Edge Energy Research Articles

Molecular Dynamics of Catalyst-Free Edge Elongation of Boron Nitride Nanotubes Coaxially Grown on Single-Walled Carbon Nanotubes.

Recent advances in low-dimensional materials have enabled the synthesis of single-walled carbon nanotubes encapsulated in hexagonal boron nitride (BN) nanotubes (SWCNT@BNNT), creating one-dimensional van der Waals (vdW) heterostructures. However, controlling the quality and crystallinity of BNNT on the surface of SWCNTs using chemical vapor deposition (CVD) remains a challenge. To better understand the growth mechanism of the BNNT in SWCNT@BNNT, we conducted molecular dynamics (MD) simulations using empirical potentials. The simulation results suggest that spontaneous BN nucleation is unlikely to occur on the outer surface of the SWCNT when we assume only vdW interaction between the BN and SWCNT layers. However, we observe the elongation of the BNNT when a short BNNT is provided as a seed nucleus on the SWCNT. This grown BNNT structure, with its sharply cut edges, aligns with experimental observations made using transmission electron microscopy (TEM). Moreover, the edge-reconstruction process favors zigzag B edges, which exhibit low edge energy according to the ReaxFF potential. Our simulation successfully provides insights into the catalyst-free growth process of this one-dimensional vdW heterostructure.

Sorption of trivalent europium Eu(III) by Na+-substituted bentonite: Mechanistic insight and stabilization effect

The sorption of Eu(III) by Na+-substituted bentonite (Na-bentonite) was investigated as a function of pH and NaNO3 concentration ([NaNO3]0). At pH < ∼7.5, Eu(III) sorption decreased with the increasing [NaNO3]0, whereas at pH > ∼7.5, it remained nearly complete, independent of [NaNO3]0. Our thermodynamic model indicated that the sorption at pH < ∼7.5 occurred via a combination of cation exchange and surface complexation, with the former diminishing as [NaNO3]0 increased. Meanwhile, the sorption at pH > ∼7.5 was primarily due to surface complexation. By X-ray diffraction, the incorporation of hydrated Eu(III) in the interlayers of montmorillonite increased its lattice spacing and crystallinity along the c-axis, where cation exchange was predominant. Also, Eu LIII-edge X-ray absorption spectroscopy revealed that the sample dominated by cation exchange had an absorption edge energy and coordination structure similar to aqueous Eu(III), indicating outersphere complex formation. In other cases, Eu(III) sorption was characterized by innersphere complexation, as indicated by increased covalency and the presence of more pronounced second coordination shells. Importantly, the analysis of dissolved Si and Al suggested that the increased stability of Na-bentonite was likely due to the surface complexation of Eu(III) with aluminol groups at the edges, especially at higher surface coverages. Given its high sorption capacity for Eu(III) and stabilization effect mediated by sorption, Na-bentonite could be serve as an effective backfill material and migration barrier for containing actinides in nuclear waste repositories.

Characterization and linear / nonlinear optical aspects of polyaniline (PANI) films incorporated with Ethylenediamine for low-cost limiting optical technologies

Polymer composite combined film with Polyaniline (PANI) and Ethylenediamine (EDA) were successfully synthesized via the spin coating technique on a glass substrate followed by different thermal annealing degrees and times. Successful incorporation of EDA into the PANI polymer matrix and the effect of the annealing temperature have been demonstrated by XRD, FTIR, FESEM and TEM. Using UV–Vis optical spectroscopy, we determine the absorption coefficient, band edge, and Urbach energy. The effects of different annealing temperatures and times on linear/nonlinear optical characteristics were investigated. The band gap of EDA-doped PANI films is reduced with the different thermal annealing from 3.43 eV to 3.19 eV, while the Urbach tail of the 100 °C/4h film which is 0.492 eV was decreased to 0.469 eV for 150 °C/1h sample. However, the absorbance and optical conductivity were both increased. Besides, the optical limiting effect assesses their potential to mitigate intense light. It was found from the study that for green wavelength 100 °C/4h film decreases the input power by 16.5 % whereas the 150 °C/1h sample shows superior limiting behavior of 99.96 %. It has been found that thermal annealing of the EDA-doped PANI films enhances the synthetic composite's optical characteristics, making the 150 °C/1h sample of EDA-doped PANI films appropriate for utilization in both energy applications and optoelectronics.

