Magnetron sputtered Ta films with different double layer structures: Growth mechanism and corrosion behavior

Ta films deposited by magnetron sputtering present a promising eco-friendly alternative to electroplated chromium for naval gun steel protection. The growth mechanism and corrosion behavior of three Ta films with α, β, and (α+β) phase structures through XRD, TEM, AFM, SEM and electrochemical analysis were investigated in this study. The results showed that all films exhibited a consistent double-layer architecture, consisting of an amorphous inner layer and a crystalline outer layer, with the phase composition being controlled by the deposition process. Specifically, an equiaxed β-Ta structure formed without bias, a mixed (α+β) phase at 30 V bias, and a columnar α-Ta structure at 150 V bias with HPPMS. Although the (α+β)-Ta film was the thinnest, it demonstrated the highest corrosion resistance in electrochemical and long-term immersion tests. This superior performance is attributed to the synergistic effect of its tough mixed-phase outer layer and dense amorphous inner diffusion barrier, which collectively minimize porosity. These findings indicate the critical role of the double-layer structural design in corrosion resistance, providing valuable guidance for engineering high-performance Ta films.