Meandering conduction channels and the tunable nature of quantized charge transport.

The discovery of the quantum Hall effect has established the foundation of the field of topological condensed matter physics. An amazingly accurate quantization of the Hall conductance, now enshrined in quantum metrology, is stable against any reasonable perturbation due to its topological protection. Conversely, the latter implies a form of censorship by concealing any local information from the observer. The spatial distribution of the current in a quantum Hall system is such a piece of information, which, thanks to spectacular recent advances, has now become accessible to experimental probes. It is an old question whether the original and intuitively compelling theoretical picture of the current, flowing in a narrow channel along the sample edge, is the physically correct one. Motivated by recent experiments locally imaging quantized current in a Chern insulator (Bi, Sb)[Formula: see text]Te[Formula: see text] heterostructure [Rosen et al., Phys. Rev. Lett. 129, 246602 (2022); Ferguson et al., Nat. Mater. 22, 1100-1105 (2023)], we theoretically demonstrate the possibility of a broad "edge state" generically meandering away from the sample boundary deep into the bulk. Further, we show that by varying experimental parameters one can continuously tune between the regimes with narrow edge states and meandering channels, all the way to the charge transport occurring primarily within the bulk. This accounts for various features observed in, and differing between, experiments. Overall, our findings underscore the robustness of topological condensed matter physics, but also unveil the phenomenological richness, hidden until recently by the topological censorship-most of which, we believe, remains to be discovered.

Activation of indistinguishability-based quantum coherence for enhanced metrological applications with particle statistics imprint.

SignificanceQuantum coherence has a fundamentally different origin for nonidentical and identical particles since for the latter a unique contribution exists due to indistinguishability. Here we experimentally show how to exploit, in a controllable fashion, the contribution to quantum coherence stemming from spatial indistinguishability. Our experiment also directly proves, on the same footing, the different role of particle statistics (bosons or fermions) in supplying coherence-enabled advantage for quantum metrology. Ultimately, our results provide insights toward viable quantum-enhanced technologies based on tunable indistinguishability of identical building blocks.

Universality and Multiplication of Gigahertz-Operated Silicon Pumps with Parts Per Million-Level Uncertainty.

The universality of physical phenomena is a pivotal concept underlying quantum standards. In this context, the realization of a quantum current standard using silicon single-electron pumps necessitates the verification of the equivalence across multiple devices. Herein, we experimentally investigate the universality of pumped currents from two different silicon single-electron devices which are placed inside the cryogen-free dilution refrigerator whose temperature (mixing chamber plate) was ∼150 mK under the operation of the pump devices. By direct comparison using an ultrastable current amplifier as a galvanometer, we confirm that two pumped currents are consistent with ∼1 ppm uncertainty. Furthermore, we realize quantum-current multiplication with a similar uncertainty by adding the currents of two different gigahertz (GHz)-operated silicon pumps, whose generated currents are confirmed to be identical. These results pave the way for realizing a quantum current standard in the nanoampere range and a quantum metrology triangle experiment using silicon pump devices.

Taming the Distribution of Light in Gate-All-Around Semiconductor Devices.

Optical metrology is ubiquitous, but image-based methods cannot resolve features of dimensions much smaller than the wavelength. However, it has recently been demonstrated that light can be nanofocused into subwavelength semiconducting lines by setting the incident polarization along the direction of these lines. This Letter extends the previous studies to systems with two perpendicular gratings, as found e.g. after replacement gate processing of gate-all-around (GAA) field-effect transistors (FETs). We show that besides the nanofocusing effect, the incident polarization also offers control over which array of lines the light couples into. The interaction of the incident light occurs with the semiconducting lines to which the polarization is parallel with remarkably low interference from the existence of another perpendicular grating. We demonstrate the use of this effect with Raman spectroscopy to simultaneously extract the SiGe volume and the strain in the Si forksheet channels and in the SiGe layers of GAA FETs.

Ultra-Large Scale Stitchless AFM: Advancing Nanoscale Characterization and Manipulation with Zero Stitching Error and High Throughput.

