Isolated metal-coordinated nitrogen embedded carbon (M–N–C) materials are potential alternatives to noble catalysts for oxygen evolution reaction (OER), and the activity of metal centers can be further modulated by adjusting the coordination environment. Recently, experimental studies have shown that the aggregation of metal atoms into small clusters or particles is inevitable during the high temperature pyrolysis, while the influences of metal clusters on the OER activity of single metal atoms in M–N–C are unclear. Herein, taking Ni-based single atom as examples, the interaction characters of NiN4 doped graphene (NiN4-graphene) with different Ni clusters were studied. The modulation effects of Ni clusters to the NiN4-graphene were systematically investigated from the geometric configurations, electronic structures, and the OER activity of the Ni single atom. It was found that the OER performance of NiN4-graphene can be remarkably improved through the addition of Ni clusters, and the lowest overpotential of 0.43 V is achieved on NiN4-graphene with the modification of Ni13 cluster, which is smaller than that of 0.69 V on NiN4-graphene. Electronic properties calculations showed that the charge transfer from Ni clusters to NiN4-graphene will alter the density of states of Ni single atom near the Fermi level, which promotes the charge transfer from NiN4-graphene to oxygen containing products and optimizes the adsorption strength of oxygen intermediate to close to the ideal adsorption free energy of 2.46 eV by enhancing the hybridization interaction between the O-p orbitals and the Ni-dxz, Ni-dyz orbitals, and finally leading to an enhanced OER activity. The current findings highlight the important role of metal clusters on improving the catalytic performance of M–N–C materials, which benefits for the rational design of M–N–C catalysts with high catalytic activity.
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Runchuan Shi et al 2024 J. Phys. D: Appl. Phys. 57 205301
Dan Guo et al 2014 J. Phys. D: Appl. Phys. 47 013001
The special mechanical properties of nanoparticles allow for novel applications in many fields, e.g., surface engineering, tribology and nanomanufacturing/nanofabrication. In this review, the basic physics of the relevant interfacial forces to nanoparticles and the main measuring techniques are briefly introduced first. Then, the theories and important results of the mechanical properties between nanoparticles or the nanoparticles acting on a surface, e.g., hardness, elastic modulus, adhesion and friction, as well as movement laws are surveyed. Afterwards, several of the main applications of nanoparticles as a result of their special mechanical properties, including lubricant additives, nanoparticles in nanomanufacturing and nanoparticle reinforced composite coating, are introduced. A brief summary and the future outlook are also given in the final part.
Alfred Leitenstorfer et al 2023 J. Phys. D: Appl. Phys. 56 223001
Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz–∼30 THz). Within its frequency boundaries exist a broad variety of scientific disciplines that have presented, and continue to present, technical challenges to researchers. During the past 50 years, for instance, the demands of the scientific community have substantially evolved and with a need for advanced instrumentation to support radio astronomy, Earth observation, weather forecasting, security imaging, telecommunications, non-destructive device testing and much more. Furthermore, applications have required an emergence of technology from the laboratory environment to production-scale supply and in-the-field deployments ranging from harsh ground-based locations to deep space. In addressing these requirements, the research and development community has advanced related technology and bridged the transition between electronics and photonics that high frequency operation demands. The multidisciplinary nature of THz work was our stimulus for creating the 2017 THz Science and Technology Roadmap (Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001). As one might envisage, though, there remains much to explore both scientifically and technically and the field has continued to develop and expand rapidly. It is timely, therefore, to revise our previous roadmap and in this 2023 version we both provide an update on key developments in established technical areas that have important scientific and public benefit, and highlight new and emerging areas that show particular promise. The developments that we describe thus span from fundamental scientific research, such as THz astronomy and the emergent area of THz quantum optics, to highly applied and commercially and societally impactful subjects that include 6G THz communications, medical imaging, and climate monitoring and prediction. Our Roadmap vision draws upon the expertise and perspective of multiple international specialists that together provide an overview of past developments and the likely challenges facing the field of THz science and technology in future decades. The document is written in a form that is accessible to policy makers who wish to gain an overview of the current state of the THz art, and for the non-specialist and curious who wish to understand available technology and challenges. A such, our experts deliver a 'snapshot' introduction to the current status of the field and provide suggestions for exciting future technical development directions. Ultimately, we intend the Roadmap to portray the advantages and benefits of the THz domain and to stimulate further exploration of the field in support of scientific research and commercial realisation.
