Optical monitoring of the deposition process of ferroelectric films

Abstract

A method of optical monitoring of deposition of ferroelectric Ba_0.8Sr_0.2TiO₃ films grown by high-frequency reactive plasma-enhanced chemical deposition has been considered. The studies of the plasma in the optical range have demonstrated that the emission spectrum at wavelengths λ > 450 nm is not changed in the range of bias voltages. At λ = 300–400 nm, a correlation takes place between the emission spectra of the film-forming medium obtained at different target-substrate voltages. The mass spectra of the film-forming medium indicate that, at bias voltages U = 350–600 V, the gaseous phase mainly contains ionized particles with the mass numbers of 220–240, which are close to the molar mass of Ba_0.8Sr_0.2TiO_{3 ± x} . At U > 650 V, the gaseous phase contains ions with mass numbers corresponding to the chemical compositions of the target components BaTiO₃, SrTiO₃, BaO, and SrO, along with multiatomic particles. It has been shown that a transition layer enriched in the substrate material exists at the interface. It has been found that the monitoring of the film-forming medium and the time factor make it possible to reproducibly grow nanosized films with given crystal-chemical parameters.