Dark-field stigmatic ion microscopy for structural contrast enhancement

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Abstract
Dark-field images are observed with a stigmatic (immersion objective lens) secondary ion mass spectroscopic ion microscope by means of an eccentric objective aperture, and are a useful extension of shadow contrast imaging. The spatial resolution in these images is comparable with conventional bright-field imaging, provided that a narrow energy bandpass is selected to minimize chromatic aberrations. It is demonstrated that the dark-field method is useful for correlating surface relief with chemical contrast in the compositional secondary ion mass spectroscopic mapping of conventional ion microscopy. Further, based on the information acquired in the dark-field imaging mode, digital techniques to compensate for asperity artifacts in conventional ion microscopy are proposed.