Effects of crystallographic orientation on the oxygen exchange rate of La0.7Sr0.3MnO3 thin films

Abstract

The oxygen surface exchange of La0.7Sr0.3MnO 3 (LSM) thin films was investigated using the electrical conductivity relaxation (ECR) method. Epitaxial (100)-, (110)-, and (111)-oriented LSM films were fabricated on corresponding SrTiO3 (STO) substrates using pulsed laser deposition. The LSM films had well-controlled surface qualities, exhibited bulk-like steady-state electrical properties, and exhibited surface dominated responses in ECR. The chemical surface exchange coefficients (k chem) were determined and varied from ≈ 1 × 10- 6 to 65 × 10- 6 cm/s, depending on temperature and orientation, with activation energies of between 0.8 and 1.2 eV. At 800 °C, a four fold variation is observed in the kchem values, with (110)/(100) being the highest/lowest, explained well by the high activation energy for (110), ≈ 1.16 eV, and the low energy for (111) and (100), ≈0.83 eV. © 2011 Elsevier B.V. All rights reserved.