Regensburg 2019 – wissenschaftliches Programm

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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: Vortrag

Montag, 1. April 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.