A statistical approach to delta layer depth profiling

作者：Wucher Andreas^*; Krantzman Kristin D

来源：Surface and Interface Analysis, 2012, 44(9): 1243-1248.

DOI：10.1002/sia.4931

• molecular depth profiling
• delta layers
• depth resolution
• response function
• statistical sputtering model

We present a simple statistical model describing the removal and relocation of material during a sputter depth profiling experiment. All input parameters are determined from low-fluence molecular dynamics simulations, making the model de facto parameter free. The model can be used to extrapolate data from the molecular dynamics simulations to projectile fluences relevant to sputter depth profiling experiments. As a result, the erosion of the surface is calculated in terms of fluence-dependent filling factors of different sample layers. Using input data determined for the 20-keV?C60 cluster bombardment of silicon, it is found that a steady-state erosion profile is reached after removal of approximately 20 monolayer equivalents of material. Plotting the contribution of particles from a specific layer to the instantaneous sputtered flux, one can directly determine the delta layer response function predicted from such a model. It is shown that this function can be parameterized by the semiempirical Dowsett response function, and the resulting fitting parameters are compared with published depth profile data. The model is then used to study the role of different processes influencing the observed depth resolution. We find that the statistical nature of the sputtering process suffices to explain many features of experimentally measured delta layer depth profiles.

• 出版日期2012-9