Abstract
In order to keep better surface morphology and in-plane orientation, thin films of Bi2Sr2CaCu2Oy(2212) and Bi2Sr2Ca2Cu3Oy(2223) were deposited by pulsed laser ablation onto MgO(100) and LaAlO3(100) single crystal substrates at temperatures about 50∼100 K lower than the decomposition point of 2212 or 2223 phases. To get the effect of ex-situ annealing on the in-plane orientation and Tc, the films were accurately post-annealed in oxygen potential controlled furnace. The results showed that the Tc of the annealing films reached to 75∼80 K depending on the in-situ substrate temperature before annealing. The annealed 2223 films showed homogeneous intergrowth mixing of 2212 phase by 10∼20% and showed the Tc at 100∼105 K.
We found that the in-plane orientation of the 2212 films on MgO(100) substrates depends on the substrate temperature during deposition. The film deposited at the higher substrate temperatures have either 2212[100]\varparallelMgO[100]±11° and 2212[100]\varparallelMgO[110] relation or 2212[100]\varparallelMgO[100]±11°. While the film deposited at the lower substrate temperatures showed only the 2212[100]\varparallelMgO[100]±11° epitaxial relation. After annealing, the in-plane direction completely rotated by 45°, and only the 2212[110]\varparallelMgO[100] epitaxial relation became observable. On the other hand, from the films deposited on LaAlO3 substrate, only the strong 2212[100]\varparallelLaAlO3[100] in-plane epitaxial relation was observed irrespective of the substrate temperature and post-annealing.
