bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic multi-color switching using ultrathin vanadium oxide on aluminum-based asymmetric Fabry–Pérot resonant structure
Authors: Saini S. , P Ashok , Verma Amit
Published: January 2024

Vanadium dioxide (VO2) exhibits strong infrared optical switching due to its insulator–metal phase-transition property. However, in the visible wavelengths, its intrinsic optical switching is quite low. Current research explores solutions like multilayering, intricate structural patterning, high thermal budget processes, and costly metals for improved color switching. Nonetheless, the color gamut coverage with these methodologies remains notably limited. This work overcomes these limitations and demonstrates dynamic multi-color switching covering a large color gamut using a simple, unpatterned, ultrathin (∼ λ14, where wavelength λ is taken as 575 nm at the center of the visible spectrum) asymmetric Fabry–Pérot structure of VO2 on aluminum (Al). We use the transfer matrix method to design the VO2/aluminium (Al)/sapphire structure for maximum visible reflectance switching. VO2 films are synthesized using a simple, low thermal budget atmospheric oxidation of vanadium (V). With varying oxidation durations, different colors of the oxidized samples are observed. Consistent and reversible color-switching is observed visibly and in reflectance measurements with the change in temperature from low (RT ∼ 30 °C) to high (HT ∼ 100 °C) or vice versa due to the phase transition property of the VO2 layer in the structure. Compared to the existing studies, this work shows a significant change in chromaticities and covers a large color gamut when plotted on the CIE chromaticity diagram. This work has potential applications in the fields of display, thermochromic structures, and visible camouflage.
Heat and drag reduction on the hypersonic nose with a nexus between active and passive control methods
Authors: Vali Shahab Esmailzadeh , Abbasi Sarallah
Published: January 2024

This study aimed to conduct an active, passive, and hybrid control analysis on the hypersonic drag and thermal reduction. To achieve this, the Reynolds-averaged Navier–Stokes equations were utilized, along with the shear-stress transport turbulence model. To this purpose, the total pressure ratio, the diameter of the opposing jet outlet, and the number of aerodisks are considered as variable parameters. By combining the above parameters, six different configurations were created. Configuration 1 includes a spike, one aerodisk, and an opposing root jet. In configurations 2–5, the number of aerodisks increments and there is no opposing root jet. Configuration 6 includes a spike, four aerodisks, and an opposing root jet. After validation and analysis of the grid independency, the effects of opposing root jet pressure in values of 0.1, 0.3, 0.5, and 0.7, the diameter of opposing root jet outlet (2, 4, and 6 mm), and the number of aerodisks (1, 2, 3, and 4) were examined thoroughly. In comparison with the optimal parametric model in configuration 1, which has a 6 mm outlet diameter and a total pressure ratio of 0.7, the parametric model under consideration exhibits reductions of 9.96% in the overall drag coefficient, 15.03% in the peak pressure, and 20.8% in the peak heat flux. However, configuration 6 has a noticeable and significant advantage in terms of stability of flow fluctuations in front of the nose. Therefore, due to the superiority of configuration 6 in terms of the stability of the flow fluctuations in front of the nose, which is an important factor in the stability of the aircraft, this configuration is the best among the configurations analyzed in this article.
Effects of gamma-irradiation on the superconducting properties of FeTe0.55Se0.45 single crystals grown by self-flux method
Authors: Chauhan Himanshu , Varma G. D.
Published: January 2024

We have investigated the effect of gamma (γ)-irradiation on the structural and superconducting properties of FeTe0.55Se0.45 single crystals grown by the self-flux method. The impact of γ-irradiation on the superconducting transition temperature (TC), critical current density (JC), and vortex pinning mechanism has been systematically studied. The x-ray diffraction study reveals the growth of single crystals along the c-axis. The superconductivity has been confirmed in pristine and γ-irradiated samples through temperature-dependent resistivity (ρ(T)) and magnetization [M(T)] measurements. After irradiation, a slight improvement is observed in the upper critical field Hc2(0) values. The values of thermally activated energy have been calculated and a crossover from a single to collective vortex pinning regime is observed. Additionally, we have analyzed the vortex phase diagrams, revealing a transition from vortex liquid to vortex glass state. Furthermore, the presence of second magnetization peak (SMP) or fishtail effect has been noticed in the M(H) loops, and with increasing temperature, the position of SMP (Hsp) shifts toward lower magnetic field regions. The critical current density has been estimated by Bean's critical state model at different magnetic fields [JC(H)] and temperatures [JC(T)]. The defects through gamma-irradiation lead to a significant threefold increase in JC compared to pristine samples in self-field and at 2 K. The pinning mechanisms have been explained using collective pinning theory and the Dew-Hughes model by analyzing the normalized pinning force density. Our analysis indicates that δl-pinning is dominant and point defects are present in all the samples.
Exciton and biexciton transient absorption spectra of CdSe quantum dots with varying diameters
Authors: Shulenberger Katherine E. , Sherman Skylar J. , Jilek Madison R. , Keller Helena R. , Pellows Lauren M. , Dukovic Gordana
Published: January 2024

