Scanning Transmission Ion Detection in the Helium Ion Microscope

The helium ion microscope has already proven its value for high-resolution imaging, composition analysis, nanofabrication, and material modification. However, imaging in transmission mode remains not fully explored. Mass-thickness contrast has been studied using a conversion plate below the specimen and collecting secondary electrons with an ET detector. Changing from bright to dark field regime was demonstrated using an annular microchannel plate and changing the acceptance angle by adjusting the distance between the sensor and the sample. Channeling and diffraction phenomena provide information about the crystal structure and can be recorded by a position-sensitive detector. In this report, we present our approach to explore this imaging mode, the challenges and main figures of merit. Our test setup with a position-sensitive detector will be shown, and simulations of the contrast mechanism will be presented.