The atomic force microscopy (AFM) is an important tool capable of characterization, measurement, and manipulation at the nanoscale with a vertical resolution of less than 0.1 nm. However, the conventional AFMs' scanning range is around 100 µm, which limits their capability for processing cross-scale samples. In this study, it proposes a novel approach to overcome this limitation with an ultra-large scale stitchless AFM (ULSS-AFM) that allows for the high-throughput characterization of an area of up to 1 × 1 mm2 through a synergistic integration with a compliant nano-manipulator (CNM). Specifically, the compact CNM provides planar motion with nanoscale precision and millimeter range for the sample, while the probe of the ULSS-AFM interacts with the sample. Experimental results show that the proposed ULSS-AFM performs effectively in different scanning ranges under various scanning modes, resolutions, and frequencies. Compared with the conventional AFMs, the approach enables high-throughput characterization of ultra-large scale samples without stitching or bow errors, expanding the scanning area of conventional AFMs by two orders of magnitude. This advancement opens up important avenues for cross-scale scientific research and industrial applications in nano- and microscale.

Label-Free Single Nanoparticle Identification and Characterization in Demanding Environment, Including Infectious Emergent Virus.

Unknown particle screening-including virus and nanoparticles-are keys in medicine, industry, and also in water pollutant determination. Here, RYtov MIcroscopy for Nanoparticles Identification (RYMINI) is introduced, a staining-free, non-invasive, and non-destructive optical approach that is merging holographic label-free 3D tracking with high-sensitivity quantitative phase imaging into a compact optical setup. Dedicated to the identification and then characterization of single nano-object in solution, it is compatible with highly demanding environments, such as level 3 biological laboratories, with high resilience to external source of mechanical and optical noise. Metrological characterization is performed at the level of each single particle on both absorbing and transparent particles as well as on immature and infectious HIV, SARS-CoV-2 and extracellular vesicles in solution. The capability of RYMINI to determine the nature, concentration, size, complex refractive index and mass of each single particle without knowledge or model of the particles' response is demonstrated. The system surpasses 90% accuracy for automatic identification between dielectric/metallic/biological nanoparticles and ≈80% for intraclass chemical determination of metallic and dielectric. It falls down to 50-70% for type determination inside the biological nanoparticle's class.

At-wavelength metrology of an X-ray mirror using a downstream wavefront modulator.

At-wavelength metrology of X-ray optics plays a crucial role in evaluating the performance of optics under actual beamline operating conditions, enabling in situ diagnostics and optimization. Techniques utilizing a wavefront random modulator have gained increasing attention in recent years. However, accurately mapping the measured wavefront slope to a curved X-ray mirror surface when the modulator is downstream of the mirror has posed a challenge. To address this problem, an iterative method has been developed in this study. The results demonstrate a significant improvement compared with conventional approaches and agree with offline measurements obtained from optical metrology. We believe that the proposed method enhances the accuracy of at-wavelength metrology techniques, and empowers them to play a greater role in beamline operation and optics fabrication.

Self-calibration strategies for reducing systematic slope measurement errors of autocollimators in deflectometric profilometry.

Deflectometric profilometers are used to precisely measure the form of beam shaping optics of synchrotrons and X-ray free-electron lasers. They often utilize autocollimators which measure slope by evaluating the displacement of a reticle image on a detector. Based on our privileged access to the raw image data of an autocollimator, novel strategies to reduce the systematic measurement errors by using a set of overlapping images of the reticle obtained at different positions on the detector are discussed. It is demonstrated that imaging properties such as, for example, geometrical distortions and vignetting, can be extracted from this redundant set of images without recourse to external calibration facilities. This approach is based on the fact that the properties of the reticle itself do not change - all changes in the reticle image are due to the imaging process. Firstly, by combining interpolation and correlation, it is possible to determine the shift of a reticle image relative to a reference image with minimal error propagation. Secondly, the intensity of the reticle image is analysed as a function of its position on the CCD and a vignetting correction is calculated. Thirdly, the size of the reticle image is analysed as a function of its position and an imaging distortion correction is derived. It is demonstrated that, for different measurement ranges and aperture diameters of the autocollimator, reductions in the systematic errors of up to a factor of four to five can be achieved without recourse to external measurements.

