Josephson properties of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ bicrystal junctions grown by a sequential deposition technique using molecular beam epitaxy

We report Josephson and crystallographic properties of the Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ junctions fabricated on MgO(100) bicrystal substrates by a molecular-beam-epitaxy method incorporating co-evaporation and sequential deposition techniques. With the sequential deposition technique which has the advantage of promoting the surface diffusion of adatoms, we obtained the highly growth-controlled films without precipitation of any second impurity phases. During the film growth, the sharp reflection high-energy electron diffraction (RHEED) patterns were also observed. However, the RHEED patterns showed the a-b twin structures due to the lattice mismatch, which influenced the Josephson transport properties at the junction boundary. The normal resistance of the bicrystal junction was 1.5 /spl Omega/ and the I/sub c/R/sub n/ product was 0.75 mV at 4.2 K. The Shapiro steps under millimeter-wave irradiation were clearly observed up to 65 K. The Josephson microwave self-radiation spectra at receiving frequency f/sub REC/=22 GHz. The observed Josephson transport properties are discussed in relation to the microscopic crystallographic properties.