Improvement of oxidation and corrosion resistance of Mo thin films by alloying with Ta

Molybdenum thin films are commonly used as electrode materials for thin film transistor liquid crystal displays. As low-temperature oxidation deteriorates their electrical resistivity, the aim of this study was to improve their oxidation resistance by alloying with tantalum. Thin films with tantalum contents ranging from 0 to 100 at.% have been synthesized by magnetron co-sputtering. Beside the evaluation of microstructure and resistivity with increasing tantalum content, special emphasis is laid on formation of surface oxides during exposure to elevated temperature and humidity. The formation of a transparent tantalum oxide minimizes surface oxidation, preventing growth of intensively colored molybdenum oxide scales. Potentio-dynamic measurements further highlight the positive influence of tantalum, evidencing the development of a passive region and a drop of the corrosion current density to almost zero. - Highlights: • Synthesis of Mo films with Ta contents ranging from 0 to 100 at.% by co-sputtering. • Electrical resistivity is almost unaffected for Ta contents up to 20 at.%. • Formation of transparent Ta oxide scales hinders growth of colored Mo oxides. • Significant drop of corrosion current density by Ta alloying.