GETTERING OF RESIDUAL GASES AND THE ADSORPTION RATE OF HYDROGEN ON EVAPORATED MOLYBDENUM FILMS AT LIQUID NITROGEN TEMPERATURES

摘要

Mass spectrometric results indicate that an evaporated molybdenum film deposited on a water-cooled substrate in an ultrahigh vacuum system is a broad spectrum getter. The partial pressures of all residual gas compo¬nents with mass-to-charge ratios of less than 45 are reduced with the excep¬tion of the inert gases. Evaporating molybdenum on a substrate at liquid nitrogen temperature further reduces the total residual pressure in the vacuum system and specifically reduces the partial pressure of argon to below the mass spectrometer sensitivity limit of 1 X 10-9 mm Hg. The maximum hydro¬gen pumping speed or sticking probability on molybdenum films at liquid nitrogen temperature is more than twice that at room temperature. It is also found that the rate of hydrogen adsorption or hydrogen sticking probability on liquid-nitrogen-cooled molybdenum films is not a monotonically decreas-ing function of the quantity of hydrogen adsorbed.