Temperature-programmed desorption study on the outgassing process from aluminum surface

Temperature-programmed desorption (TPD) has been applied for the first time to a study of time-dependent outgassing process from a metal surface. The TPD area which corresponds to the adsorbate coverage, decreased with the pumping time t, whose temporal dependence t^-β/(1~β) quantitatively agreed well with what was predicted by the Freundlich adsorption isotherm and Mizuno-Horikoshi theory. The H₂O-TPD spectra consist of a peak at around 90°C in which the desorption proceeds from lower temperatures towards higher temperatures, and a broad background appearing at 100<T<500°C, in which the desorption proceeds rather uniformly irrespective of the desorption temperature. The presence of the latter suggests an unidentified desorption mode from the metal surface.