Aberration-corrected transmission electron microscopy with Zernike phase plates

TL;DR

This paper investigates the integration of physical phase plates with aberration-corrected transmission electron microscopy, demonstrating enhanced phase contrast and compatibility for high-resolution nanomaterial imaging.

Contribution

It provides a comparative analysis of different phase plates and shows their effective application in improving contrast in aberration-corrected TEM.

Findings

Phase plates enhance phase contrast across a broad range of spatial frequencies.

Experimental validation confirms compatibility of phase plates with aberration-corrected TEM.

Certain phase plates may dampen contrast transfer at very high spatial frequencies.

Abstract

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.