Structural and optical characterization of BaTiO₃ thin films prepared by metal-organic deposition from barium 2-ethylhexanoate and titanium dimethoxy dineodecanoate

Abstract

Single phase BaTi0₃ thin films were prepared by metal-organic deposition (MOD) using barium 2-ethylhexanoate and titanium dimethoxy dineodecanoate as the metal-organic precursors. A series of experiments was conducted on the metal-organic spin-coated films and their correspondingly annealed samples by employing experimental techniques ranging from thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and scanning electron microscopy (SEM), to various optical property characterization methods. A better understanding has been achieved regarding the metal-organic decomposition mechanism, the solid-state BaTi0₃ film formation and crystallization process, as well as the relationship between the structure and the optical properties of the prepared films. The conclusions of our experiments are as follows: Upon annealing the barium 2-ethylhexanoate spin-coated films, barium carbonate (BaC0₃) is formed at a relatively low temperature of 300 °C, and at an annealing temperature around 700 °C forms the barium peroxymonocarbonate (BaCO₄). Upon annealing the titanium dimethoxy dineodecanoate spin-coated films, anatase is first formed at a low annealing temperature about 400 °C and transforms to rutile phase around an annealing temperature of 800 °C. Upon annealing the spin-coated films from the equimolar mixture of barium 2-ethylhexanoate and titanium dimethoxy dineodecanoate formulations, BaTi0₃ is formed around an annealing temperature of 600 °C via solid-state reaction between BaCO₃ and TiO₂ (anatase). The structure of MOD prepared BaTiO₃ films has several specific features: instead of the columnar structure in physical vapor deposited (PVD) films, the crystal grains in granular shape are characteristic of MOD films, and the crystallites are much larger near the surface of the film than near the substrates. Optical properties of the prepared BaTi0₃ films have been reported. Optical characterization shows that the scattering losses contribute dominantly to the total optical losses. The relationship between the structure and the optical properties of the prepared films has also been discussed.