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[SIT21-P04] Measurements of local strain in minerals using electron nanoprobe
★Invited Papers
Keywords:electron microscopy, strain analysis
Interface/surface of minerals having complex textures frequently shows local strain, which more or less affects phase transitions and/or relevant micro-texture formations. In addition, strain locally remained in natural minerals may be key information to understand various geophysical events such as tectonics or meteorite impacts. There exist some measurement methods to determine strain in minerals, for example, X-ray diffraction or micro-laser Raman spectroscopy [e.g., 1,2], but higher spatial resolution/selectivity is required to precisely analyze specific regions in nanometer order. The high spatial resolution analysis would become also important for future challenging experiments to simulate extreme environments in the Earth because amount of such experimental products is frequently very small.
As for semiconductor devices of which miniaturization rapidly progresses, local strain is utilized to control electric function, thus some strain measurements with nanometric order have already been performed [e.g., 3]. In particular, diffraction imaging method which uses scanning electron nanoprobe to obtain many diffraction patterns from nanometric regions should be able to measure local strain precisely with corresponding high magnification images [4]. This would be effective to study mineral samples, but minerals have large diversity in phase, size, morphology and/or crystal orientation, whereas experimental conditions to study the semiconductor devices can be relatively limited. Because appearance of electron diffraction pattern varies sensitively to sample conditions, it would be important to establish experimental/analytical procedures of the method adequate for mineral samples.
In this study, we obtained and analyzed diffraction imaging datasets from mineral samples by scripting control of a transmission electron microscope (TEM) and a CCD camera. Illumination electron beam was adjusted to be mostly parallel with its spot size smaller than 10 nm in diameter, which gives spotty diffraction patterns and allows us to easily determine reciprocal basis of each illuminated point. Sample damage could be reduced because electron dose in the illumination condition is much smaller than that of the convergence beam generally used in STEM (scanning TEM) method. No damage textures or contaminations due to the experiments were observed in TEM images. The obtained datasets were analyzed to construct strain maps and diffraction-contrast images by virtual objective apertures with arbitrary shapes.
References
[1] Seto, Y. (2012) Rev. High Press. Sci. Tech. 22, 144–152.
[2] Enami, M., Nishiyama, T. and Mouri, T. (2007) Am. Mineral. 92, 1303-1315.
[3] Cooper, D., Denneulin, T., Bernier, N., Béché, A. and Rouvière, J. L. (2016) Micron, 80, 145-165.
[4] Ophus, C. (2019) Microsc. Microanal. 25, 563-582.
As for semiconductor devices of which miniaturization rapidly progresses, local strain is utilized to control electric function, thus some strain measurements with nanometric order have already been performed [e.g., 3]. In particular, diffraction imaging method which uses scanning electron nanoprobe to obtain many diffraction patterns from nanometric regions should be able to measure local strain precisely with corresponding high magnification images [4]. This would be effective to study mineral samples, but minerals have large diversity in phase, size, morphology and/or crystal orientation, whereas experimental conditions to study the semiconductor devices can be relatively limited. Because appearance of electron diffraction pattern varies sensitively to sample conditions, it would be important to establish experimental/analytical procedures of the method adequate for mineral samples.
In this study, we obtained and analyzed diffraction imaging datasets from mineral samples by scripting control of a transmission electron microscope (TEM) and a CCD camera. Illumination electron beam was adjusted to be mostly parallel with its spot size smaller than 10 nm in diameter, which gives spotty diffraction patterns and allows us to easily determine reciprocal basis of each illuminated point. Sample damage could be reduced because electron dose in the illumination condition is much smaller than that of the convergence beam generally used in STEM (scanning TEM) method. No damage textures or contaminations due to the experiments were observed in TEM images. The obtained datasets were analyzed to construct strain maps and diffraction-contrast images by virtual objective apertures with arbitrary shapes.
References
[1] Seto, Y. (2012) Rev. High Press. Sci. Tech. 22, 144–152.
[2] Enami, M., Nishiyama, T. and Mouri, T. (2007) Am. Mineral. 92, 1303-1315.
[3] Cooper, D., Denneulin, T., Bernier, N., Béché, A. and Rouvière, J. L. (2016) Micron, 80, 145-165.
[4] Ophus, C. (2019) Microsc. Microanal. 25, 563-582.