Synthesis of NbN Thin Films for Superconducting Radiofrequency (SRF) Applications by Atomic Layer Deposition to Fabricate Superconductor-Insulator-Superconductor (S-I-S) Multilayer Structures

摘要

RF superconductors operate in the Meissner state, where magnetic fields are expelled from the volume of the superconductor. Presently bulk niobium is used for existing superconducting radiofrequency (SRF) cavities for accelerator technology, because of a critical magnetic field (Hcl ~170mT), which exceeds those of competing materials (1,2,3). Based on recent theoretical work by Gurevich (4, 5) multiple layers of superconductor-insulator-superconductor (S-I-S) thin films are expected to surpass the total critical field limit of bulk niobium. Atomic Layer Deposition (ALD) has been suggested as a method of depositing alternating SRF layers on insulators by employing ALD Al_2O_3 as the insulating material. NbN is considered a leading alternative material for SRF films with a critical temperature Tc of 16.2 K.