High- $\rm{T}_{\rm{c}}$ Dual-SQUIDs With Graphoepitaxial Step-Edge Junctions

The microstructural and noise properties of serially connected high-
$\mathrm{T}_{\mathrm{c}}$
dc superconducting quantum interferometer devices (high-
$\mathrm{T}_{\mathrm{c}}$
dc SQUIDs) with step-edge Josephson junctions are studied. It is shown that the implementation of novel graphoepitaxial step-edge Josephson junctions on buffered MgO substrates helps to overcome poor reproducibility of conventional step-edge high-
$\mathrm{T}_{\mathrm{c}}$
Josephson junctions due to the self-arranged growth of two identical [100]-tilted 45
$^{\circ}$
grain boundaries over a wide range of step heights. The use of such Josephson junctions in two serially connected SQUIDs that are directly coupled to a common pickup loop in a dual-SQUID configuration with current biasing of the individual SQUIDs results in a doubling of voltage swings and an improvement in magnetic field resolution of the sensors.