Regensburg 2019 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 6: Topical session (Symposium MM): Correlative and in-situ Microscopy in Materials Research
MM 6.2: Talk
Monday, April 1, 2019, 12:15–12:30, H44
Determination of 3D electrostatic field at an electron nano-emitter — •Mingjian Wu1, Alexander Tafel2, Peter Hommelhoff2, and Erdmann Spiecker1 — 1Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen — 2Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen
Revealing and quantifying the 3D electrostatic field of field emission nano-emitters is key to answer the fundamental question of how the field interacts with the sharp tips. Here, we determine the 3D electrostatic field in situ at an electron nano-emitter. Differential phase contrast in scanning transmission electron microscopy has been applied to image nanoscale electrostatic fields of a sharp tungsten electron emitter with an apex radius of about 20 nm and under field emission condition. Assuming axial symmetry of the nano-emitter, we derived a method based on the inverse Abel transform to quantitatively reconstruct an axial slice of the 3D electrostatic field from a single projection measurement. The highest field strength of 2.92 V/nm is measured at the nano-emitter apex under condition of a bias voltage of -140 V with respect to the grounded counter electrode located about 650 nm from the apex, resulting in an emission current of more than 2 uA. The experimental results are compared with simulations based on a finite element numerical Maxwell equation solver. Quantitative agreement between experiment and simulation has been achieved.