Topographic Images Research Articles

Synchronous Phase-Shifting Interference for High Precision Phase Imaging of Objects Using Common Optics.

Quantitative phase imaging and measurement of surface topography and fluid dynamics for objects, especially for moving objects, is critical in various fields. Although effective, existing synchronous phase-shifting methods may introduce additional phase changes in the light field due to differences in optical paths or need specific optics to implement synchronous phase-shifting, such as the beamsplitter with additional anti-reflective coating and a micro-polarizer array. Therefore, we propose a synchronous phase-shifting method based on the Mach-Zehnder interferometer to tackle these issues in existing methods. The proposed method uses common optics to simultaneously acquire four phase-shifted digital holograms with equal optical paths for object and reference waves. Therefore, it can be used to reconstruct the phase distribution of static and dynamic objects with high precision and high resolution. In the experiment, the theoretical resolution of the proposed system was 1.064 µm while the actual resolution could achieve 1.381 µm, which was confirmed by measuring a phase-only resolution chart. Besides, the dynamic phase imaging of a moving standard object was completed to verify the proposed system's effectiveness. The experimental results show that our proposed method is suitable and promising in dynamic phase imaging and measurement of moving objects using phase-shifting digital holography.

The correlation of embolic sources with infarct pattern in patients with embolic stroke (P6-5.015)

<h3>Objective:</h3> To exclusively identify potential embolic sources (PES) applying transesophageal echocardiography (TEE) and correlate them with topographic diffusion-weighted imaging patterns (DWI) in patients with embolic stroke. <h3>Background:</h3> Embolic stroke of undetermined source (ESUS) has been reported to show a relatively high stroke recurrence rate. Thus, early identification of potential embolic source (PES) is critical for acute treatment and/or secondary prevention. If acute topographic diffusion-weighted imaging patterns (DWI) would correlate with specific PES, it may prove very useful. <h3>Design/Methods:</h3> A total of 992 consecutive patients with embolic stroke were studied. Apart from the known embolic group (n=560), we focused on the unknown embolic group (n=366) that was defined as no arrhythmia during the first day from admission and no PES after general examination. DWI were classified based on the arterial supply. Age and sex adjusted odds ratio (OR) of each DWI for the different PESs were calculated. Middle cerebral arteries (MCA) were divided into 4 segments, i.e., M1~M4. Moreover, M2 segments were subdivided into superior and inferior branches. <h3>Results:</h3> 366 patients consisted of 168 with paroxysmal atrial fibrillation (pAf), 82 with paradoxical embolism (PxE), 71 with aorto-embolism (AoE), leaving 39 patients undetermined. The DWIs of internal carotid artery (OR: 15.0, p=0.0027), M1 (4.2, p=0.0003), inferior M2 (3.6, p=0.04) and multiple cortical branches (MCB) (21.6, p&lt;0.0001) were significantly associated with pAf. Striatocapsular infarction (SCI) (15.1, p&lt;0.0001) was significantly associated with PxE and multiple small scattered infarcts (8.6, p&lt;0.0001) with AoE. <h3>Conclusions:</h3> The correlations of DWI with different PESs have their distinctive characteristics. The DWI of inferior M2 as well as large infarcts and multiple cortical infarcts were associated with pAf, that of SCI with PxE and MSS with AoE. The characteristic histopathology and hydrodynamic mechanism of thrombi may determine DWI. <b>Disclosure:</b> Yasumasa Yamamoto has nothing to disclose.

Heavy metal remediation using chelator-enhanced washing of municipal solid waste compost based on spectroscopic characterization

