Mechanical properties and deformation mechanisms of amorphous nanoporous silicon nitride membranes via combined atomistic simulations and experiments

Abstract

The nanoscale thickness and high porosity of amorphous nanoporous silicon nitride (aNPN) membranes make them useful components in diverse biomedical applications. However, mechanical properties including low plastic deformability and strength of aNPN place significant limits on those applications. Thus, understanding how the microstructure of aNPNs controls their mechanical properties will be the key to design of robust, large-area membranes in future applications. In this work, mechanical properties and atomistic deformation mechanisms of aNPN with various microstructural parameters are investigated using molecular dynamics (MD) simulations and experiments. For all porosity and pore diameter values, our MD results show that pore distribution is the dominant characteristic parameter that controls deformation mechanisms. It is also demonstrated that while porosity and pore distribution are main factors affecting the strength of aNPN, plastic deformability is only a function of pore distribution. We further develop a mathematical model for predicting the strength of the aNPN with different microstructures. Insights for new aNPN designs that should increase plastic deformability are found by comparing pore distributions of manufactured aNPN with three cases of MD simulations. These findings suggest that new manufacturing paradigms should be designed for production of robust aNPNs in larger scale applications.