I Adamovich et al 2022 J. Phys. D: Appl. Phys. 55 373001
The 2022 Roadmap is the next update in the series of Plasma Roadmaps published by Journal of Physics D with the intent to identify important outstanding challenges in the field of low-temperature plasma (LTP) physics and technology. The format of the Roadmap is the same as the previous Roadmaps representing the visions of 41 leading experts representing 21 countries and five continents in the various sub-fields of LTP science and technology. In recognition of the evolution in the field, several new topics have been introduced or given more prominence. These new topics and emphasis highlight increased interests in plasma-enabled additive manufacturing, soft materials, electrification of chemical conversions, plasma propulsion, extreme plasma regimes, plasmas in hypersonics, data-driven plasma science and technology and the contribution of LTP to combat COVID-19. In the last few decades, LTP science and technology has made a tremendously positive impact on our society. It is our hope that this roadmap will help continue this excellent track record over the next 5–10 years.
H Amano et al 2018 J. Phys. D: Appl. Phys. 51 163001
Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.
Manuel Le Gallo and Abu Sebastian 2020 J. Phys. D: Appl. Phys. 53 213002
Phase-change memory (PCM) is an emerging non-volatile memory technology that has recently been commercialized as storage-class memory in a computer system. PCM is also being explored for non-von Neumann computing such as in-memory computing and neuromorphic computing. Although the device physics related to the operation of PCM have been widely studied since its discovery in the 1960s, there are still several open questions relating to their electrical, thermal, and structural dynamics. In this article, we provide an overview of the current understanding of the main PCM device physics that underlie the read and write operations. We present both experimental characterization of the various properties investigated in nanoscale PCM devices as well as physics-based modeling efforts. Finally, we provide an outlook on some remaining open questions and possible future research directions.
Jianmin Ma et al 2021 J. Phys. D: Appl. Phys. 54 183001
Sun, wind and tides have huge potential in providing us electricity in an environmental-friendly way. However, its intermittency and non-dispatchability are major reasons preventing full-scale adoption of renewable energy generation. Energy storage will enable this adoption by enabling a constant and high-quality electricity supply from these systems. But which storage technology should be considered is one of important issues. Nowadays, great effort has been focused on various kinds of batteries to store energy, lithium-related batteries, sodium-related batteries, zinc-related batteries, aluminum-related batteries and so on. Some cathodes can be used for these batteries, such as sulfur, oxygen, layered compounds. In addition, the construction of these batteries can be changed into flexible, flow or solid-state types. There are many challenges in electrode materials, electrolytes and construction of these batteries and research related to the battery systems for energy storage is extremely active. With the myriad of technologies and their associated technological challenges, we were motivated to assemble this 2020 battery technology roadmap.
S S Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001
Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz–30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to 'real world' applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.
I Adamovich et al 2017 J. Phys. D: Appl. Phys. 50 323001
Journal of Physics D: Applied Physics published the first Plasma Roadmap in 2012 consisting of the individual perspectives of 16 leading experts in the various sub-fields of low temperature plasma science and technology. The 2017 Plasma Roadmap is the first update of a planned series of periodic updates of the Plasma Roadmap. The continuously growing interdisciplinary nature of the low temperature plasma field and its equally broad range of applications are making it increasingly difficult to identify major challenges that encompass all of the many sub-fields and applications. This intellectual diversity is ultimately a strength of the field. The current state of the art for the 19 sub-fields addressed in this roadmap demonstrates the enviable track record of the low temperature plasma field in the development of plasmas as an enabling technology for a vast range of technologies that underpin our modern society. At the same time, the many important scientific and technological challenges shared in this roadmap show that the path forward is not only scientifically rich but has the potential to make wide and far reaching contributions to many societal challenges.
