Spherical Aberration Correction Research Articles

Composition and Element Distribution Mapping of γ' and γ″ Phases of Inconel 718 by High-Resolution Scanning Transmission Electron Microscopy and X-ray Energy-Dispersive Spectrometry.

The main strengthening mechanism for Inconel 718 (IN718), a Ni-based superalloy, is precipitation hardening by γ' and γ″ particles. It is thus essential, for good alloy performance, that precipitates with the desired chemical composition have adequate size and dispersion. The distribution of the γ' and γ″ phases and their chemical composition were investigated in the nickel-based Inconel 718 superalloy by taking advantage of the new capabilities of scanning transmission electron microscopy and energy-dispersive X-ray spectrometry using a windowless multiple detector, a high-brightness Schottky electron gun, and a spherical aberration corrector in the illumination probe optics. A small routine was developed to deconvolute the respective compositions of γ' and γ″ nanoprecipitates embedded in the γ matrix. Keeping the electron probe current low enough-a few hundred pA-prevented excessive irradiation damage during the acquisition of element maps and brought their spatial resolution down to the atomic column level to track their element compositions. The present results agree with and complement atomic probe tomography observations and Thermo-Calc predictions from the literature. The presence of an Al enrichment at the γ'/γ″ interface-which may control the γ″ phase coarsening-is observed in the last row of Al-Nb-Ti columns along this interface. In addition, a few columns with similar composition changes are found randomly distributed in the γ' phase.

Corneal asphericity and its related factors.

Proper correction of spherical aberration using intraocular lenses requires precise selection of the sphericity of intraocular lens surfaces based on individual biometric data and corneal asphericity coefficient (Q value). This study aimed to determine and analyze the corneal Q value and its related factors among Saudi participants. In this cross-sectional study, normal right eyes of healthy Saudi participants aged 17 - 58 years who visited Al-Kahhal Medical Complex, Dammam, Saudi Arabia, were included. The Pentacam rotating Scheimpflug camera was used to determine the average Q value at 6-mm diameter. Q values were obtained from each quadrant (superior, nasal, inferior, and temporal) and two meridians (horizontal and vertical). Mean Q values of the anterior and posterior corneal surfaces were also obtained. Other factors including age, sex, refractive error, and central corneal radius were documented. Five hundred right eyes from 500 participants were included. The mean (standard deviation [SD]) (range) age was 27.2 (7.1) (18 - 58) years. The mean (SD) (range) Q value of 500 eyes was - 0.24 (0.10) (- 0.71 to + 0.09) anteriorly and - 0.16 (0.14) (- 0.70 to + 0.23) posteriorly, being significantly more prolate anteriorly (P < 0.05). The corneas were significantly more prolate in the nasal than in the temporal quadrant, in the superior than in the inferior quadrant, and in the horizontal than in the vertical meridian (all P < 0.05). There were statistically significant differences in anterior, nasal, temporal, inferior, horizontal, and vertical Q values among age groups (all P < 0.05) but not in the superior or posterior Q values (both P > 0.05). The corneas became less prolate with increasing age (P < 0.05). However, Q values were comparable between the sexes (all P > 0.05). There was no significant correlation between anterior (r = + 0.08; P = 0.095) or posterior (r = - 0.08; P = 0.092) Q value and spherical equivalent, but a significant trend was detected toward more prolate shape with increasing myopia in the temporal and inferior quadrants (r = + 0.19; P < 0.001, r = + 0.10; P = 0.022, respectively). There was a significant negligible correlation between the posterior Q value and central corneal radius (r = - 0.18; P < 0.001) but no significant correlation between the anterior Q value and central corneal radius (r = + 0.02; P = 0.673). Most corneas in this Saudi population were prolate in contour. Anterior corneal asphericity was positively correlated with age and was not significantly related to sex, refractive error, or central corneal radius. Further studies are needed to verify our preliminary findings.