On the Bulk Photovoltaic Effect in the Characterization of Strained Germanium Microstructures

Strain engineering serves as an effective method for optimizing electronic and optical properties in semiconductor devices, with applications including the enhancement of optical emission in Ge and GeSn‐based devices, improvement of carrier mobility, and second harmonic generation in silicon photonics structures. Current methods for deformation characterization in semiconductors, such as X‐ray diffraction and Raman spectroscopy, often require bulky and expensive setups and are limited in vertical resolution. Consequently, techniques capable of measuring lattice strain while overcoming these drawbacks are highly desirable. This study proposes a proof of concept for a cost‐effective, compact, fast, and non‐destructive approach to probe non‐uniform strain fields and additional material properties by exploiting the bulk photovoltage effect. The method is benchmarked with an array of silicon nitride stripes deposited under varying pressure conditions on a germanium substrate. Initially, their surface strains are verified through Raman spectroscopy. The deformations are replicated in a finite element method platform by integrating mechanical simulations with deformation potential theory, thereby estimating the band edge energy landscape. Finally, the study discusses the theoretical behavior of the photovoltage signal, considering semiconductor properties, defects, doping, and deformation. The findings offer insights into the development of advanced techniques for strain and transport analysis in semiconductor materials.

Influence of Ca-substituted K-induced cluster defects on the electronic structure and optical properties of KDP crystals

Compensation mechanism following Ca substitution in K sites was computed using GULP. Utilizing density functional theory for three charge states, the impact of defect clusters CaK + VK/CaK + VH on potassium dihydrogen phosphate (KDP) crystals in both phases was assessed. Corrections to the band edge and defect formation energies were made employing hybridization floods HSE06 and FNV. Neutral and −1 valence defect states emerged. Cluster defects induced pronounced lattice distortion in PE-KDP. Notably, PE-KDP exhibited an additional photoemission of 2.89 eV, signifying a substantial structural impact. Comparative stability analysis favored FE-KDP, offering theoretical guidance for KDP crystal utilization.

Engineered Sn-TiO2@SnO2 and SnO2@Sn-TiO2 heterophotocatalysts for enhanced As(III) remediation: A comprehensive bulk and surface characterization and precise photocatalytic oxidation rates determination

Arsenite, As(III), is a highly toxic form of arsenic that poses a significant risk to human health if present in drinking water. Oxidation of As(III) to the less toxic As(V) using TiO2 as photocatalyst is an attractive solution in water treatment applications but challenged the high bandgap energy. In this study, we investigate the potential of doping TiO2 with Sn to reduce the bandgap and hence to improve the photocatalytic oxidation (PCO). To this end, we studied first the effect of varying Sn:TiO2 molar doping on the structure of the newly synthesized SnO2@TiO2 and Sn-TiO2@SnO2 hetero photocatalysts. We found that at low Sn:TiO2 doping ratios (0.1Sn:1TiO2), SnO2 tends to float on the surface and form a coat around the TiO2 (SnO2@Sn-TiO2), whereas at higher doping ratio (1Sn:1TiO2) a Sn-TiO2 coat forms alongside SnO2 clusters in the core of the catalyst (Sn-TiO2@SnO2). We assessed the PCO and observed significant shifts to lower conduction and valence band edge energies and a reduction of the bandgap at higher doping ratios. The smallest bandgap was 2.87 eV with a doping ratio of 1Sn:1TiO2. Sn-TiO2@SnO2 and as SnO2@Sn-TiO2 improved the PCO of TiO2 by ∼30 and 46 %, respectively. We finally determined the rate constant (k) for the As(III) oxidation using a combination of spectrochemical and surface sensitive techniques and determined for a 1Sn:1TiO2 (i.e. Sn-TiO2@SnO2) catalyst a value of 0.055 ±0.002 min−1, i.e., 78 folds faster than using only TiO2. We conclude that Sn doping of TiO2 is a very promising approach for improving the PCO of As(III) in water treatment.