Due to high metal toxicity, mixed municipal solid waste (MSW) compost is difficult to use. This study detected the presence of heavy metals (Cd, Cu, Pb, Ni, and Zn) in MSW compost through mineralogical analysis using X-ray diffraction (XRD) and performed topographical imaging and elemental mapping using a scanning electron microscope and energy dispersive X-ray analysis (SEM-EDX). Ethylenediaminetetraacetic acid (EDTA), a typical chelator, is tested to remove heavy metals from Indian MSW compost (New Delhi and Mumbai). It deals with two novel aspects, viz., (i) investigating the influence of EDTA-washing conditions, molarity, dosage, MSW compost-sample size, speed, and contact time, on their metal removal efficiencies, and (ii) maximizing the percentage removal of heavy metals by determining the optimal process control process parameters. These parameters were optimized in a batch reactor utilizing Taguchi orthogonal (L25) array. The optimization showed that the removal efficiencies were 96.71%, 47.37%, and 49.94% for Cd, Pb, and Zn in Delhi samples, whereas 45.55%, 79.52%, 59.63%, 82.31%, and 88.40% for Cd, Cu, Pb, Ni, and Zn in Mumbai samples. Results indicate that the removal efficiency of heavy metals was greatly influenced by EDTA-molarity. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of hydroxyl group, which aids heavy metal chelation. The results reveal the possibility of EDTA to reduce the hazardous properties of MSW compost.

Fast in-situ imaging method using non-axial scanning confocal Raman microscope

Confocal Raman microscopy (CRM) is extensively employed in numerous fields because it provides molecular fingerprint information without destroying or labeling samples. For samples with large topographic fluctuations, existing technology requires axial scanning to achieve axial focusing, which further increases the time required for Raman mapping. Herein, a method called non-axial scanning confocal Raman microscopy (NASCRM), which constructs an axial focusing system with a large range and high precision by modifying the wide-field imaging system, is proposed. The axial focusing system combined with CRM can simultaneously realize in situ high-precision topography imaging and Raman mapping. Theoretical analyses and preliminary experiments reveal that the axial focusing resolution of NASCRM is approximately 3 nm and the sensing range is approximately 60 μm. Compared with CRM using confocal microscopy (CM) focusing (CM-CRM), the speeds within sensing range for axial focusing and Raman mapping are improved by 5.3 and 2.9 times, respectively. This study provides a novel method for both conventional CRM and CRM-based imaging in various fields.

Navigated direct photocoagulation with a 30-ms short-pulse laser for treating microaneurysms in diabetic macular edema exhibits a high closure rate

This study carried out direct photocoagulation for treating microaneurysms (MAs) in diabetic macular edema (DME) using a navigation laser system with a 30-ms pulse duration. The MA closure rate after 3 months was investigated using pre and postoperative fluorescein angiography images. MAs primarily inside the edematous area based on optical coherence tomography (OCT) maps were selected for treatment, and leaking MAs (n = 1151) were analyzed in 11 eyes (eight patients). The total MA closure rate was 90.1% (1034/1151), and the mean MA closure rate in each eye was 86.5 ± 8.4%. Mean central retinal thickness (CRT) decreased from 471.9 ± 73.0 μm to 420.0 ± 87.5 μm (P = 0.049), and there was a correlation between the MA closure rate and the CRT reduction rate (r = 0.63, P = 0.037). There was no difference in the MA closure rate depending on the degree of edema thickness based on a false-color topographic OCT map image. Direct photocoagulation for DME with a short pulse using the navigated photocoagulator resulted in a high MA closure rate in just 3 months and a corresponding improvement in retinal thickness. These findings encourage the use of a new therapeutic approach for DME.

Development of antibacterial and morphological features of scaffolds based on polycaprolactone encapsulated with copper oxide/vanadium oxide for wound dressing applications

The development of highly effective dressing materials for human injuries that meet the complex requirements for clinical examination is still a challenge. In this regard, different biomaterials could be examined for wound dressing targets. Among these materials, polycaprolactone (PCL) is high biocompatible polymeric substance and has been used for numerous pharmaceutical applications. Furthermore, targeting antibacterial behavior could be done by merging additional nanoparticles such as copper oxide (CuO) and vanadium Oxide (V2O5). The scaffolds could be fabricated using the cast method, which is one of the most simple and facile methods. The morphological features and the surface roughness of the fabricated could be examined using X-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR), and scanning electron microscopy (SEM) tests. The contact angle plays a significant role in studying the wettability of the scaffolds and the hydrophilic or hydrophobic behavior of the composed films. Besides the antibacterial behavior to evaluate the effectiveness of these scaffolds to protect the injury until the healing. The cell viability against human normal cells to examine the biocompatibility of the proposed compositions. In this regard, the topographical images show a smooth surface with random pores that have diameters in the range of 0.5–1.5 μm for pure PCL while, the porosity decreased with the addition of ginger and V2O5. The blend of CuO/V2O5/ginger@ PCL represents a noticeable increase in porosity with a diameter between 0.5 and 3 μm. The contact angles were recorded respectively at 55.02°, 54.12°, 53.89°, and 53.71° which refer to the tendency of the scaffolds to the hydrophilic behavior. In addition, the anti-bacterial activity of CuO/V2O5/ginger@PCL was represented with the diameter of the inhibition zone equal to 17.6±1.2 mm for E. coli and 12.3±1.2 mm for S. aureus.

