Lead mixed-halide perovskite nanocrystals offer exceptional optical properties but suffer from ionic instability and ion migration under external stimuli, challenging their integration into devices. While such effects have been well studied in individual NCs and films, their impact on nanocrystal assemblies remains less understood. Here, we investigate the effect of strong external electric fields on self-assembled CsPbBr2.4Cl0.6 nanocrystal superlattices. By positioning individual superlattices between micrometer-sized capacitor plates, we analyze field-induced changes in photoluminescence, elemental composition, and morphology. We observe position-dependent changes in emission energy correlated with halide ion redistribution, revealed by energy-dispersive X-ray analysis, resulting from a nonuniform electric field across the superlattice, and supported by finite-element simulations. In situ mass spectrometry detects bromide sublimation, suggesting a combination of inter- and intraparticle halide diffusion. Irreversibility of photoluminescence and morphological changes further support a field-driven reorganization. These findings reveal responses of CsPbBr2.4Cl0.6 superlattices subject to external electric fields, relevant for their implementation in optoelectronic applications.

Standardisation of data collection and analysis is essential to enable commercialisation of 2D materials in a wide range of technologies. Selected area electron diffraction (SAED) in the transmission electron microscope (TEM) is one of the key methods for distinguishing monolayer from bilayer and few-layer graphene by comparing the 1st and 2nd order diffraction spot intensities. Yet there are many factors that can affect the reliability of data collection and interpretation, causing the measurement of monolayer samples to deviate from the literature boundary condition of I-{2 & strns;110}/I-{11 & strns;00}< 1 for monolayer graphene (1LG). Here we present the results of a large interlaboratory SAED comparison study, where 15 international laboratories measured and analysed nominally identical samples of chemical vapour deposited graphene. Large variations were observed in the measured ratios of diffraction spot intensities, with the largest variance associated with poor quality SAED data resulting from inadequate specimen handling and storage. To inform the reliable determination of monolayer thickness from SAED patterns we provide a description of best practice for specimen handling, TEM operation, data collection and analysis. This work was undertaken within VAMAS Technical Working Area 41: Graphene and related 2D materials-Project 9, the results of which have been directly incorporated into ISO/TS 21356-2 for the characterisation of graphene sheets. We find that when this methodology is followed, 1LG can be distinguished from bilayer or thicker material with high confidence where analysis of a single SAED pattern gives I-{2 & strns;110}/I-{11 & strns;00}< 1.2, even in the absence of precise specimen tilting.

Colloidal lead mixed-halide perovskite nanocrystals offer exceptional optical properties but suffer from ionic instability and ion migration under external stimuli, challenging their integration into devices. While such effects are well-studied in individual NCs and films, their impact on ordered nanocrystal assemblies remains less understood. Here, we investigate the effect of strong external electric fields on self-assembled CsPbBr3-xClx nanocrystal superlattices. By precisely positioning individual superlattices between micrometre sized capacitor-plates, we analyse field-induced changes in photoluminescence, elemental composition, and morphology. We observe pronounced, spatially dependent PL shifts correlated with halide ion redistribution, as revealed by energy-dispersive X-ray analysis, resulting from non-uniform electric field distribution across the superlattice indicated by finite-element simulations. In-situ mass spectrometry detects bromide sublimation, pointing to a combination of inter- and intra-particle halide diffusion. Irreversible PL changes and morphological distortions further support a field-driven reorganization. These findings show information regarding the structural responses of the CsPbBr3-xClx superlattice, under influence of an external electric field, highlighting the need for improved structural and compositional stability in future optoelectronic applications.

Flexible metasurfaces comprising arrays of sub-wavelength thick nanoparticles embedded in soft and transparent substrates have attracted significant research interest due to their ability to generate predictable, tunable, and reversible optical performances. In this work, we employ electron beam lithography combined with wet-etching techniques to fabricate flexible metasurfaces of gold elliptical nanorings arranged in square or triangular arrays on polydimethylsiloxane. Scanning electron microscope tests conducted on the soft substrate demonstrate the feasibility of the pattern transfer technique at the nanoscale, as well as the reliability of the in situ optical characterization. Continuous monitoring of reflectance under strain, complemented by numerical simulations and theoretical analysis, reveals intriguing optical behaviors for these metasurfaces, including Fano features in surface lattice resonances, spectral blueshifts in localized surface plasmonic resonances, and color changes from purple to green and orange. By integrating metasurfaces with different characteristics into a chessboard-like pattern, we propose the configuration of a flexible strain map for contactless investigation of localized surface strain, which also provides opportunities for information encryption by encoding the varied resonances under strain.

