Growth of high quality epitaxial Nb films via Sputter Beam Epitaxy

High-quality epitaxial thin films play a critical role in the creation of novel superconducting and quantum devices. In particular, nanoscale niobium films often serve as the primary material platform for superconducting quantum interference devices (SQUIDs), Josephson junctions, and thermal infrared detectors.

Thin films of Nb were grown on hexagonal Al₂O₃(11-20) substrates via an off-axis sputter beam epitaxy technique. X-ray diffractometry and reflectivity measurements demonstrated the samples to be single-crystal with low surface roughness. Rocking curve analysis indicated highly epitaxial films, with an omega-scan full width at half maximum of as little as 0.034°. Scanning electron microscopy (SEM) imaging revealed excellent surface conditions absent of defects and with minimal roughness. Variations in the Nb out-of-plane lattice constant were investigated as function of deposition rate and chamber temperature. Magnetic measurements of the Nb films will also be presented.