A comparative study of heat treatment temperature influence on the thickness of zirconia sol–gel thin films by three different techniques: SWE, SEM and AFM

A clear ethanol based precursor sol obtained using zirconium acetate hydroxide was utilized for the deposition of nanometer ZrO2 thin films on 316L stainless steel substrates by a sol–gel dip coating process. The influence of heat treatment temperature on the structural evolution of the films was examined using X-ray diffractometry (XRD) and Fourier transform-infrared spectroscopy (FT-IR). The results indicated that the adopted production route led to the formation of an amorphous structure at 200–300 °C and surface tetragonal (t-ZrO2) and monoclinic (m-ZrO2) zirconia phases at 700 °C and 900 °C temperatures, respectively. Microstructural studies by a scanning electron microscopy (SEM) showed that the morphology and size of the particles of ZrO2 films depend upon the heat treatment temperature. The effect of firing temperature on the thickness of ZrO2 nanometer thin films was studied by three different techniques: single-wavelength ellipsometry (SWE), SEM and atomic force microscopy (AFM). The film thickness measured by the SWE and SEM techniques, as a function of heat treatment temperature, was in close agreement, elucidating a major decrease when heated up to 700 °C, and a slight increase between 700 and 900 °C. As determined by the AFM studies, the thickness changes were similar to those of SWE and SEM results during the former step, up to 700 °C, but it appeared to be constant in the later temperature interval. The AFM profile images showed an increase in surface roughness of the films with rising of the heat treatment temperature.