Pub Date : 2024-09-15DOI: 10.1088/1361-6463/ad77df
Yadong Qiao, Fadi Wang, Wei Guo, Yuhang Wang and Fengping Wang
The utilization of two-dimensional van der waals heterostructures in optoelectronic synapses allows for the integration of information processing and memory, thereby providing novel operating platforms for simulating the perceptual visual systems and developing the neuromorphic computing systems due to its contactless, highly efficient and parallel computing. Herein, we have constructed a straightforward MoS2/WS2 heterostructure optoelectronic synapse and examined its capacity to imitate synaptic behaviors under optical stimulus. The MoS2/WS2 device demonstrated several synaptic functions, such as the excitatory postsynaptic current, short-term plasticity, long-term plasticity, pairs-pulse facilitation and ‘learning-experience’ behavior. Moreover, the MoS2/WS2 synaptic device can achieve a wide range of photo response wavelengths, spanning from UV to visible light, as well as the conversion from short-term plasticity to long-term plasticity. Furthermore, light-induced charge transfer due to adsorption and desorption of oxygen molecules in MoS2/WS2 heterostructure can be used to explain its working mechanism. Additionally, the synaptic plasticity of MoS2/WS2 device can be controlled by adjusting the duration, power and number of the optical pulses, which renders the MoS2/WS2-based optoelectronic synaptic device extremely favorable for implementation in the perceptual visual system.
{"title":"Multi-wavelength optoelectronic synapse based on MoS2/WS2 van der waals heterostructures","authors":"Yadong Qiao, Fadi Wang, Wei Guo, Yuhang Wang and Fengping Wang","doi":"10.1088/1361-6463/ad77df","DOIUrl":"https://doi.org/10.1088/1361-6463/ad77df","url":null,"abstract":"The utilization of two-dimensional van der waals heterostructures in optoelectronic synapses allows for the integration of information processing and memory, thereby providing novel operating platforms for simulating the perceptual visual systems and developing the neuromorphic computing systems due to its contactless, highly efficient and parallel computing. Herein, we have constructed a straightforward MoS2/WS2 heterostructure optoelectronic synapse and examined its capacity to imitate synaptic behaviors under optical stimulus. The MoS2/WS2 device demonstrated several synaptic functions, such as the excitatory postsynaptic current, short-term plasticity, long-term plasticity, pairs-pulse facilitation and ‘learning-experience’ behavior. Moreover, the MoS2/WS2 synaptic device can achieve a wide range of photo response wavelengths, spanning from UV to visible light, as well as the conversion from short-term plasticity to long-term plasticity. Furthermore, light-induced charge transfer due to adsorption and desorption of oxygen molecules in MoS2/WS2 heterostructure can be used to explain its working mechanism. Additionally, the synaptic plasticity of MoS2/WS2 device can be controlled by adjusting the duration, power and number of the optical pulses, which renders the MoS2/WS2-based optoelectronic synaptic device extremely favorable for implementation in the perceptual visual system.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"54 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142263078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1361-6463/ad7154
Sourav Mandal and Tapan Kumar Nath
Most of the ferromagnetic shape memory (FSM) Heusler alloys, which are primarily studied in bulk form in the literature, exhibit p-d type hybridization. This study conducts a thorough multidirectional investigation of a strongly d-d hybridized quinary melt-spun annealed ribbon having the composition Ni35Mn34.5Co14Fe1Ti15.5 (NMCFT-1). This off-stoichiometric, polycrystalline FSM, fabricated using the melt-spin technique, exhibits a highly textured microstructure, double magnetic transitions and super-mechanical features mitigating brittleness. It crystallizes in a perfectly B2-type disorder austenite (Pm-3m, space group number 221) phase at room temperature. It has been hypothesized that geometric frustration is the causative factor for this disorder. Curie temperature of