Measured room temperature conductivity of LSMO and LMO thin films after two-stage annealing process: Stage-I (750 °C, 300 mTorr, 15 h PLD), and Stage-II (900 °C, atmospheric O2 pressure, tube furnace).
Measured room temperature conductivity of the LSMO and LMO thin films grown at higher oxygen partial pressure. LSMO and LMO films were deposited under 210 mTorr that yielded a 100× increase in electrical conductivity compared to high resistivity constituent material thin films grown at 52 mTorr oxygen partial pressure.
XRD 2-theta-omega scan of an LMO on a STO (100) substrate confirming c-axis epitaxial behavior. The LMO grown at 52 mTorr partial oxygen pressure shows a distinguishing peak with a = 3.94 Å whereas the LMO grown at 210 mTorr peak overlaps with the STO peak.
Schematic of metallic LSMO (8 nm)/semiconducting LMO (8 nm) superlattice (LSMO/LMO)51 structure grown by PLD.
(a) XRD 2-theta-omega scan of an LSMO/LMO superlattice on a STO (100) substrate confirming c-axis epitaxial behavior with LSMO FWHM (0.187°) and (b) 110 RSM of a micron-thick LSMO/LMO superlattice confirming the LMO peak overlapping with STO peak, and pseudomorphic growth of epitaxial LSMO and LMO superlattice films.
Temperature-dependent in-plane resistivity with and without a magnetic field applied in a direction normal to the film surface for (a) LSMO, and (b) LMO.
(a) In-plane Seebeck measurement of LSMO showing that the Seebeck coefficient is consistent with metallic behavior with a magnitude of less than 15 μV/K and (b) in-plane Seebeck measurement of LMO validating p-type behavior with a room temperature Seebeck coefficient of 60 ± 3 μV/K.
Temperature-dependent cross-plane thermal conductivity of p-type LSMO/LMO superlattice.
(a) Field emission scanning electron microscope top view images of anisotropically etched LSMO/LMO superlattices by ICP-RIE, and (b) the schematic of side view of the final structure of LSMO/LMO superlattices for I-V cross-plane measurement.
Temperature-dependent in-plane resistivity of p-type LSMO/LMO superlattice.
The in-plane LSMO/LMO superlattice electrical conductivity plot fitted to extract the effective thermal activation energy of 114 ± 6 meV.
Extracted cross-plane resistivity of the p-type LSMO/LMO superlattice using temperature dependent I-V measurement.
Arrhenius plot of cross-plane LSMO/LMO superlattice electrical conductivity. The fitting extracted an effective barrier height of 223 ± 11 meV.
The LSMO/LMO superlattice cross-plane Seebeck coefficient measurement using thermal imaging technique showed a giant Seebeck coefficient of 2560 ± 130 μV/K at 300 K, which increased to 16 640 ± 830 μV/K at 360 K.
The extracted cross-plane power factor (S 2 σ) of the low resistivity p-type LSMO/LMO superlattice. The power factor increased by two orders of magnitude compared to high resistivity superlattices grown at 52 mTorr.
The extracted cross-plane thermoelectric figure-of-merit (ZT) of p-type LSMO/LMO superlattices. The cross-plane ZT increased by two orders of magnitude compared to high resistivity superlattices grown at 52 mTorr.
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