Preparation of rare earth chalcogenide thin films by the co-evaporation technique

Abstract

Co-evaporation technique is shown to be a very powerful and straight forward method for the preparation of rare earth chalcogenide thin films LnX (Ln = Eu, Yb, Sm; X = Te, Se). All the monochalcogenides crystallising in the rock-salt structure have been obtained as single crystal films. For Sm, chalcogen rich compositions SmX1+δ have been obtained crystallising in the bcc structure. Solid solutions of Eu1−y MyX (M = Pb, Yb, Gd) crystallising in the rock-salt structure have been shown to exist. The optical and magneto-optical properties of these films are studied to characterise them. As an example, the optical transitions in YbTe and YbSe are shown to arise from a diamagnetic ground state of Yb2+ ion, whereas YbSe1.5 has a paramagnetic ground state.