austenite phase ( ) between paramagnetic → ferromagnetic state is found to be ∼364.57 K, whereas martensite transformation temperature from weak magnetic martensite state to ferromagnetic austenite state is ∼174.74 K. Calculated moments (effective moment, = 5.12 ; low-temperature saturation moment, (or ) = 5.08 ) yield a Rhodes–Wohlfarth ratio of ∼1, indicating the existence of the non-itinerant nature of 3d electrons, whereas the ferromagnetism and the linear or non-linear dependency of ) on T2 around indicates the presence of long-range Rudermann–Kittel–Kasuya–Yosida-type interaction. More importantly, the maximum magnetic entropy change ( ) obtained across the first-order magneto-structural transition and second-order magnetic transition are +18.2 J·kg−1K−1 at 6 T and −8.8 J·kg−1K−1 at 2 T, respectively, while a very high working temperature span (ΔTFWHM) of 28.561 K and 6.922 K are found for the same condition. The sample exhibits a significant relative cooling power of 402.98 J·kg−1 at a magnetic field of 6 T across the FOMT and 60.19 J·kg−1 at a 2 T field across the SOMT, respectively, along with excellent mechanical features such as a Vickers hardness (HV) of 411.80 HV (∼4.04 GPa). Meanwhile, Chen’s super hard model fails to predict the ribbon’s HV value, but Miao’s hard model does, indicating that the ribbon is hard but not super hard. It also paves the way for additional investigation into innovative FSMs like this.
{"title":"Non-itinerant-type ferromagnetism and the magnetocaloric response of quinary all-d-metal ribbon: Ni35Mn34.5Co14Fe1Ti15.5","authors":"Sourav Mandal and Tapan Kumar Nath","doi":"10.1088/1361-6463/ad7154","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7154","url":null,"abstract":"Most of the ferromagnetic shape memory (FSM) Heusler alloys, which are primarily studied in bulk form in the literature, exhibit p-d type hybridization. This study conducts a thorough multidirectional investigation of a strongly d-d hybridized quinary melt-spun annealed ribbon having the composition Ni35Mn34.5Co14Fe1Ti15.5 (NMCFT-1). This off-stoichiometric, polycrystalline FSM, fabricated using the melt-spin technique, exhibits a highly textured microstructure, double magnetic transitions and super-mechanical features mitigating brittleness. It crystallizes in a perfectly B2-type disorder austenite (Pm-3m, space group number 221) phase at room temperature. It has been hypothesized that geometric frustration is the causative factor for this disorder. Curie temperature of austenite phase ( ) between paramagnetic → ferromagnetic state is found to be ∼364.57 K, whereas martensite transformation temperature from weak magnetic martensite state to ferromagnetic austenite state is ∼174.74 K. Calculated moments (effective moment, = 5.12 ; low-temperature saturation moment, (or ) = 5.08 ) yield a Rhodes–Wohlfarth ratio of ∼1, indicating the existence of the non-itinerant nature of 3d electrons, whereas the ferromagnetism and the linear or non-linear dependency of ) on T2 around indicates the presence of long-range Rudermann–Kittel–Kasuya–Yosida-type interaction. More importantly, the maximum magnetic entropy change ( ) obtained across the first-order magneto-structural transition and second-order magnetic transition are +18.2 J·kg−1K−1 at 6 T and −8.8 J·kg−1K−1 at 2 T, respectively, while a very high working temperature span (ΔTFWHM) of 28.561 K and 6.922 K are found for the same condition. The sample exhibits a significant relative cooling power of 402.98 J·kg−1 at a magnetic field of 6 T across the FOMT and 60.19 J·kg−1 at a 2 T field across the SOMT, respectively, along with excellent mechanical features such as a Vickers hardness (HV) of 411.80 HV (∼4.04 GPa). Meanwhile, Chen’s super hard model fails to predict the ribbon’s HV value, but Miao’s hard model does, indicating that the ribbon is hard but not super hard. It also paves the way for additional investigation into innovative FSMs like this.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"45 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-12DOI: 10.1088/1361-6463/ad75a0
Jiaxin Li, He Ding, Yongtian Wang and Jian Yang
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.
