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

• 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.

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.