A Simple Lift-Off Process For Sharp Step Edges And Yba2cu3o7 Josephson Junctions

A simple 'lift-off' technique was developed for fabricating sharp step without ion milling. A YBa2Cu3O7 (YBCO) film was first deposited on an SrTiO3 (STO) substrate and then patterned by using conventional photolithography. Subsequenctly an STO film was deposited on top of the patterned YBCO film. Then the YBCO film underneath was dissolved in acid, resulting in lifting off of the top STO layer in fragments, leaving half of the STO film on the substrate. A sharp step edge was obtained on the boundary of the STO film. Atomic force microscopy showed the step profile. The T-c of the step edge junctions were 88-90 K, independent of film thickness. The I-V curves were RSJ like and clear Shapiro steps were observed. I(c)R(n) products from 140 mu V to 320 mu V were obtained at 77 K. Simple DC SQUIDs fabricated with these junctions exhibited a periodic response in the presence of magnetic field.