Electron-beam recorders

Description

Upgrade of Titan ETEM GIF system with K3 Base IS direct electron detection camera. The Center for Visualizing Catalytic Processes (VISION), a center of excellence funded by DNRF (Danish National Research Foundation), wants to buy a camera to upgrade an existing instrument, an aberration-corrected Titan environmental transmission electron microscopy (ETEM) delivered by Thermo Fisher Scientific. The microscope is located at the premises of Haldor Topsoe A/S, and VISION is granted access according to a collaboration agreement between DTU Physics and Haldor Topsoe A/S. The camera has be a most sensitive detector for atomic-resolution transmission electron microscopy (TEM) measurements in order to suppress beam-induced sample alterations in the best possible way. The camera should be able to deliver images at 1Å resolution at low electron beam currents (< 10-20 e/(Å2s)) and low electron doses (< 10-20 e/(Å2)). Currently, the most sensitive detectors available are Direct Electron Detection (DED) cameras operated in single electron counting modes. The camera sensitivity expressed by its detection quantum efficiency (DQE) must be as high as possible reaching at a minimum > 50 % at ½ Nyquist and > 80 % at 0 Nyquist for 300 keV electrons. Moreover, as VISION aims for imaging dynamics of single nanoparticles in operando during catalysis, the DED also must provide a real-time single electron counting mode with online real-time data processing/acquisition for dose-fractionated imaging, focal series acquisition and drift correction. The time-resolution has therefore to be as good as possible and the full sensor readout speed has to be as high as possible reaching at a minimum > 1000 frames per second (corresponding to > 10 millions pixels). Furthermore, VISION's core scientific goal is to relate atomic structure, dynamics and functions of single nanoparticles. The camera will therefore have to be interfaced with a detector system to enable both tuning the microscope’s aberration-corrector for atomic-resolution TEM imaging of nanoparticles and simultaneous electron energy loss spectroscopy (EELS) of their catalytic functions. Such a detector system is available on the Topsoe Titan ETEM. It consists of a Gatan Image Filter (GIF) spectrometer for EELS with a post-GIF charged-coupled device (CCD) detector and a pre-GIF CCD camera that is radiation-hard for tuning the microscopes aberration-corrector. The camera must successfully pass the following site-acceptance test: (1) Mounting on-axis and pre-GIF position; (2) Demonstrate tuning the aberration-corrector to (i) enable an isotrope information transfer for spatial frequencies up to 1Å-1 at 300 keV and (ii) imaging at 1Å resolution in TEM mode, both tasks executed on the existing on-axis and pre-GIF charged-coupled device (CCD) camera. These specifications corresponds to the current performance of the microscope; (3) Demonstrate 1Å resolution on DED camera at 300keV and ca. 1s exposure with 10 e/Å^2/s in high vacuum mode of a Au/C cross-grating using electron counting mode; (4) Demonstrate focal image series acquisition and magnification readout; (5) Demonstrate EELS with zero-loss peak having a full-width half-maximum of 1eV at 300 keV, as on existing post-GIF CCD camera; (6) X-ray safety specs for Titan ETEM are maintained after mounting.