Unusual Defect Research Articles

Unusual Defect Chemistry of Thorium Doping of PbS.

The unusual defect chemistry of thorium doping in the PbS system was investigated computationally to answer several open questions arising from the experimental observations. These include finding Th in a +4 oxidation state in contrast to Pb, attracting more than two oxygen atoms on average per thorium and affecting the growth morphology of PbS and its electronic properties. We find Th to be energetically stable at the lead lattice position in PbS and to attract 2-3 oxygens, including in the adjacent interstitial position, which binds strongly to Th. This adjacent interstitial atom allows the +4 oxidation state of Th in PbS as observed experimentally. Furthermore, the bandgap of the ideal material increased due to Th incorporation, in agreement with experimental observations. Finally, we calculated the surface energies of the (100), (110), and (111) surfaces for the systems with and without thorium incorporation. Surfaces (100) and (110) were found to have negative surface energies; however, (111) surface energy was positive and, thus, preferred for the growth of Th-doped PbS thin films. These results correlate well with the experimentally observed surface topography change for PbS thin film growth from the (100) to the (111) surfaces with addition of Th.

Unusual defect properties of the one-dimensional photovoltaic semiconductor selenium.

Defect tolerance is crucial in photovoltaic absorbers. Here we report that trigonal selenium (t-Se) exhibits a perovskite-like antibonding valence band maximum arising from Se p-p coupling. This results in the shallow nature of dominant Se vacancy defects. We further reveal the unique defect self-healing characteristic of Se intrinsic point defects.

Lumbar hernia: An unusual abdominal hernia: A case report and review of literature (radiological perspective) in a tertiary center in south-south Nigeria

Lumbar hernias are unusual abdominal wall defects involving the posterolateral abdominal wall: the superior lumbar triangle of Grynfelt, which is the most common site, and the inferior lumbar triangle of Petit. They are located between the muscular layers of the abdominal wall and can be easily ignored because of abdominal obesity. In general, it is difficult to diagnose because of their unclear non-specific symptoms. However, radiographic studies have been valuable in confirming the diagnosis. The introduction of ultrasonography and computed tomography (CT) has greatly improved the diagnosis of lumbar hernia. Following the establishment of the diagnosis, operative management is indicated due to chance of incarceration. Our case study is an 80 years old man who presented to the Radiology department for an emergency abdominal ultrasound scan investigation on account of abdominal pain/abdominal swelling on the lateral aspect of the right flank of about 5 days as explained by his relative. The abdominal ultrasound shows a hyperechoic mass in the right flank that extends through a defect in the transversus abdominis muscle. This mass measures 5.3x4.9cm and shows no flow on Doppler interrogation. Note mild fluid collection seen surrounding the mass. Also note marked subcutaneous oedema. Another imaging modality was employed; non contrast computed tomography and shows a lateral abdominal wall defect in the right lower internal oblique with sac containing bowel loop and omental fat. Other visualized bowel loops are normal in caliber and wall thickness.

Defects of quantum dot cellular automata computing devices: An extensive review, evaluation, and future directions

Quantum dot cellular automata (QCA), a nanoscale technology, are more prone to faults due to their diminutive size and precise fabrication process. The defects of QCA circuits have been the topic of many research papers, and this work has conducted a comprehensive study of the defect characterisation of QCA circuits. In this work, the defects in QCA circuits are divided into four groups: faults in the synthesis phase, faults in the deposition phase, faults in the design phase, and other faults. In addition, some unusual defects, such as stuck-at faults and single electron faults, are looked at. The study of the existing QCA works shows that fault-tolerant wires, tiles, etc. are rarely discussed in the literature. The literature also lacks adequate explanations of the QCA fault-tolerant clocking mechanism and fabrication processes. This work describes the identified challenges as well as their possible solutions. Additionally, this article outlines the future direction of this research and any relevant constraints. As a result, the intended audience can have a holistic understanding of the faults associated with QCA. This effort also seeks to facilitate the understanding of QCA circuit defects by related researchers.

Anomalous Glide Plane in Platinum Nano- and Microcrystals.

