Pub Date : 2024-09-06DOI: 10.1088/1361-6463/ad7150
Zesheng Liu, Yan Liu, Xiang Chen, Ying Xie, Yuanhang Qu, Xiyu Gu, Xin Tong, Haiyang Li, Wenjuan Liu, Yao Cai, Shishang Guo, Chengliang Sun
Narrow-band filters are widely applied in the narrow-band Internet of Things (NB-IoT). To meet the diverse bandwidth requirements of NB-IoT applications, this work presents the first antisymmetric (A1) mode Lamb wave resonators (LWRs) based on aluminum nitride (AlN) and AlN/ScAlN composite films. The impact of structural parameters, including pitch (P) and duty factor (DF), on main mode excitation and suppression of spurious modes is investigated. The optimal P and DF are found to be 10 μm and 0.05, respectively. Based on spurious-free A1 LWRs, an AlN/Sc0.096Al0.904N composite film is utilized to adjust the effective electromechanical coupling coefficient keff2. The experiment results demonstrate a tunable keff2 from 0.40% (5 MHz) to 0.25% (3 MHz), realizing a 37.5% adjustment range of keff2, which establishes a foundation for narrow-band tunable filters.
{"title":"AlN/ScAlN composite films-based spurious free A1 mode lamb wave resonator with adjustable effective electromechanical coupling coefficient","authors":"Zesheng Liu, Yan Liu, Xiang Chen, Ying Xie, Yuanhang Qu, Xiyu Gu, Xin Tong, Haiyang Li, Wenjuan Liu, Yao Cai, Shishang Guo, Chengliang Sun","doi":"10.1088/1361-6463/ad7150","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7150","url":null,"abstract":"Narrow-band filters are widely applied in the narrow-band Internet of Things (NB-IoT). To meet the diverse bandwidth requirements of NB-IoT applications, this work presents the first antisymmetric (A1) mode Lamb wave resonators (LWRs) based on aluminum nitride (AlN) and AlN/ScAlN composite films. The impact of structural parameters, including pitch (<italic toggle=\"yes\">P</italic>) and duty factor (DF), on main mode excitation and suppression of spurious modes is investigated. The optimal <italic toggle=\"yes\">P</italic> and DF are found to be 10 <italic toggle=\"yes\">μ</italic>m and 0.05, respectively. Based on spurious-free A1 LWRs, an AlN/Sc<sub>0.096</sub>Al<sub>0.904</sub>N composite film is utilized to adjust the effective electromechanical coupling coefficient <inline-formula>\u0000<tex-math><?CDATA $k_{{text{eff}}}^{text{2}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msubsup><mml:mi>k</mml:mi><mml:mrow><mml:mrow><mml:mtext>eff</mml:mtext></mml:mrow></mml:mrow><mml:mrow><mml:mtext>2</mml:mtext></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href=\"dad7150ieqn1.gif\"></inline-graphic></inline-formula>. The experiment results demonstrate a tunable <inline-formula>\u0000<tex-math><?CDATA $k_{{text{eff}}}^{text{2}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msubsup><mml:mi>k</mml:mi><mml:mrow><mml:mrow><mml:mtext>eff</mml:mtext></mml:mrow></mml:mrow><mml:mrow><mml:mtext>2</mml:mtext></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href=\"dad7150ieqn2.gif\"></inline-graphic></inline-formula> from 0.40% (5 MHz) to 0.25% (3 MHz), realizing a 37.5% adjustment range of <inline-formula>\u0000<tex-math><?CDATA $k_{{text{eff}}}^{text{2}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msubsup><mml:mi>k</mml:mi><mml:mrow><mml:mrow><mml:mtext>eff</mml:mtext></mml:mrow></mml:mrow><mml:mrow><mml:mtext>2</mml:mtext></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href=\"dad7150ieqn3.gif\"></inline-graphic></inline-formula>, which establishes a foundation for narrow-band tunable filters.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"45 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222982","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 : 2024-09-06DOI: 10.1088/1361-6463/ad7301
O Krettek, P Pottkämper, P Cignoni, K Tschulik, A von Keudell
Nanosecond plasmas ignited inside water at tungsten and platinum/iridium electrode tips are used to create very small nanoparticles with radii around 1 nm. Due to the very high power density of 1016 W m–2 at an electrode hot spot with a diameter of 10 µm, the surface is ablated during the short plasma pulse, and the metal vapour expands in the cavitation bubble after the plasma. This creates a very large cooling rate and the formation of nanoparticles by condensation from the created metal vapour. Finally, the nanoparticles disperse in the liquid. This sequence is quantified by measuring the net tip erosion by shadowgraphy and the created nanoparticles by transmission electron microscopy and x-ray photoelectron spectroscopy. The condensation process is modelled in conjunction with cavitation theory for the expanding cavitation bubble, which shows very good agreement with experimental data.
