Growth of magnetron sputtered superconductor MgB2 thin films

Abstract

The discovery of superconductivity in the intermetalic compound MgB2 (39 K) in 2001 raised the great interest for the both science and technology applications. It has the highest Tc value among the intermetalic compounds. MgB2 has many properties make it very attractive for superconducting applications; these are large coherence length, high critical current density (Jc), high critical magnetic field (Bc) values. There are several methods developed to produce high quality MgB2 superconducting thin films. Magnetron sputtering system is a widely used method to deposit thin films. In this study, an MgB2/Mg target was produced by using MgB2 and Mg powders with a hot press technique. Prepared sputtering target used to grow MgB2 superconducting thin films on Al2O3 polycrystal and LaAlO3 single crystal substrate by a high vacuum magnetron sputtering system. To enhance the superconducting properties of as-grown films and to increase the crystal quality of the as-grown film an ex-situ anneal process was examined. X-Ray Diffraction (XRD) method was used to obtain crystal structure of the grown films. To observe the surface morphology of the films and to measure the thickness of the films Scanning Electron Microscopy (SEM) images were taken.Electron Dispersive X-Ray Spectroscopy (EDX) technique was used to identify the chemical contents of the films. Low temperature electrical measurement was done under various magnetic fields to observe the superconducting behavior of prepared films. The effects of ex-situ annealing process were also investigated. It was found that ex-situ annealing process develops the structural and electrical properties of MgB2 thin films.