At the nanoscale, the properties of materials depend critically on the presence of crystal defects. However, imaging and characterizing the structure of defects in three dimensions inside a crystal remain a challenge. Here, by using Bragg coherent diffraction imaging, we observe an unexpected anomalous {110} glide plane in two Pt submicrometer crystals grown by very different processes and having very different morphologies. The structure of the defects (type, associated glide plane, and lattice displacement) is imaged in these faceted Pt crystals. Using this noninvasive technique, both plasticity and unusual defect behavior can be probed at the nanoscale.

Low-dimensional antimony selenosulfide as an emerging material for solar cell applications

Antimony chalcogenides (Sb2X3), including Sb2S3, Sb2Se3, and the alloy-type Sb2(S,Se)3, have been considered as a promising absorber materials for photovoltaic applications. Owing to its unique quasi-one-dimensional crystal structure, it displays distinct defect and carrier transport properties and requires special material synthesis strategy compared with the traditional three-dimensional crystal structure semiconductor materials. Recent studies on this class of materials have generated new understandings in film fabrication, defect characteristics and passivation, interfacial engineering, and efficiency improvement. With these efforts, the power conversion efficiency of the solar cell device has been increased from below 3% to 10.7% over the past 10 years. This efficiency achievement suggests that Sb2X3 possesses great potential for practical applications with further efficiency enhancement. This perspective article presents the critical development in the Sb2X3 materials and solar cells in recent years, including the unique crystal structure for solar cells, the preparation method for obtaining high-quality Sb2X3 films, and the discovery and passivation of unusual and complex defects. Finally, we propose several strategies for future efficiency improvement.

Tungsten Oxide-based Materials: Synthesis, Properties, and Applications

Non-stoichiometric compounds of tungsten oxides that are abundant on the earth received extensive attention in electrochromic devices, electrochemistry, photothermal conversion, gas sensors, and photocatalysis because of their unique physicochemical structures and highly tunable structures. Because of its high colouring efficiency, quick optical reaction time, and reversible colour changes, tungsten oxide (WO3 ), along with various oxidation states of oxygen-deficient tungsten oxide (WO3-x), has been identified as one of the mainly effective possibilities for electrochromic materials among transition metal oxides. For example, one-dimensional nanostructures of WO3-x such as nanotubes, nanowires, and nanorods, have gotten huge attention due to their unique electrical, optoelectrical, and optical properties. Additionally, distinct oxygen-deficient tungsten oxides (WO3-x) - WO2.72, WO2.83, and WO2.9, for example - have significant light absorption characteristics up to the near-infrared (NIR) region and a stable crystal phase, which sets them apart from surface-reduced WO3 . Out of these, reduced tungsten oxide (WO2.72) is one of the most studied owing to promising properties such as unusual defect structures and abundant oxygen vacancies. These oxygen vacancies create new discrete energy bands below the conduction band thus narrowing its bandgap The other series of tungsten-based materials is tungsten bronze (MxWO3 , where M= Na, Cs, K, Rb, etc) which has mixed-valence states. These are the materials that are explored less but have excellent properties as compared to WO3 . So, in this review, the applications, synthesis methods, and properties of MxWO3 and WO2.72 are studied in detail.

Дефекты костной ткани на черепах людей энеолитического могильника Екатериновский мыс юга Среднего Поволжья. К вопросу специфики культурных традиций

Unusual defects mainly in the form of surface ellipsoid or less commonly sub-circular indentations were recorded on the skulls of mature individuals from the Eneolithic burial grounds in the forest-steppe area of the Volga region (Yekaterinovsky cape). Almost all of the defects are localized on the parietal bones. The origin of the small-sized lesions could be associated with trauma. The large defects occur due to additional surgical prophylaxis by scraping. There are separate cases of classical end-to-end trepanation (burial 57/1, 83). The authors conducted a comparative analysis of the identified defects with similar injuries on the materials from ancient burial grounds of the Volga region (Khvalynsk I, II), other regions and periods of Europe. Ritual character connected to age initiation rites was previously attributed to their origin. This thesis is supported by new source discovery (Yekaterinovsky cape). The probability of the so-called symbolic trepanation is considered. We do not exclude these types of reasons. However, priority in determining the technical content of the period of trauma development that accompanied the ritual is given to other target settings. Their natural appearance was initially associated with “shock symbols” and after the entire ceremony, if necessary, surface trepanation was used for medicinal purposes. Such marginal traditions are usually characteristic of ancient highly organized and influential societies, which is confirmed by archaeological data, in particular, regarding the fame and role of the Khvalyn Eneolithic population in the cultural processes of the central regions of Eurasia. The beginning of the trauma ritual in the Volga region was laid at least in the 6th millennium BC (Yekaterinovsky cape), then adapted and developed by the ancient Khvalyn groups.

