H2O adsorption-induced curvature of a silicon nanocantilever based on a semi-continuum method

Nano-sized silicon cantilevers have been widely studied in nanoelectromechanical systems (NEMS) because of their simplicity and ability to function in small sizes as sensors. The nanocantilever bends when adsorption is confined to a single side of the cantilever, and small molecule adsorption on the surface of the cantilever will directly cause its mechanical bending due to surface stress induced by intermolecular forces. When the cantilever is scaled down to nano level, the classical mechanical theory cannot be used to accurately model, analyze and predict its bending. And, native oxide may be unintentionally formed on the silicon nanocantilever of both sides during fabrication. In this paper, based on a semi-continuum method, a model is proposed to calculate H2O adsorption-induced curvature of the silicon nanocantilever with native oxide. According to the energy transfer between potential energy of adsorbates and elastic energy of the bending cantilever, the beam deflection is determined by using the energy theory in which the total energy in terms of beam curvature will reach a minimum value when the adsorption is stable. The model was tested with the molecular dynamics method using Material Studio software. The results agree with theoretical prediction. This model could be a simple method to analyze and estimate adsorption-induced bending of the nanocantilever.