Reliable single-target sputtering process for high-temperature superconducting films and devices

We report a simple, single-target magnetron sputtering process for films of high-temperature superconductors involving an off-axis sputtering geometry. The process lends itself both to film growth with high-temperature post-anneals and to low-temperature in situ film growth. The post-anneal process routinely yields YBa2Cu3O7−x films on SrTiO3 substrates that are fully superconducting at 86–89 K. Current densities at 77 K range from 104 to 8×105 A/cm2. A single-level superconducting quantum interference device (dc SQUID), made by photolithographically patterning a low current density film, has a flux noise level at 77 K of 3×10−4 Φ0/(Hz)1/2 at 20 Hz, dominated by low-frequency noise associated with flux motion in the film.