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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]

Contact charging of hydroxylated SiO2/metal interfaces is studied using density functional theory calculations. Atomic scale models are generated for hydroxylated α-cristobalite interfaced with three different fcc metals: Al, Pt, and Au. Regions of electron accumulation and depletion are highest in magnitude near the SiO2/Pt and SiO2/Au interfaces and lower at the SiO2/Al interface. One key finding of this work is that the presence of a metal surface near the hydroxylated SiO2 induces electronic states at the SiO2 surface within the apparent insulating bandgap. The magnitude of these states is highest for Pt and Au contacts and lowest for Al, indicating that the amount of charge transfer at the interface trends with the density of electronic defect states. Such electronic defect states reside near the fermi level of the system and it is proposed that these states from surface oxygen atoms are at least partly responsible for the electronic charge transfer mechanism between a metal and an insulator. [ABSTRACT FROM AUTHOR]

An atomic description of water dynamics and electrochemical properties at electrode-electrolyte interfaces is presented using molecular dynamics with the third generation of the charge-optimized many-body (COMB3) potential framework. Externally applied potentials in electrochemical applications were simulated by offsetting electronegativity on electrode atoms. This approach is incorporated into the variable charge scheme within COMB3 and is used to investigate electrochemical systems consisting of two Cu electrodes and a water electrolyte with varying concentrations of hydroxyls (OH-) and protons (H+). The interactions between the electronegativity offset method and the charge equilibration method in a variable charge scheme are analyzed. In addition, a charge equilibration method for electrochemical applications is proposed, where the externally applied potentials are treated by the electronegativity offset on the electrodes thus enforcing charge neutrality on the electrolyte. This method is able to qualitatively capture the relevant electrochemistry and predict consistently correct voltages with precalibration. [ABSTRACT FROM AUTHOR]