In-Situ X-Ray Absorption Spectroscopy Investigations on the Transition Metal Cations Intercalation in Ti3C2Tx MXene for Electrochemical Applications

Synchrotron X-ray absorption spectroscopy (XAS) serves as a robust and powerful technique for probing the oxidation state and coordination surrounding of specific elements. In particular, operando XAS has been employed to elucidate charge storage mechanisms by monitoring changes in the oxidation state through the absorption edge energy of metals in electrodes such as MnO2 and RuO2 during charging/discharging[1] [2]. Herein, we utilized in-situ XAS technique to uncover the charge storge mechanisms of transition metal (TM)-intercalated MXenes (Ti3C2Tx). We specifically probed the K-edges of intercalated TM and Ti MXene to reveal their oxidation states changes, shedding light on their respective contributions to capacitance. Aiming to gain further insights into the confined environment between MXene layers, we also employed ab-initio molecular dynamics (AIMD) to further interpret and validate the coordination environment obtained through in-situ extended X-ray absorption fine structure (EXAFS). This investigation lays the groundwork for tailoring the electronic and electrochemical properties of MXenes by the intercalation of various transition metal cations across diverse electrochemical systems.[1] J.-K. Chang, M.-T. Lee, W.-T. Tsai, Journal of Power Sources 2007, 166, 590-594.[2] Y. Mo, M. R. Antonio, D. A. Scherson, The Journal of Physical Chemistry B 2000, 104, 9777-9779.

(Invited) Consideration on Gate Stack Formation Processes of Ultrawide Bandgap Ga2O3 with SiO2 Dielectric Layer

MOSFETs on β-Ga2O3 are expected to be a high-efficient and cost-effective alternative option of high-voltage power devices. Taking account of the reliability and the large conduction-band offset against β-Ga2O3, it would be reasonable to employ SiO2 as the gate dieletric. In this study we investigated the effects of post-deposition annealing (PDA) on SiO2/β-Ga2O3 MOS gate stacks, in terms of the MOS electrical characteristics and the band alignment.β-Ga2O3 (001) wafers with ~2×1016 cm-3 n-type doped epitaxial layers were cleaned in diluted HF solution, and SiO2 films were deposited by electron-beam (EB) evaporation of Si in O2 ambient of ~1×10-2 Pa, followed by PDA at various temperatures from 600 to 1000℃ in either O2 or N2 ambient. Au was evaporated as gate electrode to form MOS capacitors. X-ray photoelectron spectroscopy (XPS) was conducted on the stacks with ~3nm-thick SiO2 for the evaluation of band alignment. Ultraviolet photoelectron spectroscopy (UPS) was also employed to determine the band diagram of β-Ga2O3 (001).Nearly-ideal capacitance-voltage characteristics were obtained for the MOS capacitor fabricated with O2-PDA at 1000℃. The interface state density (Dit) determined by conductance method decreased down to ~1010 cm-3 at the energy level of EC−0.2 eV by PDA at higher temperature. The hysteresis width (ΔVhys) of C-V curves was smaller for the samples annealed at higher temperatures. The flatband voltage (VFB) shift after O2-PDA resulted in VFB close to the ideal value estimated from the physical properties of Au and Ga2O3, suggesting that fixed charge density at the interface would be minimized. However, PDA in N2 at 1000℃ resulted in a negative shift of VFB, which indicates the formation of positive fixed charges in the stack. The beneficial influences of O2-PDA on those characteristics suggest that an oxygen deficiency introduced near the interface is one of the origins of interface defect states. It is noteworthy that Ga3d XPS on the surface of Ga2O3 substrate always shows a tailing in lower binding energy side, which is indicating oxygen deficiency on the surface. The intensity of this lower-binding-energy component reduced significantly when a bare-Ga2O3 substate was annealed in O2, however, it did not decrease efficiently even after O2-PDA when the surface was covered with SiO2. This is probably due to the oxygen rearrangement at SiO2/Ga2O3 interface determined by the difference of material properties of those oxides. This fact suggests that the Ga2O3 surface easily forms oxygen vacancies when it is covered with SiO2. This would be the reason why the formation of interface defect states is not suppressed without O2-PDA.Next the band diagram of β-Ga2O3 (001) substrate was investigated by UPS analysis where the energy level of valence band edge referring to the vacuum level was evaluted from the energy difference between minimum (cut-off) and maximum edges of the obtained kinetic energy spectra of photoelectrons. As a result we found the valence band edge of of β-Ga2O3 (001) was ~8.2 eV below the vacuum level, where the influences of O2 annealing at 1000℃ on the valence band edge energy level was limited to the shift within ~0.1eV. This would tell us the valence band offset between SiO2 and Ga2O3 should be around ~1.1eV, and the conduction band offset between them is to be around 2.8-2.9eV, by taking account of the well-reported SiO2 band diagram and assuming the bandgap of β-Ga2O3 as 4.7eV. On the other hand, the valence band offset estimated from the deconvolution of the XPS valence band spectrum for a ~3nm-thick SiO2/β-Ga2O3 stack from the energy edge difference between the deconvoluted spectra corresponding to SiO2 and Ga2O3, was a few hundreds of mV smaller than the above expected value (~1.1eV). This discrepancy is indicating the formation of an interface dipole layer between SiO2 and Ga2O3 with a pair of nagative and positive charges aligned at the interface to cause a shift in the band alignment. The magnitude of such dipole was indicated to be more significant (~0.5eV) for the stack after PDA at 1000℃, whereas it was less (0.2~0.3eV) after PDA at 600℃.In conclusion, we demonstrated that SiO2/β-Ga2O3 (001) MOS capacitors showed nearly-ideal electrical characteristics with significantly reduced interface defect density and small fixed charge density by applying O2-PDA. The band alignment of SiO2/β-Ga2O3 (001) MOS stack was clarified by photoelectron spectroscopy to confirm a very large conduction band offset of the stack, but an influence of the formation of interface dipole layer between SiO2 and Ga2O3 on the band alighment was also indicated.

