Effects of fused silica surface roughness on the interfacial adsorption mechanism of contaminant

TT Wang and QS Bai and WM Guo and YH Dou and P Zhang, JOURNAL OF MATERIALS SCIENCE, 58, 14284-14298 (2023).

DOI: 10.1007/s10853-023-08909-2

Since surface contaminants can make optical components such as fused silica highly susceptible to damage, how to maintain the cleanliness of fused silica is an effective way to improve the laser damage threshold. In this study, molecular dynamics techniques were employed to investigate the effect of surface roughness of fused silica on the adsorption mechanism of contaminants. Based on the Weierstrass- Mandelbrot fractal function, the three-dimensional morphology of the fused silica surface was numerically simulated, and the results were used to verify and calculate its surface roughness. With the results obtained, a model of organic contaminant adsorption on rough fused silica surfaces was established, and factors such as the center-of-mass height, adsorption energy, and number density distribution of dodecane during the adsorption process were evaluated. It was found that the adsorption behavior of dodecane molecules on the rough surface was mainly affected by the surface roughness, which reduced the interaction area with the substrate and produced smaller van der Waals and adsorption energies. In addition, with the increase of surface roughness, the extension range of dodecane molecules in the substrate gradually decreased, the parallel state of oil molecules was destroyed, and even the aggregation phenomenon occurred, and the center-of-mass height of molecules significantly increased. This study reveals the atomic-level interfacial adsorption mechanism of long chain organic molecules on the processed fused silica surface, which helps to improve the resistance of the substrate surface to contaminant.

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