Excimer laser ablated deposition of ferroelectric lead germanate thin films

Abstract

Lead germanate (Pb₅Ge₃O₁₁) thin films were prepared by the excimer laser ablation technique. The structure of the films was characterized in correlation with beam energy density, substrate temperature, post-annealing temperature, oxygen pressure and the nature of substrates. c axis preferred oriented films can be obtained at a 5 J cm^-2 beam energy density and an oxygen partial pressure of 5 × 10^-4 Torr on platinum-coated silicon substrates, while a 2 J cm^-2 beam energy density was enough at a 10^-2 Torr oxygen pressure during deposition on sapphire substrates. Composition analysis indicated that the films were stoichiometric and close to the target composition. Films were found to be ferroelectric at room temperature in terms of a remanent polarization of about 2.5 µ C cm ^-2 with a coercive field of 55 kV cm^-1. The c axis preperred oriented films also exhibited a clear onset of the ferro-paraelectric phase transition at about 175 ° C which is close to that of the single crystal.