Formation mechanism of BaZrO₃ nanorods in SmBa ₂Cu₃O_y thin films

In BaZrO₃(BZO) doped REBa₂Cu₃O _y(REBCO) films deposited by pulsed laser deposition, BZO nanorods grow almost parallel to c-axis in REBCO films. In this study, in order to understand the mechanism for the formation of BZO nanorods, we investigated the influence of the substrate temperature of the upper layer (T₈ ^upper) in the low temperature growth (LTG) technique on the growth of BZO nanorods in SmBa₂Cu₃O_y(SmBCO) films. Furthermore, we discussed the diffusion process on BZO and estimated the activation energy for surface diffusion of constituent atoms in BZO. With decreasing T₈^upper, the diameter of BZO nanorods was decreased and the number density was increased. In addition, the angle of inclination of BZO nanords with respect to c-axis in SmBCO became larger with decreasing T₈^upper It is found that the diffusion process could be dominant in the nucleation of BZO. We attributed self-organized growth of BZO nanorods to the diffusion process as well as the strain energy resulting from a lattice mismatch between SmBCO and BZO.