Optimising the Energy and Resources of Hotel Buildings in Cameroon from a Zero-Carbon Perspective

This article explores the potential for Cameroonian hotel buildings to achieve optimal energy and resource use, contributing to a zero-carbon future. It examines the opportunities that lie in high-performing hotels to achieve the country's ambitious environmental objectives such as reducing its greenhouse gas emissions by 32% by 2035 compared with the reference scenario under the Paris Agreement. Then, the article delves into the existing landscape of green building labels and certifications while focusing on those related on hotels specifically like the Green Key. It acknowledges the various hotels categories present in the country and how their specific characteristics influence resource demands. Additionally, it presents the regulations governing the construction and conversion of hotel establishments. Furthermore, the article discusses strategies for optimising the performance of building resources within the tropical context. These involve improving the insulation of the building envelope, the efficiency of systems and the use of renewable energy sources. The article highlights the importance of the prescriptive approach for assessing and the energy performance approach for optimising building performance, using the accessible EDGE energy simulation software. Those approaches are defined in the Ivorian Inter-ministerial Order No. 134/MPEER/MCLU of 18 November 2020, given that Cameroon and Côte d'Ivoire have some similar climate zones. To achieve the EDGE Zero Carbon level, it is essential to demonstrate minimum savings of 40% of energy, 20% of water and 20% of grey energy in materials, and 100% of energy- related emissions neutralised either by renewable energies or by carbon offsets. Finally, the concept of green financing is introduced, examining its potential to facilitate

Aftermath of Ag embedding on structural, optical, and supercapacitor electrode attributes of USP-grown CuO thin films