Transient absorption (TA) spectroscopy of semiconductor nanocrystals (NCs) is often used for excited state population analysis, but recent results suggest that TA bleach signals associated with multiexcitons in NCs do not scale linearly with exciton multiplicity. In this manuscript, we probe the factors that determine the intensities and spectral positions of exciton and biexciton components in the TA spectra of CdSe quantum dots (QDs) of five diameters. We find that, in all cases, the peak intensity of the biexciton TA spectrum is less than 1.5 times that of the single exciton TA spectrum, in stark contrast to a commonly made assumption that this ratio is 2. The relative intensities of the biexciton and exciton TA signals at each wavelength are determined by at least two factors: the TA spectral intensity and the spectral offset between the two signals. We do not observe correlations between either of these factors and the particle diameter, but we find that both are strongly impacted by replacing the native organic surface-capping ligands with a hole-trapping ligand. These results suggest that surface trapping plays an important role in determining the absolute intensities of TA features for CdSe QDs and not just their decay kinetics. Our work highlights the role of spectral offsets and the importance of surface trapping in governing absolute TA intensities. It also conclusively demonstrates that the biexciton TA spectra of CdSe QDs at the band gap energy are less than twice as intense as those of the exciton.
Phonon diffraction and interference using nanometric features
Authors: Desmarchelier Paul , Nikidis Efstratios , Anufriev Roman , Tanguy Anne , Nakamura Yoshiaki , Kioseoglou Joseph , Termentzidis Konstantinos
Published: January 2024

Phonon diffraction and interference patterns are observed at the atomic scale, using molecular dynamics simulations in systems containing crystalline silicon and nanometric obstacles, such as voids or amorphous inclusions. The diffraction patterns due to these nano-architectured systems of the same scale as the phonon wavelengths are similar to the ones predicted by the simple Fresnel–Kirchhoff integral. The few differences between the two approaches are attributed to the nature of the interface and the anisotropy of crystalline silicon. Based on the wave description of phonons, these findings can provide insights into the interaction of phonons with nano-objects and can have applications in smart thermal energy management.
Microwave absorption properties of oriented Sm2Fe14BHx/polyurethane with planar anisotropy
Authors: Yang Shengyu , Sheng Yanfei , Wu Wei , Xu Zhibiao , Wu Peng , Dong Yiwen , Wang Tao , Li Fashen , Qiao Liang
Published: January 2024

Realization of microwave-absorbing materials with “small thickness, light weight, broad bandwidth, and low reflectivity” is an invariable topic. In this paper, Sm2Fe14BHx/polyurethane (SFBH/PU) composites with planar anisotropy were prepared by reduction–diffusion (R/D) and water bath hydrogenation (WBH) process. A minimum reflection loss (RL) value reaches −59.7 dB at the perfect matching frequency of 13.79 GHz with a thickness of only 1.035 mm. Compared with unhydrogenated SFB, the bandwidth and reflectivity are significantly improved. It is mainly attributed to the fact that introduction of hydrogen atoms effectively modulates the electromagnetic parameters and increases the Snoek limit ((μi−1)fr), which leads to the improvement of the high-frequency microwave absorption performance. In addition, the bandwidth equation is derived and simplified from the perspective of the reflected wave at the interface, which is in good agreement with the measured results.
Access to general practice for preventive health care for people who experience severe mental illness in Sydney, Australia: a qualitative study
Authors: Spooner Catherine , O’Shea Peri , Fisher Karen R. , Harris-Roxas Ben , Taggart Jane , Bolton Patrick , Harris Mark F.
Published: January 2024

Background People with lived experience of severe mental illness (PWLE) live around 20 years less than the general population. Most deaths are due to preventable health conditions. Improved access to high-quality preventive health care could help reduce this health inequity. This study aimed to answer the question: What helps PWLE access preventive care from their GP to prevent long-term physical conditions? Methods Qualitative interviews (n = 10) and a focus group (n = 10 participants) were conducted with PWLE who accessed a community mental health service and their carers (n = 5). An asset-based framework was used to explore what helps participants access and engage with a GP. A conceptual framework of access to care guided data collection and analysis. Member checking was conducted with PWLE, service providers and other stakeholders. A lived experience researcher was involved in all stages of the study. Results PWLE and their carers identified multiple challenges to accessing high-quality preventive care, including the impacts of their mental illness, cognitive capacity, experiences of discrimination and low income. Some GPs facilitated access and communication. Key facilitators to access were support people and affordable preventive care. Conclusion GPs can play an important role in facilitating access and communication with PWLE but need support to do so, particularly in the context of current demands in the Australian health system. Support workers, carers and mental health services are key assets in supporting PWLE and facilitating communication between PWLE and GPs. GP capacity building and system changes are needed to strengthen primary care’s responsiveness to PWLE and ability to engage in collaborative/shared care.
Microscopic interactions control a structural transition in active mixtures of microtubules and molecular motors
Authors: Najma Bibi , Wei Wei-Shao , Baskaran Aparna , Foster Peter J. , Duclos Guillaume
Published: January 2024

