Structure retrieval with fast electrons using segmented detectors

Abstract

We introduce an algorithm for the reconstruction of the complex transmission function of a specimen using segmented detectors in scanning transmission electron microscopy geometry. The phase of the transmission function can be related to magnetic and electric fields within the specimen and is sensitive to lighter elements. The technique is demonstrated for simulated data and also using experimental datasets taken from a MoS 2 monolayer and a SrTiO 3 crystal. We present an extension to the algorithm to account for uncertainties in the illuminating probe. The algorithm can be implemented using fast Fourier transforms, and this provides the possibility of reconstructing specimen transmission functions in real time.

Hollow Electron Ptychographic Diffractive Imaging

“…Ptychographic coherent diffractive imaging has been successfully implemented using both visible light [10,11] and x-ray sources [12][13][14]. Using electrons, the experimental geometry required is similar to that for aberration-corrected STEM imaging and high-atomic resolution phase-sensitive information has been successfully reconstructed at both low and intermediate voltages [15][16][17][18][19][20]. Importantly, Brown et al have demonstrated that only a limited portion of electrons detected are required for reconstruction [18].…”

“…Using electrons, the experimental geometry required is similar to that for aberration-corrected STEM imaging and high-atomic resolution phase-sensitive information has been successfully reconstructed at both low and intermediate voltages [15][16][17][18][19][20]. Importantly, Brown et al have demonstrated that only a limited portion of electrons detected are required for reconstruction [18]. Wang et al [19] have also reported a ptychographic reconstruction of a LaB 6 crystal in which light B atoms were clearly resolved together with heavy La atoms in reconstructed phases.…”

“…Recent advances in fast direct electron detectors and dataprocessing algorithms have triggered a renewed interest in phase-retrieval techniques [18,24,[26][27][28][29]. In this Letter, using a fast direct counting detector [30], we propose a new configuration for iterative ptychographic reconstruction from hollow diffraction patterns using a focused scanned probe.…”

Practical aspects of diffractive imaging using an atomic-scale coherent electron probe

“…[25]) and the sputtering cross-section of sulfur atoms with the dose of × − 7.5 10 e 5 per probe position is estimated to be about 0.26 sulfur atoms per probe position on average, as discussed in detail in Ref. [26] in connection to a similar dataset. All the MoS 2 simulations in this manuscript, including those in Fig.…”

Ten implementations of ptychography

“…However, WDDM still requires the specimen to be scanned over a grid of 2D positions separated by the desired resolution in the final reconstruction and a 2D diffraction intensity to be recorded at each scan position, which gives rise to a very large 4D data set. The 4D data set, however, can be substantially reduced by using fewer and bigger detector pixels when the sample satisfies the weak phase approximation (McCallum et al ., ; Yang et al ., ; Brown et al ., ). A breakthrough in ptychography was made when iterative algorithms were used to solve for the phase problem in 2004 (Faulkner & Rodenburg, ; Rodenburg & Faulkner, ).…”