Cross-plane thermoelectric transport in p-type La0.67Sr0.33MnO3/LaMnO3 oxide metal/semiconductor superlattices

Pankaj Jha, Birck Nanotechnology Center, Purdue University
Timothy D. Sands, Birck Nanotechnology Center, Purdue University
Philip Jackson, University of California - Santa Cruz
Cory Bomberger, University of Delaware
Tela Favaloro, University of California - Santa Cruz
Stephen Hodson, Birck Nanotechnology Center, Purdue University
Joshua Zide, University of Delaware
Xianfan Xu, Birck Nanotechnology Center, Purdue University
Ali Shakouri, Birck Nanotechnology Center, Purdue University

Date of this Version



Copyright 2013 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in J. Appl. Phys. 113, 193702 (2013); and may be found at The following article has been submitted to/accepted by Journal of Applied Physics.Copyright 2013 Pankaj Jha, Timothy D. Sands, Philip Jackson, Cory Bomberger, Tela Favaloro, Stephen Hodson, Joshua Zide, Xianfan Xu and Ali Shakouri. This article is distributed under a Creative Commons Attribution 3.0 Unported License.


The cross-plane thermoelectric transport properties of La0.67Sr0.33MnO3 (LSMO)/LaMnO3 (LMO) oxide metal/semiconductor superlattices were investigated. The LSMO and LMO thin-film depositions were performed using pulsed laser deposition to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate substrates. X-ray diffraction and high-resolution reciprocal space mapping indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively, this coupled-plasma reactive-ion etching. The crossplane electrical conductivity data for LSMO/LMO superlattices reveal a lowering of the effective barrier height to 223 meV as well as an increase in cross-plane conductivity by an order of magnitude compared to high resistivity superlattices. These results suggest that controlling the oxygen deficiency in the constituent materials enables modification of the effective barrier height and increases the cross-plane conductivity in oxide superlattices. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 mu V/K at 300K that increases to 16 640 mu V/K at 360 K. The giant increase in the Seebeck coefficient with temperature may include a collective contribution from the interplay of charge, spin current, and phonon drag. The low resistance oxide superlattices exhibited a room temperature cross-plane thermal conductivity of 0.92W/mK, this indicating that the suppression of thermal conductivities due to the interfaces is preserved in both low and high resistivity superlattices. The high Seebeck coefficient, the order of magnitude improvement in cross-plane conductivity, and the low thermal conductivity in LSMO/LMO superlattices resulted in a two order of magnitude increase in cross-plane power factor and thermoelectric figure of merit (ZT), compared to the properties of superlattices with higher resistivity that were reported previously. The temperature dependence of the cross-plane power factor in low resistance superlattices suggests a direction for further investigations of the potential LSMO/LMO oxide superlattices for thermoelectric devices. (C) 2013 AIP Publishing LLC.


Nanoscience and Nanotechnology