Microtubules and molecular motors are essential components of the cellular cytoskeleton, driving fundamental processes in vivo, including chromosome segregation and cargo transport. When reconstituted in vitro, these cytoskeletal proteins serve as energy-consuming building blocks to study the self-organization of active matter. Cytoskeletal active gels display rich emergent dynamics, including extensile flows, locally contractile asters, and bulk contraction. However, it is unclear how the protein–protein interaction kinetics set their contractile or extensile nature. Here, we explore the origin of the transition from extensile bundles to contractile asters in a minimal reconstituted system composed of stabilized microtubules, depletant, adenosine 5′-triphosphate (ATP), and clusters of kinesin-1 motors. We show that the microtubule-binding and unbinding kinetics of highly processive motor clusters set their ability to end-accumulate, which can drive polarity sorting of the microtubules and aster formation. We further demonstrate that the microscopic time scale of end-accumulation sets the emergent time scale of aster formation. Finally, we show that biochemical regulation is insufficient to fully explain the transition as generic aligning interactions through depletion, cross-linking, or excluded volume interactions can drive bundle formation despite end-accumulating motors. The extensile-to-contractile transition is well captured by a simple self-assembly model where nematic and polar aligning interactions compete to form either bundles or asters. Starting from a five-dimensional organization phase space, we identify a single control parameter given by the ratio of the different component concentrations that dictates the material-scale organization. Overall, this work shows that the interplay of biochemical and mechanical tuning at the microscopic level controls the robust self-organization of active cytoskeletal materials.
Self-organized BMP signaling dynamics underlie the development and evolution of digit segmentation patterns in birds and mammals
Authors: Grall Emmanuelle , Feregrino Christian , Fischer Sabrina , De Courten Aline , Sacher Fabio , Hiscock Tom W. , Tschopp Patrick
Published: January 2024

Repeating patterns of synovial joints are a highly conserved feature of articulated digits, with variations in joint number and location resulting in diverse digit morphologies and limb functions across the tetrapod clade. During the development of the amniote limb, joints form iteratively within the growing digit ray, as a population of distal progenitors alternately specifies joint and phalanx cell fates to segment the digit into distinct elements. While numerous molecular pathways have been implicated in this fate choice, it remains unclear how they give rise to a repeating pattern. Here, using single-cell RNA sequencing and spatial gene expression profiling, we investigate the transcriptional dynamics of interphalangeal joint specification in vivo. Combined with mathematical modeling, we predict that interactions within the BMP signaling pathway—between the ligand GDF5, the inhibitor NOGGIN, and the intracellular effector pSMAD—result in a self-organizing Turing system that forms periodic joint patterns. Our model is able to recapitulate the spatiotemporal gene expression dynamics observed in vivo, as well as phenocopy digit malformations caused by BMP pathway perturbations. By contrasting in silico simulations with in vivo morphometrics of two morphologically distinct digits, we show how changes in signaling parameters and growth dynamics can result in variations in the size and number of phalanges. Together, our results reveal a self-organizing mechanism that underpins amniote digit segmentation and its evolvability and, more broadly, illustrate how Turing systems based on a single molecular pathway may generate complex repetitive patterns in a wide variety of organisms.
White matter plasticity during second language learning within and across hemispheres
Authors: Wei Xuehu , Gunter Thomas C. , Adamson Helyne , Schwendemann Matthias , Friederici Angela D. , Goucha Tomás , Anwander Alfred
Published: January 2024

Adult second language (L2) learning is a challenging enterprise inducing neuroplastic changes in the human brain. However, it remains unclear how the structural language connectome and its subnetworks change during adult L2 learning. The current study investigated longitudinal changes in white matter (WM) language networks in each hemisphere, as well as their interconnection, in a large group of Arabic-speaking adults who learned German intensively for 6 mo. We found a significant increase in WM-connectivity within bilateral temporal-parietal semantic and phonological subnetworks and right temporal-frontal pathways mainly in the second half of the learning period. At the same time, WM-connectivity between the two hemispheres decreased significantly. Crucially, these changes in WM-connectivity are correlated with L2 performance. The observed changes in subnetworks of the two hemispheres suggest a network reconfiguration due to lexical learning. The reduced interhemispheric connectivity may indicate a key role of the corpus callosum in L2 learning by reducing the inhibition of the language-dominant left hemisphere. Our study highlights the dynamic changes within and across hemispheres in adult language-related networks driven by L2 learning.
Longevity, demographic characteristics, and socio-economic status are linked to triiodothyronine levels in the general population
Authors: Lawton Ralph I. , Sabatini Bernardo L. , Hochbaum Daniel R.
Published: January 2024

