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

The oxygen surface exchange of La0.7Sr0.3MnO3 (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 (kchem) 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.

Research highlights
► Smooth, flat (100), (110), and (111) oriented La0.7Sr0.3MnO3 films were fabricated with PLD.
► All films had surface dominated responses in electrical conductivity relaxation measurements.
► From 600 to 800 °C, chemical exchange coefficients varied from Kchem ≈ 1 to 65 × 10− 6 cm/s.
► The activation energy of Kchem varied: E(110) ≈ 1.16 eV, and E(111) and E(100) ≈ 0.83 eV.
► At 800 °C, a 4-fold variation in Kchem was observed, with (110) the highest and (100) the lowest.