Sputter Synthesis of Ba₂YCu₃O_y As-Deposited Superconducting Thin Films from Stoichiometric Target–A Mechanism of Compositional Deviation and Its Control

Abstract

A mechanism of compositional deviation of Ba-Y-Cu-O films during sputtering has been investigated, and a process for obtaining as-deposited superconducting films from a stoichiometric target has been developed. The main factor of the deviation is the radiation of high-energy electrons emitted from the oxide target with a low work function onto the growing surface. By eliminating the electron bombardment, films with the same composition were obtained reproducibly. As-grown films 4000 Å thick deposited at 580°C showed T c ( ρ=0) of 82.5 K and an excellent surface smoothness.

Study of interdiffusion between thin Y–Ba–Cu–O films and MgO substrates by applying Rutherford backscattering spectrometry combined with scanning tunneling microscopy

“…Thin films of Y-Ba-Cu-O were deposited on MgO ͑100͒ substrates from a sintered target with an initial cation ratio of 1Y: 2Ba: 4.5Cu in Arϩ24%O 2 at a pressure of 2ϫ10 Ϫ2 Torr by a radio frequency magnetron sputter deposition method with a transverse magnetic field. 9 In order to obtain the 123 stoichiometric Y-Baa͒ Electronic mail: yutaka.fujino@qse.tohoku.ac.jp Cu-O films, nonstoichiometric Cu-rich target composition was deliberately chosen, considering the reported results that the conventional face-to-face substrate-to-target arrangement usually provide Y-rich and Cu-poor films compared with the target composition. 10 Although crystallized films could be obtained by heating the substrates at a temperature of about 950 K during deposition, amorphous films were used as specimens in the present study.…”

A Critical Review of Laser Ablation-Synthesis of High Temperature Superconducting Films

“…In this case, the activated oxygen was produced by the plasma established between the superconductor target (cathode) and the substrate (anode). A possible reason for the relatively low T. obtained may have been the bombardment of the growing film by negative oxygen ions and secondary electrons from the target, which can produce deleterious compositional changes as it has been demonstrated by different groups (36,37). These results indicate that not all sources of activated oxygen will be viable alternatives for the production of high quality as deposited superconducting films.…”

Working with ceramic superconducting materials: processes and problems

“…Controlling the composition is not a trivial problem, however, especially when sputtering, as oxygen ions tend to selectively resputter the film, with results which are strongly dependent on temperature and pressure. This can be overcome by using high pressures [32], or using non-standard geometries to keep the substrate away from the oxygen ions [33,34].…”