Structural characterization of the near-surface region of soda–lime–silica glass by X-ray photoelectron spectroscopy

Abstract

The structural chemistry of the near-surface region of soda–lime–silica (SLS) glass is described in terms of silicate network connectivity using X-ray photoelectron spectroscopy (XPS). A thorough investigation of O1s and Si2p spectral lines by sequential XPS measurements, accompanied by Ar+ sputtering, revealed the variation of concentration of bridging oxygen, non-bridging oxygen (NBO), and hydrous species (SiOH/H2O) as a function of depth from the glass surface. The Ototal/Si atomic ratio was calculated to vary in the range of 2.90–3.74 throughout the depth of sputtering for a total duration of 110 min, while considering each of the aforementioned oxygen speciations in the curve-fitted spectra of O1s orbital. The glass surface up to a depth of 1–3 nm had the highest Ototal/Si ratio of 3.74, which was representative for a mechanically weak structure with Q0 and Q1 species, marked by the respective linkages of four and three NBOs per silica tetrahedral unit. This dictates the vital contribution of the hydrous species associated with silanol groups to the near-surface structure of SLS glass.