Here, ultrasonic spray pyrolysis method (USP) was utilized to produce pure and silver doped copper oxide nanostructures on glass substrates. Thereafter, several characterization techniques were conducted on the grown samples to delve into their morphological, structural, electrochemical, and optical aspects. The mentioned analyses were carried out by performing x-ray photoelectron spectroscopy, scanning electron microscope, X-ray diffraction, electrochemical impedance spectroscopy, galvostatic charge-discharge, cyclic voltammetry, and UV–visible spectroscopy measurements. Thus, the impact of silver impurity doping on the relevant aspects of host material were recorded as well as the features of unspoiled copper oxide films. Accordingly, the samples, as indicated by X-ray diffraction results, possessed (002) preferential plane orientation of copper oxide material along with the crystallite sizes ranging from 52.52 nm to 75.02 nm due to the imperfections caused by the silver doping. The scanning electron microscope images exhibited that the silver doping did not form significant modifications in the host material morphology where nanowire-like structures observed. The presence of the suggested materials in the films was verified by the x-ray photoelectron spectroscopy. Also, the UV–visible spectroscopy measurements detected that optical absorbance edge and bandgap energy values red shifted as a result of the impurity doping. The electrochemical supercapacitors performances of the silver doped copper oxide nanostructured thin films were inspected by using the GCD, EIS, and CV. The silver doped copper oxide films demonstrated a specific capacitance value of 66 F/g at a current density of 1 A/g in 1 M KOH electrolyte. From Nyquist plot, Rs, Rcor, Rpo, Ccor and Cc were obtained as 2.327 × 103 Ω.cm2, 43.63 × 103 Ω.cm2, 4.580 × 103 Ω.cm2, 111.5 × 10-6 S*s^a. cm-2 and 101.1 × 10-6 S*s^a. cm-2, respectively. The results indicated that the electrochemically synthesized the silver doped copper oxide electrodes can be obtained and developed as an alternative electrode material for supercapacitors (SCs).

Successful prediction of tokamak transport in the L-mode regime

A long standing shortfall in the predicted L-mode edge energy transport by reduced quasi-linear models of gyrokinetic turbulent transport has been resolved. The improved model TGLF-SAT2 has higher fidelity to gyrokinetic simulations of the electron-scale contribution to the electron energy transport and the ion-scale flux surface shape dependence of energy transport. The success of TGLF-SAT2 in predicting the L-mode and Ohmic edge profiles is critical to whole pulse simulation and opens the door to prediction of the H-mode power threshold.

L3-edge X-ray spectroscopy of rhodium and palladium compounds.

L3-edge high-energy-resolution fluorescence-detection X-ray absorption near-edge structure (XANES) spectra for palladium and rhodium compounds are presented, with focus on their electronic structures. The data are compared with transmission XANES spectra recorded at the K-edge. A correlation between the absorption edge energy and the metal ion oxidation state is not observed. Despite the different filling of the 4d orbitals and different local coordination, the Rh and Pd compounds show remarkably similar spectral shapes. Calculation of the density of states and of the L3-XANES data reproduce the experimental results.

Simultaneous enhancements of UV-shielding properties and photostability of polyvinyl butyral by incorporation of MWCNTs

Polymer nanocomposites with proper reinforcement can simultaneously enhance both the UV-shielding and optical properties. Such composite materials are being investigated for many commercial applications, including automotive, window screens etc. However, the inherent challenge is maintaining transparency while using reinforcement to get better optical properties and UV resistance. In this study, Multiwall Carbon Nanotubes (MWCNTs) were reinforced for a range of content (0.5, 1.0, 1.5 and 2.0 wt%) in Polyvinyl Butyral (PVB) matrix to synthesize nanocomposite films for UV-shielding purposes. UV-shielding properties are enhanced as compared to PVB for all compositions. We were adding 0.5 wt% MWCNTs to PVB effectively improved UV wavelength blocking and slightly decreased visible light transparency. UV studies were performed in the 190–1100 nm wavelength range and the values of the absorption edge, direct and indirect bandgap energies and Urbach energy were evaluated. When 0.5 wt% MWCNTs were reinforced into the PVB, the direct and indirect bandgaps changed significantly from 4.50 to 4.91 eV–3.01 eV and 4.06 eV respectively, while the Urbach energy increased from 0.73 eV to 1.16 eV. These results show that the UV shielding and photostability of PVB nanocomposite films are significantly changed with the low dispersion of MWCNTs.