Alexey Kimel et al 2022 J. Phys. D: Appl. Phys. 55 463003
Magneto-optical (MO) effects, viz. magnetically induced changes in light intensity or polarization upon reflection from or transmission through a magnetic sample, were discovered over a century and a half ago. Initially they played a crucially relevant role in unveiling the fundamentals of electromagnetism and quantum mechanics. A more broad-based relevance and wide-spread use of MO methods, however, remained quite limited until the 1960s due to a lack of suitable, reliable and easy-to-operate light sources. The advent of Laser technology and the availability of other novel light sources led to an enormous expansion of MO measurement techniques and applications that continues to this day (see section 1). The here-assembled roadmap article is intended to provide a meaningful survey over many of the most relevant recent developments, advances, and emerging research directions in a rather condensed form, so that readers can easily access a significant overview about this very dynamic research field. While light source technology and other experimental developments were crucial in the establishment of today's magneto-optics, progress also relies on an ever-increasing theoretical understanding of MO effects from a quantum mechanical perspective (see section 2), as well as using electromagnetic theory and modelling approaches (see section 3) to enable quantitatively reliable predictions for ever more complex materials, metamaterials, and device geometries. The latest advances in established MO methodologies and especially the utilization of the MO Kerr effect (MOKE) are presented in sections 4 (MOKE spectroscopy), 5 (higher order MOKE effects), 6 (MOKE microscopy), 8 (high sensitivity MOKE), 9 (generalized MO ellipsometry), and 20 (Cotton–Mouton effect in two-dimensional materials). In addition, MO effects are now being investigated and utilized in spectral ranges, to which they originally seemed completely foreign, as those of synchrotron radiation x-rays (see section 14 on three-dimensional magnetic characterization and section 16 on light beams carrying orbital angular momentum) and, very recently, the terahertz (THz) regime (see section 18 on THz MOKE and section 19 on THz ellipsometry for electron paramagnetic resonance detection). Magneto-optics also demonstrates its strength in a unique way when combined with femtosecond laser pulses (see section 10 on ultrafast MOKE and section 15 on magneto-optics using x-ray free electron lasers), facilitating the very active field of time-resolved MO spectroscopy that enables investigations of phenomena like spin relaxation of non-equilibrium photoexcited carriers, transient modifications of ferromagnetic order, and photo-induced dynamic phase transitions, to name a few. Recent progress in nanoscience and nanotechnology, which is intimately linked to the achieved impressive ability to reliably fabricate materials and functional structures at the nanoscale, now enables the exploitation of strongly enhanced MO effects induced by light–matter interaction at the nanoscale (see section 12 on magnetoplasmonics and section 13 on MO metasurfaces). MO effects are also at the very heart of powerful magnetic characterization techniques like Brillouin light scattering and time-resolved pump-probe measurements for the study of spin waves (see section 7), their interactions with acoustic waves (see section 11), and ultra-sensitive magnetic field sensing applications based on nitrogen-vacancy centres in diamond (see section 17). Despite our best attempt to represent the field of magneto-optics accurately and do justice to all its novel developments and its diversity, the research area is so extensive and active that there remains great latitude in deciding what to include in an article of this sort, which in turn means that some areas might not be adequately represented here. However, we feel that the 20 sections that form this 2022 magneto-optics roadmap article, each written by experts in the field and addressing a specific subject on only two pages, provide an accurate snapshot of where this research field stands today. Correspondingly, it should act as a valuable reference point and guideline for emerging research directions in modern magneto-optics, as well as illustrate the directions this research field might take in the foreseeable future.
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P Pottkämper and A von Keudell 2024 J. Phys. D: Appl. Phys. 57 345201
Copper oxide surfaces are commonly used as the catalyst for the CO2 reduction reaction towards hydrocarbons. However, the lifetime of these catalyst surfaces is limited. In this paper, a method of production of copper oxides through in-liquid plasma is explored, which may be a suitable reactivation method in such applications. The influence of the plasma, ignited in distilled water, with copper and its oxides is monitored in − situ using infrared spectroscopy and ex-situ using scanning electron spectroscop and x-ray photoelectron spectroscopy of the samples. It is shown that the interaction of the plasma with the samples causes a reduction of the copper oxide on a fast time scale and an oxidation on a longer time scale. The formation of preferentially oriented copper nanocubes is observed.
Linda Shao and Weiren Zhu 2024 J. Phys. D: Appl. Phys. 57 343001
We review the recent developments in the field of electromagnetic metamaterials and metasurface for polarization manipulation, focusing on their operation principles and practical applications. We discussed the research progress of chiral metamaterials and anisotropic metasurfaces, and also summarized the achievements of metasurfaces for comprehensive manipulation polarization and phase in recent years. We further summarize the recent achievements on the diversified polarization manipulation functions of metasurfaces. Finally, we discuss reconfigurable metasurfaces that can dynamically control the polarizaiton and wavefronts of electromagnetic waves, including not only electrically reconfigurable metasurfaces with constitutional meta-atoms locally tuned by external stimuli, but also time-modulated metasurfaces exploiting the temporal dimension by applying dynamic switching of the coding sequences. Finally, we look forward to the possible future directions and existing challenges in this rapidly developing field.
Can Yang et al 2024 J. Phys. D: Appl. Phys. 57 345104
Due to its unique advantage of optical properties, nanophotonic metamaterials have gained extensive applications in perfect absorbers. However, achieving both dual-band and ultra-narrow linewidth in absorbers simultaneously remains a challenge for typical metal-dielectric based metamaterials. In this work, a dual-band ultra-narrow perfect absorber consisting of a double slotted silicon nanodisk array that located on a silver film with a silica spacer layer is proposed theoretically. By combining the hybrid mode excited by the coupling of diffraction wave mode and magnetic dipole mode with the anapole–anapole interaction, two absorption peaks can be induced in the near-infrared regime, achieving nearly perfect absorbance of 99.31% and 99.61%, with ultra-narrow linewidths of 1.92 nm and 1.25 nm respectively. In addition, the dual-band absorption characteristics can be regulated by changing the structural parameters of the as-proposed metamaterials. The as-designed metamaterials can be employed as efficient two-channel refractive index sensors, with sensitivity and figure of merit (FOM) of 288 nm RIU−1 and 150 RIU−1 for the first band, and sensitivity and FOM of up to 204 nm RIU−1 and 163.2 RIU−1 for the second band. This work not only opens up a new design idea for the realization of dual-band perfect absorber synchronously with ultra-narrow linewidth, but also provides potential attractive candidates for developing dual-frequency channel sensors.