Accuracy of UAV-based DEMs without ground control points

Unmanned aerial vehicles (UAVs) are increasingly used in various environmental research projects and other activities that require accurate topography images. The quality of elevation models derived from UAV measurements varies depending on many variables (e.g. UAV equipment used, terrain conditions, etc.). In order to improve the quality of digital models based on UAV image data, additional GNSS-RTK measurements are usually made at ground control points. The aim of this article is to evaluate the mathematical accuracy of terrain models created without ground control points. The accuracy of the models is considered in two directions: vertical and horizontal. Vertical (elevation) accuracy is calculated based on airborne laser scanning (ALS) data and horizontal (location) accuracy is calculated through comparison with high-resolution orthophotomaps. The average elevation accuracy of all created UAV-based DEMs is found to be 2.7–2.8 m (MAE), 3.1–3.3 m (RMSE), and the average horizontal accuracy is 2.1 m. Despite the low accuracy of the UAV models, the topography is reflected very well in the spatial images. This may be related to the regular and symmetrical distribution of height errors. To improve the accuracy parameters of UAV-based DEMs, it is proposed that they be rapidly georeferenced based on orthophotomaps.

Recent advances in the application of atomic force microscopy to structural biology

The application of atomic force microscopy (AFM) for functional imaging and manipulating biomolecules at all levels of organization has enabled great progress in the structural biology field over the last decades, contributing to the discovery of novel structural entities of biological significance across many disciplines ranging from biochemistry, biomedicine and biophysics to molecular and cell biology, up to food systems and beyond. AFM has the capability to generate high-resolution topographic images spanning from the submolecular to the (sub)cellular range and can probe biochemical and biophysical sample properties in close to native conditions with excellent temporal resolution. Instrumental developments in the past decade enable dynamical structural and conformational studies of single biomolecules and new techniques for structural and chemical modification of the AFM probe have converted the cantilever into a versatile tool to study different biological phenomena, such as the mechanical stability of biomolecular complexes or the force induced dynamic changes of mechanically stressed proteins at the nanoscopic level. To improve the functionality of AFM and approach dynamic processes of complex biological systems ex vivo, AFM is combined with complementary microscopy, nanoscopy and spectroscopy tools. These multimethodological approaches provide unprecedented possibilities of probing physical, chemical and biological properties of complex cellular systems with high spatio-temporal resolution, leading to novel applications that correlate structural results with functional biochemical, biophysical, immunological, or genetic data of the system under study.

Myomodulation Using Botulinum Toxin in Septorhinoplasty for Crooked Noses: Introducing the Concept and Application of Nasal Muscle Imbalance Theory.