在钨和铂/铱电极尖端的水中点燃的纳秒等离子体用于制造半径约为 1 纳米的超小型纳米粒子。由于在直径为 10 µm 的电极热点上具有 1016 W m-2 的极高功率密度，表面在短等离子体脉冲期间被烧蚀，金属蒸气在等离子体后的空化泡中膨胀。这就产生了非常大的冷却率，并通过所产生的金属蒸汽冷凝形成纳米颗粒。最后，纳米颗粒分散在液体中。通过阴影测量法测量尖端的净侵蚀，通过透射电子显微镜和 X 射线光电子能谱测量生成的纳米粒子，对这一过程进行量化。结合空化理论对不断扩大的空化泡的凝结过程进行了模拟，结果与实验数据非常吻合。
{"title":"Creation of tungsten and platinum nanoparticles from nanosecond plasmas in water","authors":"O Krettek, P Pottkämper, P Cignoni, K Tschulik, A von Keudell","doi":"10.1088/1361-6463/ad7301","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7301","url":null,"abstract":"Nanosecond plasmas ignited inside water at tungsten and platinum/iridium electrode tips are used to create very small nanoparticles with radii around 1 nm. Due to the very high power density of 10<sup>16</sup> W m<sup>–2</sup> at an electrode hot spot with a diameter of 10 <italic toggle=\"yes\">µ</italic>m, the surface is ablated during the short plasma pulse, and the metal vapour expands in the cavitation bubble after the plasma. This creates a very large cooling rate and the formation of nanoparticles by condensation from the created metal vapour. Finally, the nanoparticles disperse in the liquid. This sequence is quantified by measuring the net tip erosion by shadowgraphy and the created nanoparticles by transmission electron microscopy and x-ray photoelectron spectroscopy. The condensation process is modelled in conjunction with cavitation theory for the expanding cavitation bubble, which shows very good agreement with experimental data.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"10 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222983","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 : 2024-09-06DOI: 10.1088/1361-6463/ad714f
Ziyi Wan, Dongjian Jiang, Yuzhan Zheng, Ye Fu, Xiao Sun, Bo Wang, Cuixia Cui, Changping Yao, Wenjun Luo, Zhigang Zou
Two-electrode solar rechargeable devices can converse and store solar energy without external bias. However, the photo-charging and dark-discharging current of these devices is low and limits their practical applications. Here, the photo-charging and dark-discharging current of Si/poly(N-methylpyrrole) (PNMPy) photoanode increases 21 and 10 times by preparing nanostructured Si semiconductor, up to 5.09 and 2.06 mA cm−2, respectively. Further studies suggest that the improved current comes from higher separation efficiency of photo-generated carriers and new electron transfer paths on the surface of nanostructured Si. Moreover, a solar rechargeable device of Si/PNMPy/H2SO4(aq)/WO3/FTO was prepared, which indicated good cyclic stability. These results deepen our understanding on the current in solar rechargeable devices and offer guidance for the design of other high-performance devices.
