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Understanding the surface properties of glass during the hydrogen fluoride (HF)-based vapor etching process is essential to optimize treatment processes in semiconductor and glass industries. In this work, we investigate an etching process of fused glassy silica by HF gas with kinetic Monte Carlo (KMC) simulations. Detailed pathways of surface reactions between gas molecules and the silica surface with activation energy sets are explicitly implemented in the KMC algorithm for both dry and humid conditions. The KMC model successfully describes the etching of the silica surface with the evolution of surface morphology up to the micron regime. The simulation results show that the calculated etch rate and surface roughness are in good agreement with the experimental results, and the effect of humidity on the etch rate is also confirmed. Development of roughness is theoretically analyzed in terms of surface roughening phenomena, and it is predicted that the values of growth and roughening exponents are 0.19 and 0.33, respectively, suggesting that our model belongs to the Kardar–Parisi–Zhang universality class. Furthermore, the temporal evolution of surface chemistry, specifically surface hydroxyls and fluorine groups, is monitored. The surface density of fluorine moieties is 2.5 times higher than that of the hydroxyl groups, implying that the surface is well fluorinated during vapor etching. [ABSTRACT FROM AUTHOR]

Adsorption isotherm of water on silica (modeled with fused quartz) and calcium‐boroaluminosilicate (Ca‐BAS) glass surfaces as a function of relative humidity (RH) was studied using Fourier transform infrared (FTIR) spectroscopy. The effective thickness of the adsorbed water layer and the distribution of hydrogen bonding interactions of water molecules in the adsorbed layer were determined by comparing the transmission FTIR spectra collected at the Brewster incidence angle with the theoretically calculated spectra. In the sub‐monolayer regime (<30% RH), differences between the water spectra on fused quartz and Ca‐BAS glass could be related to the areal density of hydroxyl groups as well as the elemental composition of the surface determined with x‐ray photoelectron spectroscopy. In the transition regime (30%–60% RH), multilayers start growing and the difference between the fused quartz and Ca‐BAS surfaces diminishes as the humidity increases. In the multilayer regime (>60% RH), the total amount as well as the hydrogen bonding interactions of adsorbed water layers become insensitive to the surface chemistry and are governed mostly by the phase transition (vapor condensation) behavior. Overall, this study reveals how the water layer thickness and structure on the multicomponent silicate glass surface in ambient conditions are different from those on the pure silica surface. [ABSTRACT FROM AUTHOR]

Compositional changes in unleached and acid-leached soda-lime silicate surfaces were tracked with in-vacuo heating and X-ray Photoelectron Spectroscopy. Surface oxygen speciation was determined using a stoichiometry-based algorithm via elemental composition, instead of the typical O 1s peak-fitting approach. Accurate surface hydroxyl quantification is shown to require dehydration at temperatures near 200°C. On the unleached surface, no change in surface hydroxyl density (~2.5 OH/nm²) is observed in the temperature range of 200°C-500°C after the initial dehydration. However, repolymerization in the network (non-bridging oxygen→bridging oxygen) is observed due to volatilization of sodium. The acid-leached surface undergoes sodium out-diffusion from the bulk at sub-Tg temperatures with laterally resolved inhomogeneity and shows a reduction in the concentration of hydroxyls from 4.5 OH/nm² (200°C) to 3.2 OH/nm² (500°C) accompanied by an increase in bridging oxygen. These results suggest that when [OH] > 2.5~3/nm², vicinal OH undergo dehydroxylation with evolution of water, whereas when [OH] < 2.5/nm², most OHs are non-interacting and isolated (at temperatures below Tg). Furthermore, at temperatures exceeding 300°C, sodium has enough thermal energy to desorb in vacuum and diffuse from the bulk (depending on the abundance & local structure). [ABSTRACT FROM AUTHOR]

It is generally accepted that the mechanical properties of soda lime silica (SLS) glass can be affected by the interaction between sodium ions and hydrous species (silanol groups and water molecules) in its surface region. While the amount of these hydrous species can be estimated from hydrogen profiles and infrared spectroscopy, their chemical environment in the glass network is still not well understood. This work employed vibrational sum frequency generation (SFG) spectroscopy to investigate the chemical environment of hydrous species in the surface region of SLS float glass. SLS float glass shows sharp peaks in the OH stretching vibration region in SFG spectra, while the OH stretch peaks of glasses that do not have leachable sodium ions and the OH peaks of water molecules in condensed phases are normally broad due to fast hydrogen bonding dynamics. The hydrous species responsible for the sharp SFG peaks for the SLS float glass were found to be thermodynamically more stable than physisorbed water molecules, did not exchange with D2O, and were associated with the sodium concentration gradient in the dealkalized subsurface region. These results suggested that the hydrous species reside in static solvation shells defined by the silicate network with relatively slow hydrogen bonding dynamics, compared to physisorbed water layers on top of the glass surface. A putative radial distribution of the hydrous species within the SLS glass network was estimated based on the OH SFG spectral features, which could be compared with theoretical distributions calculated from computational simulations. [ABSTRACT FROM AUTHOR]