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Glass-like Thermal Conductivity in Epitaxial Oxygen-Vacancy-Ordered Oxide Films

Precise control over defects in materials is often a highly effective means to control properties and function. In oxide materials, which are the focus of enormous current attention for many existing and proposed applications, defects known as oxygen vacancies often play the key role. These vacancies, simply missing oxygen atoms in the structure, can have a significant impact on properties. Recent work by investigators in IRG-1 has shown that in a specific type of oxide (perovskite cobaltite films) oxygen vacancies can not only be created, but also controlled to form ordered patterns, in turn controlling electronic and magnetic properties. In this work, state-of-the-art capabilities in IRG-2 with measurement of thermal conductivity in nanoscale materials was used to measure the impact of this defect formation and ordering on the flow of heat. Surprisingly, the thermal conductivity in such materials was found to be extremely low, comparable to glasses, some of the best thermal insulators known. The finding that thermal insulation of this type can be obtained  even in highly ordered crystalline materials has significant potential implications in heat management in devices.