Mechanical Stress and Temperature Can Tune the Stability of Electronic Defects in Semiconducting Oxides

Functional semiconducting oxides are an attractive group of materials for energy and information applications. They are the key enabler for several important technologies, including solid oxide fuel cells, thermochemical fuel production as well as novel memory devices such as red-ox based memristive systems.

MIT MRSEC researchers have demonstrated that the combined action of temperature and mechanical stress can tune the relative stability of electronic defects in semiconducting oxides. Combining density functional theory and the quasiharmonic approximation, they were able to predict the effect of temperature and pressure on charged defects in semiconductors. By applying this approach to strontium titanate, they elucidated the rich thermodynamics underlying the free energy landscape of free electrons and small polarons.

The ability to predict temperature and pressure effects in semiconducting oxides will guide the design of optimal conditions to promote desirable forms of electronic defects in electronic or electrochemical applications. For example, at a given temperature, mechanical stress can be tuned to promote free electrons in photo-electrodes to enhance electronic conductivity. Alternatively, stress can be altered to stabilize small polarons and decelerate electronic conduction for design of corrosion-resistant coatings.