The hypothalamic–pituitary–thyroid (HPT) axis is fundamental to human biology, exerting central control over energy expenditure and body temperature. However, the consequences of normal physiologic HPT-axis variation in populations without diagnosed thyroid disease are poorly understood. Using nationally representative data from the 2007 to 2012 National Health and Nutrition Examination Survey, we explore relationships with demographic characteristics, longevity, and socio-economic factors. We find much larger variation across age in free T3 than other HPT-axis hormones. T3 and T4 have opposite relationships to mortality: free T3 is inversely related and free T4 is positively related to the likelihood of death. Free T3 and household income are negatively related, particularly at lower incomes. Finally, free T3 among older adults is associated with labor both in terms of unemployment and hours worked. Physiologic TSH/T4 explain only 1.7% of T3 variation, and neither are appreciably correlated to socio-economic outcomes. Taken together, our data suggest an unappreciated complexity of the HPT-axis signaling cascade broadly such that TSH and T4 may not be accurate surrogates of free T3. Furthermore, we find that subclinical variation in the HPT-axis effector hormone T3 is an important and overlooked factor linking socio-economic forces, human biology, and aging.
Plasma properties and discharging of dust particles in an Ar/C2H2 plasma afterglow
Authors: Denysenko I B , Mikikian M , Azarenkov N A
Published: January 2024

A global (volume averaged) model is developed for an argon-acetylene plasma afterglow. The model is used to study the electron and ion densities, electron temperature and densities of argon metastable atoms in the afterglow plasma. The calculated time dependence for the electron density is found to be in agreement with the existing experimental data. These calculated plasma characteristics are used to investigate the dust charge distribution function (DCDF) for particles with radii of 10–200 nm. The DCDF is found by solving numerically the master equation describing dust discharging as a one-step stochastic process and is also calculated as a Gaussian distribution with mean dust charge and variance, which are functions of time. The time dependences for mean dust charge, variance and dust charging time are obtained and analysed. If the electronegativity of the plasma in the steady-state is low, negative ions do not affect much discharging of dust particles in the afterglow, while at large electronegativity their role is essential. In the case of low electronegativity, discharging of dust particles is mainly due to deposition of positive ions with small and moderate masses (less than the mass of C10H6
+ ions). Increasing electronegativity, the effect of heavy positive ions on dust discharging in the late afterglow is important. Secondary electron emission from dust surface at collisions of metastable atoms appears to be negligible.
Elastocaloric effect with plateau-shape adiabatic temperature change in Ni–Co–Fe–Ga strain glass alloy
Authors: Cheng Fei , Dong Tianjiao , Wang Yu , Liang Chuanxin , Guo Yuanjun , Liu Chang , Zhai Qiang , Wang Dong , Yang Sen , Ren Xiaobing
Published: January 2024

Elastocaloric effect (eCE) is a very promising candidate for using in non-vapor compression refrigeration, which is highly efficient and eco-friendly. However, designing elastocaloric alloys with a wide reversible working temperature window at low stress is still challenging. In this work, the transition behaviors, microstructural evolutions and the eCE of a series of Ni55−x
Co
x
Fe19Ga27 alloys were systematically studied. The Ni44Co11Fe19Ga27 strain glass (STG) alloy exhibits a plateau-shape eCE, which show an average temperature change (ΔT
Adia) of ∼2.3 K covering a wide reversible working temperature range (ΔT
rev) from 135 K to 200 K. The unique eCE behavior of STG stems from that the random distribution of local free energy of the martensite coupled with the small transition energy barriers, which leads to a wide transition-temperature range and decreased hysteresis. The Ni44Co11Fe19Ga27 STG alloy achieves a balance between the considerable ΔT
Adia and wide ΔT
rev, resulting in an optimal comprehensive elastocaloric performance and contributing to improving the efficiency of elastocaloric refrigeration.
Experimental study on microwave ignition of ADN-based liquid propellant droplets doped with alumina nanoparticles
Authors: Hou Yangyang , Yu Yusong , Li Yong , Liu Xuhui , Yao Zhaopu , Zhang Shaoyun
Published: January 2024

The objective of this study was to investigate the effects of alumina (Al2O3) nanoparticles on the evaporation, ignition, and combustion of ammonium dinitramide (ADN)-based liquid propellants under microwave irradiation. The alumina nanoparticles were uniformly dispersed in the ADN-based propellant at mass ratios of 25, 50, and 100 ppm, resulting in the formation of nano-fuel. Experimental methods were employed to examine the influence of alumina nanoparticles on the micro-explosion intensity, ignition delay time, combustion duration, critical ignition power, and emission spectra of the nano-fuel droplets. The experimental findings revealed a significant increase in the intensity and frequency of micro-explosion events with the inclusion of alumina nanoparticles. Compared to pure propellant, the nano-fuel with a concentration of 25 ppm exhibited a reduction of 33.5% in ignition delay time and a decrease of 9% in critical ignition power. Furthermore, the emission spectra characteristics of the pure propellant and nano-fuel were analyzed, indicating that alumina nanoparticles notably enhanced the thermal decomposition of ADN and the exothermic reaction of methanol combustion. This study provides an effective approach to improve the evaporation and combustion performance of ADN-based liquid propellants, offering potential possibilities for future applications.
A discriminative multiscale feature extraction network for facial expression recognition in the wild
Authors: Wen Xiaoyu , Zhou Juxiang , Gan Jianhou , Luo Sen
Published: January 2024

