Synthesis of Ti₃AuC₂, Ti₃Au₂C₂ and Ti₃IrC₂ by noble metal substitution reaction in Ti₃SiC₂ for high-temperature-stable Ohmic contacts to SiC

The large class of layered ceramics encompasses both van der Waals (vdW) and non-vdW solids. While intercalation of noble metals in vdW solids is known, formation of compounds by incorporation of noble-metal layers in non-vdW layered solids is largely unexplored. Here, we show formation of Ti₃AuC₂ and Ti₃Au₂C₂ phases with up to 31% lattice swelling by a substitutional solid-state reaction of Au into Ti₃SiC₂ single-crystal thin films with simultaneous out-diffusion of Si. Ti₃IrC₂ is subsequently produced by a substitution reaction of Ir for Au in Ti₃Au₂C₂. These phases form Ohmic electrical contacts to SiC and remain stable after 1,000 h of ageing at 600 °C in air. The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.