Effect of oxygen pressure on structural modulation observed by X-ray reciprocal space mapping in epitaxial bismuth cuprate superconducting film
Bi2Sr2Ca1Cu2Ox (Bi-2212) single layers were prepared on MgO(100) substrates in different conditions of oxygen pressure using a 266 nm laser generated by slower Q-switched YAG system. Several X-ray diffraction methods were employed to investigate the crystal structure of Bi-2212. X-ray diffraction (XRD) methods of θ-2θ and phi scan were used to verify the epitaxial growth of Bi-2212(001), and reciprocal space mapping (RSM) of ω-2θ was employed to investigate in-plane lattice constants and structural modulation. Satellite peaks generated by structural modulation on the RSM showed asymmetric distribution around the main peak. The periodicity of modulation was evaluated using satellite peaks on the RSM. With increasing oxygen pressure, the lattice constant expanded along the c-axis and contracted along the b-axis, while structural modulation expanded along both b- and c-axis directions.