Driven by advancements in deep learning technologies, substantial progress has been achieved in the field of facial expression recognition over the past decade, while challenges remain brought about by occlusions, pose variations and subtle expression differences in unconstrained (wild) scenarios. Therefore, a novel multiscale feature extraction method is proposed in this paper, that leverages convolutional neural networks to simultaneously extract deep semantic features and shallow geometric features. Through the mechanism of channel-wise self-attention, prominent features are further extracted and compressed, preserving advantageous features for distinction and thereby reducing the impact of occlusions and pose variations on expression recognition. Meanwhile, inspired by the large cosine margin concept used in face recognition, a center cosine loss function is proposed to avoid the misclassification caused by the underlying interclass similarity and substantial intra-class feature variations in the task of expression recognition. This function is designed to enhance the classification performance of the network through making the distribution of samples within the same class more compact and that between different classes sparser. The proposed method is benchmarked against several advanced baseline models on three mainstream wild datasets and two datasets that present realistic occlusion and pose variation challenges. Accuracies of 89.63%, 61.82%, and 91.15% are achieved on RAF-DB, AffectNet and FERPlus, respectively, demonstrating the greater robustness and reliability of this method compared to the state-of-the-art alternatives in the real world.
Dynamics of interfacial charge transfer between CsPbBr3 perovskite nanocrystals and molecular acceptors for photodetection application
Authors: Mamgain Swati , Yella Aswani
Published: January 2024

Perovskite nanocrystals (NCs) recently emerged as a suitable candidate for optoelectronic applications because of its simplistic synthesis approach and superior optical properties. For better device performance, the effective absorption of incident photons and the understanding of charge transfer (CT) process are the basic requirements. Herein, we investigate the interfacial charge transfer dynamics of CsPbBr3 NCs in the presence of different molecular acceptors; 7,7,8,8-Tetracyanoquinodimethane (TCNQ) and 11,11,12,12 tetracyanonaphtho-2,6-quinodimethane (TCNAQ). The vivid change in CT dynamics at the interfaces of NCs and two different molecular acceptors (TCNQ and TCNAQ) has been observed. The results demonstrate that the ground state complex formation in the presence of TCNQ acts as additional driving force to accelerate the charge transfer between the NCs and molecular acceptor. Moreover, this donor (NCs)-acceptor (TCNQ, TCNAQ) system results in the higher absorption of incident photons. Finally, the photo detector based on CsPbBr3-TCNQ system was fabricated for the first time. The device exhibited a high on–off ratio (104). Furthermore, the CsPbBr3-TCNQ photodetector shows a fast photoresponse times of 180 ms/110 ms (rise/decay time) with a specific detectivity (D*) of 5.2 × 1011 Jones. The simple synthesis and outstanding photodetection abilities of this perovskite NCs-molecular acceptor system make them potential candidates for optoelectronic applications.
Silicene growth mechanisms on Au(111) and Au(110) substrates
Authors: Barboza Alexandre M , da Silva-Santos José A , Aliaga Luis C R , Bastos Ivan N , Faria Daiara F
Published: January 2024

Despite the remarkable theoretical applications of silicene, its synthesis remains a complex task, with epitaxial growth being one of the main routes involving depositing evaporated Si atoms onto a suitable substrate. Additionally, the requirement for a substrate to maintain the silicene stability poses several difficulties in accurately determining the growth mechanisms and the resulting structures, leading to conflicting results in the literature. In this study, large-scale molecular dynamics simulations are performed to uncover the growth mechanisms and characteristics of epitaxially grown silicene sheets on Au(111) and Au(110) substrates, considering different temperatures and Si deposition rates. The growth process has been found to initiate with the nucleation of several independent islands homogeneously distributed on the substrate surface, which gradually merge to form a complete silicene sheet. The results consistently demonstrate the presence of a buckled silicene structure, although this characteristic is notably reduced when using an Au(111) substrate. Furthermore, the analysis also focuses on the quality and growth mode of the silicene sheets, considering the influence of temperature and deposition rate. The findings reveal a prevalence of the Frank–van der Merwe growth mode, along with diverse forms of defects throughout the sheets.
Microfabrication of piezoelectric MEMS based on thick LiNbO3 single-crystal films
Authors: Ouhabaz Merieme , Belharet Djaffar , Micard Quentin , Costanza Mario , Giuffrida Giada , Bartasyte Ausrine , Trigona Carlo , Margueron Samuel
Published: January 2024

Microfabrication procedure of piezoelectric micro electro-mechanical systems based on 5 μm thick LiNbO3 films on SiO2/Si substrate at wafer scale including deep dry etching of thick LiNbO3 films by implementing pulsed mode of Ar/SF6 gas was developed. In particular, two (YXlt)/128°/90°LiNbO3-Si cantilevers with tip mass were fabricated and characterized in terms of resonance frequency (511 and 817 Hz), actuation and acceleration sensing capabilities. The quality factor of 89.5 and the electromechanical coupling of 4.8% were estimated from measured frequency dependency of electrical impedance, fitted by using Butterworth–Van Dyke model. The fabricated piezoelectric micro-electro-mechanical systems have demonstrated highly linear displacement with good sensitivity (5.28 ± 0.02 μm V−1) as a function of applied voltage and high sensitivity to vibrations of 667 mV g−1 indicating a suitability of the structure for actuation purposes and for acceleration or frequency sensing with high precision, respectively.
Data-driven plasma science based plasma etching process design in OLED mass production referring to PI-VM
Authors: Park Seolhye , Seong Jaegu , Park Yoona , Noh Yeongil , Lee Haneul , Bae Namjae , Roh Ki-Baek , Seo Rabul , Song Bongsub , Kim Gon-Ho
Published: January 2024

