Microstructure and Properties of Superconducting Tungsten Thin Films: Influence of Substrate Temperature and Annealing temperature

Abstract

\(\alpha\)-W thin films are widely used in superconducting transition edge sensors due to their extremely low transition temperature and weak electron–phonon coupling. However, the influence of annealing and substrate temperatures on thin film performance has not been fully understood, nor has the relationship between microstructure and thin film performance. In this study, we investigate the changes in grain size, resistivity, film stress, and transition temperature of the film by varying the annealing and substrate temperatures. Microstructure showed that annealing contributed to grain growth. With the increase in annealing temperature, the resistivity of the film decreased and the compressive stress was relieved. The minimum transition temperature reached 28.7 mK at an annealing temperature of \(470 ^{\circ }\)C. In addition, the GIXRD results showed that the preferred orientation of the films changed from (110) to (211) with the increase in the substrate temperature. \(100 ^{\circ }\hbox {C}-230 ^{\circ }\)C favorite to reduce film resistivity and transition temperature, and to relieve film compressive stress.