Low-temperature plasma technology is a promising technological route to achieve green and efficient ammonia synthesis at ambient temperature and pressure. In this work, a Laval nozzle type gliding arc plasma reactor was designed for the direct synthesis of ammonia from N2 and H2 discharges ignited by a high voltage nanosecond pulsed power supply to investigate the effect of different electrode gaps, pulse voltages, and VN2:VH2 on ammonia synthesis. The nanosecond pulsed plasma discharges were characterized through oscilloscope and optical emission spectroscopy (OES). The maximum rate of NH3 synthesis was 538.12 μmol•h-1 at 1.5 mm electrode gap, 16 kV peak pulse voltage, 6 kHz pulse repetition frequency, 100 ns pulse width, 100 ns pulse rising edge, 100 ns pulse falling edge, and 200 mL min-1 total gas flow rate with VN2:VH2=1:1. It was demonstrated that the discharge mode of the nanosecond pulsed gliding arc plasma can transit from a unipolar state to a bipolar state determined by the duty cycle accompanied with higher discharge power and vibrational temperature. Bipolar discharge mode is beneficial to improve the efficiency of plasma ammonia synthesis because of it can strengthen the plasma discharge and increase the vibrational temperature. The ammonia synthesis rate and N2 conversion rate increased with the increase of the discharge power and electron vibrational temperature.
{"title":"Nanosecond pulsed gliding arc plasma for ammonia synthesis: Better insight from discharge mode and electron temperature","authors":"Xiaofang Xu, Meng Sun, Qinlong Song, Guangyi Liu, Haibao Zhang","doi":"10.1088/1361-6463/ad5f3d","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5f3d","url":null,"abstract":"\u0000 Low-temperature plasma technology is a promising technological route to achieve green and efficient ammonia synthesis at ambient temperature and pressure. In this work, a Laval nozzle type gliding arc plasma reactor was designed for the direct synthesis of ammonia from N2 and H2 discharges ignited by a high voltage nanosecond pulsed power supply to investigate the effect of different electrode gaps, pulse voltages, and VN2:VH2 on ammonia synthesis. The nanosecond pulsed plasma discharges were characterized through oscilloscope and optical emission spectroscopy (OES). The maximum rate of NH3 synthesis was 538.12 μmol•h-1 at 1.5 mm electrode gap, 16 kV peak pulse voltage, 6 kHz pulse repetition frequency, 100 ns pulse width, 100 ns pulse rising edge, 100 ns pulse falling edge, and 200 mL min-1 total gas flow rate with VN2:VH2=1:1. It was demonstrated that the discharge mode of the nanosecond pulsed gliding arc plasma can transit from a unipolar state to a bipolar state determined by the duty cycle accompanied with higher discharge power and vibrational temperature. Bipolar discharge mode is beneficial to improve the efficiency of plasma ammonia synthesis because of it can strengthen the plasma discharge and increase the vibrational temperature. The ammonia synthesis rate and N2 conversion rate increased with the increase of the discharge power and electron vibrational temperature.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141678441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-6463/ad5f28
Muhammad Azeem, Udayan Anakha, Michal Mazur, Qaisar Abbas, A. Berezner
Signatures of strong antiferromagnetic exchange coupling at the interface of Gd2O3/GdFeO3 subphases of gadolinium nickel zinc ferrite nanoparticle ensemble have been observed. Hybridized domain walls are exchange coupled to the magnetic subphases on both sides of the interface. Origin of the coupling is in the quantum interference of the Bloch waves with the energy states within the domain walls. The coupling mechanism intensifies at low temperatures. A constriction in the middle of the hysteresis loop (at H=0) is believed to be the result of antiferromagnetic transitions which becomes narrow at 5K. The constriction at 5 K effectively divides the hysteresis loop in two parts, confining spin vector components in the positive and negative quadrants. The magnetic susceptibility clearly shows antiferromagnetic transition temperature (TN) of approximately 17 K.