双电极太阳能充电装置可以在没有外部偏压的情况下转换和储存太阳能。然而，这些器件的光充电和暗放电电流较低，限制了它们的实际应用。在这里，通过制备纳米结构硅半导体，硅/聚（N-甲基吡咯）（PNMPy）光阳极的光充电和暗放电电流分别提高了 21 倍和 10 倍，达到 5.09 mA cm-2 和 2.06 mA cm-2。进一步的研究表明，电流的提高来自于纳米结构硅表面光生载流子更高的分离效率和新的电子传输路径。此外，还制备了 Si/PNMPy/H2SO4(aq)/WO3/FTO 太阳能充电装置，该装置具有良好的循环稳定性。这些结果加深了我们对太阳能充电设备中电流的理解，并为设计其他高性能设备提供了指导。
{"title":"Remarkably improved photo-charging and dark-discharging current in a faradaic junction solar rechargeable device by regulating the morphology of a semiconductor","authors":"Ziyi Wan, Dongjian Jiang, Yuzhan Zheng, Ye Fu, Xiao Sun, Bo Wang, Cuixia Cui, Changping Yao, Wenjun Luo, Zhigang Zou","doi":"10.1088/1361-6463/ad714f","DOIUrl":"https://doi.org/10.1088/1361-6463/ad714f","url":null,"abstract":"Two-electrode solar rechargeable devices can converse and store solar energy without external bias. However, the photo-charging and dark-discharging current of these devices is low and limits their practical applications. Here, the photo-charging and dark-discharging current of Si/poly(N-methylpyrrole) (PNMPy) photoanode increases 21 and 10 times by preparing nanostructured Si semiconductor, up to 5.09 and 2.06 mA cm<sup>−2</sup>, respectively. Further studies suggest that the improved current comes from higher separation efficiency of photo-generated carriers and new electron transfer paths on the surface of nanostructured Si. Moreover, a solar rechargeable device of Si/PNMPy/H<sub>2</sub>SO<sub>4</sub>(aq)/WO<sub>3</sub>/FTO was prepared, which indicated good cyclic stability. These results deepen our understanding on the current in solar rechargeable devices and offer guidance for the design of other high-performance devices.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"40 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222984","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}
Active nanophotonic metasurfaces have attracted considerable attention for their promise to develop compact, tunable optical metadevices with advanced functions. In this work, we theoretically demonstrated the dynamically controllable dual resonances of Fano and electromagnetically induced transparency (EIT) using a graphene-loaded all-dielectric metasurface with U-shaped gallium arsenide (GaAs) nanobars operating in the near-infrared region. The destructive interference between a subradiant mode (i.e. a dark mode) supported by two vertical GaAs bars and two radiative modes (i.e. two bright modes) supported by a horizontal GaAs nanobar gives rise to a Fano resonance and an EIT window with high transmission and a large quality factor (Q-factor) in the transmission spectrum. Importantly, the transmission amplitudes can be flexibly modulated by adjusting the graphene Fermi levels without rebuilding the nanostructures. This modulation results from the controllable light absorption by the loaded graphene monolayer due to its interband losses in the near-infrared spectrum. Furthermore, the peak wavelengths of the Fano resonance and EIT window with high Q-factors are highly sensitive to variations in the refractive index (RI) of the surrounding medium, giving the proposed metasurface a relatively good sensitivity of ∼700 nm RIU−1 and a high figure of merit of 280, making it an effective RI sensor. Additionally, the metasurface features an adjustable slow light effect, indicated by the adjusted group delay time ranging from 0.12 ps to 0.38 ps. Therefore, the metasurface system proposed in this work offers a viable platform for advanced multi-band optical sensing, low-loss slow light devices, switches, and potential applications in nonlinear optical fields.
有源纳米光子元表面因其有望开发出具有先进功能的紧凑型可调光学元器件而备受关注。在这项工作中，我们从理论上证明了利用石墨烯负载的全介质元表面与工作在近红外区域的 U 型砷化镓（GaAs）纳米棒，可动态控制法诺和电磁诱导透明（EIT）双共振。由两根垂直砷化镓纳米棒支持的亚辐射模式（即暗模式）和由一根水平砷化镓纳米棒支持的两个辐射模式（即两个亮模式）之间的破坏性干涉产生了法诺共振和具有高透射率的 EIT 窗口，并且在透射光谱中具有较大的品质因数（Q 因子）。重要的是，可以通过调整石墨烯费米级来灵活调制透射幅度，而无需重建纳米结构。这种调制源于负载石墨烯单层在近红外光谱中的带间损耗所产生的可控光吸收。此外，具有高 Q 因子的法诺共振和 EIT 窗口的峰值波长对周围介质的折射率（RI）变化高度敏感，这使得所提出的元表面具有相对较好的灵敏度（RIU-1 ∼ 700 nm）和 280 的高优点，使其成为一种有效的 RI 传感器。此外，元表面还具有可调节的慢光效应，可调节的群延迟时间范围为 0.12 ps 至 0.38 ps。因此，本研究提出的元表面系统为先进的多波段光学传感、低损耗慢光器件、开关以及非线性光学领域的潜在应用提供了一个可行的平台。
{"title":"Controllable dual resonances of Fano and EIT in a graphene-loaded all-dielectric GaAs metasurface and its sensing and slow-light applications","authors":"Zhichao Wang, Huahao Huang, Hui Zhang, Miao He, Weiren Zhao","doi":"10.1088/1361-6463/ad73e4","DOIUrl":"https://doi.org/10.1088/1361-6463/ad73e4","url":null,"abstract":"Active nanophotonic metasurfaces have attracted considerable attention for their promise to develop compact, tunable optical metadevices with advanced functions. In this work, we theoretically demonstrated the dynamically controllable dual resonances of Fano and electromagnetically induced transparency (EIT) using a graphene-loaded all-dielectric metasurface with U-shaped gallium arsenide (GaAs) nanobars operating in the near-infrared region. The destructive interference between a