Amorphous 1-D nanowires of calcium phosphate/pyrophosphate: A demonstration of oriented self-growth of amorphous minerals

Amorphous inorganic solids are traditionally isotropic, thus, it is believed that they only grow in a non-preferential way without the assistance of regulators, leading to the morphologies of nanospheres or irregular aggregates of nanoparticles. However, in the presence of (ortho)phosphate (Pi) and pyrophosphate ions (PPi) which have synergistic roles in biomineralization, the highly elongated amorphous nanowires (denoted ACPPNs) form in a regulator-free aqueous solution (without templates, additives, organics, etc). Based on thorough characterization and tracking of the formation process (e.g., Cryo-TEM, spherical aberration correction high resolution TEM, solid state NMR, high energy resolution monochromated STEM-EELS), the microstructure and its preferential growth behavior are elucidated. In ACPPNs, amorphous calcium orthophosphate and amorphous calcium pyrophosphate are distributed at separated but close sites. The ACPPNs grow via either the preferential attachment of ∼2 nm nanoclusters in a 1-dimension way, or the transformation of bigger nanoparticles, indicating an inherent driving force-governed process. We propose that the anisotropy of ACPPNs microstructure, which is corroborated experimentally, causes their oriented growth. This study proves that, unlike the conventional view, amorphous minerals can form via oriented growth without external regulation, demonstrating a novel insight into the structures and growth behaviors of amorphous minerals.

Medical and technical aspects of using intraocular lenses with extended depth of field

Purpose: to analyse the medical and technical aspects of intraocular lenses (IOLs) with extended depth of field (EDOF). Literature analysis was performed in the PubMed international database, the search keywords being “IOL with extended depth of field” (EDOF), “Optical Bench Evaluation of IOL”, “Preclinical evaluation of IOL”, “Aberrations”, “Monofocal IOL” (MOFIOL), “Multifocal IOLs” (MUFIOL). A total of 226 sources were analyzed, further using systematic review filters and the authors' knowledge of the topic. The duration of the retrospective analysis was 7 years (2016–2022), some of the considered work dates back to 2023. Unlike MUFIOL, EDOF lenses create a single elongated focal point to increase the depth of field, rather than several foci. Thus, EDOFs are aimed at reducing light phenomena, glare and halos, the occurrence of which is characteristic of MUFIOL. A potential disadvantage of EDOF is the reduction in retinal image quality with an excessive increase in the number of aberrations. The factors of the medical and technical assessment of the IOL indicate a high correlation with the predicted visual acuity (VA). EDOFs, whose design features are based on a higher order aspherical design, provide comparable optical quality for the far and extended intermediate ranges, while producing halo effects comparable to those of MOFIOL. Designed to improve depth of field with a full correction of corneal spherical aberration, EDOF provides intermediate-level pupil-independent improvement in VA and maintains visual acuity unlike conventional MOFIOLs. The quality of visual perception and the predicted VA of various types of EDOFs depend on the optical technology and the correction of corneal spherical aberrations. EDOFs can be expected to provide adequate vision at an intermediate distance (with a possibility of insufficient near vision). At the same time, the expansion of the depth of field varies between models, which should be taken into account when preoperatively choosing EDOF for a specific type of daily visual activity of the patient, especially for people with visually strenuous work. The results of the medical and technical assessment are widely used in the clinical testing of specific types of EDOF IOLs.

Profile and nano-scale distribution of soil organic carbon for upland and paddy soils from an alluvial plain in South China

Understanding the heterogeneous distribution of soil organic carbon (C) (SOC) in different soil environments is essential for predicting SOC preservation. However, SOC distribution differs in profile scales and molecular levels in various farmland soils, making it challenging to elucidate the environmental behaviors of SOC. In the present study, upland and paddy soil samples were both collected at different depths (0–100 cm) from an alluvial plain in the Pearl River Delta of South China. Wet chemistry experiments coupled with 13C-nuclear magnetic resonance (NMR) and spherical aberration correction scanning transmission electron microscopy (Cs-STEM) were used to determine the vertical distribution, chemical composition, and nano-scale sequestration mechanisms of SOC in upland and paddy soils. SOC content for upland soil, which was highest at the depth of 0–20 cm (6.98 ± 0.34 g·kg−1), decreased with increasing soil depth, while that of paddy soil had the highest content at a depth of 80–100 cm (86.66 ± 5.26 g·kg−1). Statistical analysis revealed that mineral-associated organic C (MAOC) in the upland soil and particulate organic C (POC) in the paddy soil were the major C fractions that were related to SOC content. Further analysis of NMR spectra showed that the molecular composition of upland SOC differs vertically, while the molecular composition and proportion of organic C in paddy soil varied with soil depth. Cs-STEM results revealed that the relative percentage of carboxyl C decreased from 0 to 20 cm (42.1%) to 80–100 cm (28.8%) with an increase in aromatic C from 7.7 to 27.2% for the upland soil, while the four C species showed similar abundance for paddy soil at different depths, consistent with the NMR results. Overall, the upland SOC was not as easily mineralized as that of paddy soil due to a lower percentage of easily oxidized carbon, higher percentage of MAOC, and higher decomposition degree. The results of this study would enrich our quantitative understanding of the profile distribution and chemical diversity of SOC from macro to micro scales in the alluvial plain from South China, and provide insights into C preservation in natural soils.

