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.
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ISSN: 1361-6463
An international journal publishing high quality work concerned with all aspects of applied physics research, from biophysics, magnetism, plasmas, semiconductors, energy materials and devices to the structure and properties of matter.
Alfred Leitenstorfer et al 2023 J. Phys. D: Appl. Phys. 56 223001
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.
Ruoyu Han et al 2024 J. Phys. D: Appl. Phys. 57 465201
Underwater pulsed discharge, where intense reactions between ionized gas and condensed-state water exist, can be a joint problem of both physics and chemistry. The study tries to build a comprehensive visualization of nanosecond-risetime discharge initiated by a conductive coating and its successive multi-physical effects. The scenario is established via a pair of thin-plate electrodes positioned on both sides of the coating, and diagnosed using high-speed backlight photography synchronized with electrical and optical measurements. For the sprayed Cu/Ag composite coating, the current density can achieve 20 A mm−2 which is high enough to induce the surface 'electrical explosion' and breakup the conductive matrix within 500 ns. By increasing the discharge energy from 0.5 to 10 J, the explosion of coating can exhibit different discharge types as exploding wires. Adopting a thicker carbon foil or cermet sheet can reduce the current density and energy deposition rate, which converts the global explosion to partial ones, significantly increasing the lifetime. With the aid of the conductive coating, the breakdown delay diminishes, and hot plasma spots form in 100 ns due to non-uniform Joule heating of the pulsed current, which gradually evolve to a plasma bubble cluster above the lower-conductive coating (bypassing branch). Once the high-conductive plasma channel bridges two electrodes, it will be intensively heated (MW-level energy deposition rate) and rapidly expand, accompanied by underwater shock wave (102 kPa @30 cm) and bubble/cavity generation (20 mm maximum). Finally, microscopic characterization has been made, and the erosion morphology suggests typical arc erosion features (pits, cracks, etc) and nanoparticles condensation from evaporated materials.
Roshni Oommen et al 2024 J. Phys. D: Appl. Phys. 57 465102
Optoelectronic synapses are inevitable for realizing neuromorphic vision systems, which require the integration of image recognition, memory and image processing into a single platform. In this work, we present a three terminal optoelectronic synapse created using zinc oxide (ZnO) thin film transistor. The persistent photoconductivity (PPC) of ZnO thin film is utilized to demonstrate the synaptic behavior. The change in conductance of the device under UV illumination has been interpreted as the weight change in the synapse. The basic synaptic functions such as sensory memory, short term memory, long term memory, duration-time-dependent plasticity and paired pulse facilitation (PPF) have been successfully demonstrated. The device shows a PPF index of 160%, comparable to other optoelectronic synapses reported in literature. Further, to corroborate the existing theory that PPC is caused by oxygen vacancies, additional characterizations are carried out and the presence of oxygen vacancies is detected in the fabricated ZnO device. Subsequently, pattern recognition of MNIST handwritten dataset has been performed using the conductance tuning curves of the proposed ZnO TFT based synapses in a neural network architecture, thereby demonstrating their feasibility to be used in neuromorphic applications.
M De Angelis and M Tomellini 2024 J. Phys. D: Appl. Phys. 57 465301
Barium Oxyfluoride plays an important role, as a precursor species, in the nucleation and growth of YBa2Cu3O7−δ (YBCO) via the low fluorine metal organic decomposition (MOD low-fluorine) route. In this contribution, we present a study on the thermodynamics of oxyfluoride by processing experimental data on YBCO growth on LaAlO3 (LAO) substrates. The analysis allows one to determine the standard enthalpy and the standard entropy changes for oxyfluoride formation from barium oxide and barium fluoride. To identify the thermodynamically more favorable route to oxyfluoride formation in the MOD low-fluorine process, the free energy change for the formation of the precursor, through reactions involving gas water, has been determined. The free energy of formation via fluoride and water indicates higher stability of oxygen rich oxyfluoride for . In the framework of nucleation theory, the present results are needed to study the effect of precursor composition on film orientation.
