Aberration-corrected transmission electron microscopy with Zernike phase plates

We explore the possibility of applying physical phase plates (PPs) in combination with aberration-corrected transmission electron microscopy. Phase-contrast transfer characteristics are calculated and compared for a thin-film based Zernike PP, a hole-free (HF) or Volta PP and an electrostatic Zach PP, considering their phase-shifting properties in combination with partial spatial coherence. The effect of slightly converging illumination conditions, often used in high-resolution applications, on imaging with PPs is discussed. Experiments with an unheated Zernike PP applied to various nanomaterial specimens and a qualitative analysis clearly demonstrates the general compatibility of PPs and aberration-corrected transmission electron microscopy. Calculations and experiments show the benefits of the approach, among which is a strong phase-contrast enhancement of a large range of spatial frequencies. This allows the simultaneous imaging of atomic-resolution structures and morphological features at the nanometer scale, with maximum phase contrast. The calculations can explain why the HFPP damps contrast transfer at higher spatial frequencies.The authors acknowledge funding by German Research Foundation (DFG project He 7675/1-1), from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 889546, by the Spanish MICINN (PID2019-104739GB-100/AEI/10.13039/501100011033), by the Government of Aragòn (Project DGA E13-20R) and from the European Union H2020 programs ”ESTEEM3” (Grant number 823717) and ”Graphene Flagship” CORE 3 (Grant number 881603).Peer reviewe