Universal Mechanism for Gas Adsorption and Electron Trapping on Oxidized Silicon

Abstract

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 ${10}^{\ensuremath{-}3}<P<{10}^{2}\mathrm{Torr}$. 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.