在钆镍锌铁氧体纳米粒子集合的 Gd2O3/GdFeO3 亚相界面上观察到了强反铁磁交换耦合的迹象。杂化畴壁与界面两侧的磁性子相间存在交换耦合。耦合的起源是布洛赫波与畴壁内能态的量子干涉。耦合机制在低温下会加剧。滞后环中间（H=0 时）的收缩被认为是反铁磁跃迁的结果，在 5K 时收缩变窄。5 K 时的收缩有效地将磁滞回线分为两部分，将自旋矢量分量限制在正象限和负象限。磁感应强度清楚地表明反铁磁转变温度（TN）约为 17 K。
{"title":"Strong antiferromagnetic exchange coupling at Gd2O3/GdFeO3 interfaces in nanoparticle ensembles","authors":"Muhammad Azeem, Udayan Anakha, Michal Mazur, Qaisar Abbas, A. Berezner","doi":"10.1088/1361-6463/ad5f28","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5f28","url":null,"abstract":"\u0000 Signatures of strong antiferromagnetic exchange coupling at the interface of Gd2O3/GdFeO3 subphases of gadolinium nickel zinc ferrite nanoparticle ensemble have been observed. Hybridized domain walls are exchange coupled to the magnetic subphases on both sides of the interface. Origin of the coupling is in the quantum interference of the Bloch waves with the energy states within the domain walls. The coupling mechanism intensifies at low temperatures. A constriction in the middle of the hysteresis loop (at H=0) is believed to be the result of antiferromagnetic transitions which becomes narrow at 5K. The constriction at 5 K effectively divides the hysteresis loop in two parts, confining spin vector components in the positive and negative quadrants. The magnetic susceptibility clearly shows antiferromagnetic transition temperature (TN) of approximately 17 K.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141680173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-6463/ad5f38
G. R. Suwito, S. Haffouz, D. Dalacu, P. Poole, Nathaniel Quitoriano
We reported nucleation mechanisms of InP directly on Si (8% lattice mismatch) under confined structures, called micro-crucibles, at ultra-high vacuum (UHV) by chemical beam epitaxy (CBE). These micro-crucibles are used to induce lateral growth in the presence of a micro-scale Au catalyst. It is found that at this UHV condition, the kinetics is dictated predominantly by adatom surface diffusion. Using a two-step growth process ((1) In-only exposure, then, (2) simultaneous In and P exposures), InP islands have been successfully nucleated on Si substrates under micro-crucible structures. The nucleation of these InP islands strongly depends on the metal catalyst location relative to the micro-crucible opening with metal catalysts residing closer to the opening having a higher chance to get incorporated with In and P atoms. Importantly, we found that using smaller micro-crucibles with double openings can increase the possibility of having metal catalysts reside near either opening and nucleate InP under micro-crucibles.
我们报告了在超高真空（UHV）条件下，通过化学束外延（CBE）在称为微坩埚的密闭结构下直接在硅上（8% 晶格失配）形成 InP 的成核机制。这些微坩埚用于在微尺度金催化剂的作用下诱导横向生长。研究发现，在这种超高真空条件下，动力学主要由金刚原子表面扩散决定。利用两步生长过程（(1) 只暴露于 In，然后 (2) 同时暴露于 In 和 P），成功地在微脆性结构下的硅衬底上形成了 InP 岛。这些 InP 岛的成核在很大程度上取决于金属催化剂相对于微脆性开口的位置，金属催化剂越靠近开口，与 In 原子和 P 原子结合的机会就越大。重要的是，我们发现使用具有双开口的较小微坩埚可以增加金属催化剂靠近任一开口并在微坩埚下形成 InP 核的可能性。
{"title":"Nucleation of InP on Si under Micro-Crucibles at Ultra-High Vacuum using a Two-Step VLS Process","authors":"G. R. Suwito, S. Haffouz, D. Dalacu, P. Poole, Nathaniel Quitoriano","doi":"10.1088/1361-6463/ad5f38","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5f38","url":null,"abstract":"\u0000 We reported nucleation mechanisms of InP directly on Si (8% lattice mismatch) under confined structures, called micro-crucibles, at ultra-high vacuum (UHV) by chemical beam epitaxy (CBE). These micro-crucibles are used to induce lateral growth in the presence of a micro-scale Au catalyst. It is found that at this UHV condition, the kinetics is dictated predominantly by adatom surface diffusion. Using a two-step growth process ((1) In-only exposure, then, (2) simultaneous In and P exposures), InP islands have been successfully nucleated on Si substrates under micro-crucible structures. The nucleation of these InP islands strongly depends on the metal catalyst location relative to the micro-crucible opening with metal catalysts residing closer to the opening having a higher chance to get incorporated with In and P atoms. Importantly, we found that using smaller micro-crucibles with double openings can increase the possibility of having metal catalysts reside near either opening and nucleate InP under micro-crucibles.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141677825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-6463/ad5f3a
