Low-pressure large-area magnetron sputter deposition of YBa2Cu3O7-δ films for industrial applications

This paper addresses the development of a technically relevant sputter-deposition process for YBa2Cu3O7-δ films. First, the simulation of the particle transport from target to substrate indicates that only at a reduced pressure of p ≈ 1-10 Pa can a sufficiently large deposition rate and homogeneous stoichiometric distribution of the particles during large-area deposition be expected. The results of the simulations are generally confirmed by deposition experiments on CeO2 buffered sapphire and LaAlO3 substrates using a magnetron sputtering system suitable for large-area deposition. However, it is shown that in addition to the effect of scattering during particle transport, the conditions at the substrate lead to a selective growth of Y-Ba-Cu-O phases that, among others, strongly affect the growth rate. For example, the growth rate is more than three times larger for optimized parameters compared to the same set of parameters but at 100 K lower substrate temperature. Stoichiometrical and structural perfect films can be grown at low pressure (p < 10 Pa). However, the superconducting transition temperature of these films is reduced. The Tc reduction seems to be correlated with the c-axis length of YBa2Cu3O7-δ. Two possible explanations for the increased c-axis length and the correlated reduced transition temperature are discussed, i.e. reduced oxygen content and strong cation site disorder due to the heavy particle bombardment.