Coating processes for YBa₂Cu₃O_7-<i>x</i>superconductor by metalorganic deposition method using trifluoroacetates

Abstract

YBa2Cu3O7-x (YBCO) films prepared by a metalorganic deposition method using trifluoroacetats (TFA-MOD method) with spin coating have excellent properties: a critical current density (Jc) of over MA cm-2 (77 K, 0 T) and a critical temperature of over 92 K. However, films prepared by spin coating shrink at lower spinning rates or have striation at higher spinning rates. Both shrunk films and films with striation have low Jc. Moreover, even if striation is not observed by scanning electron microscopy scale observation, a structure containing pores was confirmed by transmission electron microscopy. Such pores are considered to result in a low Jc of the films. To avoid such problems we adopted dip coating as the coating process in the TFA-MOD method. The dipped YBCO films have excellent Jc compared to the spun films. A typical dipped YBCO film of 0.25 µm in thickness on LaAlO3 single-crystalline substrate has a transport Jc of 5.3 MA cm-2 (77 K, 0 T).