High demagnification probe-forming systems with spherical aberration correction for a nuclear microprobe

Probe-forming systems with high demagnification (up to 900) based on a separated orthomorphic quadruplet of magnetic quadrupole lenses are considered. Spherical aberrations are corrected using an octupole lens system. Three, two, and one lens correctors are used. The calculation of the octupoles parameters was carried out using the Matrizant method. The focusing properties of the systems are determined by optimizing the process of probe formation based on the value of the maximum reduced collimated acceptance in the range of beam spot sizes on the target from 10 to 100 nm. The possibility of implementing the considered systems in experimental setups for various applications is demonstrated by the results of the numerical analysis performed.

Interfacial reaction behavior of titanium/steel composite plate formed by cold-hot rolling

Titanium/steel composite plate was prepared by cold-hot rolling method. The influence of temperature on the interfacial reaction behavior of titanium/steel composite plate was studied by double beam focused ion beam system and spherical aberration correction transmission electron microscopy. The results show that the interfacial reaction of the cold-rolled titanium/steel composite plate mainly occurs in the heating stage, and the continuous intermetallic compounds layer formed at the interface during heating fractures during hot rolling. An interfacial layer composed of submicron TiC layer and α-Ti/α-Fe is formed when the hot rolling temperature is not higher than 850 °C, and the interfacial bonding strength increases with the increase of rolling temperature. An interface layer composed of micro (FeTi+TiC)/Fe2Ti layer, nano FeTi/Fe2Ti layer and micro pores is formed when the hot rolling temperature exceeds 900 °C. The interfacial micro (FeTi+TiC)/Fe2Ti layer and micro pores will seriously damage the interfacial bonding quality.

Spherical Aberration of Astigmatic Corneas in a Cataract Population.

To study the distribution of spherical aberration (SA) in astigmatic corneas in a cataract population and the relationship between magnitude of corneal astigmatism and fourth-order corneal SA. Data routinely collected using a Scheimpflug camera (Pentacam; Oculus Optikgeräte GmbH) were retrospectively analyzed. Patients with a minimum age of 60 years were included. Total corneal SA (from anterior and posterior corneal surface) was obtained for a 6-mm cor-neal area aligned with the pupil center. Exclusion criteria were insufficient measurement quality, total deviation index (Belin/Ambrósio Deviation) greater than 1.60, and corneal thickness at the thinnest point of less than 490 μm. One eye per patient was chosen randomly. Eyes were divided into low (≤ 1.00 diopters [D]), moderate (> 1.00 to ≤ 2.00 D), and high (> 2.00 D) astigmatism groups according to the Scheimpflug measurements. A total of 528 eyes were included in this analysis. Low astigmatism was found in 129 patients, moderate astigmatism in 265 patients, and high astigmatism in 134 patients. Mean astigmatism was 0.68 ± 0.24, 1.45 ± 0.28, and 2.91 ± 0.95 D in the low, moderate, and high astigmatism groups, respectively. Mean corneal SA in patients with moderate and high astigmatism was higher than in the low astigmatism group. The difference reached the significance level for the comparison of low and high astigmatism groups (P = .023). The fourth-order SA increased gradually with the magnitude of astigmatism with a slope of 0.015. SA was significantly larger in the cataract population with high corneal astigmatism. The increase of positive sign SA with the magnitude of astigmatism suggests that patients with moderate to high astigmatism may benefit more from intraocular lenses with negative sign SA correction. [J Refract Surg. 2023;39(8):532-538.].

