(634d) Ultra-High Frequency Electric Field Effects On Oxygen Vacancy Concentration in Oxide Thin Films

Atomistic simulations employing dynamic charge transfer between atoms are used to investigate ultra-thin oxide growth on Al(100) metal substrates in the presence of an ac electric field. In the range of 1-10 GHz frequencies, the enhancement in oxidation kinetics by ~12% over natural oxidation can be explained by the Cabrera-Mott mechanism. At field frequencies approaching 0.1-1 THz, however, we observe a dramatic lowering of the kinetics of oxygen incorporation by ~ 35% compared to the maximum oxidation achieved, resulting in oxygen non-stoichiometry near the oxide-gas interface (O/Al ~ 1.0), which is attributed to oxygen desorption from the oxide surface. Simulations were further carried out on fuel cell electrolytes such as Ceria/YSZ heterostructures to evaluate ultra-high electric field frequency effect on dopant distribution, inter-mixing and ionic conductivity. These results suggest a general strategy to tune oxygen concentration at oxide surfaces using ac electric fields that could be of interest in diverse topics in surface chemistry and applications such as tunnel barriers, thin dielectrics and oxide interfaces.

Ultra-high frequency electric field effects on oxygen vacancy concentration in oxide thin films