Oxygen lattice disorder in YBa₂Cu₃O_xepitaxial films with enlarged c-axis lattice parameter

Abstract

The behaviour of t h e crystal structure of the YBCO epitaxial films with enlarged c-axis parameter has been studied. The c-axis expansion effect is shown to be induced by low oxygen partial pressure during the film deposition. This effect cannot be explained only by oxTgen deficit in the C u 4 chains or (Y. Ea) cation disorder. A bridging oxygen disorder model shows qualitative agreement with experimental x-ray diffraction spectra. Thermodynamic analysis of the formation of oxygen vacancies shows the high theoretical density of the bridging oxygen vacancies at the film synthesis temperatures.

Local strain-driven migration of oxygen vacancies to apical sites in YBa2Cu3O7−x

“…1 YBCO has excellent superconducting performance at high magnetic fields and temperature conditions well above liquid N 2 's boiling point, thus it is a strong candidate for high current and power applications. 14 Since the observation of high-temperature superconductivity in YBCO in 1987, 15 there have been numerous reports on the influence of the oxygen in YBCO, either when grown as a single crystal [16][17][18][19][20] or as a thin film, [21][22][23] on its structure and superconducting properties. YBCO's unit cell structure, shown in Fig.…”

Direct observation of apical oxygen vacancies in the high-temperature superconductor YBa2Cu3O7−xHartman1, Mundet2, Idrobo3 et al. 2019Phys. Rev. Materials203180View full textAdd to dashboardCite

“…Nonetheless, there are a few reports of V O at sites other than the chains. For instance, neutron diffraction studies [7][8][9][10][11] have indicated small vacancy concentrations at the apical site O(4), depending on the annealing process. There have been attempts at atomic-scale characterization of V O on surfaces of cleaved YBCO crystals having optimal doping using scanning tunneling microscopy (STM) [12][13][14][15].…”

Doping and characterization of YBa2Cu3O7-δthin films prepared by pulsed laser deposition

“…(2) Oxygen deficiency due to partial occupancy of the apical O(4) site (see [5] for identification). A deficiency of 5% at the O(4) site will cause the c-axis to elongate to 11.85 Å [11,22]. Up to 10% O(4) site vacancies have been reported [5,19].…”

“…To assess the reliability of this estimation, it is also necessary to consider how other factors may affect the ratios. For example, Degoy et al [23] found that the n = 6 ratio is dependent on stoichiometry, and Shapovalov et al [22] found that apical O(4) vacancies suppress the (004) peak. In a particularly detailed study, MacManus-Driscoll et al [19] examined the effects of disorder on the (00l)/(006) ratios.…”