Structural and Superconducting Properties of MBE Grown Bi_2Sr_2CuO_(6+δ) Thin Films

摘要

Epitaxial Bi_2Sr_2CuO_(6+δ) thin films have been obtained by Molecular Beam Epitaxy (MBE) using a coevaporation method. Transport measurements show that the slope of the resistance as a function of the temperature strongly depends upon the sto-ichiometry of the samples. Reflection High Energy Electron Diffraction (RHEED) patterns show the presence of a superstructure along the b direction due to an excess of oxygen. Moreover, RHEED figures related to a - b twinning, as often seen also for Bi_2Sr_2Ca_1Cu_2O_(8+x), have been observed. The c-axis length, obtained by X-ray diffraction patterns, has been studied as a function of the sample stoichiometry.