Schematic of metallic LSMO (8 nm)/semiconducting LMO (8 nm) superlattice (LSMO/LMO)60 structure.
(a) XRD 2-theta-omega scan of an LSMO/LMO superlattice on a STO (100) substrate confirming c-axis epitaxial behavior with LSMO FWHM (0.027°) and LMO FWHM (0.102°) and (b) 110 RSM of a micron-thick LSMO/LMO superlattice. The LSMO and LMO peaks have a small degree of spread and show a consistent in-plane lattice parameter, confirming the pseudomorphic epitaxial growth of the superlattice film.
(a) Low-magnification cross-sectional bright field TEM images of an LSMO (8 nm)/LMO (8 nm) superlattice and (b) high-resolution cross-section TEM confirming epitaxial layer contrast of LSMO/LMO superlattices on aSTO (100) substrate were taken using FEI Titan operating at 300 kV. The contrast in (a) along the normal to the growth surface is due to threading dislocations.
(a) Top view SEM images of anisotropically etched LSMO/LMO superlattices with pillar heights of 1 μm and the schematic of final structure of LSMO/LMO superlattices for I-V cross-plane measurement. (b) Side view of final structure and (c) top view of final structure.
(a) Temperature-dependent in-plane resistivity of LSMO and (b) temperature-dependent in-plane resistivity of LMO with and without a magnetic field applied in a direction normal to the film surface.
(a) In-plane Seebeck measurement of LSMO shows Seebeck coefficient consistent with metallic behavior with a magnitude of less than 20 μV/K and (b) in-plane Seebeck measurement of LMO validating p-type behavior with a room temperature Seebeck coefficient of 140 ± 3 μV/K.
Photo-acoustic (PA) experimental amplitude measurement as a function of the modulation frequency for (a) LSMO sample, (b) LMO sample, and (c) LSMO/LMO superlattice.
(a) Measured in-plane resistivity and (b) extracted cross-plane resistivity of p-type LSMO/LMO superlattice using temperature dependent I-V measurement. The magnetic transition peak is shifted to T ∼ 330 K in cross-plane transport through LSMO/LMO superlattices, ∼80 K higher than the peak observed in in-plane resistivity in LSMO, LMO, or LSMO/LMO thin films.
The in-plane LSMO/LMO superlattices electrical conductivity fitting plot to extract the effective thermal activation energy of 101 ± 5 meV.
Arrhenius plot of cross-plane LSMO/LMO superlattice electrical conductivity. The fitting extracted an effective barrier height of 300 ± 15 meV.
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