Elastic Instability of Cubic Blue Phase Nano Crystals in Curved Shells.

Many crystallization processes, including biomineralization and ice-freezing, occur in small and curved volumes, where surface curvature can strain the crystal, leading to unusual configurations and defect formation. The role of curvature on crystallization, however, remains poorly understood. Here, we study the crystallization of blue phase (BP) liquid crystals under curved confinement, which provides insights into the mechanism by which BPs reconfigure their three-dimensional lattice structure to adapt to curvature. BPs are a three-dimensional assembly of high-chirality liquid crystal molecules arranged into body-centered (BPI) or simple cubic (BPII) symmetries. BPs with submicrometer cubic-crystalline lattices exhibit tunable Bragg reflection and submillisecond response time to external stimuli such as an electric field, making them attractive for advanced photonic materials. In this work, we have systematically studied BPs confined in spherical shells with well-defined curvature and boundary conditions. The optical behavior of shells has also been examined at room temperature, where the cholesteric structure forms. In the cholesteric phase, perpendicular anchoring generates focal conic domains on the shell's surface, which transition into stripe patterns as the degree of curvature increases. Our results demonstrate that both higher degrees of curvature and strong spatial confinement destabilize BPI and reconfigure that phase to adopt the structure and optical features of BPII. We also show that the coupling of curvature and confinement nucleates skyrmions at greater thicknesses than those observed for a flat geometry. These findings are particularly important for integrating BPs into miniaturized and curved/flexible devices, including flexible displays, wearable sensors, and smart fabrics.

A novel nanoprobing analysis flow by using multi-probe configuration to localize silicide defect in MOSFET

It is demonstrated that nanoprobing technique is superior in localizing silicide defect rapidly in metal-oxide-semiconductor field-effect transistor (MOSFET). Cobalt silicide (CoSi2) as an interfacial material below tungsten contact plug, various types of defects about CoSi2 often cause leakage current in MOSFET, so close studies of problematic silicide is significant regarding MOSFET reliability enhancement. When one MOSFET in a combinational logic circuit is suspected of anomaly, because this kind of circuit is composed of several devices which are sometimes arranged in an active area (AA) of unique geometric shape, it is impossible to collect MOSFET characteristic correctly based on regular nanoprobing flow since conventional method hits limit for combined circuits measurement. Such circumstance almost impedes failure analysis (FA) in device level. Nevertheless, relying on our alternative strategy of multi-probe configuration, a novel nanoprobing analysis flow is adopted for device examination. It is shown that exact I-V characteristic of failed device can be captured by proposed workflow. Following I-V curve analysis further reveals an evident electrical signature of abnormal abrupt junction. It corresponds to an active area shorting with its surrounding nwell region. In addition, sophisticated leakage current behaviors are exhaustively interpreted by simplified models. Eventually, we confirmed CoSi2 encroachment from the active area into nwell by the means of transmission electron microscopy (TEM) analysis. This paper presents an effective analysis to identify leaky junction of MOSFET in logic circuit that is rarely reported before. Furthermore, our exploration exhibits impressive flexibility of nanoprobing analysis in terms of localizing unusual silicide defect, so nanoprobe analysis is clearly an attractive option to optimize MOSFET manufacturing.

