Functionalization layer effect on the mechanical properties of silicon based micro-cantilever mass sensors: A theoretical study

In this paper we calculate the surface stress and surface elastic constants of a model functionalized Si(1 1 1) surface by means of ab initio Density Functional Theory calculations. Subsequently these values are used in Finite Element Method simulations to predict the resonance frequency shift induced in a silicon cantilever by surface functionalization; this “multiscale” approach considers both changes in mass and elasticity of the microstructure induced by molecular adsorption. Interestingly our results show that the change in surface elastic constants, often ignored in experimental analysis, may account for 50% of the frequency shift and thus lead to a large overestimation of the attached mass.