Double-edge scan wavefront metrology and its application in crystal diffraction wavefront measurements.

Achieving diffraction-limited performance in fourth-generation synchrotron radiation sources demands monochromator crystals that can preserve the wavefront across an unprecedented extensive range. There is an urgent need for techniques of absolute crystal diffraction wavefront measurement. At the Beijing Synchrotron Radiation Facility (BSRF), a novel edge scan wavefront metrology technique has been developed. This technique employs a double-edge tracking method, making diffraction-limited level absolute crystal diffraction wavefront measurement a reality. The results demonstrate an equivalent diffraction surface slope error below 70 nrad (corresponding to a wavefront phase error of 4.57% λ) r.m.s. within a nearly 6 mm range for a flat crystal in the crystal surface coordinate. The double-edge structure contributes to exceptional measurement precision for slope error reproducibility, achieving levels below 15 nrad (phase error reproducibility < λ/100) even at a first-generation synchrotron radiation source. Currently, the measurement termed double-edge scan (DES) has already been regarded as a critical feedback mechanism in the fabrication of next-generation crystals.

An active piezoelectric plane X-ray focusing mirror with a linearly changing thickness.

X-ray mirrors for synchrotron radiation are often bent into a curved figure and work under grazing-incidence conditions due to the strong penetrating nature of X-rays to most materials. Mirrors of different cross sections have been recommended to reduce the mirror's slope inaccuracy and clamping difficulty in order to overcome mechanical tolerances. With the development of hard X-ray focusing, it is difficult to meet the needs of focusing mirrors with small slope error with the existing mirror processing technology. Deformable mirrors are adaptive optics that can produce a flexible surface figure. A method of using a deformable mirror as a phase compensator is described to enhance the focusing performance of an X-ray mirror. This paper presents an active piezoelectric plane X-ray focusing mirror with a linearly changing thickness that has the ability of phase compensation while focusing X-rays. Benefiting from its special structural design, the mirror can realize flexible focusing at different focusing geometries using a single input driving voltage. A prototype was used to measure its performance under one-dimension and two-dimension conditions. The results prove that, even at a bending magnet beamline, the mirror can easily achieve a single-micrometre focusing without a complicated bending mechanism or high-precision surface processing. It is hoped that this kind of deformable mirror will have a wide and flexible application in the synchrotron radiation field.

Comparing novel small-angle x-ray scattering approaches for absolute size and number concentration measurements of spherical SiO2particles to established methods.

Biomedical analytical applications, as well as the industrial production of high-quality nano- and sub-micrometre particles, require accurate methods to quantify the absolute number concentration of particles. In this context, small-angle x-ray scattering (SAXS) is a powerful tool to determine the particle size and concentration traceable to the Système international d'unités (SI). Therefore, absolute measurements of the scattering cross-section must be performed, which require precise knowledge of all experimental parameters, such as the electron density of solvent and particles, whereas the latter is often unknown. Within the present study, novel SAXS-based approaches to determine the size distribution, density and number concentrations of sub-micron spherical silica particles with narrow size distributions and mean diameters between 160 nm and 430 nm are presented. For the first-time traceable density and number concentration measurements of silica particles are presented and current challenges in SAXS measurements such as beam-smearing, poorly known electron densities and moderately polydisperse samples are addressed. In addition, and for comparison purpose, atomic force microscopy has been used for traceable measurements of the size distribution and single particle inductively coupled plasma mass spectrometry with the dynamic mass flow approach for the accurate quantification of the number concentrations of silica particles. The possibilities and limitations of the current approaches are critically discussed in this study.

An advancement of the gravimetric isotope mixture method rendering the knowledge of the spike purity superfluous.

The gravimetric isotope mixture method is the primary method to determine absolute isotope ratios. This method, however, depends on the existence of suitable spike materials and knowledge of their purities. Determining the purity of the spikes can be tedious and labour-intensive. In this publication, an advancement of the gravimetric isotope mixture method, rendering the determination of the purity of the spike materials unnecessary, is presented. The advancement combines mass spectrometry and ion chromatography leading to an approach being independent of the purity of the spike materials. In the manuscript the mathematical background and the basic idea of the novel approach are described using a two-isotope system like copper or lithium.

