In situ layer‐by‐layer growth of YBa2Cu3O7−x thin films by multitarget sputter deposition

We have fabricated YBa2Cu3O7−x thin films using in situ layer‐by‐layer sputter deposition from metal targets. Yttrium, barium, and copper metals were deposited in the atomic monolayer sequence to construct the perovskite structure in the [001] direction. X‐ray diffraction indicates that these films are c‐axis oriented with the [001] direction normal to the film surface. Smooth films with zero‐resistance transition temperature Tc0=80 K and critical current density Jc(4.2 K)∼2×107 A/cm2, measured in zero magnetic field, have been grown on LaAlO3(100) substrates. Under the conditions studied, all films have a suppressed Tc and an expanded c‐axis lattice constant, with the degree of Tc suppression inversely proportional to the lattice constant. Tc and surface morphology were shown to be sensitive to the fractional monolayer coverage φ during each layer’s deposition. The results suggest that films grow in the layer‐by‐layer mode as opposed to island growth.