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Enhancing Electron Mobility in Oxide Materials through Dielectric Constant Increase

This study reveals that the electron mobility in semiconducting oxides can be significantly improved by increasing the material's dielectric constant. Conducted on doped crystals of KTaxNb1-xO3, findings show that optimizing the composition can tune the peak dielectric constant temperature. Current electron mobilities in functional oxides remain insufficient for key applications like photovoltaics and energy storage. This research highlights how dielectric screening can boost electron mobility, suggesting a pathway for enhancing oxide materials' technological performance.

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Enhancing Electron Mobility in Oxide Materials through Dielectric Constant Increase

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  1. CNMS User Project Highlight A Route to Improving Electron Mobility in Oxide Materials • Scientific Achievement • The electron mobility in a semiconducting oxide is shown to be dramatically enhanced by the increase of the material’s dielectric constant via screening of defects and impurities. This observation was made in doped crystals of the model ferroelectric KTaxNb1-xO3, in which the temperature at which the dielectric constant peaks, can be continuously tuned via composition. • Significance • Room-temperature electron mobilities in functional oxides are still too low for practical applications, ranging from energy harvesting (photovoltaics, thermoelectrics) to energy storage (battery materials). The observed direct link between dielectric constant and mobility points to a general approach to improving the performance of these technologically relevant oxides. Electron mobility (orange, left axis) and carrier density (green, right axis) for KTa0.91Nb0.09O3. Dashed orange line shows the expected trend without dielectric-screening enhancement. Arrow indicates the ferroelectric transition temperature Tc. Photograph: insulating (clear) and Ca-doped semiconducting (dark) KTaxNb1-xO3. • Research Details • CNMS capability: Temperature-dependent x-ray diffraction and optical measurements of band gaps were performed at the CNMS. • Hall measurements were performed in the users’ own facilities on flux-grown, Ca-doped single crystals, confirming that the high dielectric constant at the ferroelectric transition increases the electron mobility. • Resources of the National Energy Research Scientific Computing Center were used for the DFT (band structure) calculations. W.Siemons, M.A. McGuire, V.R. Cooper, M.D. Biegalski, I.N. Ivanov, G.E. Jellison, L.A. Boatner, B.C. Sales, H.M. Christen, “Dielectric-Constant-Enhanced Hall Mobility in Complex Oxides,” Advanced Materials. DOI: 10.1002/adma.201104665.

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