Scanning vortex microscopy reveals thickness-dependent pinning nano-network in superconducting niobium films

The presence of quantum vortices determines the electromagnetic response of superconducting materials and devices. Controlling the motion of vortices and their pinning on intrinsic and artificial defects is therefore essential for further development of superconducting electronics. Here we take advantage of the attractive force between a magnetic tip of the Magnetic Force Microscope and a single quantum vortex to spatially map the pinning force inside 50–240 nm thick magnetron-sputtered niobium films, widely used in various applications. The revealed pinning nanonetwork is related to the thickness-dependent granular structure of the films as well as to the characteristic microscopic scales of superconductivity. Our approach is general and can be directly applied to other type-II granular superconducting materials and nanodevices. Controlling the motion and pinning of vortices is essential for developing superconducting electronics. Here, the authors reveal the vortex pinning nano-network in thin superconducting niobium films by developing a scanning quantum vortex microscopy approach.