A water-free metal organic deposition method for YBa₂Cu₃O_7−δthin film fabrication

Abstract

During the fabrication of YBa 2 Cu 3 O 7−δ (YBCO) thin films via the metal organic deposition (MOD) method, the water content of the precursor solution should be reduced to prevent precipitation and other detriment. In most of the reported MOD-YBCO studies, water was used as a solvent, and vacuum distillation was utilized to reduce the water content of the precursor solution. In this study, we propose a water-free MOD method using propionic anhydride and methanol as the solvents. The crystal water of raw precursor salts was removed by heating, and the water content in the final precursor solution was as low as 0.2 wt%. Using this solution with low fluorine content and the optimized maximum temperature of pyrolysis, the final YBCO thin films about 250 nm thick had the critical current density (J c ) of 3.8 MA cm −2 (77 K, self-field). The water content of the precursor solution was further reduced to less than 10 −2 wt% by vacuum distillation. According to the J c performance, thermal analysis, x-ray diffraction investigations, and morphology observations, no significant improvement was found for the final YBCO thin films fabricated by the distilled solution, indicating that vacuum distillation is not necessary in the water-free MOD method.

Surface characterization of as-grown CeO<SUB>2</SUB> cap layer morphology evolution and critical current density of post-deposited YBCO films

“…There was very little amount of Y 2 Cu 2 O 5 in all the YBCO films, which was also found in our previous publication of the water-free MOD method. 20 It could be noticed in Figure 7 that the intensity of YBCO (006) diminished tremendously as the CeO 2 sputtering pressure increased from 0.5 Pa to 4.5 Pa, by two orders of magnitude. The changing of BaCeO 3 (220) intensity was relatively small, and there was no clear relationship between it and the CeO 2 morphology evolution.…”

“…The details of water-free MOD procedure were the described in our previous publication. 20 The thickness of CeO 2 cap layers was measured by an XP-1 surface profilometer of AMBIOS. Atomic force microscopy (AFM) was utilized to observe and quantify the surface morphology of CeO 2 layer, using Nanoscope III of Digital instruments.…”

“…However 1.92 MA/cm 2 was lower than the J c of YBCO film (3.8 MA/cm 2 fabricated on lanthanum aluminate (LAO) single crystal substrate in our previous water-free MOD study. 20 The MOD process would be improved in our future study by optimizing the parameters such as precursor content, crystallization temperature and gas flow, in order to enhance the J c property of YBCO films.…”

Development of a Fluorine-Free Polymer-Assisted-Deposition Route for YBa2Cu3O7−x Superconducting Films

“…These approaches consist of dissolving carboxylates, such as acetates, propionates, etc., or β-diketonates, as metal precursors in a common solvent, usually organic acids, and combining the solutions to yield the desired stoichiometry. The combination of short chain carboxylates, such as acetates, and strongly chelating β-diketonates, or propionates of all the metals dissolved in propionic acid (CH 3 CH 2 COOH) has been successfully used [13]. The use of chelating agents leads to the formation of monomeric compounds and the lower organic content of the precursors reduces excessive weight loss and shrinkage during the film decomposition, suppressing problems with film cracking.…”