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K. Dobes, P. Naderer, C. Hopf, T. Schwarz-Selinger, F. Aumayr:
"Transient effects during sputtering of a-C:H surfaces by nitrogen ions";
Nuclear Instruments & Methods in Physics Research Section B, 286 (2012), 20 - 24.

Sputtering of polymer-like amorphous hydrogenated carbon (a-C:H) thin films by 0.5-1 keV N2
+ molecular
ions has been studied in situ and real-time using a highly sensitive quartz crystal microbalance technique.
During bombardment of a fresh, plasma-deposited a-C:H layer with nitrogen ions the measured
sputtering yield decreases exponentially with ion fluence until a steady state value is reached at a fluence
of typically about 3.5 ! 1015 N2
+ ions per cm2. A chemical sputtering mechanism has to be considered in
addition to physical sputtering to explain the observed steady state sputtering values. Simulations based
on the code TRIDYN, which take into account a change of surface composition due to implantation and
erosion, are performed to understand the transient development of sputtering yields.