Variation in the density, optical polarizabilities, and crystallinity of TiO2 thin films deposited via atomic layer deposition from 38 to 150 °C using the titanium tetrachloride-water reaction

TLDR: In this article, the authors reported that the mass densities of the TiO2 films are found to increase smoothly between 38 and 125°C (3.25-3.68 cm−3), as measured by both x-ray reflectometry (XRR) and optical ellipsometry.

Abstract: Refractive index, density, and optical polarizabilities as a function of atomic layer deposition (ALD) growth temperature for titanium dioxide (TiO2) thin films are reported for the first time between 38 and 150 °C using the titanium tetrachloride-water reaction. Consistent with prior reports, Raman spectroscopy and x-ray diffraction indicate that the films are amorphous below 150 °C and form the crystalline anatase phase at deposition temperatures at or above 150 °C. Despite this change in atomic structure, mass densities of the TiO2 films are found to increase smoothly between 38 and 125 °C (3.25–3.68 g cm−3), as measured by both x-ray reflectometry (XRR) and optical ellipsometry. Molecular polarizabilities were calculated from the XRR mass densities, and ellipsometric refractive indices and were found to vary from 5.26–5.83 × 10−24 cm−3, which is consistent with prior reports of chemical vapor deposition of amorphous TiO2 thin films. Here, the authors demonstrate that the greater precision of ALD provi...