Na Xiao et al 2024 J. Phys. D: Appl. Phys. 57 445104
Here, we demonstrate a high-mobility indium oxide (In2O3) thin-film transistor (TFT) with a sputtered alumina (Al2O3) passivation layer (PVL) with a low thermal budget (200 °C). The sputtering process of the Al2O3 PVL plays a positive role in improving the field-effect mobility (µFE) and current on/off ratio (ION/IOFF) performance of the In2O3 TFTs. However, these enhancements are limited due to the high density of intrinsic trap defects in the In2O3 channels, as reflected in their large hysteresis and poor bias stability. Treating the In2O3 channel with oxygen (O2) plasma prior to sputtering the Al2O3 PVL results in notable improvements. Specifically, a high µFE of 128.3 cm2V−1 s−1, a high ION/IOFF over 106 at VDS of 0.1 V, a small hysteresis of 0.03 V, and a negligible threshold voltage shift under negative bias stress are achieved in the passivated In2O3 TFT (with O2 plasma pretreatment), representing a significant improvement compared to the passivated In2O3 TFT (without O2 plasma pretreatment) and the unpassivated In2O3 TFT. The remarkable reduction of intrinsic trap defects in the passivated In2O3 TFT compensated by O2 plasma is the primary mechanism underlying the improvement in µFE and bias stability, as validated by x-ray photoelectron spectra, hysteresis analysis, and temperature-stress electrical characterizations. Plasma treatment effectively compensates for intrinsic trap defects in oxide semiconductor (OS) channels, when combined with sputter passivation, resulting in a significant enhancement of the overall performance of OS TFTs under low thermal budgets. This approach offers valuable insights into advancing OS TFTs with satisfactory driving capability and wide applicability.
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.
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.
Miki Kajihara et al 2024 J. Phys. D: Appl. Phys. 57 505306
Graphene, a two-dimensional material, is expected to be employed as a next-generation component for structural and functional applications because of its light weight and excellent mechanical properties. For applications requiring lightness and impact resistance, preventing penetrative damage upon particle impact is critical for applications in mechanical protection. However, graphene is known to have high defect sensitivity. Graphene oxide (GO) may be a better candidate, as functional groups (e.g. hydroxy and epoxy groups) bonded to the C–C network in GO result in better deformability, ductility, and durability compared to graphene. For mechanical applications, it is crucial to understand the fracture behavior, especially the penetrative fracture behavior, of GO membranes. This study characterizes the penetration behavior and fracture morphology of GO membranes subjected to particle impact. Nanoscale experiments were conducted using an atomic force microscope and laser-induced particle impact test for GO. These material testing methods employ nanoscale spheres to induce particle penetration, with the former experiment conducted under quasi-static loading and the latter under dynamic loading. Additionally, molecular dynamics simulations were performed to elucidate the fracture mechanisms of GO. Finally, cyclic fatigue experiments and simulations revealed that GO's ductility provides resistance to catastrophic failure, indicating its durability. These comprehensive investigations provide valuable insights into the fracture properties of GO membranes under impact penetration.
Rui Tan et al 2024 J. Phys. D: Appl. Phys. 57 505305
Exploring two-dimensional (2D) tetragonal carbon nitride materials is significant for unlocking new physical properties beyond those offered by traditional hexagonal lattices. In this work, we propose three theoretically stable 2D carbon nitride monolayers with tetragonal lattices, namely T-C3N, P-C3N, and PH-C5N4. Electronic structure calculations indicate that all three monolayers exhibit semiconducting characteristics, with T-C3N showing interesting flat band features. Additionally, these three carbon nitrides exhibit anisotropic and high carrier mobilities and excellent light absorption capabilities in the visible-light and near-infrared regions. Meanwhile, the calculated thermal conductivity () of PH-C5N4 is 63.9 W m−1K−1 at room temperature, significantly outperforming T-C3N (12.2 W m−1 K−1) and P-C3N (18.9 W m−1 K−1). Phonon scattering rates and Grüneisen parameters confirm the origin for the relatively high in PH-C5N4. Our study proposes three tetragonal carbon nitride structures with novel physical properties, which lays a theoretical foundation for the multifunctional applications of 2D carbon nitride materials.
Jing Sun et al 2024 J. Phys. D: Appl. Phys. 57 503002
This article discusses the 'power-to-X' (P2X) concept, highlighting the integral role of non-thermal plasma (NTP) in P2X for the eco-friendly production of chemicals and valuable fuels. NTP with unique thermally non-equilibrium characteristics, enables exotic reactions to occur under ambient conditions. This review summarizes the plasma-based P2X systems, including plasma discharges, reactor configurations, catalytic or non-catalytic processes, and modeling techniques. Especially, the potential of NTP to directly convert stable molecules including CO2, CH4 and air/N2 is critically examined. Additionally, we further present and discuss hybrid technologies that integrate NTP with photocatalysis, electrocatalysis, and biocatalysis, broadening its applications in P2X. It concludes by identifying key challenges, such as high energy consumption, and calls for the outlook in plasma catalysis and complex reaction systems to generate valuable products efficiently and sustainably, and achieve the industrial viability of the proposed plasma P2X strategy.
