Universal Mechanism for Gas Adsorption and Electron Trapping on Oxidized Silicon

We report that common gases (such as He, Ar, ${\mathrm{H}}_2$, ${\mathrm{O}}_2$, ${\mathrm{N}}_2$, CO) experience adsorption at oxidized silicon surfaces at 300 K via electrostatic coupling. This is deduced using contact potential measurements of the work function for gas pressure in the range ${10}^{-3\mathrm{}}<P<\mathrm{}{10}^2\mathrm{Torr}$. The adsorption can be enhanced through surface charging via internal photoemission of electrons leading to mutual electron-gas transient trapping. A simple electrostatic model based on monopole-dipole coupling results in an isotherm in agreement with the data.