Muhammad Gulzari et al 2024 J. Phys. D: Appl. Phys. 57 345303
The valley degree of freedom in phononic crystals and metamaterials holds immense promise for manipulating acoustic and elastic waves. However, the impact of acoustic medium properties on valley edge state frequencies and their robustness to one-way propagation in valley topological phononic crystals remains unexplored. While significant attention has been devoted to scatterer design embedded in honeycomb lattices within acoustic and elastic media to achieve valley edge states and topologically protected nontrivial bandgaps, the influence of variations in acoustic medium properties, such as wave velocity and density affected by environmental temperature, has been overlooked. In this study, we investigate the effect of valley edge states and topological phases exhibited by topological phononic lattices in a temperature-dependent acoustic medium. We observe that a decrease in wave velocity and density, influenced by changing environmental temperature, shifts the topological valley edge states to lower frequencies. Therefore, alongside phononic lattice design, it is crucial to consider the impact of acoustic medium properties on the practical application of acoustic topological insulators. This issue becomes particularly significant when a topological phononic crystal is placed in a wave medium that transitions from incompressible to compressible, where wave velocity and density are no longer constant. Our findings offer a novel perspective on investigating topological insulators in variable acoustic media affected by changing thermodynamic and fluid properties.
Gebeyehu Dirbeba et al 2024 J. Phys. D: Appl. Phys. 57 345103
In this paper, we investigate a dielectrically chiral-core fiber for the generation of orbital angular momentum (OAM) modes. We observe that the presence of chirality induces a modal index split between the same order OAM modes with opposite topological charges and arbitrary phase front rotation directions, which are originally degenerate in achiral fibers. This split indicates the existence of circular birefringence (CB) associated with a dielectric chirality. The modal cutoff splitting results in a single polarization property without the possibility of coupling between the same order modes that correspond to a single +l or −l OAM mode guiding. However, neither of the two fundamental modes guided by the chiral fiber exhibits a cutoff, despite having different modal indices due to chirality. Upon fraction of modal power cutoff, the high-order modes in the core region display different cutoff fractions of modal power between the same order modes, while the fundamental mode has no cutoff fraction of modal power. Due to CB and different fractions of modal power in the core for different handed OAM modes, dielectrically chiral fibers have potential applications in chiral sensing, circular polarization-dependent OAM mode filters, and new kinds of OAM mode generators.
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Linda Shao and Weiren Zhu 2024 J. Phys. D: Appl. Phys. 57 343001
We review the recent developments in the field of electromagnetic metamaterials and metasurface for polarization manipulation, focusing on their operation principles and practical applications. We discussed the research progress of chiral metamaterials and anisotropic metasurfaces, and also summarized the achievements of metasurfaces for comprehensive manipulation polarization and phase in recent years. We further summarize the recent achievements on the diversified polarization manipulation functions of metasurfaces. Finally, we discuss reconfigurable metasurfaces that can dynamically control the polarizaiton and wavefronts of electromagnetic waves, including not only electrically reconfigurable metasurfaces with constitutional meta-atoms locally tuned by external stimuli, but also time-modulated metasurfaces exploiting the temporal dimension by applying dynamic switching of the coding sequences. Finally, we look forward to the possible future directions and existing challenges in this rapidly developing field.
Nguyen Tuan Hung et al 2024 J. Phys. D: Appl. Phys. 57 333002
Second-harmonic generation (SHG) is the generation of 2ω (or half wavelength) light from incident light with frequency ω as a nonlinear optical response of the material. Three-dimensional (3D) SHG materials are widely investigated for developing laser technology to obtain shorter wavelengths in photolithography fabrication of semiconductor devices and the medical sciences, such as for imaging techniques that do not use fluorescent materials. However, to obtain the optimized SHG intensity, the 3D material is required to have no spatial-inversion symmetry (or non-centrosymmetry) and special crystal structure (or so-called phase-matched condition). Recently, engineering symmetry breaking of thin two-dimensional (2D) materials whose 3D structure has the inversion symmetry can offer a breakthrough to enhance the SHG intensity without requiring the phase-matched condition. Over the past decade, many 2D SHG materials have been synthesized to have broken inversion symmetry by stacking heterostructures, twisted moiré structures, dislocated nanoplates, spiral nanosheets, antiferromagnetic order, and strain. In this review, we focus on the recent progress in breaking inversion and rotational symmetries in out-of-plane and/or in-plane directions. The theoretical calculations and experimental setup are briefly introduced for the non-linear optical response of the 2D materials. We also present our perspectives on how these can optimize the SHG of the 2D materials.
