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- Cavar, Elizabeta, et al.
(författare)
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A single h-BN layer on Pt(111)
- 2008
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 602:9, s. 1722-1726
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Tidskriftsartikel (refereegranskat)abstract
- The structure and formation of an ultrathin hexagonal boron nitride (h-BN) film on Pt(111) has been studied by a combination of scanning tunneling microscopy, low energy electron diffraction, low energy electron microscopy, X-ray absorption and high resolution core level spectroscopy. The study shows that a single boron nitride layer is formed on Pt(111), resulting in a coincidence structure. High resolution scanning tunneling microscopy (STM) images of the h-BN ultrathin film display only one of the atomic species in the unit cell. Probing the boron and nitrogen related local density of states by near edge X-ray absorption fine structure measurements we conclude that the nitrogen sublattice is visible in STM images. The growth of the single hexagonal boron nitride layer by vapourized borazine in the pressure range of 1 x 10(-6)-1 x 10(-8) at 800 degrees C is further studied by low energy electron microscopy, and reveals that the number of nucleation sites and the perfection of the growth is strongly pressure dependent. A model for the single, hexagonal, boron nitride layer on Pt(111) is proposed.
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| 3. |
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| 4. |
- Ouattara, Lassana, et al.
(författare)
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GaAs/AlGaAs nanowire heterostructures studied by scanning tunneling microscopy
- 2007
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 7:9, s. 2859-2864
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Tidskriftsartikel (refereegranskat)abstract
- We directly image the interior of GaAs/AlGaAs axial and radial nanowire heterostructures with atomic-scale resolution using scanning tunneling microscopy. We show that formation of monolayer sharp and smooth axial interfaces are possible even by vapor-phase epitaxy. However, we also find that instability of the ternary alloys formed in the Au seed fundamentally limits axial heterostructure control, inducing large segment asymmetries. We study radial core-shell nanowires, imaging even ultrathin submonolayer shells. We demonstrate how large twinning-induced morphological defects at the wire surfaces can be removed, ensuring the formation of wires with atomically flat sides.
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| 5. |
- Preobrajenski, Alexei, et al.
(författare)
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Influence of chemical interaction at the lattice-mismatched h-BN∕Rh(111) and h-BN∕Pt(111) interfaces on the overlayer morphology
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:24, s. 245412-
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Tidskriftsartikel (refereegranskat)abstract
- The atomic and electronic structure of the lattice-mismatched h-BN/Pt(111) and h-BN/Rh(111) interfaces formed by pyrolitic reactions with vaporized borazine has been studied by low-energy electron diffraction, scanning tunneling microscopy, x-ray-absorption spectroscopy, and core-level and valence-band photoemission. It has been found that on Pt(111), h-BN forms a nearly flat monolayer, insignificantly corrugated across the supercell. On Rh(111), h-BN grows in form of a nanomesh, as originally observed by Corso [Science 303, 217 (2004)]. The structural difference between the h-BN/Pt(111) and h-BN/Rh(111) interfaces is associated with the strength of chemical interaction between h-BN and the substrate surface. A stronger orbital hybridization on Rh(111) results in a stronger attraction of the monolayer to the metal surface at favorable adsorption sites resulting in a highly corrugated structure (nanomesh). It has been shown that the electronic structure of the outer (elevated) and inner (attracted to the surface) nanomesh sites is very different as a result of different chemical bonding to the substrate (weak and strong, respectively).
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| 6. |
- Williams, H., et al.
(författare)
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Density functional theory with hybrid functionals applied to defects in GaAs surfaces: Effect of doping
- 2008
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 78:20
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Tidskriftsartikel (refereegranskat)abstract
- We have analyzed the influence of a Ga vacancy on electronic properties of GaAs(110) by scanning tunneling microscopy (STM), ab initio electronic structure simulations based on density functional theory with Perdew-Becke-Ernzerhof and Heyd-Scuseria-Ernzerhof functionals and STM simulations. We find that the HSE03 functional improves the description of the band gap of the semiconductor surface in line with recent bulk simulations. The inclusion of doping in the crystal significantly affects the position of the band gap in the electronic structure and the signature of the defect. The simulated STM images show good correlation with the main features of the experimental images only for hybrid-functional simulations and only if the effects of doping and band bending are included in the description.
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