Multilayer YBa sub 2 Cu sub 3 O sub x -SrTiO sub 3 -YBa sub 2 Cu sub 3 O sub x films for insulating crossovers

We describe our procedure for fabricating YBa{sub 2}Cu{sub 3}O{sub {ital x}}-SrTiO{sub 3}-YBa{sub 2}Cu{sub 3}O{sub {ital x}} thin-film trilayer structures. Each film is grown {ital in} {ital situ} by excimer laser deposition onto a heated (100)MgO substrate. The geometrical configuration of each layer is defined by a metal mask; the vacuum chamber is opened between depositions to allow the targets and masks to be changed. The lower and upper YBa{sub 2}Cu{sub 3}O{sub {ital x}} films in the best trilayer structure had transition widths of 1 and 3 K (10--90%), respectively, and transition temperatures (zero resistance) of 87 K. The resistance between the YBa{sub 2}Cu{sub 3}O{sub {ital x}} films at 77 K was 10{sup 8} {Omega} for an overlapping area of 0.2 mm{sup 2}, corresponding to a SrTiO{sub 3} resistivity of 4{times}10{sup 9} {Omega} cm.