Structural and optical characterization of BaTiO 3 thin films prepared by metal-organic deposition from barium 2-ethylhe
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A. Singh National Optical Institute, 369, Rue Franquet, Ste-Foy, Quebec, Canada G1P 4N8
Z. L. Wu and P. K. Kuo Department of Physics, Wayne State University, Detroit, Michigan 48202 (Received 10 June 1993; accepted 9 December 1993)
Single phase BaTiO3 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 BaTiO3 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 (BaCO3) is formed at a relatively low temperature of 300 °C, and at an annealing temperature around 700 °C forms the barium peroxymonocarbonate (BaCO 4 ). 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, BaTiO3 is formed around an annealing temperature of 600 °C via solid-state reaction between BaCO 3 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 BaTiO3 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.
I. INTRODUCTION Recently, there has been increased interest in barium titanate in both crystal and thin film forms. For barium titanate crystal, interest was mainly due to its photorefractive properties and other associated effects and applications, such as phase conjugation, volume holography for optical storage, two-beam coupling, and optical computing.1 For barium titanate thin films, mainly due a
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J. Mater. Res., Vol. 9, No. 4, Apr 1994 Downloaded: 12 Mar 2015
to its exceptional electronic properties, it has a very high dielectric constant (e > 2000) and a large
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