Materials Synthesis from Atoms to Systems

Electronic properties of manganite surfaces robust against reduction

Temperature dependent electronic properties of the oxide surface as measured using scanning probe spectroscopy.

While the broad range of properties of complex oxides degrade severely with decreasing oxygen content, it has now been shown that the electronic properties at their surfaces can remain unaffected in a reducing environment. This discovery carries important implications for the design of functional complex oxides for energy efficient catalysis and batteries that depend on these surface properties.

Scanning probe studies of the electronic properties at the surface of a doped manganite with intentionally reduced oxygen content were compared with conventional measurements of the resistance of the interior of the material. Surprisingly, the electronic properties of the surface were found to exhibit a transition from insulating to metallic, similar to what is observed in fully oxygenated material. In contrast the interior of the material remained insulating as expected for a reduced manganite. The unexpected implication is that either oxygen vacancies are not formed at these surfaces, or the presence of surface oxygen vacancies does not affect surface properties. This new fundamental insight will aid in designing new energy efficient applications based on complex oxide materials.

Paul C. Snijders, Min Gao, Hangwen Guo, Guixin Cao, Wolter Siemons, Hongjun Gao, Thomas Z. Ward, Jian Shen, and Zheng Gai, “Persistent metal-insulator transition at the surface of an oxygen-deficient, epitaxial manganite film,”  Nanoscale (2013).  DOI:10.1039/C3NR02343E

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