Yujing Xu, Tong Wu, Xixi Jing, Shengduo Xu, Jishen Zhang, Hao Zhang, Dingxin Liu, Li Guo, Han Xu, Xiaohu Wang, Min-Zhi Rong
Compared with conventional 2D cell culture model, the 3D tumor model constructed in vitro is better representative of the tumor microenvironment in vivo. Here, we proposed the utilization of 3D tumor model of co-cultured cancer cells and normal cells to evaluate the selective anticancer effects of cold atmospheric plasma-activated saline (PAS), and expected to provide more precise information about PAS-tumor interactions. By cell sorting, we clarified that A375 melanoma cells and HaCaT normal skin cells purified from the 3D multicellular tumor model differ in sensitivity and responsiveness to PAS compared to the 2D culture model. And during the optimization of PAS treatment parameters, we further found that A375 cells were almost completely killed while HaCaT cells were still present in large numbers after 5 days of certain PAS treatment. Our experiment innovatively carries out the selective study of plasma technology in 3D co-culture system and provides a theoretical basis for further clinical and practical applications of PAS.
与传统的二维细胞培养模型相比，体外构建的三维肿瘤模型更能代表体内的肿瘤微环境。在此，我们提出利用癌细胞和正常细胞共培养的三维肿瘤模型来评估冷大气等离子体激活生理盐水（PAS）的选择性抗癌作用，并期望提供更精确的 PAS 与肿瘤相互作用的信息。通过细胞分选，我们明确了从三维多细胞肿瘤模型中纯化的 A375 黑色素瘤细胞和 HaCaT 正常皮肤细胞对 PAS 的敏感性和反应性与二维培养模型不同。在优化 PAS 处理参数的过程中，我们进一步发现 A375 细胞几乎被完全杀死，而 HaCaT 细胞在经过一定的 PAS 处理 5 天后仍大量存在。我们的实验创新性地开展了血浆技术在三维共培养系统中的选择性研究，为 PAS 的进一步临床和实际应用提供了理论依据。
{"title":"Selective anticancer effects of plasma-activated saline in 3D tumor model co-culturing of normal cells and cancer cells","authors":"Yujing Xu, Tong Wu, Xixi Jing, Shengduo Xu, Jishen Zhang, Hao Zhang, Dingxin Liu, Li Guo, Han Xu, Xiaohu Wang, Min-Zhi Rong","doi":"10.1088/1361-6463/ad5f3a","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5f3a","url":null,"abstract":"\u0000 Compared with conventional 2D cell culture model, the 3D tumor model constructed in vitro is better representative of the tumor microenvironment in vivo. Here, we proposed the utilization of 3D tumor model of co-cultured cancer cells and normal cells to evaluate the selective anticancer effects of cold atmospheric plasma-activated saline (PAS), and expected to provide more precise information about PAS-tumor interactions. By cell sorting, we clarified that A375 melanoma cells and HaCaT normal skin cells purified from the 3D multicellular tumor model differ in sensitivity and responsiveness to PAS compared to the 2D culture model. And during the optimization of PAS treatment parameters, we further found that A375 cells were almost completely killed while HaCaT cells were still present in large numbers after 5 days of certain PAS treatment. Our experiment innovatively carries out the selective study of plasma technology in 3D co-culture system and provides a theoretical basis for further clinical and practical applications of PAS.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141677719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-6463/ad5f3c
D. F. Santos, N. A. Almeida, L. G. Benilova, M. Benilov
