Conducting interfaces between amorphous oxide layers and SrTiO_3(110) and SrTiO_3(111)
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2015
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ELSEVIER SCIENCE BV
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Abstract
Interfaces between (110) and (111)SrTiO_3 (STO) single crystalline substrates and amorphous oxide layers, LaAlO_3 (a-LAO), Y:ZrO_2 (a-YSZ), and SrTiO_3 (a-STO) become conducting above a critical thickness tc. Here we show that t_c for a-LAO is not depending on the substrate orientation, i.e. t_c (a-LAO/(110)STO) ≈ t_c(a-LAO/(111)STO) interfaces, whereas it strongly depends on the composition of the amorphous oxide: t_c(a-LAO/(110)STO) < t_c(a-YSZ/(110)STO) < t_c(a-STO/(110)STO). It is concluded that the formation of oxygen vacancies in amorphous-type interfaces is mainly determined by the oxygen affinity of the deposited metal ions, rather than orientational-dependent enthalpy vacancy formation and diffusion. Scanning transmission microscopy characterization of amorphous and crystalline LAO/STO(110) interfaces shows much higher amount of oxygen vacancies in the former, providing experimental evidence of the distinct mechanism of conduction in these interfaces.
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© 2015 Elsevier B.V.
Financial support by the Spanish Government [Projects MAT2011- 29269-CO3 andMAT2014-56063-C2-1-R] and Generalitat de Catalunya (2014 SGR 734) is acknowledged. MS acknowledges the financial support of the Spanish Government (FPU grant). J.G. acknowledges the Ramon y Cajal program (RYC-2012-11709). Microscopy work has been conducted in the STEMGroup of the Oak Ridge National Laboratory (ORNL). This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences,Materials Science and Engineering Division (MV). Research at UCMis supported by the ERC Starting Investigator Award STEMOX 739239. We thank Dr. A. Pérez del Pino and Dr. R. Pfattner for collaboration in some transport measurements.