Surface analysis of sol-gel coatings on glass by secondary neutral mass spectrometry

Abstract

Secondary neutral mass spectrometry (SNMS) has been used to profile coatings of the systems SiO2 and 65SiO2.20TiO2.15ZrO2 (STZ). The coatings have been deposited on float glass and heat insulating glass by dip coating from alkoxide solutions. The microporous gel coatings have been densified by heat treatment. The SBM method (separate bombardment mode) has been applied to characterize the systems and the HFM method (high frequency mode) to check for matrix effects in the SBM depth profiles. Both methods show sodium diffusion from the float glass substrate into the STZ coating and no significant sodium diffusion into the SiO2 coating. Measurements of the coatings on the heat insulating glass indicate that the SnO2 interlayer acts as a diffusion barrier. The diffusion of sodium from the float glass substrate into the STZ coating during consolidation has been analyzed by SBM-SNMS. The sputtering rate decreases with increasing consolidation. Due to large differences between sputtering rates of the substrate and of the microporous coatings, the calibration of sodium intensities from time to depth at the interface has not been possible. However, a correlation between the final temperature of heat treatment and the depth of the Na2O depletion in the substrate surface under the coating can be obtained.