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 TiCI4 and elemental Se on polycrystalline Ti, Mo and Cu substrates, at 250 degreesC. 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 Cu2-xSe thin-films, respectively. Deposited Li is intercalated into both TiSe2 and MoSe2 layer compound thin-films while it interacts with the non-layered Cu2-xSe producing an alkalimetal copper selenide compound (LixCuySez). When the above LixCuuSez and Li-intercalated TiSe2, MoSe2 thin films are exposed to TiCl4 at 140 degreesC, TiCl4 dissociates, leading to a strong Li+-Cl- interaction and the formation of a LiCl overlayer. (C) 2001 Elsevier Science B.V. All rights reserved.