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.
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