Daniele Pirone et al 2024 J. Phys. D: Appl. Phys. 57 505402
Nowadays, radiotherapy (RT) is a consolidated treatment for the cancer care. In fact, ionizing radiations are employed in over 50% of cancer patients. However, some side effects are correlated with RT, such as the radiation-induced lymphopenia (RIL). RIL is due to circulating lymphocytes (LCs) that pass through the irradiation field. LCs are the most radiosensitive blood cells, therefore RT can affect the count and activity of LCs. LCs are an important component of the human immune system, thus RIL has been linked with worse outcomes in multiple solid tumors and poor survival. As the occurrence rate of RIL is ∼40%–70% of patients treated with RT, an effective tool for predicting and minimizing RIL is highly demanded. Here we propose the proof-of-concept of a minimally invasive approach to monitor alterations induced by the radiation exposure inside LCs. To this aim, we combine label-free Holographic Imaging Flow Cytometry and Machine Learning to study Jurkat cells as model of T-LCs irradiated with two x-ray doses (i.e. 2 and 10 Gy of 6 MeV photons). The proposed method allows correlating the morphological features extracted by the quantitative phase-contrast maps of irradiated LCs flowing in a microfluidic chip to their radiation response. Furthermore, we train several machine learning models at different time points after RT for assessing the best strategy to reveal its effect on irradiated LCs. The attained results pave the way to future and deeper investigations for the development of a label-free, minimally invasive, and high-throughput tool for predicting and minimizing the RIL side effects.
Hanjie Zhang et al 2024 J. Phys. D: Appl. Phys. 57 505307
CO2, CH4, CF4, CCl3F, CCl2F2, HCF2Cl, N2O and SF6 are well-known greenhouse gases that cause serious threat to the earth's ecological environment. To expand the application and development of two-dimensional (2D) materials in the field of greenhouse gas sensing, adsorption of the greenhouse gases on the pristine β-tellurene monolayer was investigated by first-principles calculations to estimate the potential application of β-tellurene as a monitor for greenhouse gas. The results indicate that β-tellurene exhibits favorable adsorption capabilities for greenhouse gases, especially demonstrating selective sensing potential for SF6 molecules due to the changes in electronic structures after gas exposure. The effects of noble metal atoms doping on structural, electronic and SF6 sensing properties were systematic estimated. The calculation results revealed that doping with different transition metal (TM) atom could bring diverse electronic properties to β-tellurene. Among them, doping with Os, Pd, Pt, Rh, and Ru could effectively enhance the electronic delocalization, improving the detection sensitivity for β-tellurene. In addition, TM doping could also improve the recovery time of β-tellurene by two orders of magnitude, and provided the possibility for β-tellurene as a work function type sensing material. By delving into the gas sensing properties of β-tellurene with TM doping, we provided a valuable guidance for the design of innovative tellurene- based sensing 2D materials for devices and technologies.
Jing Sun et al 2024 J. Phys. D: Appl. Phys. 57 503002
This article discusses the 'power-to-X' (P2X) concept, highlighting the integral role of non-thermal plasma (NTP) in P2X for the eco-friendly production of chemicals and valuable fuels. NTP with unique thermally non-equilibrium characteristics, enables exotic reactions to occur under ambient conditions. This review summarizes the plasma-based P2X systems, including plasma discharges, reactor configurations, catalytic or non-catalytic processes, and modeling techniques. Especially, the potential of NTP to directly convert stable molecules including CO2, CH4 and air/N2 is critically examined. Additionally, we further present and discuss hybrid technologies that integrate NTP with photocatalysis, electrocatalysis, and biocatalysis, broadening its applications in P2X. It concludes by identifying key challenges, such as high energy consumption, and calls for the outlook in plasma catalysis and complex reaction systems to generate valuable products efficiently and sustainably, and achieve the industrial viability of the proposed plasma P2X strategy.