Higher order wavefront correction and axial scanning in a single fast and compact piezo-driven adaptive lens.

We present a compact adaptive glass membrane lens for higher order wavefront correction and axial scanning, driven by integrated segmented piezoelectric actuators. The membrane can be deformed in a combination of rotational symmetry providing focus control of up to ± 6 m-1 and spherical aberration correction of up to 5 wavelengths and different discrete symmetries to correct higher order aberrations such as astigmatism, coma and trefoil by up to 10 wavelengths. Our design provides a large clear aperture of 12 mm at an outer diameter of the actuator of 18 mm, a thickness of 2 mm and a response time of less than 2 ms.

Spatial frequency-based correction ofthe spherical aberration inliving brain imaging.

Optical errors, including spherical aberrations, hinder high-resolution imaging of biological samples due to biochemical components and physical properties. We developed the Deep-C microscope system to achieve aberration-free images, employing a motorized correction collar and contrast-based calculations. However, current contrast-maximization techniques, such as the Brenner gradient method, inadequately assess specific frequency bands. The Peak-C method addresses this issue, but its arbitrary neighbor selection and susceptibility to the noise limit its effectiveness. In this paper, we emphasize the importance of a broad spatial frequency range for accurate spherical aberration correction and propose Peak-F. This spatial frequency-based system utilizes a fast Fourier transform as a bandpass filter. This approach overcomes Peak-C's limitations and comprehensively covers the low-frequency domain of image spatial frequencies.

HIGH RESOLUTION PROBE-FORMING SYSTEM WITH SPHERICAL ABERRATION CORRECTION FOR NUCLEAR MICROPROBE

A probe-forming system based on a separate orthomorphic quadruplet of magnetic quadrupole lenses with a short working distance is considered, allowing the system demagnification to be significantly increased. Three magnetic octupole lenses are used to correct spherical aberrations. The parameters of the octupole corrector are calculated using the matricant method. The focusing properties of the system are determined by means of a probe formation optimization process based on the value of the maximum reduced collimated acceptance. The calculations performed showed the feasibility of such a probe forming system for microanalysis and proton beam writing technique.

Design and manufacturing of aspherical GaAs-SILs for a versatile optical semiconductor failure analysis system

In this study, we have developed an aspherical solid immersion lens (SIL) made of gallium arsenide (GaAs) for semiconductor failure analysis. A SIL is an optical component to dramatically increase the numerical aperture and the spatial resolution of a microscopy system by attaching it to the backside of the device-under-test. To further enhance the spatial resolution of the optical microscopy system, a shorter wavelength light source has also been introduced. In the past, we have developed a spherical SIL made of silicon (Si), which is the same material as the device under test. However, Si is not transparent for wavelengths shorter than around 1100 nm. To enable the use of a SIL at shorter wavelengths, we chose GaAs as SIL material, which is transparent at shorter wavelengths than Si and has a refractive index very close to that of Si. However, a spherical GaAs SIL features a more pronounced spherical aberration due to the difference in refractive index between the device-under-test (Si) and that of the SIL (GaAs) deteriorating the optical resolution of the microscopy system. We have therefore designed an aspherical GaAs-SIL which makes it possible to correct spherical aberration. We applied diamond tooling as a technique for manufacturing the SIL shape with a required surface irregularity below 100 nm peak-to-valley, resulting in a diffraction limited performance of the optical system for semiconductor failure analysis with a performance at around 0.18 μm cutoff.

NH4Cl-assisted preparation of single Ni sites anchored carbon nanosheet catalysts for highly efficient carbon dioxide electroreduction

Single-atomic transition metal-nitrogen codoped carbon (M-N-C) are efficient substitute catalysts for noble metals to catalyze the electrochemical CO2 reduction reaction (CO2RR). However, the uncontrolled aggregations of metal and serious loss of nitrogen species constituting the M-Nx active sites are frequently observed in the commonly used pyrolysis procedure. Herein, single-atomic nickel (Ni)-based sheet-like electrocatalysts with abundant Ni-N4 active sites were created by using a novel ammonium chloride (NH4Cl)-assited pyrolysis method. Spherical aberration correction electron microscopy and X-ray absorption fine structure analysis clearly revealed that Ni species are atomically dispersed and anchored by N in Ni-N4 structure. The addition of NH4Cl optimized the mesopore size to 7–10 nm and increased the concentrations of pyridinic N (3.54 wt%) and Ni-N4 (3.33 wt%) species. The synergistic catalytic effect derived from Ni-N4 active sites and pyridinic N species achieved an outstanding CO2RR performance, presenting a high CO Faradaic efficiency (FECO) up to 98% and a large CO partial current density of 8.5 mA cm−2 at a low potential of –0.62 V vs. RHE. Particularly, the FECO maintains above 80% within a large potential range from –0.43 to –0.73 V vs. RHE. This work provides a practical and feasible approach to building highly active single-atomic catalysts for CO2 conversion systems.

