Mass-spectrometer analysis of the gases in a sputtering apparatus has demonstrated that: (1) Under normal sputtering conditions, copious quantities of hydrogen are evolved from the dissociation of adsorbed water vapor, and (2) hydrogen partial pressures as low as 5 × 10−7 Torr can measurably reduce sputtering rates in an argon discharge. These results have been used to develop a novel approach to thickness control of sputtered thin films. The techniques has been applied to the deposition of nickel–chromium films with a control on thickness of ±1%.