The introduction of secondary ion-electron emission into an approximate model of non-equilibrium plasma layers on hot (thermionic) cathodes of high-pressure arc discharges allows extending the model to low cathode surface temperatures. Analysis of evaluation results shows that the extended model describes glow-like discharges on cold cathodes and thermionic arc discharges on hot cathodes, as it should. In the course of glow-to-arc transitions on cold cathodes, a transient regime occurs where a hot arc spot has just formed and a significant fraction of the current still flows to the cold surface outside the spot, so that the near-cathode voltage continues to be high. The power input in the near-cathode layer is very high in this regime, and so is the electron temperature in the near-cathode region. The mean free path for collisions between the atoms and the ions in these conditions exceeds the thickness of the layer where the ion current to the cathode is generated. A new method for evaluation of the ion current under such conditions is implemented. The developed model is applicable for cathode surface temperatures below the boiling point of the cathode material and may be used for multidimensional simulations of ignition of high-current arcs on refractory cathodes.
{"title":"Model of non-equilibrium near-cathode plasma layers for simulation of ignition of high-pressure arcs on cold refractory cathodes","authors":"D. F. Santos, N. A. Almeida, L. G. Benilova, M. Benilov","doi":"10.1088/1361-6463/ad5f3c","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5f3c","url":null,"abstract":"\u0000 The introduction of secondary ion-electron emission into an approximate model of non-equilibrium plasma layers on hot (thermionic) cathodes of high-pressure arc discharges allows extending the model to low cathode surface temperatures. Analysis of evaluation results shows that the extended model describes glow-like discharges on cold cathodes and thermionic arc discharges on hot cathodes, as it should. In the course of glow-to-arc transitions on cold cathodes, a transient regime occurs where a hot arc spot has just formed and a significant fraction of the current still flows to the cold surface outside the spot, so that the near-cathode voltage continues to be high. The power input in the near-cathode layer is very high in this regime, and so is the electron temperature in the near-cathode region. The mean free path for collisions between the atoms and the ions in these conditions exceeds the thickness of the layer where the ion current to the cathode is generated. A new method for evaluation of the ion current under such conditions is implemented. The developed model is applicable for cathode surface temperatures below the boiling point of the cathode material and may be used for multidimensional simulations of ignition of high-current arcs on refractory cathodes.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141678726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-6463/ad5f3b
J. Polito, M. Kushner
Cold atmospheric plasma (CAP) devices have shown promise for a variety of plasma medical applications including wound healing and bacterial inactivation often contained in liquids. In the latter application, plasma-produced reactive oxygen and nitrogen species (RONS) interact with and damage bacterial cells, though the exact mechanism by which cell damage occurs is unclear. Computational models can help elucidate relationships between plasma-produced RONS and cell killing by enabling direct comparison between dissimilar plasma devices and by examining the effects of changing operating parameters in these devices. In biological applications, computational models of plasma-liquid interactions would be most effective in design and optimization of plasma devices if there is a corresponding prediction of the biological outcome. In this work, we propose a hierarchal model for planktonic bacterial cell inactivation by plasma produced RONS in liquid. A previously developed reaction mechanism for plasma induced modification of cysteine was extended to provide a basis for cell killing by plasma-produced RONS. Results from the model are compared to literature to provide proof of concept. Differences in time to bacterial inactivation as a function of plasma operating parameters including gas composition and plasma source configuration are discussed. Results indicate that optimizing gas-phase reactive nitrogen species (RNS) production may be key in the design of plasma devices for disinfection.
