Dresden 2006 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

HL: Halbleiterphysik

HL 14: II-VI semiconductors I

HL 14.9: Talk

Tuesday, March 28, 2006, 13:00–13:15, POT 151

Thickness dependent magnetoresistance of ZnCoO:Al thin films — •Qingyu Xu, Lars Hartmann, Heidemarie Schmidt, Holger Hochmuth, Michael Lorenz, Rüdiger Schmidt-Grund, Daniel Spemann, and Marius Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstrasse 5, D-04103 Leipzig, Germany

Zn_0.90Co_0.10O films doped with 0.5 at% Al of different thickness (689 nm, 408 nm, 355 nm) were prepared by pulsed laser deposition (PLD) on a-plane sapphire substrates. The room temperature electron concentration and mobility increase from 2× 10¹⁸ cm⁻³ and 12 cm²V⁻¹s⁻¹ to 2× 10¹⁹ cm⁻³ and 36 cm²V⁻¹s⁻¹ with increasing film thickness, respectively. Magnetoresistance (MR) effects were measured in the temperature range from 5 K to 290 K. At low temperature, the positive MR increases with decreasing film thickness. With increasing temperature, the MR of the thicker film will change to negative, while positive MR was still observed for the 355 nm thick film at room temperature. Anomalous Hall effect (AHE) provides information about the Co-generated internal field experienced by itinerant carriers. AHE was observed in the 355 nm thick film at 20 K, indicating possible intrinsic ferromagnetism in Zn_0.90Co_0.10O. The observed thickness dependence of the MR suggests that structural defects may play an important role in the ferromagnetism of ZnCoO:Al thin films.