K. Hricovini

Resonant photoemission and XMCD on Mn-based systems

Abstract We report results obtained by resonant photoemission (RPE) and X-ray magnetic circular dichroism (XMCD) in absorption with photon energies around the L 2/3 edges of manganese. The samples contain manganese in different environments and details about the dynamics of electronic structure on one side, magnetic structure on the other side are being discussed. We will present studies on the following samples: submonolayers of Mn on Cu(100), Mn in InAs and thin films of the manganese perovskite LSMO.

Quasi 1D structures at the Bi/InAs(100) surface

Thin Bi films are interesting candidates for spintronic applications due to a large spin-orbit splitting that, combined with the loss of inversion symmetry at the surface, results in a band structure that is not spin-degenerate. In recent years, applications for topological insulators based on Bi and Bi alloys have as well attracted much attention. Here we present ARPES studies of Bi/InAs(100) interface. Bismuth deposition followed by annealing of the surface results in the formation of one full Bi monolayer decorated by Bi-nanolines. We found that the building up of the interface does affect the electronic structure of the substrate. As a consequence of weak interaction, bismuth states are placed in the gaps of the electronic structure of InAs(100). We observe a strong resonance of the Bi electronic states close to the Fermi level; its intensity depends on the photon energy and the photon polarization. These states show nearly no dispersion when measured perpendicular to the nanolines, confirming their one-dimensionality.

Electronic structure of organic titanium bis-phthalocyanine on InAs(001)4

We investigated the electronic structure of ultra thin interface of organic titanium bis-phthalocyanine TiPc 2 deposited on InAs(001)(4 x 2)c-(8 x 2) clean surface, by means of high-resolution core-levels and valence band (VB) photoelectron spectroscopies. In4d, As3d, and Cls core levels were measured for different TiPc 2 thicknesses up to 1 monolayer. Surface core level shifts were found on both In4d andAs3d core levels. These shifts originate from the interaction between 4 x 2-c(8 x 2) InAs reconstruction and organic molecules suggesting the presence of strong bounds. C1 core level exhibits a line shape attributed to the C-C and C-N bonds. The VB spectroscopy shows dramatic changes related to the interaction of the TiPc 2 molecule with the InAs related surface states.

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Highly ordered array of quantum stripes are obtained on In-terminated InAs(001) reconstructed surface. We report the investigation of clean In-terminated InAs(OO1)(4x2)-c(8x2), and InAs(001)-(4x4) surfaces by low electron energy diffraction (LEED) and by high-resolution angle-resolved photoemission spectroscopy (ARPES). Monitoring the InAs(001) surface by LEED as a function of the substrate temperature, the -(4x4) and the -4x2(8x2) reconstructions were observed. ARPES measurements on both reconstructions show electronic states belonging to the In-stripes, which appear on the surface after the annealing treatment. These states are non-dispersive as a function of photon energy and in the case of 4x2-c(8x2) reconstruction the k-dispersion exists only along the [011] stripes direction, at variance on c(4x4s) surface the states have a fix energy.