Optical Properties of Hf-Ti-O Films Obtained by Atomic Layer Deposition

Optical properties of the Hf1-xTixO2 (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$x=0 \ldots 1$</tex>) films obtained by atomic layer deposition have been studied. Hf1-xTixO2 film deposition was carried out using tetrakis(diethylamino)hafnium and titanium tetrochlaride as precursors of Hf and Ti, respectively. Water was used as an oxygen source. The refractive index dispersions were determined by spectroscopic ellipsometry in the spectral range of 400-1050 nm. Transmittance spectra were recorded using UV-VIS spectrophotometry and absorption spectra were calculated on the base of the Beer-Bouguer-Lambert Law The band gap was determined using a technique that allows for calculating the energy and type of electron interband transition from the absorption coefficient. The dependences of the refractive index and the band gap on the film composition are considered. The addition of the minimal titanium amount to the films leads to a sharp change in the refractive index and the band gap. The addition of the same amount of hafnium to TiO 2 slightly changes the optical properties. A non-monotonous behavior was found on all dependencies in the x region of about 0.3-0.5 which we attribute to the HfTiO 4 compound.