Sputtering of tungsten by N+ and N2+ ions: investigations of molecular effects

Total sputtering yield of a polycrystalline tungsten surface during bombardment with both atomic N+ and molecular N-2(+) ions is determined using a highly accurate quartz crystal microbalance technique. The results thus obtained compare well with existing experimental data. At ion energies below 1 keV, an unexpected pronounced molecular effect is found, i.e. the sputtering yield per nitrogen atom for N-2(+) molecular ions is up to 25% higher than that of a single N+ ion with the same velocity. A qualitative explanation for this enhancement based on a simple energy transfer model is presented.