Sample Cooling or Rotation Improves C60 Organic Depth Profiles of Multilayered Reference Samples: Results from a VAMAS Interlaboratory Study

We demonstrate two methods to improve the quality of organic depth profiling by C-60 sputtering using multilayered reference samples as part of a VAMAS (Versailles project on Advanced Materials and Standards) interlaboratory study. Sample cooling was shown previously to be useful in extending the useful depth over which organic materials can be profiled. We reinforce these findings and demonstrate that cooling results in a lower initial sputtering yield to approximately -40 degrees C, but the improvement in useful profiling depth continues as the sample is cooled further, even though there is no further reduction in the initial sputtering yield. We report, for the first time, the use of sample rotation in organic depth profiling and demonstrate that the initial Sputtering yield at room temperature is maintained throughout the depth of the samples used in this study. Useful profiling depth and good depth resolution are both associated with a constant sputtering yield. The fact that rotation results in the maintenance of depth resolution underlines the fact that depth resolution is often limited by the development of ion-beam-induced topography. Constant sputtering yield results in a constant secondary-ion yield, after transient processes have Occurred, and this allows simple quantification methods to be applied to organic depth profiling data.