Behnam Moeini, Tahereh G. Avval, Neal Gallagher, M. Linford
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引用次数: 3
Abstract
This Insight Note follows two previous Insight Notes on X‐ray photoelectron spectroscopy (XPS) image analysis that dealt with the importance of analyzing the raw data and the use of summary statistics. As a next step in the exploratory data analysis (EDA) of XPS images, we now show principal component analysis (PCA) of an XPS image. PCA is appropriate when the spectra in a data set are correlated to some degree and the noise in the spectra is unimportant. In these cases, PCA can significantly reduce the dimensionality and complexity of data sets. Preprocessing is an important part of many PCAs. Its usefulness is illustrated with a small, mock data set, where the potential pitfalls of not preprocessing are shown. PCAs of XPS image data that were not preprocessed and preprocessed by mean centering are illustrated. Scree plots, which are used to determine the number of abstract factors (principal components, PCs) that describe a data set, are shown. The spectra in our XPS image are quite noisy, which is consistent with the moderate, but still significant, amount of variance that is captured by the first two PCs in our PCA. With both preprocessing methods, the loadings on PC1 and PC2 are remarkably smooth. The loadings on the next six PCs also appear to contain some chemical information. Scores images generated using both no preprocessing and preprocessing by mean centering reveal many of the same general features in the data set that were found in our two previous Insight Notes.
期刊介绍:
Surface and Interface Analysis is devoted to the publication of papers dealing with the development and application of techniques for the characterization of surfaces, interfaces and thin films. Papers dealing with standardization and quantification are particularly welcome, and also those which deal with the application of these techniques to industrial problems. Papers dealing with the purely theoretical aspects of the technique will also be considered. Review articles will be published; prior consultation with one of the Editors is advised in these cases. Papers must clearly be of scientific value in the field and will be submitted to two independent referees. Contributions must be in English and must not have been published elsewhere, and authors must agree not to communicate the same material for publication to any other journal. Authors are invited to submit their papers for publication to John Watts (UK only), Jose Sanz (Rest of Europe), John T. Grant (all non-European countries, except Japan) or R. Shimizu (Japan only).