{"title":"Advances in optical recording techniques for non-invasive monitoring of electrophysiological signals","authors":"Jiaxin Li, He Ding, Yongtian Wang and Jian Yang","doi":"10.1088/1361-6463/ad75a0","DOIUrl":"https://doi.org/10.1088/1361-6463/ad75a0","url":null,"abstract":"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.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76be
Yajing Wang, Chao Wang, Xinxin Wang, Shengqiang Cui, Min Hao, Chunhui Wang, Xudong Huang and Gui Yang
Polycrystalline SnSe, renowned for its environmental sustainability, holds promise as a significant thermoelectric material, attracting considerable research attention. This study focuses on the thermoelectric properties of p-type polycrystalline SnSe doped with silver copper telluride (AgCuTe). Our experimental results conclusively show that the decomposition products of AgCuTe not only fill Sn vacancies but also act as acceptors, thereby introducing additional hole carriers. This leads to a notable improvement in both carrier mobility and concentration. Importantly, the thermal conductivity of the doped samples remains largely unchanged, as the lattice flattening strategy significantly boosts electrical performance without affecting lattice thermal conductivity. Ultimately, the doped sample Sn0.97Se-0.5%AgCuTe resulted in a power factor of 6.2 mW mK−1 and a peak ZT value of 1.4 at 798 K, representing a 109% improvement in ZT value. All samples exhibits superior stability and reproducibility, emphasizing its reliability for practical applications.
多晶硒化锡以其环境可持续性而闻名，有望成为一种重要的热电材料，吸引了大量研究人员的关注。本研究的重点是掺杂了碲化银（AgCuTe）的 p 型多晶 SnSe 的热电特性。我们的实验结果确凿地表明，AgCuTe 的分解产物不仅填补了 Sn 的空位，而且还充当了受体，从而引入了额外的空穴载流子。这显著提高了载流子的迁移率和浓度。重要的是，掺杂样品的热导率基本保持不变，因为晶格扁平化策略在不影响晶格热导率的情况下显著提高了电性能。最终，掺杂样品 Sn0.97Se-0.5%AgCuTe 的功率因数达到 6.2 mW mK-1，798 K 时的 ZT 峰值为 1.4，ZT 值提高了 109%。所有样品都表现出卓越的稳定性和可重复性，突出了其在实际应用中的可靠性。
{"title":"Enhanced thermoelectric performance of AgCuTe-doped polycrystalline SnSe by lattice plainification","authors":"Yajing Wang, Chao Wang, Xinxin Wang, Shengqiang Cui, Min Hao, Chunhui Wang, Xudong Huang and Gui Yang","doi":"10.1088/1361-6463/ad76be","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76be","url":null,"abstract":"Polycrystalline SnSe, renowned for its environmental sustainability, holds promise as a significant thermoelectric material, attracting considerable research attention. This study focuses on the thermoelectric properties of p-type polycrystalline SnSe doped with silver copper telluride (AgCuTe). Our experimental results conclusively show that the decomposition products of AgCuTe not only fill Sn vacancies but also act as acceptors, thereby introducing additional hole carriers. This leads to a notable improvement in both carrier mobility and concentration. Importantly, the thermal conductivity of the doped samples remains largely unchanged, as the lattice flattening strategy significantly boosts electrical performance without affecting lattice thermal conductivity. Ultimately, the doped sample Sn0.97Se-0.5%AgCuTe resulted in a power factor of 6.2 mW mK−1 and a peak ZT value of 1.4 at 798 K, representing a 109% improvement in ZT value. All samples exhibits superior stability and reproducibility, emphasizing its reliability for practical applications.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"27 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this article, we report the hydrogen storage capacity of zirconium (Zr) decorated C24 fullerene using state-of-the-art density functional theory simulations. Our study shows that zirconium, like most other transition metals, tends to bind strongly on the C–C bridge of C24 fullerene with a maximum binding energy of −3.64 eV. Each Zr atom decorated over C24 fullerene can adsorb a maximum of 7H2 molecules with an average adsorption energy of −0.51 eV/H2, leading to a gravimetric density of 7.9 wt%, which is higher than the prescribed target of 6.5 wt% set by United States-Department of Energy. There is a charge transfer from Zr to C atoms in C24 fullerene, which is the primary cause of the binding of Zr with C24 fullerene. H2 molecules are adsorbed over Zr sorption sites via Kubas-type interactions, which include charge donation from the filled s orbitals of hydrogen to the vacant 4d orbital of Zr and subsequent back charge donation to unfilled s* orbital of hydrogen from the filled 4d orbital of Zr. The structural stability of the Zr + C24 system at a high temperature of 500 K is verified using ab-initio molecular dynamics calculations. The high diffusion energy barrier of Zr (2.33 eV) inhibits clustering between the Zr atoms decorated on the C24 fullerene and ensures the system’s practical feasibility as a high-capacity H2 adsorbing system. Therefore, our computational studies confirm that Zr decorated C24 fullerene is stable and can be regarded as a potential candidate for H2 storage systems with optimum adsorption energy range.