The production efficiencies of organic light emitting diode (OLED) displays and semiconductor manufacturing have been dramatically improving with the help of plasma physics and engineering technology by utilizing a process monitoring methodology based on physical domain knowledge. This domain knowledge consists of plasma-heating and sheath physics, plasma chemistry, and plasma-material surface reaction kinetics. They were applied to the plasma information based virtual metrology (PI-VM) algorithm with the plasma diagnostics and noticeably enhanced process prediction performance by parameterizing plasma information (PI) in various processes of OLED display and semiconductor manufacturing fabs. PI-VM has shown superior process prediction accuracy, which can trace the states of processing plasmas as an application of data-driven plasma science compared to the classical statistics and machine learning-based virtual metrologies; thus, various plasma processes have been managed and controlled with the help of the PI-VM models. More than this, we have adopted the PI-VM model to optimize the patterning architecture and plasma processes simultaneously. The best combination of the etching pattern structure and plasma condition was adjustable based on the detailed understanding of the angular distribution of sputtered atoms from the etching target surface and their interaction with the plasma sheath based on the PI-VM modeling for etching profile failure prediction.
Improvement of core heat transport in NBI plasmas of heliotron J using high-intensity gas puffing
Authors: Wang C , Kobayashi S , Nagasaki K , Qiu D , Luo M , Zhang P , Watanabe K Y , Seki R , Miyashita A , Kondo Y , Inagaki S , Kin F , Minami T , Kado S , Ohshima S , Konoshima S , Mizuuchi T , Okada H
Published: January 2024

Controlling the heat transport profile is important for high performance in magnetically confined fusion plasmas. In this study, improved electron heat transport was achieved in neutral beam injection plasmas by applying high-intensity gas puffing (HIGP) on a stellarator/heliotron device called Heliotron J. Compared with conventional gas puffing (GP) fueling discharge, a higher and more peaked electron temperature profile was obtained, and the core ion temperature was slightly higher but similarly shaped. Using similar parameters, the electron density profile for HIGP remained similar and differed from the hollow density profile observed in electron cyclotron heating-eIBT plasma. Transport analysis using the FIT3D and TR-snap codes showed a clear reduction in the effective electron heat transport coefficient in the plasma core region. However, more detailed experiments are required to understand the mechanisms underlying this improvement fully.
Oxygen reduction through specific surface area control of AlN powder for AlN single-crystal growth by physical vapor transport
Authors: Wang Ze-Ren , Zhu Xing-Yu , Zhao Qi-Yue , Wu Jie-Jun , Yu Tong-Jun
Published: January 2024

In the physical vapor transport (PVT) growth of AlN, re-oxidation of aluminum nitride (AlN) source powder happening in the process of setting seed crystal into crucible seems to be unavoidable. This process introduces oxygen just before AlN growth and has a significant impact on the crystal quality. In this paper, a high and low-temperature alternative sintering method (HLAS) is proposed based on the idea of specific surface area control to reduce the re-oxidation of AlN source powder. This method introduces cyclic sintering between 1500 °C and 1900 °C to the conventional three-step treatment repeatedly, which utilizes possible phase-transition along with the processes of powder sintering back and forth to increase the particle size and decrease the specific surface area significantly. The scanning electron microscope and Brunauer, Emmett, and Teller results showed that the specific surface area of AlN powder treated with the HLAS method can be reduced to one-third of that with the conventional method. Thus, the secondary ion mass spectrometry confirmed the reduction of oxygen impurity in AlN single-crystals to a good level of 1.5 × 1017 cm−3. It is clear that this HLAS process is an effective way of controlling the specific surface area of AlN source powder, which contributes to the suppression of oxygen influence on PVT-AlN growth.
Bi-directional threshold voltage shift of amorphous InGaZnO thin film transistors under alternating bias stress
Authors: Kim Hyunjin , Kim Beom Jung , Oh Jungyeop , Choi Sung-Yool , Park Hamin
Published: January 2024

Amorphous InGaZnO (a-IGZO) has attracted a lot of attention as a high-mobility channel material for thin film transistors (TFTs). However, the instability mechanism involving threshold voltage and subthreshold swing (SS) in a-IGZO TFTs still requires further investigation. In this study, we investigated the electrical instability of amorphous InGaZnO TFTs subjected to alternating positive and negative bias stresses. Based on the respective mechanisms under positive and negative bias stresses, including ionization and spatial movement of oxygen vacancies, bi-directional threshold voltage shifts were observed under alternating bias stress. The SS values vary with the bias stress polarity, reflecting the presence and distribution of oxygen vacancies. Our findings reveal a complementary mechanism based on oxygen vacancies, elucidating the behavior under complex bias stress schemes and extending our understanding of instability mechanisms beyond monotonous bias stress.
Strain engineering and strain measurement by spring tethers on suspended epitaxial GaN-on-Si photonic crystal devices
Authors: Wang Jun , Houdré Romuald
Published: January 2024

