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arXiv · 1312.2486

Chemistry and structure of homoepitaxial SrTiO$_3$ films and their influence on oxide-heterostructure interfaces

M. L. Reinle-Schmitt·C. Cancellieri·A. Cavallaro·S. J. Leake·E. Pomjakushina·J. A. Kilner·P. R. Willmott
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Abstract

The properties of single-crystal SrTiO$_{3}$ substrates and homoepitaxial SrTiO$_{3}$ films grown by pulsed laser deposition have been compared, in order to understand the loss of interfacial conductivity when more than a critical thickness of nominally homoepitaxial SrTiO$_{3}$ is inserted between a LaAlO$_{3}$ film and a SrTiO$_{3}$ substrate. In particular, the chemical composition and the structure of homoepitaxial SrTiO$_{3}$ investigated by low-energy ion-scattering and surface x-ray diffraction, show that for insulating heterointerfaces, a Sr-excess is present between the LaAlO$_{3}$ and homoepitaxial SrTiO$_{3}$. Furthermore, an increase in the out-of-plane lattice constant is observed in LaAlO$_{3}$, indicating that the conductivity both with and without insertion of SrTiO$_{3}$ thin film originates from a Zener breakdown associated with the polar catastrophe. When more than a critical thickness of homoepitaxial SrTiO$_{3}$ is inserted between LaAlO$_3$ and SrTiO$_3$, the electrons transferred by the electronic reconstruction are trapped by the formation of a Sr-rich secondary phase and Sr-vacancies. The migration of Sr towards the surface of homoepitaxial STO and accompanying loss of interfacial conductivity can be delayed by reducing the Sr-content in the PLD target.

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M. L. Reinle-Schmitt, C. Cancellieri, A. Cavallaro, S. J. Leake, E. Pomjakushina, J. A. Kilner, P. R. Willmott. 2013-12-09. Chemistry and structure of homoepitaxial SrTiO$_3$ films and their influence on oxide-heterostructure interfaces. https://doi.org/10.1039/c3nr06456e

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