Alexander Vahl et al 2024 J. Phys. D: Appl. Phys. 57 503001
Major efforts to reproduce functionalities and energy efficiency of the brain have been focused on the development of artificial neuromorphic systems based on crossbar arrays of memristive devices fabricated by top-down lithographic technologies. Although very powerful, this approach does not emulate the topology and the emergent behavior of biological neuronal circuits, where the principle of self-organization regulates both structure and function. In materia computing has been proposed as an alternative exploiting the complexity and collective phenomena originating from various classes of physical substrates composed of a large number of non-linear nanoscale junctions. Systems obtained by the self-assembling of nano-objects like nanoparticles and nanowires show spatio-temporal correlations in their electrical activity and functional synaptic connectivity with nonlinear dynamics. The development of design-less networks offers powerful brain-inspired computing capabilities and the possibility of investigating critical dynamics in complex adaptive systems. Here we review and discuss the relevant aspects concerning the fabrication, characterization, modeling, and implementation of networks of nanostructures for data processing and computing applications. Different nanoscale electrical conduction mechanisms and their influence on the meso- and macroscopic functional properties of the systems are considered. Criticality, avalanche effects, edge-of-chaos, emergent behavior, synaptic functionalities are discussed in detail together with applications for unconventional computing. Finally, we discuss the challenges related to the integration of nanostructured networks and with standard microelectronics architectures.
Yan Wang et al 2024 J. Phys. D: Appl. Phys. 57 493004
Chiroptical metamaterials have attracted considerable attention owing to their exciting opportunities for fundamental research and practical applications over the past 20 years. Through practical designs, the chiroptical response of chiral metamaterials can be several orders of magnitude higher than that of natural chiral materials. Chiroptical metamaterials therefore represent a special type of artificial structures for unique chiroptical activities. In this review, we present a comprehensive overview of the progresses in the development of chiroptical metamaterials. Chiroptical metamaterial progress enables applications, including asymmetric transmission, polarization conversion, chiral absorber, chiral imaging, chiral sensor and chiral emission. We also review fabrication techniques and design of chiroptical metamaterials based on deep learning. In the conclusion, we present possible further research directions in this field.
N N Misra et al 2024 J. Phys. D: Appl. Phys. 57 493003
This review explores the engineering and design aspects of plasma activated water (PAW) systems, focusing on their application in food safety and agriculture. This review aims to bridge the gap between research and practical application, paving the way for the development of robust and efficient PAW systems for enhancing food safety and agricultural productivity. By examining a variety of activation methods, including direct gas ionization, underwater discharges, and dynamic interactions of ionized gases with liquids, this work discusses the mechanical designs that facilitate these processes, highlighting their scalability and efficiency. The discussion is grounded in a comprehensive relevant scientific and patent literature, offering a critical overview of the systems' design parameters that influence the generation of reactive oxygen and nitrogen species (RONS). The designs reported in literature have employed three major approaches, viz. direct underwater discharges, gas ionization followed by introduction of plasma into the liquid, creation of gas liquid mixtures and subsequent ionization. The laboratory systems have relied on natural convective diffusion of the RONS into water, while most of the patents advocate use of forced convective diffusion of RONS to increase transfer rates. Despite widespread laboratory-scale research in PAW, the transition to industrial-scale systems remains underexplored.
Jiaxin Li et al 2024 J. Phys. D: Appl. Phys. 57 493001
The study of electrophysiological signals is crucial for understanding neural functions and physiological processes. Electrophysiological recordings offer direct insights into electrical activity across cellular membranes, aiding in diagnosing and treating neurological disorders. Different from the conventional recording method based on electrical signals and the genetically encoded with fluorescent proteins methods, this review explores label-free mechanisms for optically recording electrophysiological signals: electrochromic materials, surface plasmon resonance (SPR) responses, quantum dots (QDs), and semiconductor-based optoelectronic sensors. The sophistication and limitations of each technology have been discussed, providing insights into potential future directions in this field. Electrochromic materials change optical properties through redox reactions induced by voltages, offering high signal-to-noise ratios and rapid response capabilities. However, these materials have limited biocompatibility and stability. SPR technology modulates signals in response to local changes in electrical potential, achieving high sensitivity. However, challenges such as scattering noise and electro-optic effects still need to be addressed. QDs utilize their photoluminescent properties for high sensitivity and resolution, but concerns about connection efficiency and biocompatibility remain. Semiconductor optoelectronic technologies offer rapid response times, wireless functionality, and integration potential. However, improvements are needed in terms of toxicity, compatibility with biological tissues, and signal amplification and processing. These methods have advantages in neuroscience, medical diagnostics, and biological research, including rapid response, high sensitivity, and label-free monitoring. By combining different optical recording techniques, the performance of voltage imaging can be optimized. In conclusion, interdisciplinary collaboration and innovation are essential for advancing the optical recording of electrophysiological signals and developing diagnostic and therapeutic approaches.