Jingyu Peng et al 2024 J. Phys. D: Appl. Phys. 57 333001
Due to their unique properties, charge-generation layers (CGLs) have been used as interconnect layers for organic and quantum-dot light-emitting devices (LEDs) consisting of multiple emission units. Furthermore, CGLs have also been integrated into single-emission-unit LEDs and alternating-current LEDs. The charge-generation structures provide charge carriers (electrons and holes) to the devices under an external electric field, instead of charge injection from the electrodes. Therefore, there is no strict requirement for precise matching of energy levels between the electrodes and charge-injection layers. This affords greater flexibility for device design and enhances the efficiency and operational lifespan of devices. In this review, we summarize the development of charge-generation structures and discuss the existing challenges and opportunities. A particular focus is placed on the working mechanism of CGLs and their applications in various LEDs. Additionally, issues such as voltage drop in CGLs, charge generation efficiency, increased operating voltage for the devices, and optimizations of existing CGLs are discussed.
Yuxin Zhang et al 2024 J. Phys. D: Appl. Phys. 57 323001
Ammonia is one of the most important industrial chemicals which is commonly used for producing fertilizers and cleaning solutions, as the refrigerant gas, and as the precursors for making various chemicals. With the goal of sustainable development, ammonia is also proposed as the clean fuel for decarbonized transportation. The current the Haber–Bosch process for ammonia synthesis has large footprint and operates under harsh conditions using fossil fuels as the feedstock, being recognized as the major carbon emission source. Accordingly, call for sustainable production of green ammonia using renewable energies is proposed. Ammonia synthesis assisted by nonthermal plasmas has emerged in recent years as a novel and mild electrified technology, which can potentially be coupled with intermittent renewable energies and green hydrogen. Although being promising, significant development is still needed to advance the technology towards practical applications at scales. Hence, this review comments the progression of key aspects of the plasma-assisted ammonia synthesis such as catalyst and reactor design, mechanistic understanding, and process parameters. The snapshot of the current developments and proposed perspectives hope to provide guidance for the future research efforts to drive the technology towards higher technology readiness levels.
Zi Yang Liu et al 2024 J. Phys. D: Appl. Phys. 57 303002
Amidst the growing demand for sustainable and clean energy sources, the need for efficient and scalable technologies capable of harnessing low-temperature thermal gradients has become increasingly crucial. Low-gradient thermopower cells emerge as a promising solution to this challenge, offering the ability to generate electricity from the small temperature differences encountered in diverse applications, including industrial processes, waste heat recovery, and environmental monitoring. These novel thermal energy conversion power cells, developed based on the principles of thermo-electrochemical reaction potential difference, charge thermal diffusion, and other characteristics, exhibit enhanced conversion efficiency and hold immense application potential. Some work has reported maximum instantaneous power over 0.5 mW K−2 m−2, already reaching practical power output levels. However, there are still many challenges to overcome regarding continuous power output, stability, and efficiency of the device. Based on their power generation capabilities, we explore the potential applications of these thermopower cells in real-world scenarios, such as powering remote sensors, IoT devices, and integrating them into industrial processes for waste heat recovery.
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Chen et al
The Schottky injection barrier plays a crucial role in determining the charge movement and migration process, yet its electric field and temperature properties remain unclear. The precise determination of the Schottky injection barrier value is essential for understanding the charge migration dynamics at the interface between the metal electrode and the oil-pressboard insulating medium. This study introduces a computational approach to determine the Schottky injection barrier, derived from classical Schottky emission theory. The methodology employed in this research aligns with previous studies, utilizing the Schottky emission current mechanism to describe steady-state conduction current. Results indicate that the Schottky injection barrier increases with temperature, with a 17.09% rise for oil-electrode and an 8.3% increase for pressboard-electrode in the temperature range of 299 K to 353 K. These temperature-dependent variations are attributed to the negative temperature dependence of the Fermi energy levels of the metal electrodes. Furthermore, the impact of electric field strength on the Schottky injection barrier is found to be minimal. By developing a bipolar charge transport simulation model and validating the injection barrier for 0.5 mm oil-immersed pressboard, this study confirms the accuracy of the calculated Schottky injection barrier. The insights provided in this research could aid in simulating charge transport and analyzing charge characteristics in oil-paper/pressboard insulation systems.
