Superconducting microlimiters based on YBCO thin-films grown on SrTiO3 substrates

It has been shown recently that superconducting microbridges implemented with YBa2Cu3O7-delta (YBCO) thin-films grown on sapphire substrates could be used as very efficient fault current limiters for microelectronic devices with some elements working at temperatures below T-cI, the superconducting critical temperature and, simultaneously, under very low power conditions (below 1 W). These so-called microlimiters are then well adapted to important applications of the superconducting microelectronics, as infrared detectors or SQUID based electronics. Here we will present new results obtained by using YBCO microbridges grown on SrTiO3 substrates, which have a thermal conductivity of the order of 50 times lower than the sapphire substrates used in most of our previous work. These new measurements confirm the important role played in the behaviour of microlimiters by the thermal exchanges between the microbridges with their substrates and between these last with their environment. Our present results also show that the temperature for optimal operation of the microlimiter is substrate-dependent.