Rezaei Niya et al
The very large global demand for energy storage as inherently-variable renewable-energy sources meet an increasing proportion of total electricity demand will be difficult to meet solely with existing technologies. Hence additional storage technologies that are safe and based on abundant primary resources are likely to come into play to facilitate the transition to zero net emissions at the global level. One such promising technology is the 'proton battery', which in its most general form is a rechargeable battery based on proton transfer and reversible electrochemical hydrogen storage. In the present review, a general definition of a proton battery is first proposed, since the term has been used broadly and somewhat inconsistently to date. The literature over the past thirty years on this technology is then critically reviewed, covering both proton batteries that meet the definition proposed in this paper as well as those that are merely self-identified. To the extent possible through published information, the performances of this range of cells are compared in terms of key parameters such as electrical energy stored per unit mass, cyclability, self-discharge and scale reached. The proton battery design developed by our group at RMIT is described in more detail, both theoretically and in terms of experimentally-measured performance, as an exemplar of a system that has already demonstrated a competitive storage capacity at a significant scale. In conclusion, potential future applications for proton batteries, and some directions for the research and development necessary to enable this potential to be realised, are proposed.
Deng et al
C4F7N-CO2-O2 is currently considered the most promising replacement for SF6 in high-voltage circuit breakers. During high-current interruption conditions, arc radiation plays a pivotal role in arc modeling and is frequently accompanied by vapors ablated from the electrodes and nozzles. To investigate the influence of ablated vapors on the radiative properties of gas mixtures, net emission coefficients (NECs) for various ratios of C4F7N mixtures and PTFE and Cu vapors are calculated under the assumption of local thermodynamic equilibrium. The NECs for [C4F7N-CO2-O2]-PTFE-Cu mixtures that are obtained are required for radiation modeling and arc simulation in high-voltage circuit breakers. It has been found that neglecting the presence of PTFE vapor does not affect the
NEC at high temperatures. However, the influence of copper vapor on the radiative properties in the high-temperature region becomes apparent at elevated ratios, and self-absorption is more pronounced at very high pressures. Based on these findings, recommendations for choosing NECs for use in modeling that balance accuracy and efficiency are proposed.
Marekwa et al
The thermoelectric properties of Nb-doped (CuI)0.003Bi2-xNbxTe2.7Se0.3 compounds (x = 0, 0.005, 0.01 and 0.03), were investigated at temperatures ranging from 300 to 600 K. Among the compounds studied, the lightly substituted (CuI)0.003Bi1.995Nb0.005Te2.7Se0.3 compound exhibited the best thermoelectric performance due to the improvement in its electrical conductivity and its relatively unchanged Seebeck coefficient due to Nb doping. Its figure of merit, ZT, was greater than the undoped (CuI)0.003Bi2Te2.7Se0.3 compound for the temperature range investigated. In particular, the ZT of (CuI)0.003Bi1.995Nb0.005Te2.7Se0.3 reached a value of 0.65 at 448 K in this study.
García-Sánchez et al
Impact ionization originated by the buffer leakage current, together with high electric fields (> 3 MV/cm) at the anode corner of the isolating trenches, has been identified as the failure mechanism of shaped planar GaN Gunn diodes when biased above 20V, so that no evidence of Gunn oscillations in fabricated devices has been observed yet. In order to avoid the avalanche, we propose the addition of a Schottky substrate terminal, which, by means of Monte Carlo simulations, has been confirmed to be able to suppress such not-desired leakage current when applying a negative substrate bias. When the substrate bias is positive, impact ionization is also reduced due to the lower electric field at the hotspot, but a vertical cathode-substrate current degrades the device operation. In order to avoid such current, we propose the use a MIS configuration for the substrate contact, which is the optimal solution.
khosravizadeh et al
This study focuses on the method for determining the exact composition for CdxZn1−xO semiconducting material using secondary ion mass spectrometry. The calibration curve method was employed to establish a quantitative relationship between the intensity of the secondary ions and the concentrations of the elements in CdxZn1−xO thin films. Additionally, the study compares the relative sensitivity factors and the calibration curve method for determining the value of x in CdxZn1−xO. Furthermore, a comparison between the performances of Time of Flight and Magnetic Sector SIMS in the analysis of CdxZn1−xO thin films is presented. This approach aims to enhance the accuracy and reliability of quantitative analysis in SIMS for CdxZn1−xO thin films.