Suspended epitaxial gallium nitride (GaN) on silicon (Si) photonic crystal devices suffer from large residual tensile strain, especially for long waveguides, because fine structures tend to crack due to large stress. By introducing spring-like tethers, designed by the combination of a spring network model and finite element method simulations, the stress at critical locations was mitigated and the cracking issue was solved. Meanwhile, the tethered-beam structure was found to be potentially a powerful method for high-precision strain measurement in tensile thin films, and in this case, a strain of

2.27
(
±
0.01
)
×

10

−
3

was measured in 350 nm epitaxial GaN-on-Si.
Dual-directional SCR device with dual-gate controlled mechanism for ESD protection in photoelectric chip
Authors: Liu Yujie , Wang Yang , Yang Jian , Jin Xiangliang
Published: January 2024

The dual-directional silicon-controlled rectifier (DDSCR) is an electrostatic discharge (ESD) protection device. It can provide positive and negative ESD surge paths and has excellent robustness. However, industry-level sensors operating in strong electromagnetic interference environments impose higher reliability requirements on photoelectric chips. This paper proposed a novel DDSCR with a dual-gate controlled mechanism. By incorporating the gate diode triggering and the gate field modulation mechanism into the traditional DDSCR, and further utilizing additional parasitic bipolar junction transistors (BJTs) for diversion, the proposed device exhibits significantly improved ESD characteristics. Measurement results indicate that, compared to DDSCR, the proposed device exhibits a 27.5% reduction in trigger voltage (Vt1
), a 96.1% improvement in holding voltage (Vh
), and achieves an equivalent human body model protection level of 11.45 kV, demonstrating exceptional design area efficiency. The experimental findings validate the effectiveness of the proposed device in 5 V photoelectric chip applications.
Flexural behaviour of cementitious composites embedded with 3D printed re-entrant chiral auxetic meshes
Authors: Zahra Tatheer , Asad Mohammad , Thamboo Julian
Published: January 2024

3D printed auxetic metamaterials can be used to make high performing cementitious composites to strengthen existing structures and elements due to their negative Poisson’s ratio behaviour and high energy absorbing characteristics. In this paper, three different re-entrant chiral auxetic (RCA) meshes of various cell geometries and orientations were developed by 3D printing them using poly-lactic acid (PLA) and thermoplastic polyurethane (TPU) filament. The developed meshes were tested under out-of-plane flexure to study their load carrying capacity, ductility and energy absorption characteristics, especially to characterise the best cell orientation. The horizontal cells provided enhanced load carrying and energy absorption characteristics for all three cell geometries for both materials. These RCA meshes were then embedded into low and high strength premix cement mortar matrices to develop auxetic cementitious composites (ACCs). In total, 42 ACC specimens were casted and tested under flexural loading. The results were studied in terms of their failure patterns, load-displacement responses, flexural capacities, ductility and energy absorption. The RCA meshes made of PLA filament showed limited capacity and energy absorption as compared to RCA meshes made of TPU filament due to extended flexibility and resilience provided by TPU meshes. The RCA meshes with a denser cell structure exhibited highest flexural capacity and effective energy absorption of 14 700 kJ m−2 for TPU-RCA mesh embedded into high strength cement mortar matrix. The results obtained in this study have enabled to understand the flexural behaviour of cementitious composites embedded with 3D printed auxetic lattices and to strengthen the existing structures.
Design of auxetic cellular structures for in-plane response through out-of-plane actuation of stimuli-responsive bridge films
Authors: Chandramouli Anirudh , Rapaka Sri Datta , Annabattula Ratna Kumar
Published: January 2024

In this work, we propose novel designs of cellular structures exhibiting unconventional in-plane actuation responses to external stimuli. We strategically introduce stimuli-responsive bilayer bridge films within conventional honeycombs to achieve the desired actuation. The films are incorporated such that, in response to an external field (thermal, electric, chemical, etc), the bridge film bends out-of-plane, activating the honeycomb in the plane. The conventional out-of-plane deformation of the bridge film can lead to interesting and unconventional actuation in the plane. An analytical model of this coupled unit cell behavior is developed using curved beam theory, and the model is validated against finite element simulations. Several applications of such designs are presented. Unit cell architectures exhibiting both positive and negative macroscopic actuation are proposed, and the criterion for achieving such actuation is derived analytically. Furthermore, we demonstrate that by altering the topology, unidirectional and bidirectional negative actuation can be achieved. We also propose designs that result in the negative actuation of the structure with both monotonically increasing and monotonically decreasing stimuli. Finally, by combining two macroscopic structures with positive and negative actuation, we design actuators/sensors that bend in the plane in response to a stimulus.
In-vivo studies on PDMS-embedded fiber Bragg grating based smart laparoscopic grasper
Authors: Chandana H , Chalackal Archana Trikkaikuth , Subbaraj Pravin Kumar , Kanakambaran Srijith
Published: January 2024

