Multivariate characterization of ultra-thin nanofunctional plasma polymer films using ToF-SIMS analysis

Octadecanethiol self-assembled monolayers (SAMs) on gold substrates have been exposed to an allylamine plasma for different plasma times ranging from 0 to 9 min. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) positive spectral fragmentation patterns of SAM-allylamine plasma films of varying allylamine deposition times were analysed using multivariate techniques (PCA and PLS). Multivariate data analysis permits the exploration of the entire spectrum by forming the best linear combination of the principal components which describes the maximum amount of variance of the sample set. PLS-models have been calculated correlating spectral parameters to sample properties such as layer thickness and atomic concentration of selected ions. The predicted sample properties were in good agreement with the experimental results showing that the combination of ToF-SIMS analysis with multivariate techniques is an efficient way of sample characterization and interpretation of spectral data and should be the method of choice for future spectral data analysis.