Goyal et al
In this study, a split recessed gate Ga2O3 MOSFET has been proposed for high frequency applications. Extensive simulations have been carried out using TCAD Silvaco to examine analog characteristics as well as critical high-frequency metrics of the proposed device. A comparison has been drawn with conventional recessed gate β – Ga2O3 MOSFET and it is demonstrated that the proposed device outperforms the conventional device in terms of high frequency metrics due to significantly lower parasitic capacitances and higher intrinsic gain. In addition to this, it has also been demonstrated that proposed device exhibits a substantial increase of 127.7 % in Johnson's figure of merit, significantly higher i.e., 134.7 % higher Baliga's high frequency figure of merit as well as 3.25 % increase in Baliga's figure of merit as compared to conventional device.
Furthermore, two port network analysis has been carried out for both the devices and it has been shown that the proposed device offers higher gain with a slight trade-off in the reflections at input/output ports. The scattering parameters have also been extracted and used to perform the stability analysis. It has been observed that the proposed device exhibits higher stability for the entire frequency range. Further, a maximum gain amplifier has been designed using the proposed device. An impressive gain of 11.04 dB has been demonstrated at an ultra-high frequency of 3 GHz.
Abrahamyan et al
We experimentally demonstrate that the transmission of microwave electromagnetic fields through a bilayer metasurface (BMS) composed of thin conductive rods can abruptly change in a narrow frequency range. A theoretical analysis based on the coupled oscillator model is performed to reveal the physical mechanism behind the frequency-dependent properties of such a structure. Two conditions primarily facilitate the observed high dispersion in the BMS. The first one is the resonant interaction between the incident microwaves and rods, leading to the formation of surface standing waves. These waves with radial electric fields enable the coupling of the near-field of rods in structural layers. The second condition is the complex value of the coupling coefficient between rods of different owing to the delayed interaction process between them. The electromagnetic response here can be effectively controlled by varying the distance between layers and the dielectric properties of the interlayer medium.
Xu et al
Regarding the vast difference between the design index and the actual performance of magnetic shielding devices, this paper proposes a novel method of using precise permeability under a specific weak magnetic field, aiming to improve the design accuracy of shielding performance. Firstly, the relative permeability of the permalloy is measured under the applied magnetic field from the geomagnetic field down to 1 nT. Next, the precise shielding coefficient formulas of the single- and double-layer spherical shells are derived. For the double-layer spherical shell, the deviation of remanence between considering the ultra-weak magnetic properties and using the constant permeability is 24.3%. This clarifies the necessity of considering the ultra-weak magnetic properties in multi-layer structures. Then, a new accurate method of the shielding coefficient for the finite-length magnetic shielding cylinder is proposed, with a deviation of less than 5%. Finally, this method has been validated again by remanence measurement of the three-layer magnetic shielding cylinders. The deviation between simulation and experiment is 4.03% when considering the ultra-weak magnetic properties. While using the constant permeability, the deviation is as high as 19.31%.
Therefore, considering the ultra weak magnetic properties in multi-layer structures can-significantly improve the accuracy of the performance evaluation.
Wang et al
We report a novel approach to simultaneously tune electric dipoles and flat-band voltage (VFB) of 4H-SiC metal-oxide-semiconductor (MOS) capacitors through high-k oxide dielectrics interface engineering. With an additional HfO2 thin layer on in-situ atomic layer deposition (ALD) of SiO2 film, a dipole layer was formed at the HfO2/SiO2 interface, leading to a small positive shift VFB of 0.37 V in 4H-SiC MOS capacitors. Kelvin probe method was used to examine the dipole layers induced at the direct-contact oxides/4H-SiC interfaces. It was found that a minor difference of 0.3 V in contact-potential-difference voltage (VCPD) is observed between the SiO2/4H-SiC and HfO2/SiO2/4H-SiC stacks, which signifies the presence of a weak interface dipole layer at the interface of HfO2 and SiO2. Additionally, the investigation of interface state density reveals that the in-situ ALD of HfO2 process had negligible impact on the quality of SiO2/4H-SiC interface, suggesting that the observed small positive VFB shift origin from the HfO2/SiO2 interface rather than the SiO2/4H-SiC interface.
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P Pottkämper and A von Keudell 2024 J. Phys. D: Appl. Phys. 57 345201
Copper oxide surfaces are commonly used as the catalyst for the CO2 reduction reaction towards hydrocarbons. However, the lifetime of these catalyst surfaces is limited. In this paper, a method of production of copper oxides through in-liquid plasma is explored, which may be a suitable reactivation method in such applications. The influence of the plasma, ignited in distilled water, with copper and its oxides is monitored in − situ using infrared spectroscopy and ex-situ using scanning electron spectroscop and x-ray photoelectron spectroscopy of the samples. It is shown that the interaction of the plasma with the samples causes a reduction of the copper oxide on a fast time scale and an oxidation on a longer time scale. The formation of preferentially oriented copper nanocubes is observed.
