The fabrication and study of YBa sub(2)Cu sub(3)O sub(x) submicron Josephson junctions on bicrystal substrates

We have developed a technological process for fabrication of YBa sub(2)Cu sub(3)O sub(x) (YBCO) submicron wide Josephson junctions (JJ) on bicrystal substrates. This process is based on e-beam lithography and ion beam etching of YBCO films through carbon masks. A series of JJ with 0.4-1 mu m width have been fabricated on SrTiO sub(3) bicrystal substrates with misorientation angles theta =24 degree and 36.8 degree using this process. The analysis of the current-voltage characteristics of the fabricated junctions at high bias currents supports the model of electrons tunneling through the localized states (LS) formed in the barrier region. The approximation of experimental data on white noise of the junctions by theoretical formula, which represents the contribution of thermal noise as well as shot noise, shows that tunnel mechanism of electrons transport through the LS greatly dominates a normal metallic one. copyright 2002 Elsevier Science B.V. All rights reserved.