Low temperature scanning electron microscopy study of YBa2Cu3O7−δ multilayer dc SQUID magnetometers

Low temperature scanning electron microscopy (LTSEM) has been used to analyze the superconducting properties of integrated magnetometers involving a dc superconducting quantum interference device. The study yielded spatially resolved information on the critical temperature Tc and critical current density Jc in the upper and lower superconducting layers of the YBa2Cu3O7−δ/SrTiO3/YBa2Cu3O7−δ structure. The Tc of the lower film was depressed by several kelvin, and the Jc of the upper film was lower where it crossed the edge of a lower YBa2Cu3O7−δ film covered with SrTiO3. A gradient in Tc was observed in the lower film near the edge of a via, arising presumably from oxygen diffusion during fabrication.