Titanium di-oxide films using a less hygroscopic colloidal precursor

Abstract

We report the study of titanium dioxide films (TiO2) using titanium di-isopropoxyl di-2ethyl hexanoate Ti(OC3H7)2 (C7H15COO)2 colloidal precursor. This compound is less hygroscopic in nature and easy to use with processes like spin or dip coating. Thin films of TiO2 are made on silicon substrates and their structural and optical properties are studied. The effect of Ti content in the precursor, sintering temperature and its duration on film thickness and refractive index are investigated. Refractive index shows an increasing trend with the rise in the sintering temperature but remains unchanged with the time. The film thickness decreases with both sintering temperature and time and increases with Ti content in the precursor. Reflectivity measurements show marked reduction in the reflection losses compared to bare silicon surface wherein the film thickness is altered by spin speed. XRD results show anatase phase in the samples sintered at lower temperature (<680 °C), however, a mix of anatase, brookite and rutile phases is seen above this temperature. In the samples sintered above 1100 °C, rutile phase is dominant. These results are supported by the X-ray photoelectron spectroscopy. Atomic force microscopy reveals larger grain size at higher sintering temperature. The titanium dioxide films of desirable thickness and refractive index could be used as an antireflection coating on solar cells.