Optical monitoring of the deposition process of ferroelectric films

Abstract

A method of optical monitoring of deposition of ferroelectric Ba0.8Sr0.2TiO3 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 Ba0.8Sr0.2TiO3 ± 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.