Phase contrast scanning transmission electron microscopy imaging of light and heavy atoms at the limit of contrast and resolution

Abstract

Using state of the art scanning transmission electron microscopy (STEM) it is nowadays possible to directly image single atomic columns at sub-Å resolution. In standard (high angle) annular dark field STEM ((HA)ADF-STEM), however, light elements are usually invisible when imaged together with heavier elements in one image. Here we demonstrate the capability of the recently introduced Integrated Differential Phase Contrast STEM (iDPC-STEM) technique to image both light and heavy atoms in a thin sample at sub-Å resolution. We use the technique to resolve both the Gallium and Nitrogen dumbbells in a GaN crystal in [] orientation, which each have a separation of only 63 pm. Reaching this ultimate resolution even for light elements is possible due to the fact that iDPC-STEM is a direct phase imaging technique that allows fine-tuning the microscope while imaging. Apart from this qualitative imaging result, we also demonstrate a quantitative match of ratios of the measured intensities with theoretical predictions based on simulations.

Factors affecting electron beam damage in calcite nanoparticles

“…Collection efficiency and signal to noise ratio can further be improved through recent developments in STEM integrated differential phase contrast (iDPC) using a segmented detector as well as focussed probe ptychography with a pixelated detector, where the signal to noise ratio is able to exceed CTEM phase contrast images (Sagawa et al, 2018;Yücelen et al, 2018). Both iDPC and ptychography have shown promise for the study of beam sensitive materials and light element containing materials at atomic resolution due to the efficiency of electron collection at low probe currents.…”

Regioselective generation and reactivity control of subnanometric platinum clusters in zeolites for high-temperature catalysis

“…Herein, to identify the location of Pt atoms in Pt@MFI-SDA and K-Pt@MFI-SDA, we have employed a combination of high-resolution high-angle annular dark-field scanning transmission electron microscopy (HR HAADF-STEM) and integrated differential phase contrast (iDPC) imaging techniques to simultaneously visualize both Pt atoms and the zeolite structure with atomic resolution. 22,23 As shown in Fig. S4, by correlating the HR HAADF-STEM and iDPC images, it can be deduced that most Pt atoms are located in the sinusoidal channels of MFI zeolite structure, whereas a much smaller amount is found in the straight pore channels or at the intersectional voids.…”

Direct Imaging of Atomically Dispersed Molybdenum that Enables Location of Aluminum in the Framework of Zeolite ZSM‐5

“…The contrast of iDPC image can be easily interpreted, as it approximately corresponds to the local electrostatic potential field of the thin specimen being probed. Moreover, iDPC‐STEM allows the simultaneous imaging of heavy and light elements …”