A simple erosion dynamics model of molecular sputter depth profiling

RIMS analysis of ion induced fragmentation of molecules sputtered from an enriched U3O8 matrix

“…In addition to the energy distribution of the sputtered flux, the build-up of sub-surface chemical damage is known to increase the amount of molecular fragmentation observed during subsequent analyses [32][33][34][35]. This result has primarily been observed under dynamic sputtering conditions, but can be replicated for pulsed analysis by increasing the primary ion duty cycle.…”

Cluster secondary ion mass spectrometry of polymers and related materials

“…Equation (2) describes the initial exponential decay observed SIMS depth profiles, later referred to as region I, but does not describe any further decline in signal in the steady state region (region II). This region is discussed in greater detail in more recent work by Wucher (2008). Unlike the case described in Equation (2), which assumes a constant erosion rate with increasing fluence in the steady steady state region, this modification describes the case where the erosion rate, or sputter yield (Y), changes with fluence.…”

“…The sputtering yields at the interface can be measured via a quartz crystal microbalance (QCM) for example. In addition, film preparations have to be optimized, such that there are no ripples in the polymer films, and/or the raw data manipulated such that the depth profile is obtained only in common areas of the film where the thickness is consistent (Wucher, 2008;Mahoney, 2009 Taking the above notions into consideration, it can be stated that C þ 60 is an ideal source for depth profiling through thicker polymeric layers (Fisher et al, in press), as the signal tends to remain stable for much higher fluences, and has comparably higher sputtering yields. The following approximate sputtering yields were reported for PLA under varying conditions for both SF .…”

“…A very important model describing this equilibrium was originally presented in a publication by Gillen, Simons, and Williams (1990), and later refined by Cheng, Wucher, and Winograd (2006) and Wucher (2008). This model, referred to as the erosion model, describes the process by which the damage becomes saturated in an organic film with increasing fluence.…”

“…In polymers that are more amenable to being depth profiled (such as PLA, PGA, and PCL), the materials will undergo an initial (exponential) signal intensity drop (region 1) (in some cases, there may be an initial increase in intensity). This region has been researched thoroughly and its shape predicted somewhat by the erosion model described earlier for molecular samples (Gillen, Simons, & Williams, 1990;Cheng, Wucher, & Winograd, 2006;Wucher, 2008). Next is a constant signal intensity or steady-state signal region (region 2), and finally, an interfacial region where the signal intensity drops with a corresponding increase in substrate signal (region 3).…”