Determining the existence of the foramen of Huschke in patients with temporomandibular joint disorders using cone beam computed tomography: retrospective cohort study

BackgroundForamen of Huschke has been presented as an unusual developmental defect in anteroinferior aspect of external auditory canal. It can be associated with significant otologic complications. The purpose of this study was to determine the association between existence of foramen of Huschke and temporomandibular joint disorders in Cone Beam Computed Tomography (CBCT) images.MethodsOf an initial sample of 465 patients, we retrospectively evaluated the CBCT images of 118 individuals with clinical signs and symptoms of temporomandibular joint disorders as case group and 256 individuals as control group. The presence, size and localization of foramen of Huschke were assessed in the axial and corrected sagittal images. The sex and age distribution were determined. Fisher’s exact test, T-test and Pearson’s Chi-square were applied to assess the relationship between foramen of Huschke and temporomandibular joint disorders in the case and control groups considering age and sex.ResultsThe foramen of Huschke prevalence was slightly higher in patients with temporomandibular joint disorders (3.4%) than patients without temporomandibular joint disorders (0.8%). However, the difference was not statistically significant (P = 0.082). foramen of Huschke was found in five females and one male. There was no significant difference between case and control groups considering the age of patients with foramen of Huschke (P = 0.683). There was no significant difference between the case and control groups, considering the right and left ears in distribution of foramen of Huschke (P = 0.099) (P = 0.183).ConclusionsHigher prevalence of foramen of Huschke in patients with temporomandibular joint disorders may suggest possible mechanism for temporomandibular joint disorders development that can be affected by presence of foramen of Huschke.

Electron-Volt Fluctuation of Defect Levels in Metal Halide Perovskites on a 100 ps Time Scale.

Metal halide perovskites (MHPs) have gained considerable attention due to their excellent optoelectronic performance, which is often attributed to unusual defect properties. We demonstrate that midgap defect levels can exhibit very large and slow energy fluctuations associated with anharmonic acoustic motions. Therefore, care should be taken classifying MHP defects as deep or shallow, since shallow defects may become deep and vice versa. As a consequence, charges from deep levels can escape into bands, and light absorption can be extended to longer wavelengths, improving material performance. The phenomenon, demonstrated with iodine vacancy in CH3NH3PbI3 using a machine learning force field, can be expected for a variety of defects and dopants in many MHPs and other soft inorganic semiconductors. Since large-scale anharmonic motions can be precursors to chemical decomposition, a known problem with MHPs, we propose that materials that are stiffer than MHPs but softer than traditional inorganic semiconductors, such as Si and TiO2, may simultaneously exhibit excellent performance and stability.

Ten Years of Sb2Se3 Thin Film Solar Cells

Antimony selenide (Sb2Se3) has emerged as a promising absorber material for photovoltaic application. Since the first pure‐phase Sb2Se3 solar cell reported ten years ago, increasing research has been carried out on this system with the device efficiency now reaching 9.2%. This work aims to present the major milestones of Sb2Se3 thin film solar cells from its birth to the present, including the selection of Sb2Se3 for thin film photovoltaics, the choice of planar device configuration instead of sensitized device, switching from solution processing to vacuum processing, new concept of orientation control and benign grain boundaries, discovery of unusual and complex defects, and post selenization for defect passivation. In the end, the authors discuss the competitive applications of Sb2Se3 solar cells in flexible devices and outlook their future development.

Congenital left hemidiaphragmatic agenesis : a case report

Congenital diaphragmatic hernia is a congenital diaphragmatic disorder characterized by herniation of the abdominal viscera into the thoracic cavity. In rare diaphragmatic developmental abnormality cases, there is complete diaphragmatic agenesis. We report a case of left hemidiaphragmatic agenesis with usual postnatal course. A 13-day old female infant presented respiratory distress for a week. Chest radiograph showed left sided congenital diaphragmatic hernia. We report a left hemidiaphragmatic agenesis case. A 13-day old female infant presented respiratory distress for a week. Chest radiograph showed a left sided congenital diaphragmatic hernia. The patient undergo surgical exploration and was found to have an unusual and large defect in the left hemidiaphragm. No diaphragm is visible on the anterior and lateral sides, and the anterior sides presented only a small edge of the diaphragm. Agenesis of the left hemidiaphragm defect was identified and well managed by suturing the posterior edge of the diaphragm to the intercostal muscles. This report describes the well management of hemidiaphragmatic agenesis without incorporating a prosthetic material.