The generation of small electron probes is the basis for various techniques in which such a probe is scanned across a sample, and special probe shapes like vortices can be desirable, e.g., to gain insight into magnetic properties. Micron-scale phase plates or holographic masks, in combination with demagnifying optics, are usually used for creating such special probe wave functions. Here, we present the fabrication of nanometer-sized phase plates based on thickness-selected and stacked graphite layers as well as an analysis of their performance. First, a spiral phase plate is demonstrated that creates a vortex beam with an orbital angular momentum of 1 and an outer radius of 2.5 nm. Second, a three-level Fresnel lens built from two nanopatterned graphite membranes is presented, which achieves a focal spot with a full width at half maximum of 5.5 nm. Third, an array of electron sieves is demonstrated, each of which creates a focal spot with a radius of 2 nm, and the array is applied as a Shack–Hartmann wavefront detector. These elements allow the generation of few-nanometer sized focused probes or vortices without the need for additional optical elements.

Two-dimensional materials can be combined by placing individual layers on top of each other, so that they are bound only by their van der Waals interaction. The sequence of layers can be chosen arbitrarily, enabling an essentially atomic-level control of the material and thereby a wide choice of properties along one dimension. However, simultaneous control over the structure in the in-plane directions is so far still rather limited. Here, we combine spatially controlled modifications of 2D materials, using focused electron irradiation or electron beam induced etching, with the layer-by-layer assembly of van der Waals heterostructures. The presented assembly process makes it possible to structure each layer with an arbitrary pattern prior to the assembly into the heterostructure. Moreover, it enables a stacking of the layers with accurate lateral alignment, with an accuracy of currently 10 nm, under observation in an electron microscope. Together, this enables the fabrication of almost arbitrary 3D structures with highest spatial resolution.

The simple dependence of the intensity in annular dark field scanning transmission electron microscopy images on the atomic number provides (to some extent) chemical information about the sample, and even allows an elemental identification in the case of light-element single-layer samples. However, the intensity of individual atoms and atomic columns is affected by residual aberrations and the confidence of an identification is limited by the available signal to noise. Here, we show that matching a simulation to an experimental image by iterative optimization provides a reliable analysis of atomic intensities even in presence of residual non-round aberrations. We compare our new method with other established approaches demonstrating its high reliability for images recorded at limited dose and with different aberrations. This is of particular relevance for analyzing moderately beam-sensitive materials, such as most 2D materials, where the limited sample stability often makes it difficult to obtain spectroscopic information at atomic resolution.

Purpose: Digital platforms provide logistics service providers (LSPs) the opportunity to increase their capacity utilization. Since there are a large number of reasonable alternatives, LSPs should be able to systematically assess different platforms. How-ever, there is little knowledge on specific dimensions for such an assessment. Thus, the objective of this paper is to identify important dimensions to assess digital plat-forms from the perspective of LSPs. Methodology: We conducted semi-structured interviews with LSPs and platform operators. Based on a qualitative content analysis we identify specific dimensions for assessment of digital platforms. Findings: We find four specific dimensions for assessing platform potential. First, matching mechanisms that facilitate transaction processes and reduce search costs. Second, gatekeeping mechanisms that assure the quality of platform actors and increase trust. Third, pricing mechanisms that affect direct costs, and fourth, factors that lead to lock-in-effects. Originality: There are a large number of studies on criteria to select business partners, e.g., suppliers. Although the number of platform users increases rapidly, and their disruptive potential is high, there is only little knowledge on platform-specific evaluation criteria. In this paper, we identify relevant platform-specific dimensions for the selection of suitable platforms as an extension of existing partner selection criteria.