Process Controlled Ruthenium on 2D Engineered V-MXene via Atomic Layer Deposition for Human Healthcare Monitoring.

In searching for unique and unexplored 2D materials, the authors try to investigate for the very first time the use of delaminated V-MXene coupled with precious metal ruthenium (Ru) through atomic layer deposition (ALD) for various contact and noncontact mode of real-time temperature sensing applications at the human-machine interface. The novel delaminated V-MXene (DM-V2 CTx ) engineered ruthenium-ALD (Ru-ALD) temperature sensor demonstrates a competitive sensing performance of 1.11%°C-1 as of only V-MXene of 0.42%°C-1 . A nearly threefold increase in sensing and reversibility performance linked to the highly ordered few-layered V-MXene and selective, well-controlled Ru atomic doping by ALD for the successful formation of Ru@DM-V2 CTX heterostructure. The advanced heterostructure formation, the mechanism, and the role of Ru have been comprehensively investigated by ultra-high-resolution transmission/scanning transmission electron microscopies coupled with next-generation spherical aberration correction technology and fast, accurate elemental mapping quantifications, also by ultraviolet photoelectron spectroscopy. To the knowledge, this work is the first to use the novel, optimally processed V-MXene over conventionally used Ti-MXene and its surface-internal structure engineering by Ru-ALD process-based temperature-sensing devices function and operational demonstrations. The current work could potentially motivate the development of multifunctional, future, next-generation, safe, personal healthcare electronic devices by the industrially scalable ALD technique.

Can a Programmable Phase Plate Serve as an Aberration Corrector in the Transmission Electron Microscope (TEM)?

Abstract Current progress in programmable electrostatic phase plates raises questions about their usefulness for specific applications. Here, we explore different designs for such phase plates with the specific goal of correcting spherical aberration in the transmission electron microscope (TEM). We numerically investigate whether a phase plate could provide down to 1 Ångström spatial resolution on a conventional uncorrected TEM. Different design aspects (fill factor, pixel pattern, symmetry) were evaluated to understand their effect on the electron probe size and current density. Some proposed designs show a probe size (d50) down to 0.66 Å, proving that it should be possible to correct spherical aberration well past the 1 Å limit using a programmable phase plate consisting of an array of electrostatic phase-shifting elements.

Atomic-scale observation of calcium occupation in spinel cobalt ferrite towards the regulation of intrinsic magnetic properties.

Spinel ferrites have drawn intensive attention because of their adjustable magnetic properties by ion doping, among which calcium (Ca) is an essential dopant that is widely employed in massive production. However, its exact lattice occupation and relationship with intrinsic magnetic properties remain unclear. Here, we successfully prepared Ca-doped cobalt ferrite (CoFe2O4) nanoparticles by electrospinning. Ca2+ is observed to occupy both the tetrahedral Fe site and the octahedral Co site using spherical aberration correction transmission electron microscopy (TEM) and prefers to occupy the octahedral site at a high doping level. Such dual occupation behavior affects the tetrahedral and octahedral sublattices differently, resulting in nonmonotonic saturation magnetization variation, reduced magnetocrystalline anisotropy and negative magnetization in the zero field cooling (ZFC) process. By controlling the Ca doping amount, increased saturation magnetization and reduced coercivity can be obtained simultaneously. Our findings establish the relationship between the atomic-scale structural change and the macroscopic magnetic properties of spinel ferrites, promoting the development of new ferrite materials.

