Characterizing dynamic processes and reactions---how atoms move--is necessary to tackle key scientific issues in energy, medicine, and nanotechnology. To address this need, a multidisciplinary team of researchers are developing a new ultrafast spectroscopy system based on direct-detection technology. This state-of-the-art system enables dynamic studies of electronic and structural behavior in a wide range of materials and represents the first time in situ electron energy loss spectroscopy is being introduced to the electron microscopy marketplace, thus creating far-reaching and interdisciplinary impacts in the field of electron microscopy. Drexel's central location among many of the nation's top institutions ensures exposure to myriad universities, laboratories, and users. The development team boasts various collaborations (both in the US and internationally), which gives the new system automatic visibility. Opportunities for education and outreach include leveraging the NSF-funded Louis Stokes Alliance for Minority Participation (LSAMP) program to recruit minority students to train and be educated within the context of electron microscopy and to take advantage of Drexel's renowned co-operative engineering education program.
Energy loss spectroscopy is particularly useful to probe electronic states, band structure, and chemistry, and to improve contrast in materials. While significant advancements in electron optics have permitted fine probe analysis of structure and chemical bonding at the atomic level, the next frontier in transmission electron microscopy (TEM) relies on imaging dynamic processes and reactions beyond standard video frame rates. Key developments in post column energy filters and direct detection cameras have enabled experiments at fine temporal and spatial scales; while these developments have advanced research individually, it is clear that the combination of direct detection technology with energy filtered imaging and spectroscopy would have substantial benefits. To date, these techniques have not been combined due to the inherent mismatch between the low-dose requirements of the direct detection applications and the very high dynamic range of electron energy loss spectroscopy (EELS). This instrument development activity integrates a direct detection camera system and a high resolution spectrometer to allow for in situ EELS to be performed at low electron doses and high speeds. This unprecedented combination boosts the analytical sensitivity of inelastic scattering techniques and yields compositional and electronic structure mapping at sub-nanometer to atomic spatial scales, and high-speed (4000 frames per second) detection at low energies, permitting quantitative time-resolved data acquisition for rapid processes. The combination of expertise of energy filtering systems and energy loss spectroscopy with expertise in in situ and ultrafast TEM provides insight into key processes and bridges gaps in the understanding of mechanisms in various disciplines, with direct and specific impacts on (1) charge mediated properties in oxide and semiconductor heterostructures (2) ion transfer in energy storage materials, and (3) assembly mechanisms in biomedical and soft materials.
