FEM simulation on elastic parameters of porous silicon with different pore shapes

Abstract

Porous silicon (PSi) seems to be a promising material for acoustic transducers due to its manufacturing ease and high abilities. Yet, the investigation on wave propagation in this porous material is required to enhance the sensitivity. According to Biot’s theory, wave propagation is governed by the porous matrix moduli (i.e. Young’s modulus, bulk modulus, and shear modulus). These parameters as well as Poisson ratios are difficult to measure and are often estimated using ultrasonic measurements. In this paper, the elastic parameters of porous silicon skeleton varying with porosity are investigated using FEM simulations. The silicon substrate from which the PSi is formed has a (100) crystallographic orientation and the pores are cylinder-like. Six pore shapes were designed in order to investigate the influence of pore morphology on elastic parameters. These shapes are chosen according to the pore geometries obtained by electrochemical etchingand designed as orthotropic structures. The results show that the morphology of the pores has a significant influence on the elastic moduli, therefore, should be taken into consideration in further research. The simulation results are in good agreement with the experimental data reported in literature for Young’s modulus. Moreover, the power-law fittings of Young’s moduli and the shear moduli as functions of porosity are proposed and the fitting errors are discussed.