Thermal excitation-induced micro/nano fabrication and material modification of superconducting Nb films

Abstract

We report the thermal excitation-induced material modification and micro/nano fabrication based on the interactions between nano laser direct writing (NLDW) and superconducting films experimentally and by simulation. The niobium (Nb) films with a critical temperature of 9 K were deposited on silicon substrate via sputtering with the thickness of around 50 nm. The boundary between material modification and micro/nano fabrication was verified by changing the interaction time and laser power continuously. Specifically, as the laser power was fixed at 250 mW and the interaction time below 440 ns, the interaction is material modification. With the increasing interaction time further, the Nb films were etched away. As the interaction time was fixed at 500 ns and the laser power below 200 mW, the interaction is material modification too. With the increasing of laser power further, the Nb films were etched away. In the experiment, the oxygen content and current–voltage characteristic (IVCs) before and after laser irradiation were displayed to verify the material modification, which is in line with the simulation results. Considering the 50 nm resolution of NLDW, in the material modification region, one could trim trilayer junctions, tune shunt resistors, or adjust critical currents, etc. In the micro/nano fabrication region, one could fabricate various devices and exploit the properties of high spatial resolution, high flexibility, and fast processing.