The role of septorhinoplasty for adequate correction of deviated nose is well documented, but the rationales and patterns for recurrences after proper rhinoplasty remain unclear. There has also been little attention given to the influence of nasal musculatures on the stability of nasal structures after septorhinoplasty. The aim of this article is to propose our nasal muscle imbalance theory, which may explain the potential reason for redeviation of the noses in the initial period after septorhinoplasty. We postulate that in a chronically deviated nose, the nasal muscles on the convex side will be stretched and develop hypertrophy after prolonged period of increased contractile activity. On the contrary, the nasal muscles on the concave side will undergo atrophy due to reduced load requirement. In the initial period of recovery after a septorhinoplasty to bring the nose back to midline, this muscle imbalance is still uncorrected with unequal pulling forces on the nasal structure because the stronger nasal muscles on the previously convex side is still hypertrophied and exert stronger forces compared with the previously concave side, therefore increasing the risk of redeviation of the nose back to the preoperative side until muscle atrophy occurs in the convex side and a balanced nasal muscle pull is achieved. We believe that postseptorhinoplasty botulinum toxin injections can be used as an adjunct in rhinoplasty surgery to effectively block the pulling actions of the stronger or overacting nasal muscles by speeding up the atrophy process while allowing patient's nose to heal and stabilize in the desired position. However, further studies to objectively confirm this hypothesis is required, which include comparing topographic measurements, imaging and electromyography signals before and after injections in postseptorhinoplasty patients. The authors have already planned a multicenter study to further evaluate this theory.

Assessing 40 Years of Flood Risk Evolution at the Micro-Scale Using an Innovative Modeling Approach: The Effects of Urbanization and Land Planning

The present work is aimed at assessing the change in time of flood risk as a consequence of landscape modifications. The town of San Donà di Piave (Italy) is taken as a representative case study because, as most parts of the North Italy floodplains, it was strongly urbanized and anthropized in the last several decades. As a proxy for flood risk, we use flood damage to residential buildings. The analysis is carried out at the local scale, accounting for changes to single buildings; GIS data such as high-resolution topography, technical maps, and aerial images taken over time are used to track how the landscape evolves over time, both in terms of urbanized areas and of hydraulically relevant structures (e.g., embankments). Flood hazard is determined using a physics-based, finite element hydrodynamic code that models in a coupled way the flood routing within the Piave River, the formation of levee failures, and the flooding of adjacent areas. The expected flood damage to residential buildings is estimated using an innovative method, recently proposed in the literature, which allows estimating how the damage evolves during a single flood event. The decade-scale change in the expected flood damage reveals the detrimental effect of urbanization, with flood risk growing at the pace of a fraction of urbanized areas. The within-event time evolution of the flood damage, i.e., how it progresses in the course of past or recent flood events, reflects changes in the hydrodynamic process of flooding. The general methodology used in the present work can be viewed as a promising technique to analyze the effects on the flood risk of past landscape evolution and, more importantly, a valuable tool toward an improved, well-informed, and sustainable land planning.

Crystal distortions and structural defects at several scales generated during the growth of silicon contaminated with carbon

For all fabrication processes of the photovoltaic (PV) industry based on silicon, grain boundaries, dislocations, and impurity contamination control during solidification remains a major challenge to improve the electrical properties. In particular, carbon (C) is a major deleterious impurity for solar cells. The combination of X-ray radiography and Bragg diffraction imaging (topography) achieved in situ during silicon solidification allowed us to characterise the dynamics of the growth mechanisms involved in the formation of the grain structure and of defects, related to the presence of C. Ex situ techniques were used to characterise the grain structure and for a more precise analysis of the defects and their associated distortion fields. In the presence of C, it is shown that the resulting grain structure is constituted by a higher proportion of high-order and incoherent twin boundaries compared with the case of pure samples. Crystal distortion is characterised at the grain scale level and at a lower scale, both in situ and after cooling-down. The highest distortion at the grain scale corresponds to the position of the high order twin boundaries and is accentuated during cooling-down following solidification. Locally distorted regions and sub-grains are distributed all over the samples. They are observed in situ during the solidification from various seeds containing C (mono-crystals, industrial ribbons and multi-crystalline samples) and are retrieved after solidification. A model implying the presence of SiC precipitates at the solid-liquid interface is proposed to explain the formation during solidification of these sub-grains and of the associated local distortion.