Isotopic measurements of carbon dioxide: the role of measurement science and standards.

Isotopic measurements provide valuable information about the origin of greenhouse gases - as carbon dioxide levels increase, there is a corresponding shift towards lighter isotopic composition similar to that of fossil fuels. Detecting such isotopic shifts, however, requires extremely precise measurements, which must also be globally reproducible in order to make reliable policy decisions. This feature article outlines the collective search for the ideal standard for carbon isotope measurements since the 1950s. This tragicomedy of errors, if you wish, has strengthened the reliability of today's measurements and has taken us from fictional oceans, to toilet seat marbles, and complex mathematical conventions that separate data from reliable results.

Insights on trends in the management of metrological analysis of devices in blood and transfusion medicine services: Verification based on their fitness for purpose and suitability for their respective applications.

In the field of blood and transfusion medicine, European Directorate for the Quality of Medicines & HealthCare recommends practices for metrological devices. Monitoring and measurement resources, as well as their permitted metrological limits, must be considered in this regard. We must understand variables such as metrological domains, the International System of Units, metrological traceability, and metrological requirements and controls in the field of transfusions in order to understand these metrological devices. An approach to metrological analysis and subsequent actions was constructed using flowcharts. As part of this methodology, a metrological device was selected, along with regulatory and normative requirements. A calibration and a test were conducted to demonstrate the application of the figure based on current recommendations. Current recommendations are consistent with the suggested ROC approach. The metrological devices must be verified based on their suitability for their respective applications (fitness-for-purpose).

Spectral effects and enhancement quantification in healthy human saliva with surface-enhanced Raman spectroscopy using silver nanopillar substrates.

OBJECTIVES: Raman spectroscopy as a diagnostic tool for biofluid applications is limited by low inelastic scattering contributions compared to the fluorescence background from biomolecules. Surface-enhanced Raman spectroscopy (SERS) can increase Raman scattering signals, thereby offering the potential to reduce imaging times. We aimed to evaluate the enhancement related to the plasmonic effect and quantify the improvements in terms of spectral quality associated with SERS measurements in human saliva. METHODS: Dried human saliva was characterized using spontaneous Raman spectroscopy and SERS. A fabrication protocol was implemented leading to the production of silver (Ag) nanopillar substrates by glancing angle deposition. Two different imaging systems were used to interrogate saliva from 161 healthy donors: a custom single-point macroscopic system and a Raman micro-spectroscopy instrument. Quantitative metrics were established to compare spontaneous RS and SERS measurements: the Raman spectroscopy quality factor (QF), the photonic count rate (PR), the signal-to-background ratio (SBR). RESULTS: SERS measurements acquired with an excitation energy four times smaller than with spontaneous RS resulted in improved QF, PR values an order of magnitude larger and a SBR twice as large. The SERS enhancement reached 100×, depending on which Raman bands were considered. CONCLUSIONS: Single-point measurement of dried saliva with silver nanopillars substrates led to reproducible SERS measurements, paving the way to real-time tools of diagnosis in human biofluids.

Refractive power profiles of commercially available soft multifocal contact lenses for myopia control.

PURPOSE: Lens power profiles can provide valuable insights on the imposed optical defocus and visual experience of contact lens wearers, especially in the context of myopia control. This study measured the refractive power profiles of multifocal soft contact lenses (MFCLs) currently used or that have the potential for use in myopia control using high spatial resolution aberrometry. The instrument's repeatability for determining MFCLs power profiles was also assessed. METHOD: The power profiles of 10 MFCLs of various designs (centre-distance, centre-near and extended depth of focus) were measured using the Lambda-X NIMOEVO, a phase shifting Schlieren-based device. Power profiles were graphically expressed as measured power at each chord position and the maximum add power was calculated. The repeatability of the NIMOEVO was expressed as the within-subject standard deviation at each chord position for a subset of five MFCLs. RESULTS: The measured distance powers differed from nominal powers for more than half of the MFCLs with a definable distance zone. There were variations in the chord position of the distance and near correction zones, rate of power transitions and calculated maximum add between the MFCLs which did not depend on lens design. For half of the MFCLs, the power profile shape was inconsistent between different nominal back vertex powers of the same design. The repeatability of the NIMOEVO was dependent on the lens design, with designs featuring faster rates of power change exhibiting worse repeatability. CONCLUSIONS: Significant differences in MFCL power profiles were found which were not adequately represented in labelling. This is likely due to the small number of parameters used to define lens power characteristics. Eye health care practitioners should be aware of potential differences in power profiles between different MFCLs, which will impact the retinal defocus introduced during lens wear and the wearer's visual experience.