{"title":"A hierarchal model for bacterial cell inactivation in solution by direct and indirect treatment using cold atmospheric plasmas","authors":"J. Polito, M. Kushner","doi":"10.1088/1361-6463/ad5f3b","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5f3b","url":null,"abstract":"\u0000 Cold atmospheric plasma (CAP) devices have shown promise for a variety of plasma medical applications including wound healing and bacterial inactivation often contained in liquids. In the latter application, plasma-produced reactive oxygen and nitrogen species (RONS) interact with and damage bacterial cells, though the exact mechanism by which cell damage occurs is unclear. Computational models can help elucidate relationships between plasma-produced RONS and cell killing by enabling direct comparison between dissimilar plasma devices and by examining the effects of changing operating parameters in these devices. In biological applications, computational models of plasma-liquid interactions would be most effective in design and optimization of plasma devices if there is a corresponding prediction of the biological outcome. In this work, we propose a hierarchal model for planktonic bacterial cell inactivation by plasma produced RONS in liquid. A previously developed reaction mechanism for plasma induced modification of cysteine was extended to provide a basis for cell killing by plasma-produced RONS. Results from the model are compared to literature to provide proof of concept. Differences in time to bacterial inactivation as a function of plasma operating parameters including gas composition and plasma source configuration are discussed. Results indicate that optimizing gas-phase reactive nitrogen species (RNS) production may be key in the design of plasma devices for disinfection.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141680410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.1088/1361-6463/ad5f39
W. He, Shilin Wu, Zhaotian Zhang, Qing Yang
Electrolysis of water for producing hydrogen is an effective and sustainable technique to meet the continuously increasing energy demand. Nevertheless, its advancement is impeded by the inadequate catalytic efficacy for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Vacancy defect engineering is a rational approach to simultaneously enhance the catalytic performance for both the half-reactions. However, controlling the vacancy defects is quite challenging. Here, we have employed a radio-frequency Ar plasma-assisted treatment strategy to prepare highly efficient graphene-supported FeNi2S4 bifunctional catalysts with abundant vacancies. The plasma treatment induces the formation of vacancy structures in the catalyst, modifying the free energy of reaction intermediates, surface morphology, and electronic structure as well as reducing the reaction barriers, thereby enhancing the catalytic performance. The optimized graphene-supported FeNi2S4 catalyst possesses abundant sulfur vacancies, demonstrating excellent electrocatalytic performance. At 50 mA cm-2, the overpotentials for OER and HER are 240 and 256 mV, respectively, indicating exceptional stability. Overall, this work offers valuable insights into the development of cost-effective and high-performance electrocatalysts for water electrolysis.
电解水制氢是一项有效且可持续的技术，可满足不断增长的能源需求。然而，氧进化反应（OER）和氢进化反应（HER）的催化效率不足阻碍了该技术的发展。空位缺陷工程是同时提高两种半反应催化性能的合理方法。然而，控制空位缺陷相当具有挑战性。在此，我们采用射频氩等离子体辅助处理策略制备了具有丰富空位的高效石墨烯支撑 FeNi2S4 双功能催化剂。等离子体处理可诱导催化剂中空位结构的形成，改变反应中间产物的自由能、表面形貌和电子结构，降低反应壁垒，从而提高催化性能。优化后的石墨烯支撑 FeNi2S4 催化剂具有丰富的硫空位，表现出优异的电催化性能。在 50 mA cm-2 的条件下，OER 和 HER 的过电位分别为 240 mV 和 256 mV，显示出卓越的稳定性。总之，这项研究为开发具有成本效益和高性能的水电解电催化剂提供了宝贵的见解。