Mass Defect Filter for Removing Noise and Detector Oscillation Artifacts in Centroided Time-of-Flight Mass Spectra.

Spurious peaks in centroided mass spectra resulting from detector oscillation or "ringing" can be identified by their unusual mass defects. Mass defect plots (fractional m/z vs measured m/z) for the single-charge mass spectrum of a pure compound show data points falling along lines with well-defined slopes. Detector oscillation and electronic noise peaks were removed from database spectra of pure compounds and mixtures by eliminating points outside two standard deviations of the slope of the major peaks. No loss of chemical information was observed, even for compounds with isobaric fragment peaks.

Difficult Ventilation in a patient after Endotracheal Intubation: an Unusual Manufacturing Defect in E.T.T. Connecter

Summary: Airway resistance depends upon the diameter of endotracheal tube (E.T.T) and other respiratory organs. Actually resistance to flow through a tube increases up to sixteen times if diameter is reduced to half of the original size. Disposable E.T.T which are currently used in anaesthesia practice are made up of P.V.C with a connecter which is fitted on proximal end of endotracheal tube and proximal end of connector I attached with breathing circuit. Usually the internal diameter of connector should be equal to internal diameter of endotracheal tube.

Van Hove singularities, moiré-superlattices and rhombohedral stacking in exfoliated sublattices of highly oriented pyrolytic graphite

The presence of twisted sublattices in exfoliated lamellae of highly oriented-pyrolytic-graphite (HOPG) has been recently shown to induce a significant enhancement of percolative-ferromagnetic ordering at low temperature, opening new directions towards possible applications of graphitic lamellae in spintronics. Despite the significant progress, additional work is needed to elucidate possible magnetic effects arising from rhombohedral phases. In this work, we report a novel structural, electronic, and magnetic investigation. TEM allowed for the observation of multiple hexagonal moiré-superlattices and unusual staircase-like defects in those sublattices exposed by the exfoliation process. STM and STS further evidenced the appearance of multiple singularities in LDOS spectra acquired from certain sublattice-areas comprised within comparable staircase-defect features. Unusual effects involving a sharp enhancement in the density of states near the Fermi level are reported. These observations possibly imply the coexistence of both moiré superlattices and rhombohedral domains in certain twisted-sublattice regions. Further, Raman spectroscopy, through area mapping of the D, G, and D′ bands, evidenced additional signals in the proximity of ∼1,800–2,100 cm−1, attributable to electronic Raman-scattering (ERS). These effects arise locally from emerging rhombohedral domains possibly created by (1) slip-induced transformation of stacking order during tape exfoliation and (2) twisted sublattices, with θrot ∼0.1°. T-EPR measurements also evidenced an unusual enhanced broadening and peak shift in the differential π-electron feature acquired from some of the lamellae exfoliated from the inner regions of the main HOPG.

Unusual defect properties in multivalent perovskite Cs2Au2I6 : A first-principles study

