Nano-meter bridge with epitaxially deposited NbN on MgO film

Nanometer-thickness bridges have been produced through the RF reactive sputtering of NbN films. Those NbN films epitaxially deposited on RF-sputtered MgO films have a high superconducting transition temperature T(c). The T(c) value for the case of a 5-nm thickness film was about 14 K, which is noted to be much higher than values for those deposited on Al2O3 films or Si substrates. Two types of nm-thickness bridges have been reproducibly fabricated with epitaxial NbN-film deposition on MgO. Both ac and dc quantum effects were observed in dc SQUIDS over the 4.2-11.4 K temperature range.