Deposition Of Titanate Dielectric Thin Films By Micro-arc Oxidation

BaTiO3, SrTiO3 and Ba0.5Sr0.5TiO3 are typical electronic materials and earlist developed as perovskite ferrectrics. They are widely used in many technical industries. In recent years, it receives recognition in studies of physics, chemistry, material and micro-electronics.As a new kind of technology to produce ceramic films, Micro-arc Oxidation (MAO) has been well developed in recent decades. The MAO method is easy to operate and no environmental pollution. The oxidation coating is combined with the substrate in metallurgic and/or chemical reaction ways and has exellent properties of combination. Therefore, the MAO is employed to fabricate many kinds of ceramic coating on the substrate of Al, Mg, Ti, ectal.In this paper, studies the effects of the factors on the growth principle of the coationg are investigated, such as the solution compositions and their concentrations and electric parameters, The chief results are given as below:The MAO method was proposed firstly to fabricate the films of Ba0.5Sr0.5TiO3 and SrTiO3; The main solutes are NaOH, Sr(OH)2 for the forming of SrTiO3 coating and Ba(OH)2 and Sr(OH)2 for the forming of Ba0.5Sr0.5TiO3 coating on pure Ti substrate in DCelectric mode.The morphologies of the films were observed and anlysed. It was found that the lower the temperature of the electrolyte was, the more smooth the film was; and the greater the electrolyte concentration was, the more rough the dielectric film was, and the film thickness increased; and the larger the current density was, the more rough the dielectric film was, and the film thickness increased; It was also shown that the faster the frequency was, the more smooth the dielectric film was, but the film thickness became less; and the longer the reaction time was, the more rough dielectric film was,and the film thickness became greater.The growth principle of the films was investigated, and the empirical formula kinetic equation of coating growth was worked out, which is consistent with the experimental results.The dielectric constant of SrTiO3 thin films was tested and shown that the decrement as the frequency increased.