Coexistence of Rocksalt and Wurtzite Structure in Nanosized CoO Films

W. Meyer, D. Hock, K. Biedermann, M. Gubo, S. Müller, L. Hammer, and K. Heinz

Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany

(Received 25 April 2008; published 3 July 2008)

Cobalt oxide (CoO) films epitaxially grown on Ir(100) in (111) orientation were investigated by means of quantitative low-energy electron diffraction and scanning tunneling microscopy. We find with high crystallographic precision that in the bulk of the films the rocksalt structure prevails while near the surface there is a switch towards the wurtzite structure. As a consequence, nanosized CoO cannot be considered as a single structural phase. The film surfaces prove to be metallic, apparently connected with polarity compensation.