Growth and ellipsometric characterizations of highly (111)-oriented Bi ₂Ti₂O₇ films on platinized silicon by metal organic decomposition method

Optical properties and electronic structure of Bi2 Ti2 O7 (BTO) films on platinized silicon substrates have been investigated using near-infrared- ultraviolet spectroscopic ellipsometry. The optical dispersion in the photon energy range of 0.73-5.8 eV has been extracted by fitting the experimental data with a four-phase layered model. The Tauc-Lorentz dispersion function has been fundamentally applied and describes the optical response of the BTO films well. The refractive index in the transparent region can be reasonably fitted by a single oscillator function and the maximum electronic transition occurs near 4.2 eV for the BTO material. The long wavelength refractive index n (0) can be estimated to about 1.7 at zero point. The fundamental band gap energy was determined to be about 3.2 eV, which was supported by different theoretical evaluation methods. The present results can be important for future applications of BTO-based electro-optics and optoelectronic devices.