Fabrication of a/c axes oriented grain boundaries in YBCO films by selective growth

The a/c axes grain boundaries of YBCO films are very interesting from the viewpoints of Josephson junction technology and the magnetic flux pinning. In this paper, we intend to flow superconducting current along the grain boundary and to prevent the magnetic flux motion from passing across the grain boundary. The a/c axes grain boundaries were fabricated on SrLaGaO₄ (100) substrates by pulsed laser deposition on Gd₂CuO₄ (GCO) buffer layers. The preferred orientation and in-plane orientation of the films were characterized by X-ray θ/2θ diffraction and φ-scan spectroscopy. 4-micrometer pitch GCO patterns were fabricated by a lithography technology. Subsequently, the YBCO films were deposited on the pattern. A TEM image showed that a-axis grains grew over c-axis grains.