Influence of composition and multilayer architecture on electrical conductivity of high temperature Pt-alloy films

A multilayer film architecture has been investigated as a means to stabilize the morphology and electrical conductivity of Pt-based nanocomposite films that are exposed to temperatures up to 1200 °C in air. The multilayer architecture consists of a 150 nm thick conducting Pt-alloy electrode inserted between a 10 nm thick adhesion layer and a 50 nm thick protective capping layer on sapphire or langasite substrates. The Pt-alloy films were fabricated by e-beam co-evaporation of a Pt or Pt83Rh17 source and a range of different alloying elements (Co, Ni, Cr, Rh, Ta, Ti, Nb, Al, Sn) or oxides (HfO2, ZrO2, Nb2O3, Y2O3, RuO2, CeO2, NiO, CoO, MnO2). Second phase inclusions or interlayers within the Pt-alloy films provide grain boundary pinning and hinder agglomeration of Pt grains, resulting in films that retain conductivities > 1 × 106 S/m after annealing in air. Pt-Al2O3, Pt-HfO2, and nanolaminate Pt-Ni/Pt-Zr films performed the best, remaining conductive after annealing to 1050-1150 °C. For Pt-Rh/HfO2 films, adhesion layers of Ni, Zr, Y, and CeOx yielded the highest film stability temperature. Capping layers of ZrO2 or Y2O3 did not significantly improve the film stability. Electrically conducting films that remain stable above 1000 °C in oxidizing high temperature environments have potential applications as electrodes in a wide range of technologies, including microwave acoustic sensors, MEMS devices, and fuel cells.