Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 31: Surface Magnetism / Magnetic Imaging II
MA 31.13: Vortrag
Donnerstag, 25. März 2010, 18:30–18:45, H23
Wurtzite-type CoO nanocrystals in ultrathin ZnCoO films observed by surface x-ray diffraction — •Meyerheim H. L.1, Tusche C.1, Ernst A.1, Ostanin S.1, Maznichenko I.2, Mohseni K.1, Jedrecy N.3, Zegenhagen J.4, Roy J.4, Mertig I.2, and Kirschner J.1 — 1MPI f. Mikrostrukturphysik, Halle, Germany — 2Institut f. Physik, Martin-Luther-Univ. Halle-Wittenberg, Halle, Germany — 3INSP, Université P. et M. Curie-Paris 6 and CNRS-UMR7588, Paris, France — 4ESRF, B.P. 220, Grenoble, France
We present a surface x-ray diffraction study on 2-5 monolayer thick Co-doped (25 at. %) ZnO-films deposited on Ag(111) by pulsed laser deposition to study the arrangement of the Co-atoms within the ZnO host in the ultrathin film limit [1]. The film structure is dramatically different from a random alloy commonly assumed: Wurtzite (WZ) type CoO nanocrystals are coherently embedded within the ZnO host. In contrast to the WZ-CoO nanoislands, ZnO adopts the hexagonal Boron-Nitride (h-BN) type structure within the first layers next to the Ag(111) surface. In the h-BN structure the metal atoms are surrounded by O-atoms in a planar trigonal coordination, whereas in the WZ-structure the metal atoms are tetrahedrally coordinated. Our study supports the proposed phase separation model to explain the weak ferromagnetic signatures of doped ZnO films and other systems [2]. [1] H. L. Meyerheim, C. Tusche, A. Ernst, S. Ostanin, I.V. Maznichenko, K. Mohseni, N. Jedrecy, J. Zegenhagen, J. Roy, I. Mertig, and J. Kirschner, Phys. Rev. Lett. 102, 156102 (2009); [2] T. Dietl, T. Andrearczyk, A. Lipinska, M. Kiecana, M. Tay, and Y. Wu, Phys. Rev. B 76, 155312 (2007);