Deposition of mullite and mullite-like coatings on silicon carbide by dual-source metal plasma immersion

Mullite and mullite-like coatings on silicon carbide have been produced by a metal plasma immersion ion implantation and deposition (Mepiiid) technique based on two cathodic vacuum are sources and concurrent pulse biasing of the substrate in an oxygen atmosphere. The deposition was carried out at oxygen partial pressures of between 0.66 and 3.33 Pa. The Al:Si ratio in the films varied from 1:1 to 8:1 and was controlled by varying the pulse duration of the separate plasma guns. High bias voltage was used early in the deposition process in order to produce atomic mixing at the film-substrate interface, while lower bias voltage was used later in the deposition; low ion energy allows control of the physical properties of the film as well as faster deposition rates. The as-deposited films were amorphous, and crystalline mullite was formed by subsequent annealing at 1100 degrees C for 2 h in air. Strong adhesion between the mullite and the SiC was achieved, in some cases exceeding the 70 MPa instrumental limit of our pull-tester.