ANGSTROM - A next generation STEM for multidimensional imaging and fast dynamic spectroscopy

Electron microscopy (EM), and particularly scanning transmission EM (STEM), is at the heart of some of the fundamental questions in the natural sciences. It is the only technique that allows for versatile imaging, diffraction and spectroscopy, all from the same location, down to the atomic scale. Key to atomic-level information was the break-through of spherical (Cs) aberration correction. The increased beam currents, high acceleration voltages and damaging beam doses, however, were realized to have detrimental effects on delicate atomic structures (and defects therein) even in materials science. For a wide range of innovative and topical material and life science systems, this often significantly hampers a meaningful image interpretation and reconstruction. Currently, EM witnesses a second, more silent revolution taking place in the development of ultra-sensitive and faster direct-electron detectors. Centrally positioned as Austrian´s largest facility for EM research, the Institute of Electron Microscopy and Nanoanalysis (FELMI) at the Graz University of Technology (the applicant of this proposal) and its partners seek to establish a cutting-edge STEM instrument, complying with the latest detector technologies to allow for innovative characterization possibilities. The customized microscope shall excel in performance, flexibility and throughput over existing systems. Based on a high-brightness cold field-emission gun, the instrument will incorporate the latest generation Cs-corrector, allowing for deep sub-Ångstrom lateral resolution, picometer scale image precision and nanometer-scale depth sensitivity for optical sectioning. Operated at voltages down to 30kV only, featuring dose control as well as a piezo-controlled stage, a large pole-piece gap allows for 2D and 3D tomographic in-situ investigations of highly beam sensitive materials. This setup will be complimented by a large solid angle X-ray detection system as well as a segmented STEM detector but most importantly by next generation direct-electron detectors (DED). Being far more resilient to radiation damage, they outperform existing technology in terms of robustness, dynamic range, low voltage behaviour and speed. Teaming up with spectrometer vendors, it is envisioned to incorporate this respective technology into an energy-filter. Depending on the sensor, fast pixelated 4D energy-filtered STEM as well as energy-loss spectroscopy and imaging applications become possible and dynamic in-situ studies are conceivable even down to the microsecond time scale. This configuration introduces a plethora of innovative characterization modes and would represent Austria´s most powerful arrangement for low-dose, low-kV, high resolution STEM applications, spatially and potentially momentum resolved spectroscopy and in-situ dynamic studies. It will be widely deployed to study the electronic properties and chemical makeup of materials in condensed matter physics, applied material science, as well as chemistry, life science and medicine.