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Daniele Pirone et al 2024 J. Phys. D: Appl. Phys. 57 505402
Nowadays, radiotherapy (RT) is a consolidated treatment for the cancer care. In fact, ionizing radiations are employed in over 50% of cancer patients. However, some side effects are correlated with RT, such as the radiation-induced lymphopenia (RIL). RIL is due to circulating lymphocytes (LCs) that pass through the irradiation field. LCs are the most radiosensitive blood cells, therefore RT can affect the count and activity of LCs. LCs are an important component of the human immune system, thus RIL has been linked with worse outcomes in multiple solid tumors and poor survival. As the occurrence rate of RIL is ∼40%–70% of patients treated with RT, an effective tool for predicting and minimizing RIL is highly demanded. Here we propose the proof-of-concept of a minimally invasive approach to monitor alterations induced by the radiation exposure inside LCs. To this aim, we combine label-free Holographic Imaging Flow Cytometry and Machine Learning to study Jurkat cells as model of T-LCs irradiated with two x-ray doses (i.e. 2 and 10 Gy of 6 MeV photons). The proposed method allows correlating the morphological features extracted by the quantitative phase-contrast maps of irradiated LCs flowing in a microfluidic chip to their radiation response. Furthermore, we train several machine learning models at different time points after RT for assessing the best strategy to reveal its effect on irradiated LCs. The attained results pave the way to future and deeper investigations for the development of a label-free, minimally invasive, and high-throughput tool for predicting and minimizing the RIL side effects.
Seyed Mohammad Rezaei Niya et al 2024 J. Phys. D: Appl. Phys.
The very large global demand for energy storage as inherently-variable renewable-energy sources meet an increasing proportion of total electricity demand will be difficult to meet solely with existing technologies. Hence additional storage technologies that are safe and based on abundant primary resources are likely to come into play to facilitate the transition to zero net emissions at the global level. One such promising technology is the 'proton battery', which in its most general form is a rechargeable battery based on proton transfer and reversible electrochemical hydrogen storage. In the present review, a general definition of a proton battery is first proposed, since the term has been used broadly and somewhat inconsistently to date. The literature over the past thirty years on this technology is then critically reviewed, covering both proton batteries that meet the definition proposed in this paper as well as those that are merely self-identified. To the extent possible through published information, the performances of this range of cells are compared in terms of key parameters such as electrical energy stored per unit mass, cyclability, self-discharge and scale reached. The proton battery design developed by our group at RMIT is described in more detail, both theoretically and in terms of experimentally-measured performance, as an exemplar of a system that has already demonstrated a competitive storage capacity at a significant scale. In conclusion, potential future applications for proton batteries, and some directions for the research and development necessary to enable this potential to be realised, are proposed.
Dmitriy Yavorskiy et al 2024 J. Phys. D: Appl. Phys.
Hg1−xCdxTe alloys are unique because by increasing the Cd content x, one modifies the band structure from inverted to normal, which fundamentally modifies the dispersion of bulk and surface or edge (in the case of quantum wells) energy states. Using alloys with x close to the concentration xcat which the band inversion transition is observed and with additional application of hydrostatic pressure (p), one creates a favorable playground for studying the evolution of Dirac matter and its topological properties. In this work, cryogenic magnetospectroscopy in quantizing magnetic fields (B) at the far-infrared is used to study inter-Landau-level transitions in high-quality Hg1−xCdxTe MBE-grown epitaxial layers with x ∼ xc as a function of p up to 4.2 kbar. Special attention is paid to elucidate the role of the substrate and buffer layers, which usually modify the pressure coefficients of epitaxial layers. For this purpose, comparative measurements were carried out on as-grown epilayers with a GaAs substrate and on free-standing layers obtained by etching off the substrate. Spectra registered as a function of B (at given p) were analyzed with the help of the Kane model modified to include magnetic field. The pressure coefficient as well as the difference between conduction and valence band deformation potentials of the free-standing layer were determined at 2 K. Surprisingly, the deformation potentials and pressure coefficients of the epitaxial layer and those of the free-standing layer differed by no more than 10% in the pressure range up to 4.2 kbar. This finding questions the common belief of a dominant influence of the substrate on the pressure coefficients of epitaxial layers. We attribute the smallness of this difference to the presence of a highly disordered CdTe buffer separating the substrate from the epitaxial layer, which relaxes the transmission of strain from the substrate to the layer. Our results contribute to a better understanding of pressure experiments carried out on epitaxial layers on a substrate.
