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Spin splitting in EuO(111)/Si(111) spin-filter tunnel junctions with atomically sharp interface
摘要： We demonstrate the tunneling in spin-split barriers made of ferromagnetic EuO grown on Si(111) substrates by molecular beam epitaxy. For 6 nm thick EuO films with high crystal quality and atomically sharp interfaces, we find a barrier height lowering driven by the spin splitting below the Curie temperature of 35 K. We determined the splitting energy to be 0.56 + 0.03 eV at 20 K which results in a spin polarization above 90%.
关键词： molecular beam epitaxy,atomically sharp interface,EuO(111)/Si(111),spin splitting,spin-filter tunnel junctions
更新于2025-09-04 15:30:14
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Quantitative determination of a model organic/insulator/metal interface structure
摘要： By combining X-ray photoelectron spectroscopy, X-ray standing waves and scanning tunneling microscopy, we investigate the geometric and electronic structure of a prototypical organic/insulator/metal interface, namely cobalt porphine on monolayer hexagonal boron nitride (h-BN) on Cu(111). Specifically, we determine the adsorption height of the organic molecule and show that the original planar molecular conformation is preserved in contrast to the adsorption on Cu(111). In addition, we highlight the electronic decoupling provided by the h-BN spacer layer and find that the h-BN–metal separation is not significantly modified by the molecular adsorption. Finally, we find indication of a temperature dependence of the adsorption height, which might be a signature of strongly-anisotropic thermal vibrations of the weakly bonded molecules.
关键词： hexagonal boron nitride,X-ray standing waves,X-ray photoelectron spectroscopy,cobalt porphine,Cu(111),scanning tunneling microscopy,organic/insulator/metal interface
更新于2025-09-04 15:30:14
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Growth of Millimeter-Sized Graphene Single Crystals on Al <sub/>2</sub> O <sub/>3</sub> (0001)/Pt(111) Template Wafers Using Chemical Vapor Deposition
摘要： The synthesis of graphene using chemical vapor deposition on platinum surfaces is discussed. The crystalline nature of the platinum substrates as well as the graphene growth conditions play a key role to yield monolayer graphene with low defectivity. The need for template wafers with a single Pt orientation emerges due to graphene overgrowth on untextured polycrystalline Pt foils. Single-crystalline Pt foils can be obtained after long annealing steps. However, these Pt foils remain rough and are therefore less suitable during subsequent graphene transfer procedures. On the other hand, highly oriented platinum thin films avoid the overgrowth issues but result in differing nucleation phenomena on different oriented grains. An optimized graphene growth template is found in Al2O3(0001)/Pt(111), which is more than one order of magnitude flatter compared to the annealed Pt(111) foils and serves as an ideal catalyst to grow graphene grains exceeding 7 mm in diameter.
关键词： chemical vapor deposition,single crystals,platinum,Al2O3(0001)/Pt(111),graphene
更新于2025-09-04 15:30:14
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Building two-dimensional metal–organic networks with tin
摘要： We show that Sn atoms combined with organic ligands can be used to build 2D coordination networks on Au(111) surfaces. The use of metal–organic bonding has been recognized as a powerful strategy for the generation, directly on solid surfaces, of 2D modular functional materials with potential application in catalysis, organic electronics, and magnetism. This has lead to the important progress observed in recent years in the engineering of a great variety of surface-supported 2D metal–organic networks (MONs). In this Communication, we report the first example of a surface-confined Sn-based MON. With only a few studies of surface-supported MONs based on p-block metals reported in the literature, the possibilities of building modular 2D MONs based on this group of metals remains almost unexplored to date. Tin, with formal oxidation states 2 and 4, forms a large diversity of metal–organic compounds (organotin compounds) which have a wide range of applications ranging from all sorts of biological activity to industrial catalytic processes. Organotin compounds have also attracted the attention of the condense-matter community, especially since stanene-cyanide was proposed as a candidate topological-insulator material. We thus investigated the synthesis, directly on Cu(100) and Au(111) surfaces, of Sn-based MONs using 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules as ligands.
关键词： Au(111) surfaces,TCNQ molecules,2D coordination networks,Sn-based MON,metal–organic bonding
更新于2025-09-04 15:30:14
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Features of the Initial Stage of GaN Growth on Si(111) Substrates by Nitrogen-Plasma-Assisted Molecular-Beam Epitaxy
摘要： The results of investigations of the effect of the initial conditions (nitridation of the Si(111) substrate, the GaN growth temperature, and the stoichiometry of GaN growth) on the growth kinetics and the GaN/Si(111)-layer polarity under nitrogen-plasma-assisted molecular-beam epitaxy are presented. It is experimentally established that the optimal initial condition for GaN epitaxy on Si(111) substrates is high-temperature nitridation of the Si(111) substrate carried out immediately before GaN growth. It is shown that it is possible to control the polarity of GaN by means of appropriate choice of the growth under conditions with N or Ga enrichment at the initial stage of GaN/Si(111) epitaxy.
关键词： GaN,polarity,Si(111),nitridation,molecular-beam epitaxy
更新于2025-09-04 15:30:14