Energy-Loss Spectroscopy in a Scanning Electron Microscope

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This proposal requests funding for a novel electron energy loss spectrometer (EELS) to be installed on SuperSTEM4, a Hitachi SU9000 high-resolution scanning electron microscope that is part of the instrumentation suite at SuperSTEM, the EPSRC National Research Facility (NRF) for Advanced Electron Microscopy (EM). In response to needs identified through a continuous and on-going review of capabilities and services offered to its user community, SuperSTEM recently made substantial investments in underpinning equipment for specimen preparation and upstream sample characterisation. This investment was directed at capabilities to ensure allocated beamtime on the Facility's main high-resolution instruments is maximised. This includes the provision of the NRF's newest instrument, SuperSTEM4, which is a novel type of low-voltage (transmission) scanning electron microscope, or (T)SEM, combining a high spatial resolution of below 0.2nm (at 30kV acceleration voltage) with the flexibility and high-throughput capabilities of an SEM. This EPSRC Capital Award for Core Equipment will enable the upgrade of SuperSTEM4 with an electron energy loss spectrometer in transmission geometry, a unique capability in an SEM. This will offer the Facility's users access to spectroscopic information on their samples at primary beam acceleration voltage lower than the Facility's main instrumentation (0.5-30kV), within a high-throughput yet high-resolution microscope. The STEM-in-a-SEM nature of SuperSTEM4 opens up larger length-scales for preliminary chemical imaging of fabricated samples, providing providing more representative information from wider areas of samples for subsequent investigation on the Facility's primary instruments. Furthermore, thanks to the numerous SEM-specific detectors installed on the instrument (e.g. backscattered and secondary electron detectors), surface and topographical information will be available simultaneously with chemical information from EELS, allowing for a multidimensional characterisation of materials (multiple signals enabling data-fusion-based analyses, with 2D and 3D information compiled through photogrammetry). Thanks to its cold-field-emission electron source, the native high resolution of SuperSTEM4 (<0.4eV) will also ensure chemical and bonding information in EELS comparable to the higher-kV SuperSTEM2 is obtained, also directly supporting users for high-end EELS applications, e.g. in the field of plasmonics or electronic structure determination. The equipment will help support the entire facility user base of over 120 active users, including numerous early career researchers and doctoral students with on-going projects at the facility, and it will also attract interest from a broadened research base able to take advantage of ease-of-use and relatively easier-to-meet demands regarding sample quality.