A study on attenuation patterns of acoustic waves in waveguide structures with flexural boundaries

This research article investigates the attenuation patterns of acoustic waves within waveguide structures featuring flexural boundaries. By employing advanced methods in vibrations and controls, the study aims to enhance our understanding of waveguide behavior and offer valuable insights for optimizing acoustic wave propagation in diverse applications. The entire waveguide structure is tuned through cooperative interactions involving elastic plates, membranes, and rigid boundary surfaces. The lower boundary of the expansion chamber consists of a rigid plate, with elastic membranes covering the upper surfaces of the cavity. The problem is formulated in terms of transmission and reflection coefficients of the modes, enabling the solution of the scattering problem. Matching acoustic pressure and velocity at the waveguide junction yields the scattering coefficients. The results reveal that the scattering coefficients are intricately influenced by both the geometric characteristics of the waveguide and the frequency of the incident waves. Notably, the first higher-order mode of the cut-off frequency of the waveguide structure corresponds to the frequency at which the dissipation coefficient reaches its maximum value. This research provides valuable insights into the scattering behavior of acoustic waves in waveguide configurations, contributing to the design of acoustic devices and systems. Rigorous support and justification for all aspects of the mode-matching method, including pressure and velocity matching, eigen properties, physical edge conditions, convergence criteria, and energy conservation, are provided through thorough algebraic and numerical analyses, confirming the validity of the solution methodology.

Surface Engineering of BiVO4 Photoanodes for Photoelectrochemical Water Splitting: Recent Advances

AbstractEnergy demand worldwide demands clean, cheap, and renewable energy. Through the use of photoelectrochemical (PEC) conversion, solar energy can be transformed into chemical energy. Bismuth vanadate (BiVO4), a material exhibiting visible light activity, favourable conduction band edge energies, and ease of synthesis, has become increasingly popular in recent years. In BiVO4, charge carriers recombine rapidly, which adversely affects the PEC performance and stability. There have been several strategies developed to mitigate these deficiencies, including novel heterojunctions, doping with metals, coupling with cocatalysts, interface modification and modifying morphology. To achieve the best results, it is required to develop PEC devices with exceptional cost‐to‐efficiency ratios and long‐term durability. This review also examines novel yet commercially viable applications for BiVO4‐based photoanodes. Lastly, we discuss the challenges and perspectives facing PEC water splitting systems based on BiVO4.

Federated learning inspired Antlion based orchestration for Edge computing environment.

Edge computing is a scalable, modern, and distributed computing architecture that brings computational workloads closer to smart gateways or Edge devices. This computing model delivers IoT (Internet of Things) computations and processes the IoT requests from the Edge of the network. In a diverse and independent environment like Fog-Edge, resource management is a critical issue. Hence, scheduling is a vital process to enhance efficiency and allocation of resources properly to the tasks. The manuscript proposes an Artificial Neural Network (ANN) inspired Antlion algorithm for task orchestration Edge environments. Its aim is to enhance resource utilization and reduce energy consumption. Comparative analysis with different algorithms shows that the proposed algorithm balances the load on the Edge layer, which results in lower load on the cloud, improves power consumption, CPU utilization, network utilization, and reduces average waiting time for requests. The proposed model is tested for healthcare application in Edge computing environment. The evaluation shows that the proposed algorithm outperforms existing fuzzy logic algorithms. The performance of the ANN inspired Antlion based orchestration approach is evaluated using performance metrics, power consumption, CPU utilization, network utilization, and average waiting time for requests respectively. It outperforms the existing fuzzy logic, round robin algorithm. The proposed technique achieves an average cloud energy consumption improvement of 95.94%, and average Edge energy consumption improvement of 16.79%, 19.85% in average CPU utilization in Edge computing environment, 10.64% in average CPU utilization in cloud environment, and 23.33% in average network utilization, and the average waiting time decreases by 96% compared to fuzzy logic and 1.4% compared to round-robin respectively.

