Deposition of MAX phase-containing thin films from a (Ti,Zr)2AlC compound target

Highlights: • (Ti,Zr)C films with up to 17 at.% of dissolved Al were obtained at 500 °C. • Longer depositions at 900 °C led to multiphase films containing the MAX phase. • (Ti,Zr)₂AlC forms close to Al-rich areas (Al₂O₃ substrates and/or intermetallics). This work reports on sputter depositions carried out from a compound (Ti,Zr)₂AlC target on Al₂O₃(0 0 0 1) substrates at temperatures ranging between 500 and 900 °C. Short deposition times yielded 30–40 nm-thick Al-containing (Ti,Zr)C films, whereas longer depositions yielded thicker films up to 90 nm which contained (Ti,Zr)C and intermetallics. At 900 °C, the longer depositions led to films that also consisted of solid solution MAX phases. Detailed transmission electron microscopy showed that both (Ti,Zr)₂AlC and (Ti,Zr)₃AlC₂ solid solution MAX phases were formed. Moreover, this work discusses the growth mechanism of the thicker films, which started with the formation of the mixed (Ti,Zr)C carbide, followed by the nucleation and growth of aluminides, eventually leading to solid state diffusion of Al within the carbide, at the highest temperature (900 °C) to form the MAX phases.