Josephson Junctions Fabricated by Focused Ion Beam from Ex Situ Grown MgB2 Thin Films
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http://www.sciencedirect.com/science/article/pii/S0921453404000978
We prepared MgB2 thin films on SrTiO3 (1 0 0) and Al2O3 (1 1̄ 0 2) substrates by e-beam evaporation of MgB2 pellet. The films were deposited at room temperature and post-annealed at 900 °C in Mg vapour for 5–30 min. Superconducting transition temperatures were observed between 22 and 30 K. Structure and surface morphology of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The films grown on Al2O3 substrates are c-axis oriented while a film grown on SrTiO3 substrate is aligned with the (1 0 1) direction normal to the substrate planes. The films have grain sizes of about 70 nm. The films were patterned into 4 and 8 μm wide microbridges. The microbridges were observed to carry large critical current densities of approximately 1 MA/cm2 at 6.7 K. Focused ion beam (FIB) was used on the bridges in order to fabricate Josephson junctions. A cut 50 nm in width was made across the microbridges followed by an in situ platinum (Pt) deposition into the cut made. SNS-like weak-link junctions were formed in the process.
We prepared MgB2 thin films on SrTiO3 (1 0 0) and Al2O3 (1 1̄ 0 2) substrates by e-beam evaporation of MgB2 pellet. The films were deposited at room temperature and post-annealed at 900 °C in Mg vapour for 5–30 min. Superconducting transition temperatures were observed between 22 and 30 K. Structure and surface morphology of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). The films grown on Al2O3 substrates are c-axis oriented while a film grown on SrTiO3 substrate is aligned with the (1 0 1) direction normal to the substrate planes. The films have grain sizes of about 70 nm. The films were patterned into 4 and 8 μm wide microbridges. The microbridges were observed to carry large critical current densities of approximately 1 MA/cm2 at 6.7 K. Focused ion beam (FIB) was used on the bridges in order to fabricate Josephson junctions. A cut 50 nm in width was made across the microbridges followed by an in situ platinum (Pt) deposition into the cut made. SNS-like weak-link junctions were formed in the process.
Keywords
Superconducting, MgB2, Thin films, Ex situ, E-beam evaporation