Efficient phase contrast imaging in STEM using a pixelated detector. Part II: Optimisation of imaging conditions

Yang, Hao; Pennycook, Timothy J.; Nellist, Peter D.

doi:10.1016/j.ultramic.2014.10.013

Cited by 157 publications

(134 citation statements)

References 18 publications

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“…As presented above, DPC offers a simple and fast constructive algorithm for phase reconstruction, but it is not the only approach to phase reconstruction from 4D data, the most established alternative in the STEM geometry perhaps being ptychography. Constructive algorithms exist for ptychography from weakly scattering objects, which have been shown to constitute an optimally electron-efficient processing of 4D data [7,9]. For strong phase objects, ptychography tends to involve iterative approaches [36][37][38].…”

Section: Phase Reconstruction From Dpc Imagesmentioning

confidence: 99%

“…In addition, requiring fewer pixels can relax the restriction on the physical size of each pixel/sensor, reducing the commercial expense and increasing the SNR [42]. Yang et al [9] have explored the minimum number of pixels needed to maximize peak SNR for ptychography. We explore the number of pixels needed in terms of edge detection and preservation of information content in the CBED patterns.…”

Section: Sampling Of the Diffraction Patternmentioning

confidence: 99%

“…Recent developments in fast-readout pixel detectors and powerful computers significantly improve the speed of data acquisition and transfer, and make possible the acquisition of two-dimensional CBED patterns with two dimensional probe scanning positions -a four dimensional (4D) dataset -at atomic resolution [5][6][7]. Such 4D datasets have been shown to allow synthesizing multiple imaging modes [4,8], differential phase contrast imaging [6] and ptychographic phase reconstruction [7,9]. However, the full potential of 4D datasets for quantitative analysis has yet to be established.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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a b s t r a c tFour-dimensional scanning transmission electron microscopy (4D-STEM) is a technique where a full twodimensional convergent beam electron diffraction (CBED) pattern is acquired at every STEM pixel scanned. Capturing the full diffraction pattern provides a rich dataset that potentially contains more information about the specimen than is contained in conventional imaging modes using conventional integrating detectors. Using 4D datasets in STEM from two specimens, monolayer MoS 2 and bulk SrTiO 3 , we demonstrate multiple STEM imaging modes on a quantitative absolute intensity scale, including phase reconstruction of the transmission function via differential phase contrast imaging. Practical issues about sampling (i.e. number of detector pixels), signal-to-noise enhancement and data reduction of large 4D-STEM datasets are emphasized.

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Section: Phase Reconstruction From Dpc Imagesmentioning

confidence: 99%

Section: Sampling Of the Diffraction Patternmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…4D-STEM can deliver much more structural information [1,2] than conventional STEM where only integrated electron intensities are acquired. The 4D dataset of CBED patterns can be utilized for structural analysis such as ptychographic reconstruction [3][4][5][6][7][8][9], strain mapping [10][11][12], electric and magnetic fields imaging using differential phase contrast [13,14], and composition and thickness measurements [15] with position-averaged CBED (PACBED) [16].…”

Section: Introductionmentioning

confidence: 99%

4D-Data Acquisition in Scanning Confocal Electron Microscopy for Depth-Sectioned Imaging

Hamaoka

Hashimoto

Mitsuishi

et al. 2018

e-J. Surf. Sci. Nanotech.

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We propose an experimental depth-sectioned imaging method based on annular dark-field scanning confocal electron microscopy (ADF-SCEM). Four-dimensional (4D) datasets, consisting of 2D probe images taken at every probe position during 2D raster scanning, were acquired with an aberration-corrected scanning transmission electron microscope. A series of depth-sectioned images were constructed by processing a single 4D dataset. A pinhole and a stage-scan system used in earlier studies were not required in the present data acquisition. Optimal observation conditions for the 4D data acquisition in the ADF-SCEM mode are outlined from multislice simulations.

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“…Ultimately, however, the most flexible STEM experiment would be to record the entire back focal plane of the specimen onto a pixelated detector, and then post-process the dataset to access whichever features in the contrast are desired. This could produce all the above-mentioned signals, but many more besides, including ptychographic reconstruction of the exit wave [7,8].In order to achieve this aim, we need to have a detector that is capable of recording single electron events at typical beam energies for a scanning TEM (e.g. 100 or 200 keV) with enough pixels to allow significant flexibility for performing different imaging modes, a readout speed far quicker than that available of previous pixelated detectors such as traditional scintillator-CCD devices (typically < 30 frames per second), and synchronization to the scan system.…”

mentioning

confidence: 99%

Use of a hybrid silicon pixel (Medipix) detector as a STEM detector

et al. 2015

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Scanning transmission electron microscopy has traditionally relied on the high angle annular dark field technique for imaging atoms [1,2], which provides a simple and easy to understand contrast, which is strongly related to atomic number. More recently, there has been a resurgence of interest in alternative imaging modes, including bright field [3,4] and annular bright field imaging [5,6]. Ultimately, however, the most flexible STEM experiment would be to record the entire back focal plane of the specimen onto a pixelated detector, and then post-process the dataset to access whichever features in the contrast are desired. This could produce all the above-mentioned signals, but many more besides, including ptychographic reconstruction of the exit wave [7,8].In order to achieve this aim, we need to have a detector that is capable of recording single electron events at typical beam energies for a scanning TEM (e.g. 100 or 200 keV) with enough pixels to allow significant flexibility for performing different imaging modes, a readout speed far quicker than that available of previous pixelated detectors such as traditional scintillator-CCD devices (typically < 30 frames per second), and synchronization to the scan system. We have installed a Medipix-3 detector onto our JEOL ARM200F STEM (probe-corrected, cold FEG version), which is a silicon based hybrid pixel detector with a CMOS readout architecture and 256 x 256 pixels. The Medipix family of detectors are true counting detectors. Each of the 55µmx55µm pixels contains amplifiers and digitisation circuitry that determines whether energy deposited by the incident radiation lies within the range set by userdefined low and high thresholds, counting digitally those that do. Medipix2 detectors have been investigated for TEM by us [9,10] and others [11]. Presently we are exploring the capabilities of the third generation Medipix-3 detector coupled to a high-speed read-out system. The MERLIN read-out system [12] is capable of frame rates of 1200fps for durations that are limited only by the ability to transfer frame data to non-volatile storage. Constant frame rates of 100fps are guaranteed but we have found no problems running continuously at 500fps. Figure 1 shows that for 200keV electrons, single electron detection is achieved but the detector settings have a strong influence on the spatial frequency response of recorded images. Utilising an exposure time of 1µs and values of 70 and 240 for the pixel low energy threshold, it can be seen that the effects of charge-sharing between pixels can be drastically reduced, but at the expense of reducing the counting efficiency from 100% to ~50%. We are currently measuring the performance of the detector with respect to Detective Quantum Efficiency (DQE) and Modulation Transfer Function (MTF). An exciting aspect of the Medipix3 is its novel architecture, which allows the detection of charge-sharing and re-attribution back to a single pixel. For high-energy electrons we expect this to significantly improve MTF values.For STEM mode d...

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Efficient phase contrast imaging in STEM using a pixelated detector. Part II: Optimisation of imaging conditions

Cited by 157 publications

References 18 publications

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

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

4D-Data Acquisition in Scanning Confocal Electron Microscopy for Depth-Sectioned Imaging

Use of a hybrid silicon pixel (Medipix) detector as a STEM detector

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