Growth of superconducting MgB2 thin films via postannealing techniques

TL;DR

This study explores how postannealing temperature and time affect the superconducting properties and microstructure of MgB2 thin films, identifying optimal conditions for high-quality superconductivity.

Contribution

It provides new insights into the effects of annealing parameters on MgB2 thin film quality and superconducting performance, including microstructural evolution and optimal annealing conditions.

Findings

Optimal annealing at 900°C for 30 min yields Tc of 39 K and Jc of ~10^7 A/cm^2.

Higher annealing temperatures increase grain size and improve crystal orientation.

Extended annealing times degrade superconductivity due to interfacial reactions.

Abstract

We report the effect of annealing on the superconductivity of MgB2 thin films as functions of the postannealing temperature in the range from 700 C to 950 C and of the postannealing time in the range from 30 min to 120 min. On annealing at 900 C for 30 min, we obtained the best-quality MgB2 films with a transition temperature of 39 K and a critical current density of ~ 10^7 A/cm^2. Using the scanning electron microscopy, we also investigated the film growth mechanism. The samples annealed at higher temperatures showed the larger grain sizes, well-aligned crystal structures with preferential orientations along the c-axis, and smooth surface morphologies. However, a longer annealing time prevented the alignment of grains and reduced the superconductivity, indicating a strong interfacial reaction between the substrate and the MgB2 film.