Incident energy dependence of the scattering dynamics of water molecules on silicon and graphite surfaces: the effect on tangential momentum accommodation
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- 作者：Ikuya Kinefuchi ; Yusuke Kotsubo ; Kenichi Osuka…
- 关键词：Rarefied gas flows ; Tangential momentum accommodation ; Velocity slip ; Gas–surface interaction ; Molecular beam
- 刊名：Microfluidics and Nanofluidics
- 出版年：2017
- 出版时间：February 2017
- 年：2017
- 卷：21
- 期：2
- 全文大小：
- 刊物类别：Engineering
- 刊物主题：Engineering Fluid Dynamics; Biomedical Engineering; Analytical Chemistry; Nanotechnology and Microengineering;
- 出版者：Springer Berlin Heidelberg
- ISSN：1613-4990
- 卷排序：21
文摘
The scattering dynamics of water molecules on solid surfaces was investigated using the molecular beam technique. In contrast to the experiments previously reported in the literature, the range of incident energy was chosen to cover the typical kinetic energies of gas molecules in equilibrium at room temperature (35–130 meV). Even in such a narrow energy range, the angular distribution of scattered molecules is heavily affected by the incident energy, exhibiting both a nearly cosine distribution and a lobular distribution, which has a clear peak close to the specular direction. Interestingly, the tangential momentum accommodation coefficients (TMACs) estimated from the scattering experiments show opposite energy dependences on graphite (0001) and silicon (100) surfaces. As the incident energy increases, the TMAC decreases on the graphite surface, whereas it increases on the silicon surface. These trends can be attributed to the relatively large adsorption energy of water molecules on these surfaces and the atomic-scale surface corrugation, although a rigorous understanding requires further analysis by molecular dynamics simulations. Our findings suggest the need for an elaborate slip-flow model that takes account of the incident energy effect to accurately analyze water vapor flow in micro/nanostructures, which is ubiquitous in nature and engineering applications.