Muhammad Gulzari et al 2024 J. Phys. D: Appl. Phys. 57 345303
The valley degree of freedom in phononic crystals and metamaterials holds immense promise for manipulating acoustic and elastic waves. However, the impact of acoustic medium properties on valley edge state frequencies and their robustness to one-way propagation in valley topological phononic crystals remains unexplored. While significant attention has been devoted to scatterer design embedded in honeycomb lattices within acoustic and elastic media to achieve valley edge states and topologically protected nontrivial bandgaps, the influence of variations in acoustic medium properties, such as wave velocity and density affected by environmental temperature, has been overlooked. In this study, we investigate the effect of valley edge states and topological phases exhibited by topological phononic lattices in a temperature-dependent acoustic medium. We observe that a decrease in wave velocity and density, influenced by changing environmental temperature, shifts the topological valley edge states to lower frequencies. Therefore, alongside phononic lattice design, it is crucial to consider the impact of acoustic medium properties on the practical application of acoustic topological insulators. This issue becomes particularly significant when a topological phononic crystal is placed in a wave medium that transitions from incompressible to compressible, where wave velocity and density are no longer constant. Our findings offer a novel perspective on investigating topological insulators in variable acoustic media affected by changing thermodynamic and fluid properties.
Yusuf Yüksel 2024 J. Phys. D: Appl. Phys. 57 335302
Due to the lack of inversion symmetry, very large Dzyaloshinskii–Moriya interaction (DMI) has been reported for a series of Janus monolayers of manganese dichalcogenides within the framework of first-principles calculations (Liang et al 2020 Phys. Rev. B 101 184401). However, from the viewpoint of potential applications, the current ongoing research mainly focuses on the magnetism in pristine two-dimensional (2D) materials exhibiting non-zero DMI, and the effects of disorder in such systems remain an open problem since the influence of randomness may create some drastic effects on the magnetism of low dimensional systems. Here, we present Monte Carlo simulation results regarding the magnetic properties of a 2D manganese based Janus dichalcogenide material in the presence of quenched random magnetic fields where the local field variables have been sampled from a Gaussian distribution. For the selected benchmark material, it has been found that the magnetic skyrmion vortexes emerging at (10 K, 3 T) may survive in the presence of weak and moderate quenched randomness, which is important from the viewpoint of technological applications. In both the pristine and random field cases, the stabilization of magnetic skyrmions are achieved by the major contribution of the ferromagnetic exchange energy to the total energy of the system, and the materials exhibiting large DMI/exchange ratios may exhibit resilient magnetic skyrmion vortexes in the presence of weak and moderate amount of randomness.
James Shaffer et al 2024 J. Phys. D: Appl. Phys. 57 335204
Plasma ignition can significantly improve the efficiency and performance of combustion devices through the enhancement of combustibility limits. Investigating plasma development for fundamental experimental flame conditions (i.e. spherical flame experiments) can provide insight into how plasma thermalizes the combustible mixture and, therefore a better understanding of flame development in future experimental studies. This study observed an ignition system designed to produce spherical flames in quiescent gas inside a constant-volume combustion chamber. Rotational and vibrational temperature measurements of dry atmospheric air glow plasma are reported. Measurements were taken for a transient discharge with currents less than 0.5 A. The electrode wire geometry and discharge variation resulted in an ellipsoid-shaped kernel and plasma region with an abnormal glow discharge. The measured temperatures were compared to the conductive thermal kernel boundary observed with Schlieren imaging. Maximum rotational and vibrational temperatures of 3000 K and 10 000 K, respectively, were observed near the anode electrode for a 0.5 A current. The temperature decreased with the axial distance from the anode, while a constant temperature was observed in the radial direction. Lower currents resulted in a smaller temperature, with minimum measured rotational and vibrational temperatures of 1500 K and 5000 K, respectively. The results were compared with available experimental literature and the variation observed was a result of the transient nature, which resulted in hysteresis in temperature vs discharge current measurements.
Monica La Mura et al 2024 J. Phys. D: Appl. Phys. 57 335105
In the growing scenario of 2D material-based metamaterials and metasurfaces for Terahertz (THz) applications, assessing the impact of ageing and wear due to environmental stressors on the components' performance is becoming mandatory to understand the long-term reliability of novel technologies. This paper introduces approaches to assess the ageing and wear effects on THz passive components through numerical simulations. For this purpose, common techniques for introducing 2D materials and thin metal layers in numerical models are discussed. As a case study, this work explores the effects of graphene degradation and reflective metal ageing on the electromagnetic response of a graphene-enhanced reflective grating for THz absorption and modulation by finite element (FE) analysis. The developed FE model is validated against experimental data obtained through THz Time-Domain Spectroscopy. By computing the device's transmission, reflection, and absorption spectra for degrading graphene and metal conductive properties, this work provides insights into the influence of ageing and wear on THz passive components.
