Effects of 50 keV²H⁺-ion implantation and rapid thermal annealing on the microstructure of YBCO thin films

Abstract

A YBCO film with thickness of about 200 nm was deposited on LaAlO₃[100] by direct current (d.c.) sputtering. The film, which was found to be mainlyc-axis orientated, was irradiated at room temperature with 50 keV²H⁺ ions to a dose of 1×10¹⁶ cm⁻². This implantation destroyed the superconductivity and made the film textured, with the “epitaxial” crystalline structure of the film being mainly maintained. Transmission electron microscope studies show that there are a considerable number of amorphous islands, which are Y rich and Cu poor compared with the 123 phase in the as-received YBCO film. These amorphous islands are found to be unstable under the irradiation, as after implantation some polycrystalline regions, rather than amorphous islands, can be seen by TEM. Rapid thermal annealing in flowing O₂ ambient can induce oxygen reordering and results in partial recovery of critical temperature,T _c . After RTA, the polycrystalline regions have not changed.