Surface Diffusion Constants and Supersaturations in SmBCO Films Prepared by Pulsed Laser Deposition Method

REBa₂Cu₃O_y (REBCO, RE = rare earth) coated conductors are required for high current carrying capability. Self-organization of Ba-M-O (BMO, M = Zr, Sn, Hf...) is available to improve critical current density (J_c) in magnetic field, and suppression of a-axis grain growth contributes to enhance J_c. The former and latter are affected by the surface diffusion of adatoms and supersaturation in the REBCO film growth, respectively. We focused on surface morphologies of SmBa₂Cu₃O_y (SmBCO) films deposited by the pulsed laser deposition method in this paper, and estimated surface diffusion constant and supersaturation from the surface morphologies. As a result, an activation energy of the surface diffusion was approximately 2.2 eV and the value is somewhat smaller than 2.5 eV for YBCO films. Additionally, we found that a-axis grains appeared when supersaturation (Δμ) became higher than a threshold Δμ. Interestingly, a seed layer consisting of c-axis oriented SmBCO suppressed a -axis grain growth. These findings are useful to improve J_c in REBCO coated conductors.