subradiant mode (i.e. a dark mode) supported by two vertical GaAs bars and two radiative modes (i.e. two bright modes) supported by a horizontal GaAs nanobar gives rise to a Fano resonance and an EIT window with high transmission and a large quality factor (Q-factor) in the transmission spectrum. Importantly, the transmission amplitudes can be flexibly modulated by adjusting the graphene Fermi levels without rebuilding the nanostructures. This modulation results from the controllable light absorption by the loaded graphene monolayer due to its interband losses in the near-infrared spectrum. Furthermore, the peak wavelengths of the Fano resonance and EIT window with high Q-factors are highly sensitive to variations in the refractive index (RI) of the surrounding medium, giving the proposed metasurface a relatively good sensitivity of ∼700 nm RIU<sup>−1</sup> and a high figure of merit of 280, making it an effective RI sensor. Additionally, the metasurface features an adjustable slow light effect, indicated by the adjusted group delay time ranging from 0.12 ps to 0.38 ps. Therefore, the metasurface system proposed in this work offers a viable platform for advanced multi-band optical sensing, low-loss slow light devices, switches, and potential applications in nonlinear optical fields.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"27 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223014","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 the last few decades, interference has been extensively studied in both the quantum and classical fields, which reveals light volatility and is widely used for high-precision measurements. We have put forward the phenomenon in which the discrete diffraction and interference phenomena, presented by the time-varying voltage of a Su–Schrieffer–Heeger circuit model with an anti-PT (APT) symmetry. To demonstrate Young’s double-slit phenomenon in an APT circuit, we initially explore the coupled mode theory of voltage in the broken phase, observe discrete diffraction under single excitation and interference under double excitations. Furthermore, we design a phase-shifting circuit to observe the effects of phase difference and distance on discrete interference. Our work combines the effects in optics with condensed matter physics, show the Young’s double-slit phenomenon in electrical circuits theoretically and experimentally.
{"title":"Observation of Young’s double-slit phenomenon in anti-PT-symmetric electrical circuits","authors":"Keyu Pan, Xiumei Wang, Xizhou Shen, Haoyi Zhou, Xingping Zhou","doi":"10.1088/1361-6463/ad73e2","DOIUrl":"https://doi.org/10.1088/1361-6463/ad73e2","url":null,"abstract":"In the last few decades, interference has been extensively studied in both the quantum and classical fields, which reveals light volatility and is widely used for high-precision measurements. We have put forward the phenomenon in which the discrete diffraction and interference phenomena, presented by the time-varying voltage of a Su–Schrieffer–Heeger circuit model with an anti-PT (APT) symmetry. To demonstrate Young’s double-slit phenomenon in an APT circuit, we initially explore the coupled mode theory of voltage in the broken phase, observe discrete diffraction under single excitation and interference under double excitations. Furthermore, we design a phase-shifting circuit to observe the effects of phase difference and distance on discrete interference. Our work combines the effects in optics with condensed matter physics, show the Young’s double-slit phenomenon in electrical circuits theoretically and experimentally.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"60 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223002","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}
An electromagnetic optimization technique based on a long short-term memory–feedforward neural network (LSTM-FNN) and transfer functions is proposed for microwave filter design. The proposed optimization method addresses the situation where a neuro-transfer function model repeatedly trains at each optimization iteration process. The proposed surrogate model combines the LSTM-FNN and polynomial model to map nonlinear relationships between geometric variables and transfer functions. Firstly, by combining the gate mechanism of LSTM with the high generalization ability of an FNN, the proposed LSTM-FNN effectively learns nonlinear relationships between geometric variables and frequency responses at specific frequencies. Secondly, the transfer functions can be accurately approximated via polynomial fitting. Frequency responses at any interesting frequency range can be accurately expressed using the transfer functions. Finally, the trained surrogate model, exploiting the trust-region algorithm, can accurately and efficiently achieve optimization convergence. An example of a low-pass filter (LPF) is adopted to validate the proposed optimization method.
