Synchrotron radiation studies of transition metal selenide thin-films formation on Ti, Mo and Cu substrates: in and out diffusion of Li

In this paper we study the formation of transition metal selenide thin-films. The investigation took place in ultra high vacuum (UHV) by means of photoemission spectroscopy with synchrotron radiation. The films were produced by simultaneous co-adsorption of TiCl₄ and elemental Se on polycrystalline Ti, Mo and Cu substrates, at 250°C. The above co-adsorption on Ti produces thin-films of TiSe₂ layer compounds, whereas, on the Mo and Cu substrates, Se interacts directly with the substrate producing a MoSe₂ layer compound and Cu_2-xSe thin-films, respectively. Deposited Li is intercalated into both TiSe₂ and MoSe₂ layer compound thin-films while it interacts with the non-layered Cu_2-xSe producing an alkalimetal copper selenide compound (Li_xCu_ySe_z). When the above Li_xCu_ySe_z and Li-intercalated TiSe₂, MoSe₂ thin films are exposed to TiCl₄ at 140°C, TiCl₄ dissociates, leading to a strong Li⁺-Cl^– interaction and the formation of a LiCl overlayer.