Carbon‐film‐based Zernike phase plates with smooth thickness gradient for phase‐contrast transmission electron microscopy with reduced fringing artefacts

Phase plates (PPs) in transmission electron microscopy (TEM) improve the contrast of weakly scattering objects under in-focus imaging conditions. A well-established PP type is the Zernike (Z)PP, which consists of a thin amorphous carbon (aC) film with a microscaled hole in the centre. The mean inner potential of the aC film is exploited to shift the phase of the scattered electrons while the unscattered electrons in the zero-order beam propagate through the hole and remain unaffected. However, the abrupt thickness increase at the hole edge induces an abrupt change of the phase-shift distribution and leads to fringing, that is, intensity oscillations around imaged objects, in TEM images. In this work, we have used focused-ion-beam milling to fabricate ZPPs with abrupt and graded thickness profiles around the centre hole. Depending on the thickness gradient and inner hole radius, graded-ZPP-TEM images of an aC/vacuum interface and bundles of carbon nanotubes (CNTs) show strongly reduced fringing. Image simulations were performed with ZPP-phase-shift distributions derived from measured thickness profiles of graded ZPPs, which show good agreement with the experimental images. - Fringing artefacts, that is, intensity oscillations around imaged objects, are strongly reduced for Zernike phase plates with a graded thickness profile around the centre hole. - Focused-ion-beam milling is used to fabricate graded Zernike phase plates with specific inner hole radius and thickness gradients. - The phase-shift distribution is obtained from measured thickness profiles around the centre hole. - Image simulations based on experimentally measured thickness/phase-shift distributions show good agreement with experimental Zernike phase-plate TEM images

Fano Interference in Microwave Resonator Measurements

Resonator measurements are a simple but powerful tool to characterize a material's microwave response. The losses of a resonant mode are quantified by its internal quality factor $Q_\mathrm{i}$, which can be extracted from the scattering coefficient in a microwave reflection or transmission measurement. Here we show that a systematic error on $Q_\mathrm{i}$ arises from Fano interference of the signal with a background path. Limited knowledge of the interfering paths in a given setup translates into a range of uncertainty for $Q_\mathrm{i}$, which increases with the coupling coefficient. We experimentally illustrate the relevance of Fano interference in typical microwave resonator measurements and the associated pitfalls encountered in extracting $Q_\mathrm{i}$. On the other hand, we also show how to characterize and utilize the Fano interference to eliminate the systematic error

Defect Engineering of Two-dimensional Molybdenum Disulfide

Two-dimensional (2D) molybdenum disulfide (MoS2) holds great promise in electronic and optoelectronic applications owing to its unique structure and intriguing properties. The intrinsic defects such as sulfur vacancies (SVs) of MoS2 nanosheets are found to be detrimental to the device efficiency. To mitigate this problem, functionalization of 2D MoS2 using thiols has emerged as one of the key strategies for engineering defects. Herein, we demonstrate an approach to controllably engineer the SVs of chemically exfoliated MoS2 nanosheets using a series of substituted thiophenols in solution. The degree of functionalization can be tuned by varying the electron withdrawing strength of substituents in thiophenols. We find that the intensity of 2LA(M) peak normalized to A1g peak strongly correlates to the degree of functionalization. Our results provide a spectroscopic indicator to monitor and quantify the defect engineering process. This method of MoS2 defect functionalization in solution also benefits the further exploration of defect free MoS2 for a wide range of applications

Amorphous NiCu Thin Films Sputtered on TiO2 Nanotube Arrays: A Noble-Metal Free Photocatalyst for Hydrogen Evolution

In this work, NiCu co-catalysts on TiO2 are studied for photocatalytic hydrogen evolution. NiCu co-catalyst films are deposited at room temperature by argon plasma sputtering on high aspect-ratio anodic TiO2 nanotubes. To tune the Ni : Cu atomic ratio, alloys of various compositions were used as sputtering targets. Such co-catalyst films are found to be amorphous with small nanocrystalline domains. A series of parameters is investigated, i. e., i) Ni : Cu relative ratio in the sputtered films, ii) NiCu film thickness, and iii) thickness of the TiO2 nanotube layers. The highest photocatalytic activity is obtained with 8 μm long TiO2 nanotubes, sputter-coated with a 10 nm-thick NiCu films with a 1 : 1 Ni : Cu atomic ratio. This photocatalyst reaches a stable hydrogen evolution rate of 186 μL h−1 cm−2, 4.6 and 3 times higher than that of Ni- and Cu-TiO2, respectively, demonstrating a synergistic co-catalytic effect of Ni and Cu in the alloy co-catalyst film

Granular aluminium nanojunction fluxonium qubit

Mesoscopic Josephson junctions, consisting of overlapping superconducting electrodes separated by a nanometre-thin oxide layer, provide a precious source of nonlinearity for superconducting quantum circuits. Here we show that in a fluxonium qubit, the role of the Josephson junction can also be played by a lithographically defined, self-structured granular aluminium nanojunction: a superconductor–insulator–superconductor Josephson junction obtained in a single-layer, zero-angle evaporation. The measured spectrum of the resulting qubit, which we nickname gralmonium, is indistinguishable from that of a standard fluxonium. Remarkably, the lack of a mesoscopic parallel plate capacitor gives rise to an intrinsically large granular aluminium nanojunction charging energy in the range of tens of gigahertz, comparable to its Josephson energy. We measure coherence times in the microsecond range and we observe spontaneous jumps of the value of the Josephson energy on timescales from milliseconds to days, which offers a powerful diagnostics tool for microscopic defects in superconducting materials

Direct laser writing of μ-chips based on hybrid C–Au–Ag nanoparticles for express analysis of hazardous and biological substances

Micro-chips based on organic–inorganic hybrid nanoparticles (NPs) composed of nanoalloys of gold (Au) and silver (Ag) embedded in an amorphous carbonaceous matrix (C–Au–Ag NPs) were prepared directly on a substrate by the laser- induced deposition (for short: LID) method. The C–Au–Ag NPs show a unique plasmon resonance which enhances Raman scattering of analytes, making the μ-chips suitable to detect ultra-low-volumes (10−12 liter) and concentrations (10−9 M) of bio-agents and a hazardous compound. These micro-chips constitute a novel, flexible solid-state device that can be used for applications in point-of-care diagnostics, consumer electronics, homeland security and environmental monitoring

Coloration in supraparticles assembled from polyhedral metal-organic framework particles

Supraparticles are spherical colloidal crystals prepared by confined self-assembly processes. A particularly appealing property of these microscale structures is the structural color arising from interference of light with their building blocks. Here, we assemble supraparticles with high structural order that exhibit coloration from uniform, polyhedral metal-organic framework (MOF) particles. We analyse the structural coloration as a function of the size of these anisotropic building blocks and their internal structure. We attribute the angle-dependent coloration of the MOF supraparticles to the presence of ordered, onion-like layers at the outermost regions. Surprisingly, even though different shapes of the MOF particles have different propensities to form these onion layers, all supraparticle dispersions show well-visible macroscopic coloration, indicating that local ordering is sufficient to generate interference effects

Responsible Human-Robot Interaction with Anthropomorphic Service Robots: State of the Art of an Interdisciplinary Research Challenge

Anthropomorphic service robots are on the rise. The more capable they become and the more regular they are applied in real-world settings, the more critical becomes the responsible design of human-robot interaction (HRI) with special attention to human dignity, transparency, privacy, and robot compliance. In this paper we review the interdisciplinary state of the art relevant for the responsible design of HRI. Furthermore, directions for future research on the responsible design of HRI with anthropomorphic service robots are suggested