Structure of β-tantalum-tungsten alloy films produced by the codeposition of sputtered metals

Abstract

Ion-plasma sputtering and the codeposition of Ta and W ultrafine particles is used to produce solid solutions in the entire concentration range of the Ta-W binary system in the form of alloy coatings. The formation of solid-solution alloys directly during the codeposition process confirms the theory of thermal-fluctuation melting of small particles and the coalescence of quasi-liquid clusters of subcritical size. During the formation of coatings based on Ta and W layers with a thickness less than 0.5 nm mutual dissolution of the components occurs. Starting at a concentration of 34 at % W in the alloy, tungsten atoms specify their own type of crystal-lattice symmetry. Apart from the formation of [beta]-tantalum and tungsten phases, an increase in the thickness of the tantalum and tungsten sublayers leads to the appearance of metal solid solutions, amorphous inclusions, and nanocluster superlattices of one metal in the matrix of another. At high tungsten concentrations a superstructure of tantalum nanoclusters is not observed in the coating. It is supposed that the size factor is the origin of superstructure formation.