Deposition of NbN Superconducting Thin Films Using Ion Beam Assisted Sputtering

Transition metal nitrides are a large family of materials with wide range of electronic and mechanical properties, making them a popular choice for applications in protective coatings, quantum optics or superconducting electronic devices. Typical member of this family is NbN, which is a superconductor used predominantly in the field of single photon detectors. Using the common preparation method of reactive magnetron sputtering, temperatures of up to 650 ^oC are required to achieve high-T_c supercondicting crystal phase in this material, making it incompatible with many processes and materials. In this presentation, we report on a new method of deposition of NbN films, where we utilize ion beam assisted sputtering. Using this method, high-T_c NbN films deposited at room temperature can be achieved with added benefit of dramaticaly reduced sensitivity of T_c to N₂ concentration. We also present results of systematic study of the materials electric, magnetic and structural properties as functions of the nitrogen ion concentration and energy and compare them to films deposited by reactive magnetron sputtering.