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

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 O_total/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 O_total/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.