Low temperature diffusion measurements on d.c. sputtered multilayers of Nb/Ta

Niobium tantalum multilayers have been shown to be particularly well suited to metal superlattice formation due to their similar lattice parameters. The diffusion study reported here on NbTa is the result of preliminary work on the formation of a variety of alloy/alloy and alloy/element multilayer structures. The samples were prepared in a getter sputtering system incorporating two d.c. magnetron sources. Experimental details are given. The samples show clearly the zero and first order X-ray diffraction peaks. The satellite peaks of the best sample have 50% of the theoretical maximum intensity. The resistivity data indicates that the composition change at the interfaces is sharp and that the defect density is low. The diffusion coefficient is measured from the decay of the X-ray satellites. Results of resistance measurements and superconducting transition temperature are given. (U.K.)