Pub Date : 2020-12-04DOI: 10.1103/PhysRevMaterials.5.055002
A. Rattanachata, L. Nicolaï, H. Martins, G. Conti, M. Verstraete, M. Gehlmann, S. Ueda, Keisuke L. I. Kobayashi, I. Vishik, C. Schneider, C. Fadley, A. Gray, J. Minár, S. Nemšák
We investigate the bulk electronic structure of lanthanum hexaboride using tender-hard x-ray photoemission spectroscopy, measuring both core-level and angle-resolved valence-band spectra. We compare the La 3d core level spectrum to cluster model calculations in order to understand the bulk-like core-hole screening effects. The results show that the La 3d well-screened peak is at a lower binding energy compared to the main poorly-screened peak and the relative intensity between these peaks depends on how strong the hybridization is between La and B atoms. We show that the recoil effect, negligible in the soft x-ray regime, becomes prominent at higher kinetic energies for lighter elements, such as boron, but is still negligible for heavy nuclei, such as lanthanum. In addition, we report the bulk-like band structure of lanthanum hexaboride determined by tender-hard x-ray angle-resolved photoemission spectroscopy (HARPES). We compare HARPES experimental results to the free-electron final-state calculations and to the more precise one-step photoemission theory including matrix element and phonon excitation effects. The agreement between the features present in the experimental ARPES data and the theoretical calculations is remarkable. In addition, we consider the nature and the magnitude of phonon excitations in order to interpret HARPES experimental data measured at different temperatures and excitation energies. We demonstrate that one step theory of photoemission and HARPES experiments provide, at present, the only approach capable of probing, both experimentally and theoretically, true bulk-like electronic band structure of rare-earth hexaborides and strongly correlated materials.
{"title":"Bulk electronic structure of lanthanum hexaboride (\u0000LaB6\u0000) by hard x-ray angle-resolved photoelectron spectroscopy","authors":"A. Rattanachata, L. Nicolaï, H. Martins, G. Conti, M. Verstraete, M. Gehlmann, S. Ueda, Keisuke L. I. Kobayashi, I. Vishik, C. Schneider, C. Fadley, A. Gray, J. Minár, S. Nemšák","doi":"10.1103/PhysRevMaterials.5.055002","DOIUrl":"https://doi.org/10.1103/PhysRevMaterials.5.055002","url":null,"abstract":"We investigate the bulk electronic structure of lanthanum hexaboride using tender-hard x-ray photoemission spectroscopy, measuring both core-level and angle-resolved valence-band spectra. We compare the La 3d core level spectrum to cluster model calculations in order to understand the bulk-like core-hole screening effects. The results show that the La 3d well-screened peak is at a lower binding energy compared to the main poorly-screened peak and the relative intensity between these peaks depends on how strong the hybridization is between La and B atoms. We show that the recoil effect, negligible in the soft x-ray regime, becomes prominent at higher kinetic energies for lighter elements, such as boron, but is still negligible for heavy nuclei, such as lanthanum. In addition, we report the bulk-like band structure of lanthanum hexaboride determined by tender-hard x-ray angle-resolved photoemission spectroscopy (HARPES). We compare HARPES experimental results to the free-electron final-state calculations and to the more precise one-step photoemission theory including matrix element and phonon excitation effects. The agreement between the features present in the experimental ARPES data and the theoretical calculations is remarkable. In addition, we consider the nature and the magnitude of phonon excitations in order to interpret HARPES experimental data measured at different temperatures and excitation energies. We demonstrate that one step theory of photoemission and HARPES experiments provide, at present, the only approach capable of probing, both experimentally and theoretically, true bulk-like electronic band structure of rare-earth hexaborides and strongly correlated materials.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91367302","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}
We present a rigorous theoretical framework for designing full-space spatial power dividers using metagratings. In our study, the current restrictions of spatial power dividing platforms such as reflection-only performance, operating at normal incidence, and small reflection/refraction angles have been totally relaxed. A modal expansion analysis based on Floquet-Bloch (FB) theorem is established so that a discrete set of spatial harmonics is considered in both reflection and transmission sides of a compound metallic grating in which the unknown coefficients are calculated by applying proper boundary conditions. By eliminating the unwanted scattering harmonics, the proposed metagrating has the ability to realize different functionalities from perfect anomalous refraction to reflection-transmission spatial power dividing, without resorting to full-wave numerical optimizations. The numerical simulations confirm well the theoretical predictions. Our findings not only offer possibilities to realize arbitrary spatial power dividers but also reveal a simple alternative for beamforming array antennas.