Double halide perovskites have attracted increasing interest due to their great potential to eliminate the toxicity and instability issues in lead halide perovskites. Unfortunately, octahedral cation antisites easily form in common double halide perovskites and induce deep defect levels. Here, using first-principles calculation methods, we report unusual defect properties in the double halide perovskite ${\mathrm{Cs}}_{2}{\mathrm{Au}}_{2}{\mathrm{I}}_{6}$, including the coexistence of shallow and deep defect transition energy levels of iodine vacancies, absent of octahedral cation antisites, and different dominant donor defects such as interstitials $({\mathrm{Au}}_{\mathrm{i}})$ and I substituting Au $({\mathrm{I}}_{\mathrm{Au}})$. We attribute these unusual defect properties to the multivalence effect of Au and strong covalent bonding between Au and I. Based on the defect properties, we propose two possible applications of ${\mathrm{Cs}}_{2}{\mathrm{Au}}_{2}{\mathrm{I}}_{6}$. On one hand, ${\mathrm{Cs}}_{2}{\mathrm{Au}}_{2}{\mathrm{I}}_{6}$ could be a useful candidate for photodetectors under I-rich growth conditions due to its relatively low carrier densities because the Fermi level is pinned near the middle of the band gap due to the strong compensation of the dominant donors ${\mathrm{Au}}_{\mathrm{i}}$ and acceptor ${\mathrm{V}}_{\mathrm{Cs}}$. On the other hand, ${\mathrm{Cs}}_{2}{\mathrm{Au}}_{2}{\mathrm{I}}_{6}$ can be made $n$-type if it is grown under I-poor conditions, which can be further enhanced by growing the sample at 600 K and then quenching to 300 K. Consequently, ${\mathrm{Cs}}_{2}{\mathrm{Au}}_{2}{\mathrm{I}}_{6}$ has potential as an $n$-type photovoltaic absorber. Our studies not only enrich the defect physics in multivalent double halide perovskites but also provide useful information for advancing ${\mathrm{Cs}}_{2}{\mathrm{Au}}_{2}{\mathrm{I}}_{6}$ technologies.

Carrier gradients and the role of charge selective contacts in lateral heterojunction all back contact perovskite solar cells

Realizing photovoltaic devices that achieve the full potential of the metal halide perovskite material will require improved insight regarding the role of selective contacts and how key interfaces operate when mobile defects are present. However, measuring interface properties in typical device stacks where the perovskite layer is thin and sandwiched between two contacts has been a challenge. Here, we fabricate p-i-n and p-n lateral heterojunctions with nickel oxide/titanium oxide all back contacts, permitting us to employ a comprehensive analysis approach, including ultraviolet and X-ray photoemission spectroscopy (UPS/XPS), angle-resolved X-ray absorption spectroscopy (XAS), Kelvin probe force microscopy (KPFM), surface photovoltage (SPV), hyperspectral imaging (HSI), and time-resolved fluorescence lifetime imaging microscopy (TR-FLIM) to discern the role of selective contacts. Specifically, we tune the selectivity of the contacts, changing the gradient in the carrier concentration across the surface of the active layer, which is connected to carrier extraction at the buried interface, and thus the device functionality. • Charge selective contacts shift the Fermi level in metal halide perovskites (MHPs) • Effect is readily observable because of low defect and doping concentrations in the MHP • Contact selectivity determines carrier extraction across MHP/contact interfaces • Tailoring charge selective contacts to design MHP-based lateral heterojunction devices Metal halide perovskites (MHPs) define an emerging field of novel optoelectronics. For MHP-based applications, such as interdigitated back contact solar cells, the right choice of charge selective contacts remains the principal challenge to overcome; however, relatively few design rules exist because of the unusual defect properties of MHPs. Here, Dunfield et al. employ a range of techniques to discern the role of selective contacts.

The growth of methane hydrate with impingement influenced by thermodynamic inhibitor

Thermodynamic inhibitors have been widely used to prevent hydrate formation in natural gas hydrate exploitation and oil/gas transportation. In this article, molecular dynamics simulations of hydrate growth with impingement influenced by thermodynamic inhibitors including NaCl, KCl and ethylene glycol are performed. Consistent with the experimental results, we found that NaCl, KCl and ethylene glycol indeed delay the moment of hydrate come into accelerated growth stages, decreasing the growth rate of the hydrate and reducing the concentration of methane in the water solution. The Cl− ions are observed more frequently to insert into the cages than Na+ ions during the growth stage. The ethylene glycol molecules tend to occupy 51262 cages and occur in pairs or in clusters. The crystal clusters of NaCl are more complete and the ions of KCl are more widely distributed. The salt ions cause some unusual water-occupied defect structures to appear frequently near the ions. The microscopic mechanism of hydrate impingement by salts and ethylene glycol effects has been revealed for the first time and the dual role of the thermodynamic inhibitors: inhibition effect in the growth stage and destroy effect in the impingement stage, has been demonstrated. Our simulation result is not only beneficial for understanding the inhibition mechanisms of traditional inhibitors, but also guiding for the exploitation of novel inhibitors.