Universal mechanism for gas adsorption and electron trapping on oxidized silicon

We report that common gases (such as He, Ar, H-2, O-2, 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) < P < 10(2) Torr. The adsorption can be enhanced through surface charging via internal photoemission of electron s leading to mutual electron-gas transient trapping. A simple electrostatic model based on monopole-dipole coupling results in an isotherm in agreemen t with the data.