ARRAYS OF HIGH TEMPERATURE SUPERCONDUCTOR JOSE

We present results on parallel, series and two dimensional arrays of high temperature superconductor junctions. The parallel arrays show the expected field dep- endence of critical current, and can function as Vortex Flow Transistors. The series arrays give us data about the spread in junction critical currents for our present process. The two dimensional arrays show many of the phenomena previously observed in low To technology, such as field frustration of the phase transition, some evidence for superlattice states, and the tentative indications of giant Shapiro steps, showing large scale cooperative behaviour in the device. I. INTRODUCTION Grain boundary Josephson junctions have sufficient performance to allow the exploration of many of the types of device that have been studied with low temperature superconductors. We report the fabrication of multiplejunction devices of three types. Parallel arrays can form the basis of a form of Vortex Flow Transistor (VFT). Series arrays allow us to study the spread in critical currents of our junctions, and in principle they can be used as oscillators or mixers with greater dynamic range than a single junction. Finally we have made two dimensional arrays. The increase in internal coupling paths leads to much greater robustness of synchronisation of the junctions in the voltage state. The low T, realisations show great promise as agile and highly tuneable oscillators with much larger powers than single junctions. They have also been extensively studied as a prototype system for two-dimensional phase transitions. 11. SAMPLE PREPARATION