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Magnetron Sputtered Non-Toxic and Precious Element-Free Ti-Zr-Ge Metallic Glass Nanofilms with Enhanced Biocorrosion Resistance

The chemical composition and structural state of advanced alloys are the decisive factors in optimum biomedical performance. This contribution presents unique Ti-Zr-Ge metallic glass thin-film compositions fabricated by magnetron sputter deposition targeted for nanocoatings for biofouling prevention. The amorphous nanofilms with nanoscale roughness exhibit a large relaxation and supercooled liquid regions as revealed by flash differential scanning calorimetry. Ti\textsubscript{68}Zr\textsubscript{8}Ge\textsubscript{24} shows the lowest corrosion (0.17 \textmu A cm\textsuperscript{\textminus2}) and passivation (1.22 \textmu A cm\textsuperscript{\textminus2}) current densities, with the lowest corrosion potential of \textminus0.648 V and long-range stability against pitting, corroborating its excellent performance in phosphate buffer solution at 37 {\textdegree}C. The oxide layer is comprised of TiO\textsubscript{2}, TiO\textsubscript{\emph{x}} and ZrO\textsubscript{\emph{x}}, as determined using X-ray photoelectron spectroscopy by short-term ion-etching of the surface layer. The two orders of magnitude increase in the oxide and interface resistance (from 14 to 1257 {\textOmega} cm\textsuperscript{2}) along with an order of magnitude decrease in the capacitance parameter of the oxide interface (from 1.402 x 10\textsuperscript{\textminus5} to 1.677 x 10\textsuperscript{\textminus6} S s\textsuperscript{n} cm\textsuperscript{\textminus2}) of the same composition is linked to the formation of carbonyl groups and reduction of the native oxide layer during linear sweep voltammetry.