gives rise to unique properties. In this paper, we have utilized the novel high entropy route to synthesize a new tetragonal high entropy spinel material (Fe0.2Co0.2Ni0.2Cu0.2Zn0.2)Mn2O4. Despite high disorder, the magnetic investigations demonstrate a complex magnetic behavior with a ferrimagnetic-type transition at 150 K. An unusually high value of coercivity (1.1 T) and high magnetic frustration is observed here. Additionally, an element-sensitive synchrotron-based X-ray absorption spectroscopy has been utilized to discern its local geometric and electronic structure.
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Ag growth on the Ag2Bi Rashba alloy Mahatha, Sanjoy Kr; Sheverdyaeva, Polina M.; Carbone, Carlo ...
Surface science,
September 2022, 2022-09-00, 20220901, Letnik:
723
Journal Article
Recenzirano
•Photoemission spectroscopy is used to explore the stability of the Ag2Bi alloy upon Ag deposition.•Most of the Bi atoms migrate to the surface of deposited Ag and retain the original embedded local ...coordination.•The long-range order of the Ag2Bi domains worsens pronouncedly as a function of the Ag thickness.
Multilayer structures comprising Bi/Ag bilayers display spin-charge conversion, a phenomenon of interest in spintronics whose origin (inverse Rashba-Edelstein vs. inverse spin Hall effects) is still debated. The Bi/Ag interfaces are assumed to be stable in model calculations, but the experimental determination of their structural properties is missing. Here, we explore by photoemission spectroscopy the stability and electronic structure of a Bi/Ag interface with strong Rashba interaction. We saturate the surface of a Ag(111) crystal with the Ag2Bi alloy, which presents surface-embedded Bi atoms and characteristic Rashba-split surface states, and deposit Ag layers on top of it at room temperature. The intensity of the Rashba-split bands weakens sizably after the deposition of few Ag monolayers, although most of the Bi atoms segregate at the surface and retain the original local coordination. These findings are consistent with the surfactant behavior of Bi atoms, which favors a layer-by-layer Ag growth without preserving the long-range order of the Ag2Bi alloy. They also suggest the need of detailed chemical and structural analysis for an accurate description of Bi/Ag bilayers.
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Tuning the ambipolar behavior in charge carrier transport via defect-engineering is crucial for achieving high mobility transistors for nonlinear logic circuits. Here, we present the electric-field ...tunable electron and hole transport in a microchannel device consisting of highly air-stable van der Waals (vdW) noble metal dichalcogenide (NMDC), PdSe2, as an active layer. Pristine bulk PdSe2 constitutes Se surface vacancy defects created during the growth or exfoliation process and offers ambipolar transfer characteristics with a slight electron dominance recorded in field-effect transistor (FET) characteristics showing an ON/OFF ratio <10 and electron mobility ∼21 cm2/(V·s). However, transfer characteristics of PdSe2 can be tuned to a hole-dominated transport while using hydrochloric acid (HCl) as a p-type dopant. On the other hand, the chelating agent EDTA, being a strong electron donor, enhances the electron-dominance in PdSe2 channel. In addition, p-type behavior with a 100 times higher ON/OFF ratio is obtained while cooling the sample down to 10 K. Low-temperature angle-resolved photoemission spectroscopy resembles the p-type band structure of PdSe2 single crystal. Also, first principle density functional theory calculations justify the tunability observed in PdSe2 as a result of defect-engineering. Such a defect-sensitive ambipolar vdW architecture may open up new possibilities toward future CMOS (Complementary Metal-Oxide-Semiconductor) device fabrications and high performance integrated circuits.
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