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Nano-meter bridge with epitaxially deposited NbN on MgO film

1985; IEEE Magnetics Society; Volume: 21; Issue: 2 Linguagem: Inglês

10.1109/tmag.1985.1063621

1941-0069

Takashi Yamashita, Koji Hamasaki, Yoshimitsu Kodaira, T. Komata,

Particle accelerators and beam dynamics

Nano-meter(nm)-bridges with high-T c materials hold great technological interest because of their smaller capacitance and expected higher I o R n -product. They are promising especially for applications such as high speed logic and high frequency radiation detectors. Also they can operate over a wide temperature range and are stable against thermal cycles as are incorporating the refractory high-T c superconductors. One of the essential ingredient for high quality bridges is to have NbN films. Ultra-thin NbN films have been prepared by rf reactive-sputtering. NbN films deposited epitaxially on rf sputtered MgO films have high superconducting transition temperature T c . T c value of the film with thickness of about 5nm was about 14K, and is much higher than those deposited on Al 2 O 3 films and Si substrates. Two types of nm-bridges were reproducibly fabricated with NbN films deposited epitaxially on MgO films. The obtained I o R n -products were in a range of 0.5 to 3.6mV. The microwave-induced voltage steps were observed up to the voltage comparable to I o R n - product. The dc and ac quantum effects of the dc SQUIDs were observed in quite wide range of temperature, 4.2 to 11.4K.