In situ annealing of superconducting MgB2 films prepared by pulsed laser deposition

TL;DR

This study investigates the effects of in situ annealing conditions on the superconducting properties of MgB2 films prepared by pulsed laser deposition, identifying optimal parameters for high-quality superconducting films.

Contribution

It provides a detailed analysis of how annealing temperature, time, and heating rate influence the superconductivity of MgB2 films, offering optimized conditions for improved film quality.

Findings

Optimal annealing at 680-690°C for 1 min yields Tc onset of 28K.

Superconductivity is absent in unannealed MgB2 films.

Magneto-optical imaging shows homogeneous magnetic flux penetration.

Abstract

The in situ annealing conditions of pulsed laser deposited MgB2 films were studied. The precursor films were deposited at 250 C from a stoichiometric MgB2 target in a 120mTorr Ar atmosphere. The films were then in situ annealed at a temperature from 450 C to 800 C and an annealing time from 1 minute to 10 minutes. We found that the superconducting properties depend in a crucial way on the annealing conditions: temperature, heating rate and time. The best film with a thickness of ~600nm was obtained under the following annealing conditions: Tanneal=680-690 C, tanneal=1 min, heating rate= 38 C/min. The Tc onset of the film is 28K with a transition width of ~10K. The hysteresis loop of magnetic moment of the film indicates weak field dependence in high fields. Magneto-optical imaging of the film showed quite homogeneous magnetic flux penetration, indicating structural homogeneity. The films without annealing showed no superconductivity.