Berlin 2012 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 41: Thermoelectric materials III: Heterostructures (Focused session – Organizers: Meyer, Heiliger)

DS 41.3: Vortrag

Freitag, 30. März 2012, 10:00–10:15, H 2032

Epitaxial growth and control of sodium content in Na_xCoO₂ thin films grown by pulsed laser deposition — •Sandra Hildebrandt, Philipp Komissinskiy, Marton Major, Wolfgang Donner, and Lambert Alff — Institut für Materialwissenschaft, Technische Universität Darmstadt, 64287 Darmstadt, Germany

A variety of interesting phenomena such as large thermoelectric power and (possibly) unconventional superconductivity of the water-intercalated compound are observed in sodium cobaltate Na_xCoO₂ depending on sodium content^1,2. We have grown c-axis oriented Na_xCoO₂ thin films on SrTiO₃(100) using pulsed laser deposition. The sodium stoichiometry of the films is controlled within 0.38 <x< 0.84 by varying the post-deposition annealing conditions in oxygen. Thus, low sodium content (x< 0.5) can be achieved without the commonly used chemical deintercalation of Na using a Br₂- (or I₂-) based solution. X-ray diffraction analysis demonstrates that the Na_xCoO₂ films grow in two twin domains rotated by 15 and 45 degrees relative to [100] SrTiO₃. After annealing for 15-20 minutes single-crystalline films are obtained with a full width at half maximum of the (002) reflection below 0.2 degrees.

1. I. Terasaki, Y. Sasago, and K. Uchinokura, Physical Review B 56, 12685 (1997).

2. K. Takada, H. Sakurai, E. Takayama-Muromachi, F. Izumi, R. A. Dilanian, and T. Sasaki, Nature 422, 53 (2003).

This study was supported by DFG through project AL560/6-1.