{"title":"Zr doped C24 fullerene as efficient hydrogen storage material: insights from DFT simulations","authors":"Ajit Kundu, Ankita Jaiswal, Pranoy Ray, Sridhar Sahu and Brahmananda Chakraborty","doi":"10.1088/1361-6463/ad75a1","DOIUrl":"https://doi.org/10.1088/1361-6463/ad75a1","url":null,"abstract":"In this article, we report the hydrogen storage capacity of zirconium (Zr) decorated C24 fullerene using state-of-the-art density functional theory simulations. Our study shows that zirconium, like most other transition metals, tends to bind strongly on the C–C bridge of C24 fullerene with a maximum binding energy of −3.64 eV. Each Zr atom decorated over C24 fullerene can adsorb a maximum of 7H2 molecules with an average adsorption energy of −0.51 eV/H2, leading to a gravimetric density of 7.9 wt%, which is higher than the prescribed target of 6.5 wt% set by United States-Department of Energy. There is a charge transfer from Zr to C atoms in C24 fullerene, which is the primary cause of the binding of Zr with C24 fullerene. H2 molecules are adsorbed over Zr sorption sites via Kubas-type interactions, which include charge donation from the filled s orbitals of hydrogen to the vacant 4d orbital of Zr and subsequent back charge donation to unfilled s* orbital of hydrogen from the filled 4d orbital of Zr. The structural stability of the Zr + C24 system at a high temperature of 500 K is verified using ab-initio molecular dynamics calculations. The high diffusion energy barrier of Zr (2.33 eV) inhibits clustering between the Zr atoms decorated on the C24 fullerene and ensures the system’s practical feasibility as a high-capacity H2 adsorbing system. Therefore, our computational studies confirm that Zr decorated C24 fullerene is stable and can be regarded as a potential candidate for H2 storage systems with optimum adsorption energy range.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"4 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76b8
Xiaojun Huang, Ke Li, Wei Hou, Yanpei Wang and Yutao Ma
This paper investigates a highly selective frequency selective rasorber (FSR) utilizing interdigitated resonators, characterized by a passband exhibiting low insertion loss (IL) and the introduction of a second-order passband response in the lossless layer enhances selectivity on both sides of the passband. The lossy unit is implemented by inserting interdigitated resonators on an octagonal ring loaded with lumped resistors, while the lossless layer is constructed with a five-layer structure. Simulation results demonstrate a low IL value of 0.78 dB at 3.5 GHz. At vertical incidence, the S21>−3 dB bandwidth ranges from 3.41 to 3.67 GHz, and the S11<−10 dB range spans from 2.2 to 8.2 GHz, obtaining two absorption bands on either side of the passband, with absorption rates exceeding 80%. The operating frequency bands are 1.95–3.27 GHz and 3.8–8.4 GHz. The designed FSR exhibits polarization insensitive. To validate simulation results, a prototype FSR was fabricated and tested, with experimental data aligning with simulation results.
