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DS: Fachverband Dünne Schichten

DS 54: Nanoengineered Thin Films

DS 54.5: Talk

Thursday, March 17, 2011, 19:00–19:15, GER 38

(contribution withdrawn) Sodium engineering in multifunctional Na_xCoO₂ thin films grown by pulsed laser deposition — •Sandra Hildebrandt¹, Ingo Fritsch², Dirk Becker¹, Philipp Komissinskiy¹, Hanns-Ulrich Habermeier², Wolfram Jaegermann¹, and Lambert Alff¹ — ¹Institut für Materialwissenschaft, TU Darmstadt, Petersenstr. 23, 64287 Darmstadt, Germany — ²Max Planck Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart, Germany

We report on the growth of Na_xCoO₂ thin films by pulsed laser deposition. The sodium content in as grown films is always about x=0.6. By annealing, x can be varied between 0.58 and 0.77. Further Na deintercalation down to x=0.35 is achieved by chemical treatment of the film with a bromine solution. In the presence of water, a phase mixture of Na_0.35CoO₂ and Na_0.35CoO₂·0.9H₂O is obtained. This can be transformed into the superconducting compound Na_0.35CoO₂·1.3H₂O by subsequent water intercalation [1]. The Na_xCoO₂ films with higher sodium content (0.6<x<1) have typical resistivities of about 7 mΩcm at room temperature. This material already known for its large thermoelectric power, now comes in the focus as substitutional material for Li_xCoO₂ in solid state batteries. A high sodium ion conductance still has to be confirmed. We would like to acknowledge the financial support from DFG-Project AL560/6-1.

[1] Y. Krockenberger, I. Fritsch, G. Christiani, H.-U. Habermeier, Li Yu, C. Bernhard, B. Keimer, and L. Alff. Appl. Phys. Lett. 88, 162501 (2006).