Effect of Gas Flow Ratio on the Chemical and Electrochemical Properties of Bismuth-Oxygen Films Deposited in Reactive Phase Sputtering

In this work, the study of chemical, physical, and electrochemical behavior of bismuth and oxygen-based thin films, produced through an unbalanced magnetron sputtering (UMS) technique in reactive phase, is presented. The main aim of this investigation is to analyze the influence of Ar/O₂ gas flow on the microstructure, chemical composition, and corrosion properties of bismuth and oxygen-based thin films. Coatings were grown keeping the power at 50 W with a mixture of Ar:O₂ (80/20) as constants, while the gas flow rate was varied taking values of 12, 15, 20, 25, and 30 sccm. X-ray diffraction (XRD) analyses were carried out showing that films exhibited a polycrystalline Bi phase and no crystalline bismuth oxide phases. For elemental composition analysis, the Rutherford backscattering spectroscopy (RBS) technique was used. The results suggested that film compositions were a mixture of metallic bismuth and amorphous bismuth oxide; moreover, chemical elemental distribution was studied using proton-induced X-ray emission (PIXE) measurements determining that before the corrosion analysis, samples exhibited a uniform distribution of Bi and O. Finally, the influence of the gas flow on the films anticorrosive properties was discussed. Potentiodynamic polarization technique results revealed that the corrosive behavior highly depends on the sample production parameters; samples grown at 20 and 30 sccm showed the best corrosion resistance represented in lower corrosion current density. This behavior is probably due to the thickness of these films.