A perspective on two chemometrics tools: PCA and MCR, and introduction of a new one: Pattern recognition entropy (PRE), as applied to XPS and ToF-SIMS depth profiles of organic and inorganic materials
Autor: | H. Dennis Tolley, Bhupinder Singh, Matthew R. Linford, Shiladitya Chatterjee, Zheng Rong Lee, Anubhav Diwan, Mark H. Engelhard, Neal B. Gallagher, Jeff Terry |
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Rok vydání: | 2018 |
Předmět: |
Multivariate statistics
Chemistry business.industry Analytical chemistry Univariate General Physics and Astronomy Pattern recognition 02 engineering and technology Surfaces and Interfaces General Chemistry Mutual information 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics Information theory 01 natural sciences 0104 chemical sciences Surfaces Coatings and Films Secondary ion mass spectrometry Chemometrics X-ray photoelectron spectroscopy Principal component analysis Artificial intelligence 0210 nano-technology business |
Zdroj: | Applied Surface Science. 433:994-1017 |
ISSN: | 0169-4332 |
Popis: | X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) are much used analytical techniques that provide information about the outermost atomic and molecular layers of materials. In this work, we discuss the application of multivariate spectral techniques, including principal component analysis (PCA) and multivariate curve resolution (MCR), to the analysis of XPS and ToF-SIMS depth profiles. Multivariate analyses often provide insight into data sets that is not easily obtained in a univariate fashion. Pattern recognition entropy (PRE), which has its roots in Shannon’s information theory, is also introduced. This approach is not the same as the mutual information/entropy approaches sometimes used in data processing. A discussion of the theory of each technique is presented. PCA, MCR, and PRE are applied to four different data sets obtained from: a ToF-SIMS depth profile through ca. 100 nm of plasma polymerized C3F6 on Si, a ToF-SIMS depth profile through ca. 100 nm of plasma polymerized PNIPAM (poly (N-isopropylacrylamide)) on Si, an XPS depth profile through a film of SiO2 on Si, and an XPS depth profile through a film of Ta2O5 on Ta. PCA, MCR, and PRE reveal the presence of interfaces in the films, and often indicate that the first few scans in the depth profiles are different from those that follow. PRE and backward difference PRE provide this information in a straightforward fashion. Rises in the PRE signals at interfaces suggest greater complexity to the corresponding spectra. Results from PCA, especially for the higher principal components, were sometimes difficult to understand. MCR analyses were generally more interpretable. |
Databáze: | OpenAIRE |
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