Formation of buried superconducting Mo 2 N by nitrogen-ion-implantation.

Nitrogen ion implantation is a useful technique to put nitrogen ions into lattices. In this work, nitrogen ion implantation into epitaxial Mo films is performed to create a buried superconducting γ-Mo 2 N. Atomically flat epitaxial (110) Mo films are grown on (0001) Al 2 O 3 . By impinging nitrogen ions, where the beam energy is fixed to 20 keV, we observe (111) γ-Mo 2 N diffraction and the formation of a γ-Mo 2 N layer from X-ray reflectivity. Magnetization and transport measurements clearly support a superconducting layer in the implanted film. Our strategy shows that formation of a buried superconducting layer can be achieved through ion implantation and self-annealing.