{"title":"Modulating Vacancies of Graphene Supported FeNi2S4 electrocatalysts by Radio-frequency Plasma for Overall Water Splitting","authors":"W. He, Shilin Wu, Zhaotian Zhang, Qing Yang","doi":"10.1088/1361-6463/ad5f39","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5f39","url":null,"abstract":"\u0000 Electrolysis of water for producing hydrogen is an effective and sustainable technique to meet the continuously increasing energy demand. Nevertheless, its advancement is impeded by the inadequate catalytic efficacy for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Vacancy defect engineering is a rational approach to simultaneously enhance the catalytic performance for both the half-reactions. However, controlling the vacancy defects is quite challenging. Here, we have employed a radio-frequency Ar plasma-assisted treatment strategy to prepare highly efficient graphene-supported FeNi2S4 bifunctional catalysts with abundant vacancies. The plasma treatment induces the formation of vacancy structures in the catalyst, modifying the free energy of reaction intermediates, surface morphology, and electronic structure as well as reducing the reaction barriers, thereby enhancing the catalytic performance. The optimized graphene-supported FeNi2S4 catalyst possesses abundant sulfur vacancies, demonstrating excellent electrocatalytic performance. At 50 mA cm-2, the overpotentials for OER and HER are 240 and 256 mV, respectively, indicating exceptional stability. Overall, this work offers valuable insights into the development of cost-effective and high-performance electrocatalysts for water electrolysis.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141679586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1088/1361-6463/ad5dc9
Huolin Huang, Yun Lei, Sun Nan
With the continuous improvement of the power density and operating frequency in power conversion systems, it is necessary to develop the new power electronic products with better performances than the conventional semiconductors. As a typical representative of the wide-bandgap semiconductors, gallium nitride (GaN)-based heterostructure has unique high-density two-dimensional electron gas (2DEG) and hence can be used to fabricate the fast high electron mobility transistors (HEMTs) with low power loss. Therefore, they are considered as a promising candidate for the next-generation power devices to improve the switching efficiency and speed. Compared with the depletion mode (D-mode, also known as normally-on) devices, the enhancement-mode (E-mode, also known as normally-off) devices have the advantages of safety, energy-saving, and better circuit topology design, making them more attractive for industry applications. In this paper, the different structure schemes and fabrication technologies of the GaN-based E-mode HEMTs are reviewed and summarized. Their technical characteristics are systematically compared. The influences of material epitaxial structure, ohmic contact, material etching, field plate design, and passivation process on the device performances are discussed in detail wherein the fabrication process of the recessed-gate MIS-HEMTs are emphatically illustrated, focusing on the interface treatment technology and dielectric engineering. In addition, the complicated reliability issues and physical mechanisms in the E-mode HEMTs induced by high temperature, high voltage, and high frequency switching are introduced and discussed. Finally, the potential technical solutions are proposed and the future application fields of GaN-based E-mode HEMTs are prospected.
随着功率转换系统中功率密度和工作频率的不断提高，有必要开发出性能优于传统半导体的新型电力电子产品。作为宽带隙半导体的典型代表，基于氮化镓（GaN）的异质结构具有独特的高密度二维电子气体（2DEG），因此可用于制造低功率损耗的快速高电子迁移率晶体管（HEMT）。因此，它们被认为是提高开关效率和速度的下一代功率器件的理想候选材料。与耗尽模式（D-mode，又称常开）器件相比，增强模式（E-mode，又称常闭）器件具有安全、节能和更好的电路拓扑设计等优点，因此在工业应用中更具吸引力。本文回顾并总结了基于氮化镓的 E 模式 HEMT 的不同结构方案和制造技术。系统地比较了它们的技术特性。本文详细讨论了材料外延结构、欧姆接触、材料蚀刻、场板设计和钝化工艺对器件性能的影响，其中重点阐述了凹栅 MIS-HEMT 的制造工艺，着重介绍了界面处理技术和介电工程。此外，还介绍并讨论了高温、高电压和高频开关在 E 模式 HEMT 中引起的复杂可靠性问题和物理机制。最后，提出了潜在的技术解决方案，并展望了基于氮化镓的 E-mode HEMT 的未来应用领域。
