Satoka Aoyagi

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) provides chemical images with a high spatial resolution, approximately 100 nm, and detailed chemical information. It is, however, often necessary to obtain images of higher spatial resolution and to detect high mass secondary ions with greater sensitivity, higher than several 100 Da. In this study, in order to improve the TOF-SIMS spatial resolution, image fusion using an image with a higher spatial resolution was evaluated based on principal component analysis (PCA). Moreover, in order to effectively detect important secondary ions with lower intensity, the intensity of one pixel was enhanced by integrating neighboring several pixels. According to the pixel reduction, the rank of the TOF-SIMS data matrix should be reduced. Due to the sparsity of TOF-SIMS data, sparse modeling techniques such as robust PCA were employed to the decomposition of the original data. In terms of image data fusion, PCA score distribution images of the model samples indicate the improvement of the spatial resolution without significant changes in PCA loadings after data fusion of TOF-SIMS and microscopy images. Regarding the improvement of low intensity secondary ion detection, PCA results before and after pixel reduction suggested that the pixel reduction was useful in detecting important low intensity secondary ions effectively. (C) 2018 Author(s).