Unraveling the Role of Interface in Photogenerated Charge Separation at the Anatase/Rutile Heterophase Junction

Heterophase junctions have emerged as an effective strategy for spatial charge separation in photocatalysis. However, the photogenerated charge separation pathway at the junction region remains in doubt, and how the interfacial structure affects charge separation is unclear. Herein, we fabricate well-defined TiO2 heterophase junctions between rutile and anatase and employ in situ photochemical probing reactions to track the interfacial charges distribution by means of spherical aberration correction transmission electron microscope (CS aberration TEM). The photoreduction deposition of platinum (Pt) nanoclusters and photo-oxidation deposition of metal oxide nanoparticles demonstrate that the photogenerated electrons smoothly migrate across the interfacial phase junction from rutile to anatase phases and the photogenerated holes move in an opposite direction, which provides direct evidence on the spatial charge separation at the heterophase junction. Moreover, the atomic interfacial structure of anatase/rutile TiO2 heterophase junction formed is conducive for photogenerated charges moving from one phase to the other. This study revises the photogenerated charge separation at the anatase/rutile heterophase junction and demonstrates the important role of the interfacial structure on spatial charge separation.

Microstructural evolution and dimensional stability of 45vol% SiC/Al composites under long-term aging

Long-term aging will inevitably affect the dimensional stability of the material, which causes reliability decrease of the precision instruments. Currently, the dimensional stability mechanism of SiC/Al composites under long-term aging is unclear. Specifically, how the alloying elements, precipitates, dislocations and internal stress together cause the dimensional change of SiC/2024Al composites and how to regulate the microstructure to improve dimensional stability. In this paper, 45 vol% SiC/Al composites were successfully prepared by pressure infiltration method. The dimensional stability mechanism of SiC/2024Al composites under long-term aging was revealed through in-situ heating XRD, spherical aberration correction transmission electron microscopy and high-precision thermal dilatometer. The results showed that the precipitates and alloying elements coupled with other factors to affect the dimensional change. There were mainly two sources of the dimensional change in the SiC/2024Al composites. One was the combined effect of precipitates-dislocations, which led to dimensional decrease. The other was the combined effect of precipitates-alloying elements-internal stress, which led to dimensional increase. The former was similar to the dimensional stability mechanism in 2024Al alloys, while the latter was a unique mechanism which only existed in SiC/Al composites. And the dimensional change of SiC/2024Al composites caused by the two sources could be regulated from + 10-4 to + 10-5 by changing aging temperature.

Deep-Learning Pipeline for Statistical Quantification of Amorphous Two-Dimensional Materials

Aberration-corrected transmission electron microscopy enables imaging of two-dimensional (2D) materials with atomic resolution. However, dissecting the short-range-ordered structures in radiation-sensitive and amorphous 2D materials remains a significant challenge due to low atomic contrast and laborious manual evaluation. Here, we imaged carbon-based 2D materials with strong contrast, which is enabled by chromatic and spherical aberration correction at a low acceleration voltage. By constructing a deep-learning pipeline, atomic registry in amorphous 2D materials can be precisely determined, providing access to a full spectrum of quantitative data sets, including bond length/angle distribution, pair distribution function, and real-space polygon mapping. Accurate segmentation of micropores and surface contamination, together with robustness against background inhomogeneity, guaranteed the quantification validity in complex experimental images. The automated image analysis provides quantitative metrics with high efficiency and throughput, which may shed light on the structural understanding of short-range-ordered structures. In addition, the convolutional neural network can be readily generalized to crystalline materials, allowing for automatic defect identification and strain mapping.

Tunable doublets: piezoelectric glass membrane lenses with an achromatic and spherical aberration control.

We present two versions of tunable achromatic doublets based on each two piezoelectrically actuated glass membranes that create the surface of fluid volumes with different dispersions: a straightforward back-to-back and a more intricate stack of the fluid volumes. In both cases, we can control the chromatic focal shift and focal power independently by a suitable combination of actuation voltages on both active membranes. The doublets have a large aperture of 12 mm at an outer diameter of the actuator of 18 mm, an overall thickness of 3 mm and a short response time of around 0.5 ms and, in addition, provide spherical aberration correction. The two designs have an achromatic focal power range of ±2.2 m-1 and ±3.2 m-1 or, for the purpose of actively correcting chromatic errors, a chromatic focal shift at vanishing combined focal power of up to ±0.08 m-1 and ±0.12 m-1.