The role of surface energy anisotropy in the formation of a stepped relief of polycrystalline W under sputtering with Ar ions

Abstract

This paper is devoted to the study of the effect of surface energy anisotropy on the tungsten surface relief modification under ion sputtering. In our experiments, the sputtering of textured polycrystalline tungsten with Ar ions resulted in a stepped surface relief formation. The surface after sputtering was analyzed using the electron backscatter diffraction and confocal laser scanning microscopy techniques. The formation of the stepped relief is explained by different surface energies of differently oriented grains (surface energy anisotropy). The surface energies of the three low-index W planes were calculated in the model of broken bonds. It is shown for the first time that the ratio of the sputtering depth of differently oriented grains of W is equal to the ratio of the differences of the surface energies of these grains. In that way, the ratio of the sputtering yields of differently oriented grains of tungsten can be quantified by knowing the surface energy, which depended on the reticular grain density and the number of broken bonds with nearest and next-nearest neighboring atoms on the surface using the broken bond model. It is shown that ion sputtering can be used as an instrument for studying the surface energy of solids.