Thermally assisted tunneling transport in La_(0.7)Ca_(0.3)MnO_(3)/SrTiO_(3):Nb Schottky-like heterojunctions

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We report on the electrical transport properties of all-oxide La_(0.7)Ca_(0.3)MnO_(3)/SrTiO_(3):Nb heterojunctions with lateral size of just a few micrometers. The use of lithography techniques to pattern manganite pillars ensures perpendicular transport and allows exploration of the microscopic conduction mechanism through the interface. From the analysis of the current-voltage characteristics in the temperature range 20–280 K we find a Schottky-like behavior that can be described by a mechanism of thermally assisted tunneling if a temperature-dependent value of the dielectric permittivity of SrTiO_(3):Nb (NSTO) is considered. We determine the Schottky energy barrier at the interface, qVB = 1.10 ± 0.02 eV, which is found to be temperature independent, and a value of ξ = 17 ± 2 meV for the energy of the Fermi level in NSTO with respect to the bottom of its conduction band.
© 2012 American Physical Society. This work has been supported by the Spanish MICINN under Projects No. MAT2008-06517, No. MAT2010-18933, No. MAT2011-27470, and No. CSD2009-00013 (IMAGINE), by CAM under PHAMA Grant No. S2009/MAT-1756, and by an ERC Starting Investigator Award, Grant No. 239739 STEMOX (G.S.S.). Research at ORNL (M.V.) was sponsored by the Materials Sciences and Engineering Division of the US Department of Energy.
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