{"title":"Interdigitated resonator based frequency selective rasorber with high selectivity","authors":"Xiaojun Huang, Ke Li, Wei Hou, Yanpei Wang and Yutao Ma","doi":"10.1088/1361-6463/ad76b8","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76b8","url":null,"abstract":"This paper investigates a highly selective frequency selective rasorber (FSR) utilizing interdigitated resonators, characterized by a passband exhibiting low insertion loss (IL) and the introduction of a second-order passband response in the lossless layer enhances selectivity on both sides of the passband. The lossy unit is implemented by inserting interdigitated resonators on an octagonal ring loaded with lumped resistors, while the lossless layer is constructed with a five-layer structure. Simulation results demonstrate a low IL value of 0.78 dB at 3.5 GHz. At vertical incidence, the S21>−3 dB bandwidth ranges from 3.41 to 3.67 GHz, and the S11<−10 dB range spans from 2.2 to 8.2 GHz, obtaining two absorption bands on either side of the passband, with absorption rates exceeding 80%. The operating frequency bands are 1.95–3.27 GHz and 3.8–8.4 GHz. The designed FSR exhibits polarization insensitive. To validate simulation results, a prototype FSR was fabricated and tested, with experimental data aligning with simulation results.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"59 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad7473
Chao Fang, Xiaogang Zheng, Jue Liu, Han Du and George J Weng
This paper uses a Monte Carlo method to study the thermal conductivity of graphene nanoplatelet (GNP) composites. Firstly, a large number of GNPs are randomly set in a representative volume element. Then, based on a temperature satisfying the Laplace equation in a matrix, a coated surface (CS) is set up on each GNP surface, and the temperature of the CS and GNP can be obtained by the walk-on-spheres (WoS) method. Finally, the WoS method continues to be applied to calculate the heat flux density of the composite materials, further obtaining the thermal conductivity of the composites. We add the influence of interlayers in random walks. We incorporate the influence of interlayers in the WoS process, and the points that walk onto the interlayer surface have a very low probability of reaching the GNP due to the extremely low thermal conductivity of the interlayer. The calculated results are consistent with the experimental data. The model also studies the effects of the size, orientation, and aggregation of GNPs on the thermal conductivity of composite materials.
{"title":"Uncovering the thermal conductivity of graphene nanoplatelet composites with interlayers using a Monte Carlo model","authors":"Chao Fang, Xiaogang Zheng, Jue Liu, Han Du and George J Weng","doi":"10.1088/1361-6463/ad7473","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7473","url":null,"abstract":"This paper uses a Monte Carlo method to study the thermal conductivity of graphene nanoplatelet (GNP) composites. Firstly, a large number of GNPs are randomly set in a representative volume element. Then, based on a temperature satisfying the Laplace equation in a matrix, a coated surface (CS) is set up on each GNP surface, and the temperature of the CS and GNP can be obtained by the walk-on-spheres (WoS) method. Finally, the WoS method continues to be applied to calculate the heat flux density of the composite materials, further obtaining the thermal conductivity of the composites. We add the influence of interlayers in random walks. We incorporate the influence of interlayers in the WoS process, and the points that walk onto the interlayer surface have a very low probability of reaching the GNP due to the extremely low thermal conductivity of the interlayer. The calculated results are consistent with the experimental data. The model also studies the effects of the size, orientation, and aggregation of GNPs on the thermal conductivity of composite materials.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"1 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad7038
Zhao-Yang Ma, Jin-Shan He, Gan-Yun Huang and Liao-Liang Ke
The tendency of relative motion via rolling between contacting objects exists in various aspects of industry and nature because, in many practical situations, forces and moments may be simultaneously induced at the contacting interfaces. Due to the presence of adhesion, which may be prominent on small scales, research on contacts with the tendency to roll, termed herein as rolling adhesion, is very limited. In the present work, a novel double-Hertz model is developed for adhesive contact between spherical objects subjected to the combined action of normal forces and moments. The results from the new model agree well with available numerical simulations and experimental results. It has been demonstrated that the contact behavior with the effect of rolling adhesion seemingly resembles that of conventional adhesive contact, but the applied moment may impact the pull-off force and may even induce novel contact instability if large enough. The resistance moment at the interface has also been obtained analytically, which is proportional to adhesion hysteresis and contact area. Given the applicability to the full range of the Tabor parameter and nonsingular stresses involved, these results might shed light on adhesive contacts with rolling adhesion and help to characterize them better than existent models.
