Among perovskites, SrTiO₃ (STO) is one of the most widely studied oxides because of its potential in many applications in oxide electronics. Recently it has been shown that irradiated STO surfaces exhibit high-mobility conduction in contrast to the insulating behaviour of stoichiometric STO single crystals [1]. The possibility of modifying the properties of solids just by etching their surfaces opens up new perspectives for engineering of the functional properties of materials. But for that purpose, a deeper knowledge of damage extension and its consequences on the physical properties is highly desired. Bearing this in mind, we have characterized the spatial distribution and the nature of vacancy defects in insulating as-received as well as in ion-irradiated STO substrates exhibiting high-mobility conduction. Because tiny amounts of oxygen vacancies can trigger substantial modifications of the physical properties of STO, positron annihilation spectroscopy techniques appear as an appropriate characterization tool. We show that Ti-vacancies are native defects homogeneously distributed in as-received substrates. In contrast, the dominant vacancy defects consist of non-homogeneous distributions of cation-oxygen vacancy complexes in ion-etched substrates [2]. Their spatial extension is tuned over a few microns in ion-etched samples. Our results shed light on the transport mechanisms of conductive STO crystals and on strategies for defect-engineered oxide quantum wells, wires and dots.

 

[1] D. Reagor and V.Y. Butko, Nature Materials 4 (2005) 593.

[2] A. Gentils, O. Copie, G. Herranz, et al., Phys. Rev. B (2010) in press.

Aurelie Gentils*, CSNSM, CNRS-IN2P3-Univ. Paris-Sud 11, France
Olivier Copie, Unité Mixte de Physique CNRS/Thalès associée à l'Université Paris-Sud, Campus de Polytechnique, 1 avenue A. Fresnel, 91767 Palaiseau, France
Gervasi Herranz, Unité Mixte de Physique CNRS/Thalès associée à l'Université Paris-Sud, Campus de Polytechnique, 1 avenue A. Fresnel, 91767 Palaiseau, France, and Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC Campus de la UAB, Bellaterra 08193, Catalonia, Spain
Franck Fortuna, CSNSM, CNRS-IN2P3-Univ. Paris-Sud 11, France
Manuel Bibes, Unité Mixte de Physique CNRS/Thalès associée à l'Université Paris-Sud, Campus de Polytechnique, 1 avenue A. Fresnel, 91767 Palaiseau, France
Karim Bouzehouane, Unité Mixte de Physique CNRS/Thalès associée à l'Université Paris-Sud, Campus de Polytechnique, 1 avenue A. Fresnel, 91767 Palaiseau, France
Eric Jacquet, Unité Mixte de Physique CNRS/Thalès associée à l'Université Paris-Sud, Campus de Polytechnique, 1 avenue A. Fresnel, 91767 Palaiseau, France
Cécile Carrétéro, Unité Mixte de Physique CNRS/Thalès associée à l'Université Paris-Sud, Campus de Polytechnique, 1 avenue A. Fresnel, 91767 Palaiseau, France
Mario Basletic, Department of Physics, Faculty of Science, University of Zagreb, Bijenicka 32, P. O. Box 331, HR-10002 Zagreb, Croatia
Emil Tafra, Department of Physics, Faculty of Science, University of Zagreb, Bijenicka 32, P. O. Box 331, HR-10002 Zagreb, Croatia
Amir Hamzic, Department of Physics, Faculty of Science, University of Zagreb, Bijenicka 32, P. O. Box 331, HR-10002 Zagreb, Croatia
Agnès Barthélémy, Unité Mixte de Physique CNRS/Thalès associée à l'Université Paris-Sud, Campus de Polytechnique, 1 avenue A. Fresnel, 91767 Palaiseau, France

*presenting author