Tritiated ethanol is adsorbed on the surface of silicon oxide, the oxide is metallized to form an MOS capacitor, and an electric field is applied at elevated temperature to generate ion injection into the oxide film. It is shown that during positive bias‐temperature stress, protons, derived from the hydrogens of the ethanol, are transported to the oxide‐silicon interface, and that sodium ion transport (examined via neutron activation analysis) is negligible.