The role of the substrate temperature on superconducting properties of sputtered Nb films

The influence of the substrate temperature T-S on the superconducting properties of 100 nm sputtered Nb films, prepared directly onto orientated Si (100) substrate, was systematically investigated by measuring their structural, morphological and magnetic properties. Within the T-S interval 293-373 K no significant change is observed either in the Nb lattice parameter or in the superconducting transition temperature T-C. For T-S > 373 K, a degradation of the Nb superconducting properties was observed concomitantly with an increase of the Nb lattice parameter. This effect was attributed to an interdiffusion at the Si/Nb interface and/or an enhancement of the internal stress caused by high temperature deposition. The temperature dependence of the critical current density J(C)(T) was estimated from magnetization measurements and its behavior is explained based on the granular morphology of Nb films. This work provides some insights on the optimum T-S responsible for the highest J(C) value. It also brings information on how T-S affect the superconducting properties of Nb films sputtered directly on Si (100) by DC magnetron sputtering. (C) 2016 Elsevier B.V. All rights reserved.