UV optical properties of ferromagnetic Mn-doped ZnO thin films grown by PLD Mariana Diaconu a , Heidemarie Schmidt a, * , Holger Hochmuth a , Michael Lorenz a , Gabriele Benndorf a ,Jfrg Lenzner a , Daniel Spemann a , Annette Setzer a , Karl-Wilhelm Nielsen b , Pablo Esquinazi a , Marius Grundmann a a Universita ¨t Leipzig, Institut fu ¨r Experimentelle Physik II, Abteilung Halbleiterphysik, Linne ´strasse 5, 04103 Leipzig, Germany b Walther-Meigner-Institut fu ¨r Tieftemperaturforschung, Bayerische Akademie der Wissenschaften, Walther-Meigner-Str. 8, 85748 Garching, Germany Available online 5 February 2005 Abstract The incorporation of 3d transition metals into ZnO can produce ferromagnetism above room temperature. For Mn-doped ZnO films grown at low temperatures around 500 8C by pulsed laser deposition, the ferromagnetic behavior is correlated to their textured structure. For optimized films showing homogeneous magnetic domain formation in magnetic force microscopy, the saturation magnetization and coercive field strength amount to 0.013 emu/g and 234 Oe at 300 K, respectively. Compared to undoped ZnO films, the luminescence of Mn-doped ZnO films is strongly quenched. However, luminescence can be observed around antiferromagnetic MnO or MnO 2 clusters that crystallize during the growth process on the film surface. D 2005 Elsevier B.V. All rights reserved. Keywords: Ferromagnetism; Zinc oxide; Diluted semiconductors; Luminescence 1. Introduction Diluted magnetic semiconductors (DMS) in which mag- netic ions substitute for cations of the host semiconducting material are assumed to be ideal systems for spintronics. Based on theoretical studies for p-type III–V and II–VI DMS by Dietl et al. [1], attention was focussed on wide band gap semiconductors as prospective DMS for achieving mag- netic ordering at ambient temperatures. For example, the intrinsically n-type II–VI semiconductor ZnO that is already widely used in surface acoustic wave devices, gas sensors, microactuators, and as a transparent, con- ducting oxide appears to be a good starting point for investigating ZnO-based DMS [2–5]. Only recently, Venkatesan et al. [6] proposed the spin-split impurity band model to explain the exchange mechanism exper- imentally observed in n-conducting, ferromagnetic ZnO films. Ferromagnetism near or above room temperature has already been reported for Mn-doped ZnO pellets and thin films [2,5] whereas in other studies only para- magnetic behavior was reported [4,7–10]. Since Mn is paramagnetic, any ferromagnetism detected in Mn-doped ZnO cannot be due to Mn or Mn-oxide precipitates eventually formed during the growth process. However, MnO and MnO 2 precipitates are antiferromagnetic. We succeeded in growing Mn-doped ZnO films with a Curie temperature above 375 K by pulsed laser deposition (PLD) [3] and emphasized the importance of polycrystallinity in ZnO-based DMS for obtaining a soft magnetic material with homogeneous magnetic domain formation. Despite the close analogy to Mn-doped ZnS that is an efficient phosphor [11], it has been shown that the luminescence in Mn-doped ZnO powder or bulk material 0040-6090/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2004.11.211 * Corresponding author. Tel.: +49 341 97 32666; fax: +49 341 9732668. E-mail address: Heidemarie.Schmidt@physik.uni-leipzig.de (H. Schmidt). Thin Solid Films 486 (2005) 117 – 121 www.elsevier.com/locate/tsf