{"title":"EM optimization of microwave filter based on long short-term memory–feedforward neural network and transfer functions","authors":"Xin Zhang, Jian Wu, Yong-Qiang Chai, Shui Liu, Yuan Peng","doi":"10.1088/1361-6463/ad6fb1","DOIUrl":"https://doi.org/10.1088/1361-6463/ad6fb1","url":null,"abstract":"An electromagnetic optimization technique based on a long short-term memory–feedforward neural network (LSTM-FNN) and transfer functions is proposed for microwave filter design. The proposed optimization method addresses the situation where a neuro-transfer function model repeatedly trains at each optimization iteration process. The proposed surrogate model combines the LSTM-FNN and polynomial model to map nonlinear relationships between geometric variables and transfer functions. Firstly, by combining the gate mechanism of LSTM with the high generalization ability of an FNN, the proposed LSTM-FNN effectively learns nonlinear relationships between geometric variables and frequency responses at specific frequencies. Secondly, the transfer functions can be accurately approximated via polynomial fitting. Frequency responses at any interesting frequency range can be accurately expressed using the transfer functions. Finally, the trained surrogate model, exploiting the trust-region algorithm, can accurately and efficiently achieve optimization convergence. An example of a low-pass filter (LPF) is adopted to validate the proposed optimization method.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"35 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222998","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 : 2024-09-05DOI: 10.1088/1361-6463/ad7302
Edoardo Negri, Walter Fuscaldo, Paolo Burghignoli, Alessandro Galli
Graphene ohmic losses notably hinder the efficiency of graphene-based terahertz (THz) devices. Hybrid metal–graphene structures have recently been proposed to mitigate this issue in a few passive devices, namely waveguide and Vivaldi antennas, as well as frequency selective surfaces. In this work, such a technique is extensively investigated to optimize the radiation performance of a THz Fabry–Perot cavity leaky-wave antenna based on a hybrid metal–graphene metasurface consisting of a lattice of square metallic patches interleaved with a complementary graphene strip grating. Theoretical, numerical, and full-wave results demonstrate that, by properly selecting the unit-cell features, a satisfactory trade-off among range of reconfigurability, antenna directivity, and losses can be achieved. The proposed antenna can find application in future wireless THz communications.
{"title":"Reconfigurable THz leaky-wave antennas based on innovative metal–graphene metasurfaces","authors":"Edoardo Negri, Walter Fuscaldo, Paolo Burghignoli, Alessandro Galli","doi":"10.1088/1361-6463/ad7302","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7302","url":null,"abstract":"Graphene ohmic losses notably hinder the efficiency of graphene-based terahertz (THz) devices. Hybrid metal–graphene structures have recently been proposed to mitigate this issue in a few passive devices, namely waveguide and Vivaldi antennas, as well as frequency selective surfaces. In this work, such a technique is extensively investigated to optimize the radiation performance of a THz Fabry–Perot cavity leaky-wave antenna based on a hybrid metal–graphene metasurface consisting of a lattice of square <italic toggle=\"yes\">metallic</italic> patches interleaved with a complementary <italic toggle=\"yes\">graphene</italic> strip grating. Theoretical, numerical, and full-wave results demonstrate that, by properly selecting the unit-cell features, a satisfactory trade-off among range of reconfigurability, antenna directivity, and losses can be achieved. The proposed antenna can find application in future wireless THz communications.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"59 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223001","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 : 2024-09-05DOI: 10.1088/1361-6463/ad70c4
Wenxiong Xu, Feiyang Hou, He Zhang, Chuansheng Xia, Zhixuan Li, Yuanyuan Li, Chunxiang Xu, Qiannan Cui
Coherent acoustic phonon (CAP) oscillation of a 2D layered semiconductor/3D dielectric heterostructure generated by femtosecond laser pulse excitation can realize ultrafast photoacoustic conversion by emitting picosecond acoustic (PA) pulse; however, the photoacoustic conversion efficiency suffers from interfacial phonon scattering of simultaneously laser-induced lattice heat. Here, taking advantage of graphene’s high thermal conductivity and large acoustic impedance, we demonstrate that phonon scattering can be markedly mediated in a MoS2/graphene/glass heterostructure via femtosecond laser pump–probe measurements. The equilibrium temperatures of the MoS2 lattice have been cooled down by about 45%. As a benefit, both the lifetime of CAP oscillations and the pump pulse-picosecond acoustic pulse energy conversion efficiency have been enhanced by a factor of about 2. Our results offer insights into CAP and PA pulse manipulations via interfacial engineering that are fundamentally important for ultrafast photoacoustics based on 2D layered semiconductors.