Multiresponse optimization of performance indicators through Taguchi-grey relational analysis in EDM of cemented carbide

Cemented carbide is mostly used in the mold and tool industry due to their high hardness, temperature and wear resistance, and it is very difficult to shape with conventional machining methods. Because, during the machining of certain geometry from these materials, microcracks on surface and flaking at the machined edges due to their brittleness as well as rapid tool wear mostly due to their high hardness occur. In this case, EDM is considered one of the most suitable machining technologies for brittle material such as carbides, as it provides a non-contact shaping with electrical sparks between the tool and the workpiece. This study focused on the simultaneous optimization of the most important performance indicators namely material removal rate, tool wear rate and surface roughness in creating a keyway on WC-15Co material with the die-sinking EDM. As a result of experiments using copper electrode, the impacts on performance indicators of discharge current, pulse time and pulse interval were investigated with 3D surface topography images. It was determined that the peaks and craters formed on the machined surface expanded with the increase of pulse time, and the decreased with the increase in the pulse interval. As a result of the Taguchi-grey relational analysis (TGRA) application, discharge current of 6 A, pulse time of 25 µs and pulse interval of 100 µs were found as optimum parameters. ANOVA results showed that Ip, Ton and Toff affected GRG values by 44.23%, 28.77% and 5.87%, respectively. A 23.95% improvement in performance indicators was achieved thanks to the TGRA multiresponse optimization.

Research of Moisture Sorption by Laminated Composite Materials

This article focuses on the moister sorption by laminated composites. Moisture sorption was carried out on layered polymer composite materials consisting of layers of basalt fabric and fiberglass based on epoxy-diane resin. It is shown that the process of moisture absorption for glass fiber-reinforced polymers is more intense and with a higher concentration of moisture in comparison with basalt fiber-reinforced polymer. Curves of the sorption processes of moisture absorption and water absorption are obtained. The diffusion coefficients for the corresponding processes are calculated. Alteration in the surface structure of polymer composite materials were recorded using surface topography and REM images before and after exposure in the climate of Yakutsk (Russia).

Comparative physiological, morphological, histological, and AQP2 immunohistochemical analysis of the Arabian camels (Camelus dromedarius) and oxen kidney: Effects of adaptation to arid environments

Compared to other mammals, Arabian camels are ideal models for exploring the structural adaptations that enable camels to survive in arid environments. Thus, this study aimed to explore how evolutionary adaptation to arid conditions modifies the characteristics of the kidneys in Arabian camels (Camelus dromedarius) compared to oxen. Urine samples were physically and chemically analyzed. Harvested kidneys were subjected to topographical and fast spin echo magnetic resonance (FSE-MR) imaging. Histology, histomorphometry, and Aquaporin-2 (AQP2) expression by immunohistochemistry were also performed. Here, in dromedaries, sodium and potassium values in the urine were much higher (p=0.001, for both), whereas chloride was much lower (p=0.004) than the values of oxen. Compared with oxen, the level of the hormone aldosterone in serum was significantly lower (p=0.002), whereas creatinine and urea were significantly higher (p=0.005 and p=0.001, respectively). Uric acid in dromedaries and oxen did not differ significantly (p=0.349). Like sodium levels (p=0.001) in dromedary serum, chloride was also much higher (p=0.002) than in oxen. The average value of potassium was much lower (p=0.009) than that of oxen. Morphologically, anatomical and FSE MRI studies revealed that minor and major calyces were not found in dromedary kidneys. The renal pelvis was not found in oxen, and the major calyx was directly connected to the ureter. The dromedary kidney contained a wider medullary portion as well as increased diameters for renal corpuscles (RCs), proximal convoluted tubules (PCTs), and collecting tubules (CTs, p&amp;lt;0.05) compared with the oxen. We also noted that AQP2 was significantly expressed in dromedary nephron components, except for RCs, compared with oxen as shown by immunohistochemistry. Overall, these data strongly suggest that the dromedary has a greater ability to adapt to harsh desert conditions in terms of producing highly concentrated urine than oxen.

Surgical outcomes of complicated cataract with pediatric trematode granulomatous uveitis.

