Improved cationic stoichiometry and insulating behavior at the interface of LaAlO3/SrTiO3 formed at high oxygen pressure during pulsed-laser deposition

• Published in: Europhysics letters 2011-02, Vol.93 (3), p.37001
• Main Authors: Kalabukhov, A, Boikov, Yu. A, Serenkov, I. T, Sakharov, V. I, Börjesson, J, Ljustina, N, Olsson, E, Winkler, D, Claeson, T
• Format: Article
• Language: English
• Subjects: 73.20.-r; 73.21.Ac; 73.40.-c; oxides
• ISSN: 0295-5075; 1286-4854; 1286-4854
• DOI: 10.1209/0295-5075/93/37001

Medium-energy ion spectroscopy, MEIS, and scanning transmission electron microscopy, STEM, were used to correlate the atomic structure of LaAlO3/SrTiO3 interfaces with their electrical properties. Interfaces were prepared at high (5×10−2 mbar) and low (10−4 mbar) oxygen pressure by pulsed-laser deposition. The high-oxygen-pressure heterostructures were insulating for all thicknesses while the low-oxygen-pressure ones became metallic for thicknesses above 4 unit cells. MEIS data show enhancement of the Sr surface peak and suppression of the La one in interfaces prepared at low oxygen pressure, which is interpreted as a La-Sr intermixing. The effect was considerably smaller in high-oxygen-pressure samples. Analysis of high-angle annular-dark-field STEM images of the LAO films also indicates intermixing between La and Sr in low-oxygen-pressure samples, supporting MEIS data. Our results reveal the important role of oxygen pressure on the formation of the interface electron gas.