Nanodimensional superconducting quantum interference devices

The fabrication methods, principle of operation, microstructural, and electron transport properties, as well as the application of nanoscale superconducting quantum interference devices (nanoSQUIDs) are considered. NanoSQUIDs by definition have a submicrometer loop size, which limits dimensions of Josephson junctions to about 100 nm or less. This makes the use of tunnel junctions problematic, but encourages the use of nanobridges and other types of Josephson junctions with high critical current densities. The use of nitride superconductors helps to optimize the superconducting parameters and enhances the corrosion resistance of the nanobridge Josephson junctions and nanoSQUIDs. Additional passivation by a Si layer improves thermal sink and protects against the mechanical and electrical fragility of the devices. Nanosculpturing of cantilevers makes it possible to position the nanoSQUID at a distance of 10–100 nm from the objects under study in the nanoSQUID scanning measurement system. Several promising applications of nanoSQUIDs are briefly reviewed.