| AVS 62nd International Symposium & Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS-MoA |
| Session: | Practical Surface Analysis I: Interpretation Challenges |
| Presenter: | Alexander Shard, National Physical Laboratory, UK |
| Correspondent: | Click to Email |
Argon cluster sources for 3D analysis of organic materials are starting to become routinely used in material analysis. Most new XPS and SIMS instruments are now equipped with such sources and are finding widespread use in both academia and industry. The purpose of a depth profile is to measure the distribution of chemical species and therefore it is important to assess the ability of various techniques and approaches to provide this information. One of the most popular analytical methods to combine with cluster beam sputtering is SIMS. This method provides excellent specificity, high sensitivity in most cases and enables discrimination of compounds that cannot be matched by other methods such as XPS. However, there are a number of factors that prevent organic SIMS from being quantitative. For XPS there is a well-established route to obtain chemical compositions, which is its primary advantage in organic depth profiling.
Until recently, organic SIMS data could be used to identify compounds, and could only measure concentrations in special cases. The major limiting factor in SIMS is the ‘matrix effect’ which has not been the subject of any substantive or coordinated investigation since the genesis of organic SIMS analysis in the 1980s. Fortunately, the ability provided by argon cluster sources to perform nearly damage-free profiles of organic materials allows us to begin to address this effect.
Mixed molecular materials of known composition have been made with sufficient precision and stability for a reliable analysis to be performed. The materials demonstrate, unambiguously, that matrix effects are significant in molecular SIMS experiments, but also that these effects can be measured and described. It is found that the matrix effects are remarkably consistent between laboratories and appear to depend upon two main factors: the identity of the secondary ion and; the analytical source used. Furthermore, it is possible to establish normalization schemes that compensate for the matrix effect whilst also eliminating the other major source of error in quantitative SIMS: instability and drift in the primary beam current.
This talk will describe VAMAS project A3(g), the SIMS matrix effect and implications in the quantitative analysis of SIMS depth profiles. These effects are not restricted to compositional analysis but also have a profound influence on the apparent position of interfaces, often contributing the major source of uncertainty to the measurement of the thickness of an organic layer.