Sputtering of amorphous metallic alloys

Abstract

The sputtering process of a multicomponent alloy depends significantly on its structural state and the phase condition and on the temperature attained during the irradiation process since in multicomponent materials, the mass transfer processes can occur at relatively low temperatures (e0.2 Tmp) due to the radiation-induced segregation of impurities, the radiation-stimulated diffusion, and the diffusion associated with the selective (preferential) nature of sputtering. A study of the sputtering process of amorphous metallic alloys is extremely important from the physical standpoint owing to the absence of different types of segregation and excess phases (i.e., the regions differing significantly with respect to atomic structure and chemical composition) in this case. Besides this, amorphous alloys always form single-phase systems that do not exhibit crystalline anisotropy and do not contain lattice defects such as dislocations, grain boundaries, blocks, and stacking faults. All these facts make amorphous metallic alloys exceptional experimental objects for studying the specific features of the selective sputtering process of the components of the alloys, the regularities in the angular and the energy distributions of the sputtered particles, and the effect of the chemical composition on the total (complete) coefficient of sputtering of the alloys. A study of the physics of sputtering of amorphous metallic alloys has at least two aspects related to the practical problems of materials science in the first wall of thermonuclear reactors. Firstly, during the interaction of plasma with the wall, amorphous layers can form, in particular, during disruption of plasma at the walls of the vacuum chamber where the energy of plasma is liberated for a short time (~i0 -~ sec) leading to the fusion and evaporation of the material. Steels and the Fe-CrNi alloys are frequently treated as promising materials for the first wall. Secondly, the experimental data concerning the radiation-induced surface erosion of the amorphous metallic alloys during bombardment with He + ions [i] and the first experiments on the sputtering process indicate their higher radiation resistance (as compared to the analogous crystalline alloys) and, therefore, they form promising structural materials for thermonuclear reactors.