Boumans' equation revisited. Part II: A new sputtering equation

In Part II, a modified form of Boumans' equation for the sputtering rate in a Grimm‐style glow discharge lamp is presented where q is the sputtering rate, C Q and V 0 are matrix‐dependent constants, i g and V g are the lamp current and voltage, respectively, and n ≈︁0.74. Previous work in support of the original equation is shown to be in error because this earlier work used a constant time for sputtering to measure the effect of varying current and voltage. This meant that sputtering rates were being recorded over widely varying depths. It is shown, in a Grimm‐style glow discharge lamp, that sputtering rate increases with depth. The new equation is supported by measurements on thin films and on bulk samples where the time has been varied to keep the depth nearly constant. The impact of the new equation on bulk analysis and quantitative depth profiling is also described.