Ptychography at the carbon K-edge

Nicolas Mille,Adam P Hitchcock,Vincent Favre-Nicolin,Jaianth Vijayakumar,Sufal Swaraj,Stefan Stanescu,Hao Yuan,Kewin Desjardins,Rachid Belkhou

doi:10.1038/s43246-022-00232-8

Abstract

Ptychography is a coherent diffraction imaging technique that measures diffraction patterns at many overlapping points on a sample and then uses an algorithm to reconstruct amplitude and phase images of the object and probe. Here, we report imaging, spectroscopy and linear dichroism ptychographic measurements at the carbon K-edge. This progress was achieved with a new generation of scientific Complementary Metal Oxide Semiconductor (sCMOS) X-ray cameras with an uncoated image sensor which has fast image transfer and high quantum efficiency at the carbon K-edge. Reconstructed amplitude and phase contrast images, C 1s spectral stacks, and X-ray linear dichroism of carbon nanotubes at the carbon K-edge were measured with ptychography. Ptychography and conventional Scanning Transmission X-ray Microscopy (STXM) are compared using results acquired from the same area. Relative to STXM, ptychography provides both improved spatial resolution and improved image quality. We used defocus ptychography, with an X-ray beam spot size of 1.0 micron, in order to reduce radiation damage and carbon deposition. Comparable spatial resolution was achieved to that of ptychography performed with a focused beam. Ptychography at the carbon K-edge offers unique opportunities to perform high resolution spectromicroscopy on organic materials important in medicine, biology, environmental science and energy materials.

Highlights

Ptychography is a coherent diffraction imaging technique that measures diffraction patterns at many overlapping points on a sample and uses an algorithm to reconstruct amplitude and phase images of the object and probe
The ptychographic dataset consists of a 50 × 50 square array of diffraction patterns like the one in Fig. 1a, recorded with the sample positioned in the focal plane of the Fresnel zone plate (FZP), and using 500 ms exposure time per pattern
The results presented in this work show that an scientific Complementary Metal Oxide Semiconductor (sCMOS) camera with an uncoated sensor is able to record ptychographic data sets in the carbon K-edge energy range (280–320 eV) with sufficient signal to noise ratio and stable background to allow imaging and spectroscopy based on ptychography

Summary

Introduction

Ptychography is a coherent diffraction imaging technique that measures diffraction patterns at many overlapping points on a sample and uses an algorithm to reconstruct amplitude and phase images of the object and probe. We report imaging, spectroscopy and linear dichroism ptychographic measurements at the carbon K-edge This progress was achieved with a new generation of scientific Complementary Metal Oxide Semiconductor (sCMOS) X-ray cameras with an uncoated image sensor which has fast image transfer and high quantum efficiency at the carbon K-edge. STXM at the carbon K-edge (C 1 s, 280–320 eV) has been applied extensively to study polymers[8,14,15], organic electronics[16,17,18], aerosols important in climate change[19,20], and biological materials[21,22] among many other areas. The Tucsen Dhyana 95 sCMOS camera (http://www.tucsen.com/ products) equipped with a prototype uncoated GSENSE400BSIGP image sensor provides single X-ray photon sensitivity in the carbon K-edge region and rapid image transfer The readout time for the version of the camera used for these measurements, along with software overhead issues, meant the fastest sampling our system could achieve was 100 ms

Methods

Results

Conclusion