Alexander Vahl et al 2024 J. Phys. D: Appl. Phys. 57 503001
Major efforts to reproduce functionalities and energy efficiency of the brain have been focused on the development of artificial neuromorphic systems based on crossbar arrays of memristive devices fabricated by top-down lithographic technologies. Although very powerful, this approach does not emulate the topology and the emergent behavior of biological neuronal circuits, where the principle of self-organization regulates both structure and function. In materia computing has been proposed as an alternative exploiting the complexity and collective phenomena originating from various classes of physical substrates composed of a large number of non-linear nanoscale junctions. Systems obtained by the self-assembling of nano-objects like nanoparticles and nanowires show spatio-temporal correlations in their electrical activity and functional synaptic connectivity with nonlinear dynamics. The development of design-less networks offers powerful brain-inspired computing capabilities and the possibility of investigating critical dynamics in complex adaptive systems. Here we review and discuss the relevant aspects concerning the fabrication, characterization, modeling, and implementation of networks of nanostructures for data processing and computing applications. Different nanoscale electrical conduction mechanisms and their influence on the meso- and macroscopic functional properties of the systems are considered. Criticality, avalanche effects, edge-of-chaos, emergent behavior, synaptic functionalities are discussed in detail together with applications for unconventional computing. Finally, we discuss the challenges related to the integration of nanostructured networks and with standard microelectronics architectures.
Fency Sunny et al 2024 J. Phys. D: Appl. Phys.
2D transition metal dichalcogenides (TMDs) especially MoTe2 is an attractive topic of the modern era due to its unique properties. Although, research progress on 2D materials has been gained a lot of attentions due to new synthesis methods, extraordinary properties compared to bulk counterparts etc., there is room for modification for large scale production and tailoring output performance in some specific applications such as solar cells, energy storage and conversion devices etc. Compared to other 2D TMDs, MoTe2 offers lower bandgap which in turn gives the possibility to replace Si in many applications. This review is an attempt to assemble and encapsulate the structural properties, recent developments in the fabrication of 2D-MoTe2 and its different application in the field of batteries, transistors, energy conversion, solar cells etc. This review will help to provide a deep insight into the research on MoTe2 for modifying the structure and enhancing the properties of these layered materials.
Sung-Hyeon Jung et al 2024 J. Phys. D: Appl. Phys.
Atomic layer processing technology has advanced significantly since semiconductor devices have evolved from 2D to 3D stacked structures. Creating a uniform temperature distribution across the entire wafer during repeated heating and cooling cycles is an important aspect of atomic layer processing. Conventional embedded heaters rely on thermal conduction, resulting in slow heating rates. This can delay the cycle time of atomic layer processes, where rapid temperature changes are crucial. To overcome these problems, this study adopted a method to directly heat the wafer using gigahertz band microwaves. While there has been research on the heating mechanisms and effects of microwave irradiation on Si Wafers, studies on uniformity are lacking. Microwave heating depends on the distribution of the field, thus this study presents methods for improving uniformity by optimizing the antennas and controlling the cavity modes. A 2.45 GHz microwave was propagated in the TE10 mode in a WR-340 waveguide and radiated into the chamber through a slot located on a toroidal antenna designed for uniform heating. The radiated microwaves formed cavity modes within the chamber, thereby heating the 300 mm wafer. The wafer temperature was measured using a fiber Bragg grating sensor array; the heating rate at the top and back of the wafer was 6.5 °C /kW/s, and the within-wafer non-uniformity was 11.68 % and 10.94 %, respectively, after applying 500 W power for 60 s. A comparison of the temperature characteristics of the top and back sides of the wafer indicated no significant differences in uniformity, heating rate, and temperature profile. Based on these findings, it is anticipated that in atomic layer processes, where temperature control is crucial, the proposed method could reduce the process time and increase yield.
