Journal of the American Ceramic Society, Vol.102, No.5, 2415-2425, 2019
Surface engineering of the flexible metallic substrate by SDP-Gd-Zr-O layer for IBAD-MgO templates
Tuning substrate properties is an effective methodology to modulate the texture development of MgO films deposited by ion beam-assisted deposition (IBAD) process for epitaxial oxide films. Herein, a solution deposition planarization (SDP) technique is employed to deposit Gd-Zr-O layer for engineering surface properties of the flexible metal substrate. The correlation between the Gd-Zr-O thin film microstructure and the IBAD-MgO texture is investigated. The coordinated study on atomic force microscopy (AFM) and reflection high-energy electron diffraction (RHEED) reveal that the grain coarsening during high-temperature sintering negatively influences the texture formation of IBAD-MgO. Moreover, the chemical environment of the atoms on the surface of Gd-Zr-O seed layer also plays a critical role, which is normally overlooked. The X-ray photoelectron spectroscopy (XPS) analysis indicates that the carbon residue and intermediate phase result in the poor texture of the IBAD-MgO. This phenomenon is related to the partial decomposition and synthesis reactions due to the lower sintering temperature or reduced surface to volume ratio. We demonstrate the high-quality texture of IBAD-MgO layer, deposited on mono-coated thick Gd-Zr-O film, by using optimal heat-treatment conditions. The cross-sectional TEM images present the dense Gd-Zr-O film with Gd2Zr2O7 nanograins. The multifunctionalities, such as planarization, a barrier layer, and seed layer, of Gd-Zr-O layers are realized in full-stacked CeO2/LaMnO3/IBAD-MgO/SDP-Gd-Zr-O/C276 samples. This work demonstrates a route for simplifying the architecture of 2G-HTS using Gd-Zr-O layer and explores the effect of the surface properties on texture formation in IBAD-MgO layer.