Gas permeability of porous silicon nanostructures

Abstract

The gas (air and hydrogen) flow through porous silicon ($\mathrm{PS}$) nanostructures is studied. Being well described by Darcy’s law, the gas flow measurements allow us to deduce PS permeability values, which are measured to be ${10}^{–16}–{10}^{-15}{\mathrm{m}}^2$, corresponding to the $50–70\%$ porosity range. A strong porosity dependence of the $\mathrm{PS}$ intrinsic permeability is found to be in good agreement with Kozeny’s model. The influence of nanoscale morphology on the porous layer permeability is shown and discussed, taking into account the fractal-like specific surface of the PS nanostructures. In particular, the liquid permeability of the PS nanostructure is estimated to be $6.4\times {10}^{-18}{\mathrm{m}}^2$ from the observed Klinkenberg effect for gas flow.