Peter D. Nellist's research while affiliated with University of Oxford and other places

... [29] Differently, the low stability feature of Cu 2 O was also utilized to activate the reactant molecules with the formed Cu 0 species in the electrochemical/chemical conversions. [41,42] As a unique COFs, TpPa-2-COF is a narrow band gap photocatalytic material with high reduction ability and wide visible light response. So, we reasoned that the exposed Cu ions in Cu 2 O have the chance to be reduced into Cu 0 when receiving electrons from COFs in photocatalytic reaction under visible light, which may benefit photocatalytic H 2 evolution reaction by Cu 0 serving as cocatalyst. ...

Reference:

Self‐Accelerating H2 Evolution Activity by In Situ Transformation on Noble‐Metal‐Free Photocatalyst of Covalent Organic Framework and Cu2O Composite

... However, at significantly reduced dwell times the temporal response of the detector becomes important. Several works have previously shown how scintillator-based detectors have a scintillation decay time which causes the duration of single electron events to last over 0.5 µs, sometimes as long as 1.5 µs [35][36][37][38][39][40][41]. When scanning at dwell times slower than around twice the scintillator decay time, the effects of this afterglow is negligible, but for faster scans, the image begins to suffer from streaking artefacts as a result of scintillator decay [35,40]. ...

Reference:

Ultra-fast Digital DPC Yielding High Spatio-Temporal Resolution for Low-Dose Phase Characterisation

... On one hand, the structural information of materials can be imaged with a much lower electron dose and a wavelength limited spatial resolution compared to conventional STEM imaging techniques. This broadens the application scope of STEM imaging to include high-resolution structural characterization of beamsensitive materials (Pennycook et al., 2019;Jannis et al., 2021;Pennycook et al., 2020;Hao Yang et al., 2016;Lozano et al., 2018;Song et al., 2019), and even biological samples (Zhou et al., 2020;Pei et al., 2023). On the other hand, accurate correction of residual lens aberrations enables delivery of electromagnetic fields related to material functionalities with high fidelity(H. . ...

Reference:

Robust Ptychographic Reconstruction with an Out-of-Focus Electron Probe

... hydrogen energy. [1,2] However, the quantum efficiency of the hydrogen evolution reaction (HER) in overall water splitting is significantly hindered by the lethargic kinetics of water oxidation. [3] While the use of sacrificial reagents (e.g., triethanolamine, lactic acid, Na 2 S/Na 2 SO 3 , etc.) as hole scavengers can accelerate the oxidation half-reaction and H 2 production, [4,5] this approach is counterproductive due to the inevitable waste of hole energy, increased costs and carbon emissions. ...

Reference:

Full‐Space Electric Field in Mo‐Decorated Zn2In2S5 Polarization Photocatalyst for Oriented Charge Flow and Efficient Hydrogen Production

... For quite a range of thicknesses, central focusing of the beam offers phase images free from contrast reversals and with the strongest contrast overall [5,15,20]. However this conflicts with the optimal focus for ADF imaging, the entrance surface. Thus optimizing the probe focus for the phase images during acquisition can significantly degrade the quality of simultaneously acquired ADF images, especially as the sample thickness increases and the distance between the entrance surface and optimal focus for ptychography widens. ...

Reference:

Phase offset method of ptychographic contrast reversal correction

... The improvement in column position measurements over all dose settings again indicates the proper correction of scan-line and fast-scan distortions. The improvement of SCS measurement accuracies, especially at low-dose conditions greatly decreases the chance of miscounting atoms in the structure, which in turn may be very beneficial, e.g., for the reconstruction of 3D information from atom counts 52,53 . ...

Reference:

Deep convolutional neural networks to restore single-shot electron microscopy images

... In the cases where the resolution is strongly restricted, it is possible that there is no option to improve the sensitivity using any GPA based strain characterization method and obtain unusable strain mappings. Alternative strain characterization methods should be considered such as Precession Electron Diffraction and Four-dimensional STEM [38][39][40][41][42] or simply directly measure the lattice deformation in real space using the Peak Pair algorithm, Peak Finding methods, template matching, atomap, StatSTEM, etc. [43][44][45][46][47][48][49][50][51]. For electron diffraction methods, the strain sensitivity and precision are independent of the probe position. ...

Reference:

Relation between sampling, sensitivity and precision in strain mapping using the Geometric Phase Analysis method in Scanning Transmission Electron Microscopy

... Particularly, because the orientations of the octahedra in Li layers of O1 and O3 phases are different, reconstruction of oxygen ions is supposed to occur at the interface. Techniques that are sensitive to light elements such as annular bright-field (ABF) imaging 38 or other approaches 39,40 could be used in the future to deepen our understanding of these O1-O3 interfaces formed in the chemomechanically deformed structures. Yet, the beam sensitivity of the O1 phase as well as the sample thickness requirement are two big challenges. ...

Reference:

Direct observation of chemomechanical stress-induced phase transformation in high-Ni layered cathodes for lithium-ion batteries

... Similar to the PIO-YSZ sample, alignment of the 4D-STEM defocus series was performed using simultaneously acquired HAADF-STEM images. However, in this case a method for non-rigid registration of images (Jones et al. (2015)) was extended to a series of 4D-STEM data sets (O'Leary et al. (2022)). The deformations found from synchronously acquired HAADF data were applied to the 4D-STEM data sets by flattening the diffraction space, registering each real-space slice and transforming back to 4D. ...

Reference:

Improved Three-Dimensional Reconstructions in Electron Ptychography through Defocus Series Measurements

... We relaxed the runtime by utilizing the PRISM STEM-EELS approximation, achieving over a ten-fold speedup (see Methods) [33]. Future work may explore the effects of smaller ADF collection angles with increased coherence lengths and crystallographic contrast [15,34], or thicker specimens where electron channeling becomes more concerning [35,36]. ...

Reference:

Imaging Atomic-Scale Chemistry from Fused Multi-Modal Electron Microscopy