2020 年 115 巻 5 号 p. 407-415
A focused ion beam (FIB) scanning electron microscope (SEM) equipped with a low–energy Ar–ion gun, an electron back–scattered diffraction (EBSD) detector, and an energy dispersive spectrometer (EDS) was newly developed for microfabrication, followed by submicroscopic chemical and crystallographic analyses in an identical sample chamber. The surface condition of mineral samples requires extreme care during FIB milling process, especially for EBSD measurement, as the EBSD pattern is greatly affected by a damaged amorphous surface caused by a high–energy Ga–ion beam (30 keV), even when this damaged layer is only tens of nanometers in thickness. Low–energy broad Ar–ion beam milling (1 keV) overcomes this problem and allows us to obtain sharp EBSD patterns. We applied the microfabrication–analysis protocol to a cosmic spherule. Comprehensive mineralogical datasets from SEM images, X–ray elemental maps, and EBSD patterns were successfully obtained from a minute mineral sample, where conventional cutting and polishing processes are not possible.