{"title":"On adhesive contact between spheres with rolling adhesion","authors":"Zhao-Yang Ma, Jin-Shan He, Gan-Yun Huang and Liao-Liang Ke","doi":"10.1088/1361-6463/ad7038","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7038","url":null,"abstract":"The tendency of relative motion via rolling between contacting objects exists in various aspects of industry and nature because, in many practical situations, forces and moments may be simultaneously induced at the contacting interfaces. Due to the presence of adhesion, which may be prominent on small scales, research on contacts with the tendency to roll, termed herein as rolling adhesion, is very limited. In the present work, a novel double-Hertz model is developed for adhesive contact between spherical objects subjected to the combined action of normal forces and moments. The results from the new model agree well with available numerical simulations and experimental results. It has been demonstrated that the contact behavior with the effect of rolling adhesion seemingly resembles that of conventional adhesive contact, but the applied moment may impact the pull-off force and may even induce novel contact instability if large enough. The resistance moment at the interface has also been obtained analytically, which is proportional to adhesion hysteresis and contact area. Given the applicability to the full range of the Tabor parameter and nonsingular stresses involved, these results might shed light on adhesive contacts with rolling adhesion and help to characterize them better than existent models.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"11 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad773d
Zhaoying Xi, Zeng Liu, Junpeng Fang, Ang Bian, Shaohui Zhang, Jia-Han Zhang, Lei Li, Yufeng Guo and Weihua Tang
Etching plays a key role in processing and manufacturing electronic and optoelectronic devices. For ultra-wide bandgap semiconductor gallium oxide (Ga2O3), its etching investigations and evolution mechanism are still at the earlier stage, and some more research gumption should be invested. In this review, we make a summary on the etching of Ga2O3, including dry (plasma) etching, wet chemical etching, and photoelectrochemical etching, and discuss the etching results, existing problems, and feasible solutions, in order to provide guidance and advises for furtherly developing the Ga2O3 etching and Ga2O3-based electronic and optoelectronic devices.
{"title":"Etching of Ga2O3: an important process for device manufacturing","authors":"Zhaoying Xi, Zeng Liu, Junpeng Fang, Ang Bian, Shaohui Zhang, Jia-Han Zhang, Lei Li, Yufeng Guo and Weihua Tang","doi":"10.1088/1361-6463/ad773d","DOIUrl":"https://doi.org/10.1088/1361-6463/ad773d","url":null,"abstract":"Etching plays a key role in processing and manufacturing electronic and optoelectronic devices. For ultra-wide bandgap semiconductor gallium oxide (Ga2O3), its etching investigations and evolution mechanism are still at the earlier stage, and some more research gumption should be invested. In this review, we make a summary on the etching of Ga2O3, including dry (plasma) etching, wet chemical etching, and photoelectrochemical etching, and discuss the etching results, existing problems, and feasible solutions, in order to provide guidance and advises for furtherly developing the Ga2O3 etching and Ga2O3-based electronic and optoelectronic devices.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"30 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76b7
Qi Yuan, Guoxiang Sun, Haorui Xue, Weidong Ding, Shaohao Nie and Kunhao Yu
High-power pulse generators are widely used in civil and military fields. The main switch directly determines the output characteristics of the high-power pulse generators, such as the voltage front time (tf). Pseudospark switches (PSS) show a promising future for middle voltage, high repetitive frequency pulse power applications. However, how to further improve the breakdown behavior without reducing its advantages is a challenging task. In this paper, the influence of operating parameters (anode voltage UA and gas pressure p) and structural parameter (number of cathode holes) on the breakdown behavior are investigated, the related mechanism are explained, and specific improvement schemes are proposed. It is found that the tf of the single channel PSS (SCPSS) decreased significantly with increasing p, but hardly varied with UA under moderate p. However, it is not a sound solution to increase the p excessively to reduce tf. Besides, increasing the number of cathode holes can obtain a shorter tf at low pressures (which implies superior repetition frequency performance). However, at 25 Pa, the jitter (which is defined as the standard deviation of tf in multiple tests) of the 2-channel PSS is larger than that of the SCPSS. And the jitter of the 4-channel and 8-channel PSS is also greater than 6 ns and 2 ns, respectively. Through experimental and simulation analyses, it can be explained as the stepwise penetration of the virtual anode and the non-simultaneous ignition of the channels. A scheme to increase the trigger energy (ϵ) has been adopted to improve the simultaneous ignition probability, while shortening tf and reducing jitter. After optimization, the good ignition probability of the 4-channel PSS has been improved to 82% and the jitter has been reduced to less than 1 ns at 25 Pa and 14.7 mJ.
