Metallic ion generation from ceramic rods by ECR ion source and thermodynamic feature of vaporization

Abstract Metallic ion generation from eight kinds of ceramic rods such as Al 2 O 3 , Mo 2 C, BN was examined by an ECR ion source with a direct insertion method, and stable ion beams were observed from six. Vapor pressure of possible products from a solid phase or a solid-liquid condensed phase of the examined materials was evaluated by thermodynamic calculation and ranged over more than nine orders of magnitude at high temperatures. A clear correlation was found between the beam stability of metallic ions and the surface condition of the rod ends exposed to the plasma, and it is completely explained by the magnitudes of the calculated vapor pressure. This indicates that the vaporization process can be understood as sublimation. Sputtering of the ceramic rods by ECR-plasma ions is considered not to be able to provide sufficient vapor pressure of metallic elements because of the low ion energy close to the sputtering threshold energy.