Mariusz Ciorga 2024 J. Phys. D: Appl. Phys.
The spin field effect transistor (sFET), proposed by Datta and Das in 1990, has long been regarded as a model semiconductor spintronic device, offering potential for new, more energy-efficient functionalities in electronic devices. Here, the overview is given how the pursuit of meeting the requirements for implementing the sFET concept has influenced spintronic research, leading to a greater understanding of spin phenomena in solids and resulting in numerous exciting effects. After looking back, based on the recent developments, the possible future directions of the sFET-related research is described.
Jonathan Crêpellière et al 2024 J. Phys. D: Appl. Phys.
n contemporary optoelectronic devices, the transparent conductive oxides commonly demonstrate
n-type conduction characteristics, with indium-doped tin oxide emerging as a prominent example.
However, in applications involving fully invisible electronics that necessitate p-type conductive ox-
ides, there exists a demand for a quintessential material possessing properties akin to its n-type
counterpart. CuCrO2, a delafossite semiconductor based on copper, presently represents a notable
compromise between optical and electrical attributes within the realm of p-type semiconductors.
Despite numerous studies focusing on this material, the charge carrier transport regime within the
material remains unclear. The commonly reported hole transport mechanism in CuCrO2 is the small
polaron model. However, this work evidences several contradictions when this transport mechanism
is assumed. Using the same methodology as previous studies, we investigated the holes' transport
mechanism by the means of the measurement of electrical conductivity and the Seebeck coefficient
at varying temperatures. Different charge transport models in high intrinsic defect doped CuCrO2
thin films are explored: small polarons, grain boundaries scattering in degenerate semiconductors,
and variable range hopping with nearest neighbor hopping. The small polaron model does not
provide conclusive results within the temperature range analyzed. Interestingly, no specific hole
transport mechanism can be undoubtedly selected. The limitations of the models highlight the in-
fluence of peculiar defects within CuCrO2 thin films on the hole transport mechanism, particularly
the adoption of well-ordered copper vacancies columns
Karthick Murukesan et al 2024 J. Phys. D: Appl. Phys.
In this report a comprehensive review of the variations in threshold voltage (VTH) resulting from diverse VTH measurement bias conditions employed by leading manufacturers, as well as VTH extraction techniques is made. Notably, a standard deviation of 15% is observed in threshold voltage values due to variations in measurement bias conditions. This variation is attributed to the change in the lateral electic field conditions across gate and drain which occurs due to the change in bias conditions. Additionally, a simplified physical interpretation of the gate stack in p-GaN gate normally-off AlGaN/GaN on Si HEMTs is made. The formation of the two-dimensional electron gas (2DEG), the charge balance within the pGaN/AlGaN/GaN gate stack, and an analytical expression for threshold voltage are examined. Furthermore, various trapping mechanisms within the gate stack are reviewed to comprehend the dynamic conditions potentially contributing to threshold voltage instability during nominal operation.
Taaresh Sanjeev Taneja et al 2024 J. Phys. D: Appl. Phys.
This work is a self-consistent 1D modeling of streamers in ammonia-oxygen-nitrogen-water mixtures. A fluid model that includes species transport, electrostatic potential, and detailed chemistry was developed and verified. This model is then used to simulate the avalanche, streamer formation and propagation phases, driven by a nanosecond voltage pulse, at different thermochemical conditions derived from a 1D laminar premixed ammonia-air flame. The applicability of the Meek's criterion in predicting the streamer inception location was successfully confirmed. Streamer formation and propagation duration were found to vary significantly with different thermochemical conditions, due to the difference in ionization rates. The thermochemical state also affected the breakdown characteristics which was tested by maintaining the background reduced electric field constant. Detailed kinetic analyses revealed the importance of O(1D) in the production of key radicals, such as O, OH, and NH2. Furthermore, the contributions of the dissociative electronic excitation of NH3 towards the production of H and NH2 radicals have also been reported. Spatial and temporal evolution of the electron energy loss fractions for various inelastic collision processes at different thermochemical states uncovered the input plasma energy spent of fuel dissociation and the large variability in the dominant processes during the avalanche and streamer propagation phases. The methodology and analyses reported in this work are key towards developing effective strategies for controlled nanosecond-pulsed non-equilibrium plasma sources used for ammonia ignition and flame stabilization.