Sarah E Mann et al 2024 J. Phys. D: Appl. Phys.
A neutron sensitive scintillator employing nanoparticles of ZnS:Ag has been developed for the first time. Pulse shape differences between neutron and gamma signals were observed in this material and neutron-gamma discrimination was applied. With initial signal processing parameters, gamma sensitivities of 8.5 × 10-6 to 60Co gammas were achieved. The average primary decay of neutron scintillation in nanoparticle ZnS:Ag/6LiF was measured to be 18ns, and afterglow was significantly suppressed in comparison to standard ZnS:Ag/6LiF scintillators that employ micron sized ZnS:Ag. Fast decay times and minimal afterglow indicate potential for use in high count rate capability applications. Prospective count rate capabilities were investigated here as proof of concept, with rates of 1.12Mcps measured for a single readout channel with less than 3.5% count loss. This is approximately 70 times greater than the count rate capability of the current standard ZnS:Ag/6LiF scintillation detectors. With improvements to signal processing and scintillator composition, nanoparticle ZnS:A/6LiF could be a promising candidate for future high rate capability neutron detectors.
Zichang Xiong et al 2024 J. Phys. D: Appl. Phys.
The in-flight reduction of iron ore particles using an atmospheric pressure hydrogen plasma is investigated. Iron ore particles with a size less than 75 µm are aerosolized and carried with an argon-hydrogen (90%-10%) gas mixture through an atmospheric pressure microwave plasma. After the treatment, the collected particles are observed to follow three distinct populations: (i) fully reduced nanoparticles, (ii) partially reduced spheres, larger than the feedstock, and (iii) partially melted, partly reduced agglomerates. A model is developed to explain the possible mechanism for the origin of the three populations. The nanoparticles (i) are found to be likely formed from the previously evaporated material whereas the particles (ii) and (iii) result from the partial/complete melting of the particles and agglomerates flowing through the reactor. The gas temperature is estimated to be more than 2000 K, which enables the rapid melting, evaporation, and reduction of these particles within residence times of only a few 10 ms.
Tahereh Shah Mansouri et al 2024 J. Phys. D: Appl. Phys.
The ability to detect gas molecule and assign a concentration offers an inventive solution in the field of plasma integrated with Machine Learning (ML). The most important finding of this work is firstly, to develop an algorithm for gas-molecule identification using three different hydrocarbons (CH4, C2H2, C2H6) and secondly, organise a model for detecting gas concentration (classification). For this reason, initially eight different gases evaluated. The study confirms the present of the unique emission lines as a gas indicator, i.e., a wavelength peak related to hydrocarbons identified via increasing in CxHy concentration. By means of unique Variable Important in Projection (VIP), hydrocarbons can be distinguished. Our proposed Chemometric analysis strategy examined on >1000 samples and results development of suitable techniques that are sufficiently rapid, accurate and innovative. This demonstrates the potential for real-time, portable, and continuous monitoring of trace gases with potential applications in medical, environmental, and industrial gas sensing.
Marnik Metting van Rijn et al 2024 J. Phys. D: Appl. Phys.
A revised set of electron-molecule-scattering cross section for the refrigerant R134a (CF3CH2F) is presented. Swarm studies acquired on a Pulsed Townsend apparatus experimentally verified the electron-transport-coefficient simulations. Increasing the cross sections' quality enhances the accuracy in modelling particle detectors operating with R134a, as the cross sections serve as input for the simulations.
Paola Perion et al 2024 J. Phys. D: Appl. Phys.
Spectral K-edge subtraction (SKES) is an imaging technique that takes advantage of the sharp rise in the mass attenuation coefficient of specific elements within an object at their K-edge to produce separate and quantifiable distributions of each element. In this paper, a high-sensitivity and wide bandwidth SKES imaging system for computed tomography applications on biological samples is presented. X-ray images are acquired using a wide and continuous energy spectrum that encompasses the absorption edges of the target materials. System characterization shows that high energy resolution (approximately 3×10−3) and unprecedented large energy bandwidth (around 15 %) are achieved over a field-of-view of several centimeters. Imaging results obtained on contrast elements relevant for biomedical applications, namely silver, iodine, xenon, and barium, demonstrate the system sensitivity to concentrations down to 0.5 mg/mL. The achievement of a large energy bandwidth allowed the simultaneous imaging of the K-edges of iodine, xenon, and barium and provided an accurate concentration estimation and distinction of co-localized contrast elements, leading the way for future simultaneous cardiovascular (iodine), pulmonary (xenon), and gastrointestinal/inflammatory (barium) imaging applications.