Ion sputter-deposition and in-air crystallisation of Cr2AlC films

Ternary alloys of composition close to Cr2AlC have been deposited by ion beam sputtering onto unheated and heated to 380 °C Si substrates. As-deposited films are amorphous. Annealing of the film in vacuum at 700 °C leads to crystallisation with 39.2 nm crystallites. Crystallisation also can be achieved by annealing in air but there is also partial oxidation of the film surface to the depth of approximately 120 nm, which represents an oxide layer less than 5% of the total film thickness. There is an increase of lattice size along the c-axis during crystallisation in air, which indicates a small incorporation of oxygen. Film structure and crystallisation have also been analysed by Raman spectroscopy. Changes in Raman spectra in Cr2AlC have been correlated with the film crystallisation and it was observed that MAX-phase related peaks become clearly defined for the crystallised film.