High critical currents in strained epitaxial YBa2Cu3O7−δ on Si

Abstract

Epitaxial YBa2Cu3O7−δ (YBCO) films were grown on Si (100) using an intermediate buffer layer of yttria-stabilized zirconia. Both layers are grown via an entirely in situ process by pulsed laser deposition. All films consist of c-axis oriented grains as measured by x-ray diffraction. Strain results from the large difference in thermal expansion coefficients between Si and YBCO. Thin (<500 Å) YBCO films are unrelaxed and under tensile strain with a distorted unit cell. Rutherford backscattering spectroscopy indicates a high degree of crystalline perfection with a channeling minimum yield for Ba as low as 12%. The normal-state resistivity is 280 μΩ cm at 300 K; the critical temperature Tc (R=0) is 86–88 K with a transition width (ΔTc) of 1 K. Critical current densities of 2×107 A/cm2 at 4.2 K and 2.2×106 A/cm2 at 77 K have been achieved.