Minimally invasive surgeries are often associated with the risk of tissue damage due to improper force feedback mechanisms to notify surgeons regarding the force thresholds. This work evaluates the grasping forces during tissue handling to offer force feedback and assist surgeons during tissue manipulation. A polydimethylsiloxane embedded fiber Bragg grating sensor was developed and integrated at the tip of the laparoscopic grasper to measure the grasping force. Simulation studies have been performed to investigate the performance of the embedded grating sensor. The sensitivity of the sensor embedded within polydimethylsiloxane was found to be around 31.4 pm N−1 which was better compared to that of a silicone embedded counterpart. In-vivo studies were performed with soft tissue phantoms prepared with silicone rubber interspersed with different concentrations of mineral oil. Experimental results reveal a decrease in the peak wavelength shift as the tissue gets softer which is consistent with the nature of grasping force for softer tissues.
Very strong levitation force and stability achieved with a large MgB2 superconductor disc
Authors: Xing Yiteng , Russo Giacomo , Ribani Pier Luigi , Morandi Antonio , Bernstein Pierre , Rossit Julie , Lemonnier Sebastien , Delorme Fabian , Noudem Jacques
Published: January 2024

This rapid communication highlights a remarkable achievement obtained with a 120 mm diameter large cylindrical MgB2 bulk: the measurement of magnetic levitation forces up to 700 N at 20 K, levitation being stable up to levitation forces exceeding 400 N. The investigated sample, which has one of the largest dimensions reported in the literature, was fabricated using the unconventional spark plasma sintering technique. This method is known as one of the most efficient methods for producing dense MgB2 samples. This breakthrough holds significant potential for advancing high-performance levitation systems and superconducting applications, including high-speed transportation systems and magnetic bearings.
Review of materials for HTS magnet impregnation
Authors: Feldman Joshua , Stautner Wolfgang , Kovacs Christopher , Miljkovic Nenad , Haran Kiruba S
Published: January 2024

Construction of high-temperature superconducting magnets typically involves impregnation of a coil in a liquid medium, such as epoxy, which is then solidified. This impregnation provides mechanical integrity to the magnet and facilitates heat transfer. The choice of material used for impregnation requires careful consideration of the material properties and the performance requirements in order to ensure optimal magnet operation. This paper offers a comprehensive educational resource on this topic, reviewing the literature available on materials for magnet impregnation. A detailed explanation of considerations for selecting an impregnation material are presented, along with a review of several types of materials and their characteristics as reported in the literature. The materials are compared, and their suitability to different applications is discussed. Topics for future research are suggested.
A novel method for temperature self-sensing of reinforced concrete
Authors: Ozturk Murat
Published: January 2024

In this work, a temperature-sensing reinforced concrete has been developed using capacitance and resistance-based measurements. No additives are required for self-temperature sensing. Steel bars in the reinforced concrete are used as electrodes. To determine the self-sensing properties of the reinforced concrete specimen, it is cooled from room temperature to −9 °C and heated from room temperature until it reaches 50.9 °C. The varying capacitance and resistance values of the sample concerning temperature changes are evaluated. Fractional changes in capacitance and resistance upon cooling are 80.6% and 276%, respectively. Fractional changes in capacitance and resistance upon warming are 60% and 35%, respectively. Temperature coefficients of capacitance and resistance (fractional change in capacitance and resistance per unit change in temperature) upon cooling are 2.5 × 10−2/°C and 8.6 × 10−2/°C, while upon warming they are 2.2 × 10−2/°C and 1.3 × 10−2/°C. This study aims to use capacitance and resistance-based sensing techniques to detect temperature variations in steel-reinforced concrete structures. Further studies are planned to investigate various factors such as moisture, porosity, aggregate proportion, and water content that affect the self-temperature-sensing performance of reinforced concrete.
Electronic, optical, and thermoelectric properties of vacancy-ordered double perovskite K2SnX6 (X = Cl, Br, I) from first-principle calculations
Authors: Zikem A , Baaziz H , Ghellab T , Charifi Z , Soyalp F
Published: January 2024

The present study explores the structural, optoelectronic, and thermoelectric properties of potassium tin halide vacancy-ordered double perovskites K2SnX6 (X = Cl, Br, and I) in their stable monoclinic phase. Our study uses first-principles calculations based on density functional theory (DFT). Electronic band structures reveal direct band gaps for K2SnCl6 and K2SnBr6, while K2SnI6 exhibits an indirect band gap. Theoretical computations utilising the modified Becke-Johnson potential (mBJ-GGA) demonstrate that the optical band gaps of K2SnCl6, K2SnBr6, and K2SnI6 decrease in the following order: 2.581 eV, 1.707 eV, and 4.126 eV, respectively. These values render the materials suitable for photovoltaic applications. Analysis of dielectric functions, absorption coefficients, and refractive indices demonstrates their potential as light-absorbing materials. We evaluate the thermoelectric properties, including electronic and lattice thermal conductivities, Seebeck coefficients, and power factors, which lead to favorable thermoelectric performance. The maximum figure of merit (ZT) values of 0.58, 0.69, and 0.50 are achieved for K2SnCl6, K2SnBr6, and K2SnI6, respectively, at 500 K. These findings highlight the potential of these materials for applications in solar cells and thermoelectric devices, emphasising their effectiveness at elevated temperatures.