飞秒激光脉冲激发二维层状半导体/三维电介质异质结构产生的相干声子（CAP）振荡可以通过发射皮秒声子（PA）脉冲实现超快光声转换；然而，光声转换效率却受到同时激光诱导的晶格热的界面声子散射的影响。在这里，我们利用石墨烯的高热导率和大声阻抗，通过飞秒激光泵浦探针测量证明了声子散射在 MoS2/石墨烯/玻璃异质结构中的显著介导作用。MoS2 晶格的平衡温度降低了约 45%。我们的研究结果为通过界面工程操纵 CAP 和 PA 脉冲提供了见解，这对于基于二维层状半导体的超快光声学具有根本性的重要意义。
{"title":"Mediating coherent acoustic phonon oscillation of a 2D semiconductor/3D dielectric heterostructure by interfacial engineering","authors":"Wenxiong Xu, Feiyang Hou, He Zhang, Chuansheng Xia, Zhixuan Li, Yuanyuan Li, Chunxiang Xu, Qiannan Cui","doi":"10.1088/1361-6463/ad70c4","DOIUrl":"https://doi.org/10.1088/1361-6463/ad70c4","url":null,"abstract":"Coherent acoustic phonon (CAP) oscillation of a 2D layered semiconductor/3D dielectric heterostructure generated by femtosecond laser pulse excitation can realize ultrafast photoacoustic conversion by emitting picosecond acoustic (PA) pulse; however, the photoacoustic conversion efficiency suffers from interfacial phonon scattering of simultaneously laser-induced lattice heat. Here, taking advantage of graphene’s high thermal conductivity and large acoustic impedance, we demonstrate that phonon scattering can be markedly mediated in a MoS<sub>2</sub>/graphene/glass heterostructure via femtosecond laser pump–probe measurements. The equilibrium temperatures of the MoS<sub>2</sub> lattice have been cooled down by about 45%. As a benefit, both the lifetime of CAP oscillations and the pump pulse-picosecond acoustic pulse energy conversion efficiency have been enhanced by a factor of about 2. Our results offer insights into CAP and PA pulse manipulations via interfacial engineering that are fundamentally important for ultrafast photoacoustics based on 2D layered semiconductors.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142222999","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 : 2024-09-05DOI: 10.1088/1361-6463/ad7270
Chunmin Cheng, Xiang Sun, Wei Shen, Qijun Wang, Lijie Li, Fang Dong, Kang Liang, Gai Wu
The utilization of diamond, the ultimate semiconductor, in electronic devices is challenging due to the difficulty of n-type doping. Phosphorus (P)-doped diamond, the most prevalent type of n-type diamond, is still limited by the low solubility of P dopant and undesirable compensating defects such as vacancy defects and hydrogen incorporation. In order to overcome this limitation, strain engineering is introduced to the n-type P-doped diamond theoretically in this work. Uniaxial, equibiaxial, and hydrostatic triaxial strains are applied to the P-doped diamond. The formation energy, charge transition level, defect binding energy and other physical properties of the P-doped diamond are then calculated based on first-principles calculations. The results show that uniaxial, equibiaxial, and hydrostatic triaxial tensile strain can reduce the formation energy and the donor ionization energy of P dopant, and also reduce the binding energy of phosphorus–vacancy (PV) and phosphorus–hydrogen (PH) defects. Our results indicate that under tensile strain, the solubility of the P dopant and the n-type conductivity of the P-doped diamond can be increased, and the formation of compensating defects can be suppressed. Therefore, strain engineering is anticipated to be used to enhance the n-type characteristics of the P-doped diamond, facilitating its application in electronic devices.
