The NG-ETEM will for the first time ever combine the following and separately demonstrated technologies:
— Single-atom sensitive imaging: aberration-corrected high-resolution transmission electron micro-scope (TEM) images offers the highest information level for the fewest scattered electrons. Combining the acquisition of low-doses, single-projections and focal series of TEM images enables reconstruction of the exit wave presenting the most informative fingerprint of 3D nanostructures. Hereby, 3D atomic structures can be rendered from single-atom-sensitive TEM employing electron optics operating at 300 keV with an information limit in the 50 pm range, since it corresponds to a focal spread < 1.0 nm (depth precision) and image spread < 10-15 pm (lateral precision) and is facilitated by axial and off-axial aberration-correction up to 5th order as well as aberration coefficient stabilities and focus linearity of better than 10 % over a minimum of a few minutes time-scale. The TEAM0.5 microscope (LBNL) serves as a reference (Kisielowski et al, Microsc Microanal 14, 454 (2008), Kisielowski et al. Micron 68, 186 (2014), Chen et al, Nature Comm 7:10603 (2016), Kisie-lowski et al, Adv Struct Chem Imag 2:13 (2016);
— Gas reaction environments: Differentially pumped gas cell with a base vacuum < 1*10^-6 mbar to ensure gasses added at a pressure of up to 20 mbar in the sample region have a cleanness limited by their inherent cleanness. With all vacuum pumps running the optical performance should be minimally affected, preferably to within 10 % of any specification and specifically for optical stability. Sample heating of up to at least 900 C is achieved through microfabricated chips for low sample drift (< 50 pm/s) compatible with focal series acquisition;
— Electron dose and dose-rate control: Monochromatized, Nelsionian electron illumination with an energy spread of < 0.1 eV at 300 keV to ensure the targeted 50 pm information limit as well as dose-rate control (0.01 – 10000 e/(Å^2s)) to achieve the weakest sample excitation and matching of the illuminated and detected sample areas to restrict sample illumination (Kisielowski et al, Microsc Microanal 14, 454 (2008), Micron 68, 186 (2014));
— Sensitive electron detection: Most sensitive electron detector capable of delivering high signal-to-noise (> 1-5) TEM images at 1Å resolution and 300 keV at low electron beam currents (< 10-20 e/(Å^2s)) and low electron doses (< 10-20 e/(Å^2)) for the weakest sample excitation. Currently, the most sensitive detectors (direct electron counters) have detection quantum efficiency (DQE) reaching > 50 % at ½ Nyquist and > 80 % at 0 Nyquist for 300 keV electron beams. Such a camera configured with a real-time single electron counting mode is needed with online real-time data processing/acquisition for dose-fractionated imaging, focal series acquisition and drift correction. Time-resolution compatible with catalytic turnover frequencies (0.1 Hz- 1kHz) is key for VISIONs experiments so the highest full sensor readout speed will be requested about 1000 frames/second (10 billion pixels/second);
— Spectro-imaging capability: Focused, scanning probe mode combining bright, dark field and integrated differential phase contrast (iDPC) detection as well as electron energy loss spectroscopy (EELS) to advance low-electron-dose scanning TEM-EELS measurements of nanostructures and gas compositions at resolutions down to 0.3 nm in space and 0.1 eV in energy (over the widest variable energy window and highest precision).