Standard-Deviation-Based Adaptive Median Filter for Elimination of Batwing Effects in Step Microstructure Measurement Using Digital Holography.

Digital holography has transformative potential for the measurement of stacked-chip microstructures due to its non-invasive, single-shot, full-field characteristics. However, significant light scattering and diffraction at steep edges in step microstructures cause the batwing effect, leading to measurement errors. Herein, we propose a standard-deviation-based adaptive median filter to eliminate batwing effects in step microstructure measurement using digital holography. The standard deviation determines the positions of the steps and the range of the batwing effect. During filtering, the filter window size varies: it adjusts according to the center's position within the batwing effect range and reduces outside this range to prevent distortion in other regions. Filtering weights are set to maintain information integrity while using larger filter windows. Experiments on the Standard Resolution Target USAF 1951 and the standard step height target show that our method successfully eliminates batwings while preserving the integrity of the remaining profile.

Extended-Aperture Shape Measurements Using Spatially Partially Coherent Illumination (ExASPICE).

We have recently demonstrated that the 3D shape of micro-parts can be measured using LED illumination based on speckle contrast evaluation in the recently developed SPICE profilometry (shape measurements based on imaging with spatially partially coherent illumination). The main advantage of SPICE is its improved robustness and measurement speed compared to confocal or white light interferometry. The limited spatial coherence of the LED illumination is used for depth discrimination. An electrically tunable lens in a 4f-configuration is used for fast depth scanning without mechanically moving parts. The approach is efficient, takes less than a second to capture required images, is eye-safe and offers a depth of focus of a few millimeters. However, SPICE's main limitation is its assumption of a small illumination aperture. Such a small illumination aperture affects the axial scan resolution, which dominates the measurement uncertainty. In this paper, we propose a novel method to overcome the aperture angle limitation of SPICE by illuminating the object from different directions with several independent LED sources. This approach reduces the full width at half maximum of the contrast envelope to one-eighth, resulting in a twofold improvement in measurement accuracy. As a proof of concept, shape measurements of various metal objects are presented.

Laser Triangulation Sensors Performance in Scanning Different Materials and Finishes.

The variety of equipment implementing laser triangulation technology for 3D scanning makes it difficult to analyse their performance, comparability, and traceability. In this study, three laser triangulation sensors arranged in different configurations are analysed using high precision spheres made of different materials and surface finishes. Three types of reference parameters were used: diameter, form error, and standard deviation of the point cloud. The experimentation was based on studying the quality of the point clouds generated by the three sensors, which enabled us to find and quantify an edge effect in the horizon of the scanned surface. A procedure to reach the optimal filtering conditions was proposed, and a chart of recommended usage of each sphere (material and finish) was created for the different types of sensors. This filter enables removal of both spurious points and those few points that spoil the form error, greatly improving the quality of the measurement.

A Novel Method for Obtaining Analytical Parameters Based on Double-Flank Measurement.

Double-flank measurement is the most commonly used method for full inspection of mass-produced gears and has high measurement efficiency, but it cannot obtain the analytical parameters and is not helpful enough to evaluate the NVH performance of the gears. Based on the double-flank rolling tester with a new principle, a simulation method for double-flank measurement and a solving method for analytical parameters are proposed. Using the simulation method, the double-flank measurements without random error can be obtained through the collision detection algorithm. The solving method uses the iteration to obtain the minimum rolling length of each position of the tooth surface, then obtains the analytical parameters of the gear. In the experiments, the difference between the profile deviations obtained by the solving method and superimposed in the simulation method is less than 0.03 µm. The experiment results have verified the correctness of the simulation method and the solving method. These methods can greatly improve the value of double-flank measurement.