大功率脉冲发生器广泛应用于民用和军用领域。主开关直接决定了大功率脉冲发生器的输出特性，如电压前沿时间（tf）。伪火花开关（PSS）在中压、高重复频率脉冲功率应用方面前景广阔。然而，如何在不降低其优势的情况下进一步改善击穿行为是一项具有挑战性的任务。本文研究了工作参数（阳极电压 UA 和气体压力 p）和结构参数（阴极孔数）对击穿行为的影响，解释了相关机理，并提出了具体的改进方案。研究发现，单通道 PSS（SCPSS）的 tf 随 p 的增大而显著减小，但在中等 p 条件下几乎不随 UA 的变化而变化。此外，增加阴极孔的数量可以在低压下获得更短的 tf（这意味着更优越的重复频率性能）。然而，在 25 Pa 时，双通道 PSS 的抖动（定义为多次测试中 tf 的标准偏差）大于 SCPSS。而 4 通道和 8 通道 PSS 的抖动也分别大于 6 ns 和 2 ns。通过实验和模拟分析，这可以解释为虚拟阳极的逐步穿透和通道的非同时点火。为了提高同时点火概率，同时缩短 tf 和减少抖动，我们采用了增加触发能量（ϵ）的方案。经过优化，4 通道 PSS 的良好点火概率提高到了 82%，在 25 Pa 和 14.7 mJ 条件下，抖动降低到了 1 ns 以下。
{"title":"Influence factors and improvement scheme on the breakdown behavior of pseudospark switch","authors":"Qi Yuan, Guoxiang Sun, Haorui Xue, Weidong Ding, Shaohao Nie and Kunhao Yu","doi":"10.1088/1361-6463/ad76b7","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76b7","url":null,"abstract":"High-power pulse generators are widely used in civil and military fields. The main switch directly determines the output characteristics of the high-power pulse generators, such as the voltage front time (tf). Pseudospark switches (PSS) show a promising future for middle voltage, high repetitive frequency pulse power applications. However, how to further improve the breakdown behavior without reducing its advantages is a challenging task. In this paper, the influence of operating parameters (anode voltage UA and gas pressure p) and structural parameter (number of cathode holes) on the breakdown behavior are investigated, the related mechanism are explained, and specific improvement schemes are proposed. It is found that the tf of the single channel PSS (SCPSS) decreased significantly with increasing p, but hardly varied with UA under moderate p. However, it is not a sound solution to increase the p excessively to reduce tf. Besides, increasing the number of cathode holes can obtain a shorter tf at low pressures (which implies superior repetition frequency performance). However, at 25 Pa, the jitter (which is defined as the standard deviation of tf in multiple tests) of the 2-channel PSS is larger than that of the SCPSS. And the jitter of the 4-channel and 8-channel PSS is also greater than 6 ns and 2 ns, respectively. Through experimental and simulation analyses, it can be explained as the stepwise penetration of the virtual anode and the non-simultaneous ignition of the channels. A scheme to increase the trigger energy (ϵ) has been adopted to improve the simultaneous ignition probability, while shortening tf and reducing jitter. After optimization, the good ignition probability of the 4-channel PSS has been improved to 82% and the jitter has been reduced to less than 1 ns at 25 Pa and 14.7 mJ.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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