To describe the clinical characteristics and surgical outcomes of complicated cataract with pediatric trematodal granulomatous uveitis (TGU). Patients of cataract with TGU in the membranous (inactive) stage underwent cataract surgery with intraocular lens (IOL) implantation. Preoperative history and ophthalmic examination were conducted for all cases, whereas Schimphlug imaging and corneal topography were done for some patients. Postoperative follow up was done on the 1st, 2nd, and 5th postoperative days after surgery. Then, it was done at least at one, three, and six months postoperatively. Intraoperative and postoperative complications and the methods of their management were reported. Twelve eyes of 12 male children were included in this study ranging from 8 to 16y. The mean best corrected Snellen visual acuity (BCVA) was significantly improved from 0.09±0.06 preoperatively to 0.37±0.11 at the final visit 6mo postoperatively (P<0.001). Schimphlug imaging and corneal topography showed flattening of the anterior surface of the inferior cornea. Intraoperative difficulties and complications included the poor dilatability of the drown down pupil, strong posterior synechia between the anterior lens capsule and the iris at the site of the inferior retrocorneal vascularized membrane and hyphema. All cases underwent primary hydrophobic IOL implantation. Surgery for this type of cataract is relatively safe and effective. It is associated with some specific difficulties and complications that should be considered during surgery and follow up.

Charge Mapping of Pseudomonas aeruginosa Using a Hopping Mode Scanning Ion Conductance Microscopy Technique.

Scanning ion conductance microscopy (SICM) is a topographic imaging technique capable of probing biological samples in electrolyte conditions. SICM enhancements have enabled surface charge detection based on voltage-dependent signals. Here, we show how the hopping mode SICM method (HP-SICM) can be used for rapid and minimally invasive surface charge mapping. We validate our method usingPseudomonas aeruginosaPA14 (PA) cells and observe a surface charge density of σPA = -2.0 ± 0.45 mC/m2 that is homogeneous within the ∼80 nm lateral scan resolution. This biological surface charge is detected from at least 1.7 μm above the membrane (395× the Debye length), and the long-range charge detection is attributed to electroosmotic amplification. We show that imaging with a nanobubble-plugged probe reduces perturbation of the underlying sample. We extend the technique to PA biofilms and observe a charge density exceeding -20 mC/m2. We use a solid-state calibration to quantify surface charge density and show that HP-SICM cannot be quantitatively described by a steady-state finite element model. This work contributes to the body of scanning probe methods that can uniquely contribute to microbiology and cellular biology.

The relationship between minor coronal asymmetry of the spine and measures of spinal sagittal shape in adolescents without visible scoliosis

The purpose of this work is to identify what features of overall spinal sagittal shape are associated with coronal asymmetry in those without scoliosis. Using a longitudinal analysis of Integrated Shape Imaging System 2 (ISIS2) surface topography images of those without scoliosis, measures of coronal asymmetry, along with measures of spinal sagittal shape (kyphosis, lordosis and sagittal imbalance, which is a measure of the position of the top of the thoracic spine relative to the sacrum) were analysed using linear mixed effect models (LMEM), which is a method of analysing the components of a complex model (such as that describing overall spinal shape), to ascertain the relative relationships between the parameters. Data was also analysed when subdivided for the anatomical level of coronal asymmetry (thoracic or thoracolumbar/lumbar pattern). There were 784 measures from 196 children. Kyphosis had little effect on coronal asymmetry for males and females, lordosis increased with coronal asymmetry in females only and sagittal imbalance increased with coronal asymmetry in males only. The results of the LMEM modelling were that the parameters related to coronal asymmetry were lordosis and sagittal imbalance. In thoracic coronal asymmetry, whilst lordosis was predominant, kyphosis played more of a role. In thoracolumbar/lumbar coronal asymmetry, lordosis and sagittal imbalance were the larger coefficients. Coronal asymmetry of the spine in those without scoliosis is related to features of spinal sagittal shape, particularly lordosis and sagittal imbalance. This knowledge adds to the understanding of the aetiology of adolescent idiopathic scoliosis.

