Ion dose dependence of the sputtering yield of Ru(0001) at very low fluences

The neutral sputtered flux from a Ru single crystal oriented along the (0001) axis has been determined as a function of primary ion dose in real time using nonresonant photoionization techniques coupled with time-of-flight mass spectrometry. The data reveal, surprisingly, that the sputtering yield is twice as large from an undamaged surface as that from a slightly damaged surface. The sputtering yield decreases until steady state is reached at a primary ion fluence of only 2×{}10¹⁵ ions cm^-2. Data analysis results in an estimated cross section for damage of (2.7±{}1.0)×{}10^-15 cm².