Ptychographic electron microscopy using high-angle dark-field scattering for sub-nanometre resolution imaging

Abstract

Diffractive imaging, in which image-forming optics are replaced by an inverse computation using scattered intensity data, could, in principle, realize wavelength-scale resolution in a transmission electron microscope. However, to date all implementations of this approach have suffered from various experimental restrictions. Here we demonstrate a form of diffractive imaging that unshackles the image formation process from the constraints of electron optics, improving resolution over that of the lens used by a factor of five and showing for the first time that it is possible to recover the complex exit wave (in modulus and phase) at atomic resolution, over an unlimited field of view, using low-energy (30 keV) electrons. Our method, called electron ptychography, has no fundamental experimental boundaries: further development of this proof-of-principle could revolutionize sub-atomic scale transmission imaging.

Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects

“…Our results provide a step towards developing an approach that could be used to measure the electric field around a needle-shaped specimen during an APT experiment. 26 They are also relevant for the interpretation of similar results obtained from needle-shaped specimens using other phase contrast techniques, including in-line electron holography, [27][28][29] ptychography, 30 diffractive imaging and differential phase contrast microscopy. 31 …”

Structure retrieval with fast electrons using segmented detectors

“…However, the approach introduced here can also be applied to data obtained from "fixed-configuration" segmented detectors, where each segment is a bucket detector rather than being defined in terms of a number of pixels on a fast-readout 2D electron camera [10,14,20,21]. In cases in which the full 4D dataset is recorded, the relative simplicity of SDP-a small number of Fourier transform operations is applied to a reduced 2D projection of the dataset-can complement other ptychographic approaches such as ePIE [3] and Wigner distribution deconvolution [35].…”

“…When treated as a whole, such 4D datasets are overdetermined if there are regions of overlap of the area of the specimen illuminated for different probe positions. The quantity that it is then convenient to work with in such ptychographic approaches is the transmission function of the specimen rather than the exit-surface wave, as has been done in several applications along these lines [2][3][4]. The transmission function is defined as the quantity that multiplies the incident probe wave function to give the exit-surface wave function.…”

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

“…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].…”