Nickel adsorption on Bi$_{2}$Se$_{3}$ surface

The effect of the physical adsorption of nickel on a surface of a topological Bi$_{2}$Se$_{3}$ insulator on the electronic structure has been studied. The influence of the adsorbate on the chemical bond between Bi and Se atoms has been studied by X-ray photoelectron spectroscopy. It is shown as well that nickel atoms diffuse into the topological insulator volume at room temperature.