Control of dopant crystallinity in electrochemically treated cuprate thin films

Abstract

We present a methodology based on ex-situ (post-growth) electrochemistry to control the oxygen concentration in thin films of the superconducting oxide La2CuO4+y grown epitaxially on substrates of isostructural LaSrAlO4. The superconducting transition temperature, which depends on the oxygen concentration, can be tuned by adjusting the pH level of the base solution used for the electrochemical reaction. As our main finding, we demonstrate that the dopant oxygens can either occupy the interstitial layer in an orientationally disordered state or organize into a crystalline phase via a mechanism in which dopant oxygens are inserted into the substrate, changing the lattice symmetry of both the substrate and the epitaxial film. We discuss this mechanism, and describe the resulting methodology as a platform to be explored in thin films of other transition metal oxides. arXiv:1907.01079v1 [cond-mat.mtrl-sci] 1 Jul 2019

Influence of Anodic Oxidation on the Organizational Structure and Corrosion Resistance of Oxide Film on AZ31B Magnesium Alloy

“…At 12.5 V, the film thickness slightly increases, but deeper cracks appear, Figure 2 illustrates the cross-sectional morphology of the anodic oxide film on AZ31B magnesium alloy prepared under various voltages. As shown in Figure 2, the oxide film layer of AZ31B magnesium alloy exhibits an "interlocking" connection with the substrate, a characteristic due to the in situ growth of the anodic oxide film, resulting in an indistinct boundary between the film and the substrate [28,29]. The film layer internally harbors pores and cracks of varying sizes and depths; yet, overall, it maintains a relatively good adhesion with the substrate.…”