{"title":"Progress of GaN-Based E-mode HEMTs","authors":"Huolin Huang, Yun Lei, Sun Nan","doi":"10.1088/1361-6463/ad5dc9","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5dc9","url":null,"abstract":"\u0000 With the continuous improvement of the power density and operating frequency in power conversion systems, it is necessary to develop the new power electronic products with better performances than the conventional semiconductors. As a typical representative of the wide-bandgap semiconductors, gallium nitride (GaN)-based heterostructure has unique high-density two-dimensional electron gas (2DEG) and hence can be used to fabricate the fast high electron mobility transistors (HEMTs) with low power loss. Therefore, they are considered as a promising candidate for the next-generation power devices to improve the switching efficiency and speed. Compared with the depletion mode (D-mode, also known as normally-on) devices, the enhancement-mode (E-mode, also known as normally-off) devices have the advantages of safety, energy-saving, and better circuit topology design, making them more attractive for industry applications. In this paper, the different structure schemes and fabrication technologies of the GaN-based E-mode HEMTs are reviewed and summarized. Their technical characteristics are systematically compared. The influences of material epitaxial structure, ohmic contact, material etching, field plate design, and passivation process on the device performances are discussed in detail wherein the fabrication process of the recessed-gate MIS-HEMTs are emphatically illustrated, focusing on the interface treatment technology and dielectric engineering. In addition, the complicated reliability issues and physical mechanisms in the E-mode HEMTs induced by high temperature, high voltage, and high frequency switching are introduced and discussed. Finally, the potential technical solutions are proposed and the future application fields of GaN-based E-mode HEMTs are prospected.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141685819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-02DOI: 10.1088/1361-6463/ad5dca
Zhiyuan He, Liang He, Kun Jiang, Xiaoyue Duan, Yijun Shi, Xinghuan Chen, Yuan Chen, Hualong Wu, Guoguang Lu, Y. Ni
In this work, we investigate the degradation behavior and mechanism of p-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) for the first time under hydrogen (H2) atmosphere. The experimental results reveal significant decrease in drain-to-source current, negative drift in threshold voltage, increase in off-state gate leakage current, and deterioration of subthreshold swing in the p-gate AlGaN/GaN HEMT after H2 treatment. The degradation of the electrical parameters is considered to hydrogen poisoning phenomenon. Through secondary ion mass spectrometry and variable temperature photoluminescence spectroscopy, we observe the increase in hydrogen concentration in the p-GaN layer and the formation of electrically inactive Mg-H complexes after H2 treatment. As results, the effective hole concentration decreases and the trap density of the device increases, which are confirmed by Hall effect measurement and low-frequency noise analysis, respectively. The detrimental effect of hydrogen on p-gate AlGaN/GaN HEMTs can be attributed primarily to the compensation of Mg doping and the generation of defects.
在这项工作中，我们首次研究了 p 栅极 AlGaN/GaN 高电子迁移率晶体管 (HEMT) 在氢（H2）气氛下的降解行为和机制。实验结果表明，经氢气处理后，p栅AlGaN/GaN HEMT的漏极至源极电流明显下降、阈值电压出现负漂移、离态栅漏电流增加、亚阈值摆幅恶化。电气参数的下降被认为是氢中毒现象造成的。通过二次离子质谱法和变温光致发光光谱法，我们观察到 H2 处理后 p-GaN 层的氢浓度增加，并形成了电性不活泼的 Mg-H 复合物。其结果是，器件的有效空穴浓度降低，陷阱密度增加，霍尔效应测量和低频噪声分析分别证实了这一点。氢气对 p 栅极 AlGaN/GaN HEMT 的不利影响主要归因于掺杂镁的补偿和缺陷的产生。
{"title":"Effect of Hydrogen Poisoning on p-gate AlGaN/GaN HEMTs","authors":"Zhiyuan He, Liang He, Kun Jiang, Xiaoyue Duan, Yijun Shi, Xinghuan Chen, Yuan Chen, Hualong Wu, Guoguang Lu, Y. Ni","doi":"10.1088/1361-6463/ad5dca","DOIUrl":"https://doi.org/10.1088/1361-6463/ad5dca","url":null,"abstract":"\u0000 In this work, we investigate the degradation behavior and mechanism of p-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) for the first time under hydrogen (H2) atmosphere. The experimental results reveal significant decrease in drain-to-source current, negative drift in threshold voltage, increase in off-state gate leakage current, and deterioration of subthreshold swing in the p-gate AlGaN/GaN HEMT after H2 treatment. The degradation of the electrical parameters is considered to hydrogen poisoning phenomenon. Through secondary ion mass spectrometry and variable temperature photoluminescence spectroscopy, we observe the increase in hydrogen concentration in the p-GaN layer and the formation of electrically inactive Mg-H complexes after H2 treatment. As results, the effective hole concentration decreases and the trap density of the device increases, which are confirmed by Hall effect measurement and low-frequency noise analysis, respectively. The detrimental effect of hydrogen on p-gate AlGaN/GaN HEMTs can be attributed primarily to the compensation of Mg doping and the generation of defects.