Amorphization and crystalline regrowth of GdBa 2Cu 3O 7 thin films by ion implantation and RTA

Abstract

Thin films (about 300 nm) of GdBa 2Cu 3O 7 (GBCO), sputtered onto MgO substrates, have been implanted with 20Ne + ions, to doses of 5 × 10 14 ions cm −2 (200 keV) and 3 × 10 14 ions cm −2 (150 keV). Either implant causes amorphization above a damage threshold, the former extending throughout the film thickness, while the latter leaves some crystalline material near to the substrate interface. Rapid thermal annealing (20 s, in oxygen, at a temperature around 840 °C), induces recrystallization, which can lead to a recovery of the superconducting phase. By patterning the film with arrays of dots, it is possible to retain columnar crystalline seeds (masked from the amorphizing radiation by the dots) surrounded by an amorphous field. Subsequent annealing will induce solid-solution grain growth, leading to arrays of c-axis-oriented crystals with centres in defined positions. The ultimate aim is to extend this seeded crystal growth to cover the entire film area. While TEM is the preferred method for following the grain growth, a technique of differentially etching amorphous, micro-polycrystalline and polycrystalline material has been devised to speed up characterization. Results are presented from T c, XRD, optical microscopy, and TEM investigations.