Kinetic roughening of the color phase boundaries in ionic conducting oxide thin films

Ionic migration in oxides is a basic mechanism for the operation of various devices, such as solid oxide fuel cells and resistive switching memories. Here, we explore Bi_0.7Ca_0.3FeO_3-δ thin films, which show ionic conduction and electrochromism [1], to study kinetic roughening of the boundaries between oxygen-vacancy-poor phase (δ = 0) and stoichiometric phase (δ = 0.15) [2,3]. Each of the phases can be spatially separated by electric fields and distinguished by color contrast through optical microscope. The width of the boundaries between two phases varies depending on applied voltage. Roughness exponents(ζ) of the boundaries saturate to ζ = 1. The dynamic motion of ionic phase boundaries is described based on the universal kinetic roughening theory.



[1] J. Seidel et al., Nature Communications 3, 799 (2012)

[2] J. S. Lim et al., NPG Asia Materials 10, 943 (2018)

[3] H.-S. Park et al., Applied Physics Letter 115, 183901 (2019)