Solution-processed crack-free oxide films formed using SiO2 nanoparticles and organoalkoxysiloxane precursors

Crack-free uniform oxide films were deposited by spin-on-glass method using a mixture solution of organoalkoxysiloxane network former and SiO2 nanoparticles. In the range of molar ratio of SiO2 nanoparticles to oragnoalkoxysiloxanes between 0.6:1 and 1:1, stable sols were formed and smooth and uniform oxide films could be obtained. Fourier-transform infrared (FT-IR) spectroscopy was used to investigate the chemical properties of the films, and we found that SiOSi structures were effectively formed via condensation reactions during curing at 150 °C. The effect of three different organic side groups in the organoalkoxsiloxane on the film properties was investigated. Precursors containing methyl groups effectively formed SiOSi network with SiO2 nanoparticles, which was confirmed by the increased intensity of the SiO asymmetric stretching mode at 1080 cm−1 in the FT-IR spectra. Smooth and continuous films were obtained using precursors containing methyl and phenyl groups, with root-mean-square surface roughness of 1.05 nm (methyl precursor) and 1.16 nm (phenyl precursor). The shrinkage of the oxide film formed with phenyl groups was less than 1%. The dielectric properties of the oxide films were characterized, and we observed leakage currents in the range of 10−9 to 10−8 A/cm2 just prior to the dielectric breakdown with the films formed using precursors containing methyl and phenyl groups