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141687107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-25DOI: 10.1088/1361-6463/ad4365
Lei Dai, Jinggang Hao, Mei Cui, Yanfang Zhang, Y. Kuang, Zhengpeng Wang, F. Ren, S. Gu, J. Ye
Unintentionally doped carbon impurities from organometallic precursors are primary sources of carrier compensation and mobility degradation in wide bandgap semiconductors, leading to lowered performance of power devices. To address this challenge, carbon-free α-Ga2O3 single crystalline thin-films were heteroepitaxially grown on sapphire substrates by using gallium inorganic precursors through mist chemical vapor deposition technique. Determined through temperature dependence of growth rates, three distinct growth regimes are identified: the surface reaction limited regime below 480°C, the mid-temperature mass-transport limited regime (480-530 °C) and the high temperature limited regime related to desorption or phase transition. With an optimized around 530 °C, the densities of screw and edge dislocations are reduced to 7.17×10^6 and 7.60×10^9 cm-2, respectively. Notably, carbon incorporation was eliminated in the α-Ga2O3 grown by inorganic GaCl3, as evidenced by the absence of carbon-related vibrational bands in Raman scattering analysis, while crystalline quality was comparable to that grown with organometallic precursors. The high solubility of GaCl3 in water is expected to enable the rapid growth of high-purity α-Ga2O3 with improved electronic performances. Keywords: ultrawide bandgap semiconductor, chemical vapor deposition, impurity contamination.
{"title":"Temperature-dependent epitaxial evolution of carbon-free corundumα-Ga2O3 on sapphire","authors":"Lei Dai, Jinggang Hao, Mei Cui, Yanfang Zhang, Y. Kuang, Zhengpeng Wang, F. Ren, S. Gu, J. Ye","doi":"10.1088/1361-6463/ad4365","DOIUrl":"https://doi.org/10.1088/1361-6463/ad4365","url":null,"abstract":"\u0000 Unintentionally doped carbon impurities from organometallic precursors are primary sources of carrier compensation and mobility degradation in wide bandgap semiconductors, leading to lowered performance of power devices. To address this challenge, carbon-free α-Ga2O3 single crystalline thin-films were heteroepitaxially grown on sapphire substrates by using gallium inorganic precursors through mist chemical vapor deposition technique. Determined through temperature dependence of growth rates, three distinct growth regimes are identified: the surface reaction limited regime below 480°C, the mid-temperature mass-transport limited regime (480-530 °C) and the high temperature limited regime related to desorption or phase transition. With an optimized around 530 °C, the densities of screw and edge dislocations are reduced to 7.17×10^6 and 7.60×10^9 cm-2, respectively. Notably, carbon incorporation was eliminated in the α-Ga2O3 grown by inorganic GaCl3, as evidenced by the absence of carbon-related vibrational bands in Raman scattering analysis, while crystalline quality was comparable to that grown with organometallic precursors. The high solubility of GaCl3 in water is expected to enable the rapid growth of high-purity α-Ga2O3 with improved electronic performances. Keywords: ultrawide bandgap semiconductor, chemical vapor deposition, impurity contamination.","PeriodicalId":507822,"journal":{"name":"Journal of Physics D: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140657659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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