Jun 21, 2019

Adhesion of single- and multi-walled carbon nanotubes to silicon substrate: atomistic simulations and continuum analysis

The radial deformation of carbon nanotubes (CNTs) adhering to a substrate may prominently affect their mechanical and physical properties. In this study, both classical atomistic simulations and continuum analysis are carried out, to investigate the lateral adhesion of single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) to a silicon substrate. A linear elastic model for analyzing the adhesion of 2D shells to a rigid semi-infinite substrate is constructed in the framework of continuum mechanics. Good agreement is achieved between the cross-section profiles of adhesive CNTs obtained by the continuum model and by the atomistic simulation approach. It is found that the adhesion of a CNT to the silicon substrate is significantly influenced by its initial diameter and the number of walls. CNTs with radius larger than a certain critical radius are deformed radially on the silicon substrate with flat contact regions. With increasing number of walls, the extent of radial deformation of a MWCNT on the substrate decreases dramatically, and the flat contact area reduces—and eventually vanishes—due to increasing equivalent bending stiffness. It is analytically predicted that large-diameter MWCNTs with a large number of walls are likely to 'stand' on the silicon substrate. The present work can be useful for understanding the radial deformation of CNTs adhering to a solid planar substrate.


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