Correlation of Radiation-Induced Interface Traps With Band Edge Energy Through Band Structure-Based Analysis of Electrostatics of UTB SOI Devices

Correlation of Radiation-Induced Interface Traps With Band Edge Energy Through Band Structure-Based Analysis of Electrostatics of UTB SOI Devices

Energy band engineering in GaS/InS and GaSe/InS van der Waals bilayers by interlayer stacking design and applied vertical electric field - An ab-initio theoretical calculation based approach

In this work, for the first time, an extensive theoretical investigation of the structural and electronic properties of the van der Waals (vdW) bilayer heterostructures of two-dimensional (2D) Gallium Sulphide (GaS)/Indium Sulphide (InS) and Gallium Selenide (GaSe)/Indium Sulphide (InS), is performed using density functional theory calculation. In this context, the effects of natural and artificial interlayer stacking configurations, and externally applied out-of-plane direction electric field are emphasized. The structural, thermal, and dynamic stabilities of individual bilayers are assessed from the cohesive energy/interlayer interaction energy, phonon spectrum, and molecular dynamics evolution, respectively. The effects of the vdW bilayer environment on the in-plane structural parameters like lattice vector, bond length, and bond angle of the constituent monolayers are comprehensively investigated. The electronic properties are estimated from the band edge energy, the density of states, energy bandgap, and interlayer energy band alignment, which are systematically analysed from the interlayer interactions in terms of interlayer distance, out-of-plane charge distribution, and interlayer charge transfer. The key findings demonstrate that the interlayer stacking engineering and applied out-of-plane electric field can induce unique and tailor-made modulations in the overall electronic properties of GaS/InS and GaSe/InS bilayer, which can be exploited in favour of electronic/optoelectronic applications.

An improvement method for pancreas CT segmentation using superpixel-based active contour

Objective. Pancreas is one of the most challenging organs for Computed Tomograph (CT) image automatic segmentation due to its complex shapes and fuzzy edges. It is simple and universal to use the traditional segmentation method as a post-processor of deep learning method for segmentation accuracy improvement. As the most suitable traditional segmentation method for pancreatic segmentation, the active contour model (ACM), still suffers from the problems of weak boundary leakage and slow contour evolution speed. Therefore, a convenient post-processor for any deep learning methods using superpixel-based active contour model (SbACM) is proposed to improve the segmentation accuracy. Approach. Firstly, the superpixels with strong adhesion to edges are used to guide the design of narrowband and energy function. A multi-scale evolution strategy is also proposed to reduce the weak boundary leakage and comprehensively improve the evolution speed. Secondly, using the original image and the coarse segmentation results obtained from deep learning methods as inputs, the proposed SbACM method is used as a post-processor for fine segmentation. Finally, the pancreatic segmentation public dataset TCIA from the National Institutes of Health(NIH, USA) is used for evaluation, and the Wilcoxon Test confirmed that the improvement of proposed method is statistically significant. Main results. (1) the superpixel-based narrowband shape and dynamic edge energy of the proposed SbACM work for boundary leakage reduction, as well as the multi-scale evolution strategy and dynamic narrowband width for the evolution speed improvement; (2) as a post-processor, SbACM can increase the Dice similarity coefficients (DSC) of five typical UNet-based models, including UNet, SS-UNet, PBR UNet, ResDSN, and nnUNet, 2.35% in average and 9.04% in maximum. (3) Based on the best backbone nnUNet, the proposed post-processor performs better than either adding edge awareness or adding edge loss in segmentation enhancement without increasing the complexity and training time of deep learning models. Significance. The proposed SbACM can improve segmentation accuracy with the lowest cost, especially in cases of squeezed fuzzy edges with similar neighborhood , and complex edges.

Effect of bonding description and strain regulation on the conductive transition of Bi semimetal

Due to the differences in the treatment methods of the electron–ion interaction and the critical strain mode of the transition from semimetals to semiconductors, the corresponding strain modulation mechanism in layered bismuth (Bi) crystals remains elusive. In this work, the effects of van der Waals (vdW) correction on the crystal structure and electrical properties of Bi in an equilibrium/strained state are comparatively studied based on the density functional theory. It is found that vdW corrections can better describe the layered crystal and bandgap structure of Bi under equilibrium/strain conditions. With the vdW modification, bismuth can be converted from a semimetal to a semiconductor within a small compression range that is experimentally available. This transition is induced by the transfer of the conduction band minimum and the valence band maximum and is related to the competition of the near-band edge energy state near the Fermi level of bismuth. The present results not only provide guidance for the accurate study of the crystal structure and electronic properties of complex model systems, such as Bi or Bi-based inherently nanostructured materials, but also reveal strain regulation mechanism of Bi and predict its potential application in the semiconductor electronic devices.