由于难以进行 n 型掺杂，在电子设备中利用金刚石这种终极半导体具有挑战性。磷（P）掺杂金刚石是最常见的 n 型金刚石，但仍受限于 P 掺杂剂的低溶解度以及空位缺陷和氢结合等不良补偿缺陷。为了克服这一局限性，本研究从理论上将应变工程引入 n 型 P 掺杂金刚石。对掺杂 P 的金刚石施加了单轴、等轴和静压三轴应变。然后根据第一性原理计算了掺 P 金刚石的形成能、电荷转移水平、缺陷结合能和其他物理性质。结果表明，单轴、等轴和静压三轴拉伸应变能降低掺杂 P 的形成能和供体电离能，也能降低磷-空位（PV）和磷-氢（PH）缺陷的结合能。我们的研究结果表明，在拉伸应变条件下，掺杂 P 的金刚石的 P 溶解度和 n 型电导率可以提高，补偿缺陷的形成也会受到抑制。因此，应变工程有望用于增强掺杂 P 的金刚石的 n 型特性，从而促进其在电子设备中的应用。
{"title":"Enhancing n-type doping in diamond by strain engineering","authors":"Chunmin Cheng, Xiang Sun, Wei Shen, Qijun Wang, Lijie Li, Fang Dong, Kang Liang, Gai Wu","doi":"10.1088/1361-6463/ad7270","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7270","url":null,"abstract":"The utilization of diamond, the ultimate semiconductor, in electronic devices is challenging due to the difficulty of n-type doping. Phosphorus (P)-doped diamond, the most prevalent type of n-type diamond, is still limited by the low solubility of P dopant and undesirable compensating defects such as vacancy defects and hydrogen incorporation. In order to overcome this limitation, strain engineering is introduced to the n-type P-doped diamond theoretically in this work. Uniaxial, equibiaxial, and hydrostatic triaxial strains are applied to the P-doped diamond. The formation energy, charge transition level, defect binding energy and other physical properties of the P-doped diamond are then calculated based on first-principles calculations. The results show that uniaxial, equibiaxial, and hydrostatic triaxial tensile strain can reduce the formation energy and the donor ionization energy of P dopant, and also reduce the binding energy of phosphorus–vacancy (PV) and phosphorus–hydrogen (PH) defects. Our results indicate that under tensile strain, the solubility of the P dopant and the n-type conductivity of the P-doped diamond can be increased, and the formation of compensating defects can be suppressed. Therefore, strain engineering is anticipated to be used to enhance the n-type characteristics of the P-doped diamond, facilitating its application in electronic devices.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"29 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223000","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 : 2024-09-05DOI: 10.1088/1361-6463/ad73e3
Rabia Hassan, Fei Ma, Yan Li, Rehan Hassan
Defect engineering is a powerful strategy for enhancing the catalytic properties of monolayer VSe2. In this work, we used density functional theory (DFT) to investigate the impact of point defects and hydrogen adsorption sites on the hydrogen evolution reaction (HER) activity of VSe2. We analyzed the formation energies and hydrogen adsorption behavior of single and double vacancies in VSe2. The results show that V vacancy defect (D2), consecutive V-Se double vacancy defect (D3), and separate V-Se double defect (D4) exhibit the enhanced HER activity with Gibbs free energies (ΔGH* = 0.04 eV, 0.04 eV and 0.06 eV, respectively) even surpassing that of platinum (ΔGH* = − 0.1 eV). This study highlights the potential of defect-engineered VSe2 for efficient hydrogen evolution.
{"title":"Defect engineering strategies in monolayer VSe2 for enhanced hydrogen evolution reaction: a computational study","authors":"Rabia Hassan, Fei Ma, Yan Li, Rehan Hassan","doi":"10.1088/1361-6463/ad73e3","DOIUrl":"https://doi.org/10.1088/1361-6463/ad73e3","url":null,"abstract":"Defect engineering is a powerful strategy for enhancing the catalytic properties of monolayer VSe<sub>2</sub>. In this work, we used density functional theory (DFT) to investigate the impact of point defects and hydrogen adsorption sites on the hydrogen evolution reaction (HER) activity of VSe<sub>2</sub>. We analyzed the formation energies and hydrogen adsorption behavior of single and double vacancies in VSe<sub>2</sub>. The results show that V vacancy defect (D2), consecutive V-Se double vacancy defect (D3), and separate V-Se double defect (D4) exhibit the enhanced HER activity with Gibbs free energies (Δ<italic toggle=\"yes\">G</italic><sub>H</sub>* = 0.04 eV, 0.04 eV and 0.06 eV, respectively) even surpassing that of platinum (Δ<italic toggle=\"yes\">G</italic><sub>H</sub>* = − 0.1 eV). This study highlights the potential of defect-engineered VSe<sub>2</sub> for efficient hydrogen evolution.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"61 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223003","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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