Microstructural and Mechanical Characterization of Al Nanocomposites Using GCNs as a Reinforcement Fabricated by Induction Sintering

High-energy ball milling is a process suitable for producing composite powders whose achieved microstructure can be controlled by the processing parameters. Through this technique, it is possible to obtain a homogeneous distribution of reinforced material into a ductile metal matrix. In this work, some Al/CGNs nanocomposites were fabricated through a high-energy ball mill to disperse nanostructured graphite reinforcements produced in situ in the Al matrix. To retain the dispersed CGNs in the Al matrix, avoiding the precipitation of the Al4C3 phase during sintering, the high-frequency induction sintering (HFIS) method was used, which allows rapid heating rates. For comparative purposes, samples in the green and sintered state processed in a conventional electric furnace (CFS) were used. Microhardness testing was used to evaluate the effectiveness of the reinforcement in samples under different processing conditions. Structural analyses were carried out through an X-ray diffractometer coupled with a convolutional multiple whole profile (CMWP) fitting program to determine the crystallite size and dislocation density; both strengthening contributions were calculated using the Langford-Cohen and Taylor equations. According to the results, the CGNs dispersed in the Al matrix played an important role in the reinforcement of the Al matrix, promoting the increase in the dislocation density during the milling process. The strengthening contribution of the dislocation density was ~50% of the total hardening value, while the contribution by dispersion of CGNs was ~22% in samples with 3 wt. % C and sintered by the HFIS method. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology, size, and distribution of phases present in the Al matrix. From the analyses carried out in AFM (topography and phase images), the CGNs are located mainly around crystallites and present height profiles of 1.6 to 2 nm.

Growth of Zr/ZrO2 Core–Shell Structures by Fast Thermal Oxidation

This research has been conducted to characterize and validate resistive heating as a synthesis method for zirconium oxides (ZrO2). A wire of Zr has been oxidized to form a core–shell structure, in which the core is a metal wire, and the shell is an oxide layer that is around 10 μm thick. The characterization of the samples has been performed by means of several techniques based on Scanning Electron Microscopy (SEM). The topography images show that thermal gradient appears to have little influence on morphology, unlike time, which plays an important role. The chemical composition was analyzed by X-ray spectroscopy (EDX) and X-ray diffraction (XRD), and Raman spectroscopy has been used to assess crystallinity and crystal structure. The oxide layer is mainly formed by monoclinic ZrO2, alongside other, less significant, phases. Photoluminescence (PL) and cathodoluminescence (CL) measurements have allowed us to study the distribution of defects along the shell and to confirm the degree of uniformity. The oxygen vacancies, either as isolated defects or forming complexes with impurities, play a determinant role in the luminescent processes. Color centers, mainly electron centers such as F, FA and FAA, give rise to several visible emissions extending from blue to green, with main components at around 2 eV, 2.4–2.5 eV and 2.7 eV. The differences between PL and CL in relation to distinct recombination paths are also discussed.

A simple KPFM-based approach for electrostatic- free topographic measurements: the case of MoS2 on SiO2

A simple implementation of Kelvin probe force microscopy (KPFM) is reported that enables recording topographic images in the absence of any component of the electrostatic force (including the static term). Our approach is based on a close loop z-spectroscopy operated in data cube mode. Curves of the tip-sample distance as a function of time are recorded onto a 2D grid. A dedicated circuit holds the KPFM compensation bias and subsequently cut off the modulation voltage during well-defined time-windows within the spectroscopic acquisition. Topographic images are recalculated from the matrix of spectroscopic curves. This approach is applied to the case of transition metal dichalcogenides (TMD) monolayers grown by chemical vapour deposition on silicon oxide substrates. In addition, we check to what extent a proper stacking height estimation can also be performed by recording series of images for decreasing values of the bias modulation amplitude. The outputs of both approaches are shown to be fully consistent. The results exemplify how in the operating conditions of non-contact AFM under ultra-high vacuum (nc-AFM), the stacking height values can dramatically be overestimated due to variations in the tip-surface capacitive gradient, even though the KPFM controller nullifies the potential difference. We show that the number of atomic layers of a TMD can be safely assessed, only if the KPFM measurement is performed with a modulated bias amplitude reduced at its strict minimum or, even better, without any modulated bias. Last, the spectroscopic data reveal that certain kind of defects can have a counterintuitive impact on the electrostatic landscape, resulting in an apparent decrease of the measured stacking height by conventional nc-AFM/KPFM compared to other sample areas. Hence, electrostatic free z-imaging proves to be a promising tool to assess the existence of defects in atomically thin TMD layers grown on oxides.