{"title":"Analytical Design for Full-space Spatial Power Dividers Using Metagratings","authors":"Hamid Rajabalipanah, A. Abdolali","doi":"10.1364/JOSAB.437379","DOIUrl":"https://doi.org/10.1364/JOSAB.437379","url":null,"abstract":"We present a rigorous theoretical framework for designing full-space spatial power dividers using metagratings. In our study, the current restrictions of spatial power dividing platforms such as reflection-only performance, operating at normal incidence, and small reflection/refraction angles have been totally relaxed. A modal expansion analysis based on Floquet-Bloch (FB) theorem is established so that a discrete set of spatial harmonics is considered in both reflection and transmission sides of a compound metallic grating in which the unknown coefficients are calculated by applying proper boundary conditions. By eliminating the unwanted scattering harmonics, the proposed metagrating has the ability to realize different functionalities from perfect anomalous refraction to reflection-transmission spatial power dividing, without resorting to full-wave numerical optimizations. The numerical simulations confirm well the theoretical predictions. Our findings not only offer possibilities to realize arbitrary spatial power dividers but also reveal a simple alternative for beamforming array antennas.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83574481","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}
Chiral edge modes in photonic topological insulators host great potential to realize slow-light waveguides with topological protection. Increasing the winding of the chiral edge mode around the Brillouin zone can lead to broadband topological slow light with ultra-low group velocity. However, this effect usually requires careful modifications on a relatively large area around the lattice edge. Here we present a simple and general scheme to achieve broadband topological slow light through coupling the chiral edge modes with flat bands. In this approach, modifications inside the topological lattice are not required. Instead, only several additional resonators that support the flat bands need to be attached at the lattice edge. We demonstrate our idea numerically using a gyromagnetic photonic crystal, which is ready to be tested at microwave frequencies.
{"title":"Topological slow light via coupling chiral edge modes with flatbands","authors":"Letian Yu, Haoran Xue, Baile Zhang","doi":"10.1063/5.0039839","DOIUrl":"https://doi.org/10.1063/5.0039839","url":null,"abstract":"Chiral edge modes in photonic topological insulators host great potential to realize slow-light waveguides with topological protection. Increasing the winding of the chiral edge mode around the Brillouin zone can lead to broadband topological slow light with ultra-low group velocity. However, this effect usually requires careful modifications on a relatively large area around the lattice edge. Here we present a simple and general scheme to achieve broadband topological slow light through coupling the chiral edge modes with flat bands. In this approach, modifications inside the topological lattice are not required. Instead, only several additional resonators that support the flat bands need to be attached at the lattice edge. We demonstrate our idea numerically using a gyromagnetic photonic crystal, which is ready to be tested at microwave frequencies.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81861114","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}
P. Kharel, C. Reimer, K. Luke, Lingyan He, Mian Zhang
Electro-optic modulators with low voltage and large bandwidth are crucial for both analog and digital communications. Recently, thin-film lithium niobate modulators have enable dramatic performance improvements by reducing the required modulation voltage while maintaining high bandwidths. However, the reduced electrode gaps in such modulators leads to significantly higher microwave losses, which limit electro-optic performance at high frequencies. Here we overcome this limitation and achieve a record combination of low RF half-wave voltage of 1.3 V while maintaining electro-optic response with 1.8-dB roll-off at 50 GHz. This demonstration represents a significant improvement in voltage-bandwidth limit, one that is comparable to that achieved when switching from legacy bulk to thin-film lithium niobate modulators. Leveraging the low-loss electrode geometry, we show that sub-volt modulators with $>$ 100 GHz bandwidth can be enabled.
{"title":"Breaking voltage–bandwidth limits in integrated lithium niobate modulators using micro-structured electrodes","authors":"P. Kharel, C. Reimer, K. Luke, Lingyan He, Mian Zhang","doi":"10.1364/OPTICA.416155","DOIUrl":"https://doi.org/10.1364/OPTICA.416155","url":null,"abstract":"Electro-optic modulators with low voltage and large bandwidth are crucial for both analog and digital communications. Recently, thin-film lithium niobate modulators have enable dramatic performance improvements by reducing the required modulation voltage while maintaining high bandwidths. However, the reduced electrode gaps in such modulators leads to significantly higher microwave losses, which limit electro-optic performance at high frequencies. Here we overcome this limitation and achieve a record combination of low RF half-wave voltage of 1.3 V while maintaining electro-optic response with 1.8-dB roll-off at 50 GHz. This demonstration represents a significant improvement in voltage-bandwidth limit, one that is comparable to that achieved when switching from legacy bulk to thin-film lithium niobate modulators. Leveraging the low-loss electrode geometry, we show that sub-volt modulators with $>$ 100 GHz bandwidth can be enabled.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75417177","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}
Jung-Woo Kim, Seong-Jin Lee, Jun-Yeong Jo, Semyun Wang, Sang-Hoon Kim
A three-dimensional acoustic Luneburg lens, or acoustic Luneburg ball, has the advantage of refracting sound waves for all incident angles and concentrating higher sound pressure compared to a two-dimensional lens. A lens with a radius of 60 mm was designed with thousands of unit atoms comprising lattice columns to maintain its shape. The focusing performance of the lens was simulated using COMSOL Multiphysics, a finite element analysis program. Acoustic imaging was performed at a frequency of 10 kHz using a microphone, transducer, three-axis linear stage, and LabVIEW-based measurement program for a plastic lens made by a selective laser sintering 3D printer. The omnidirectional property was confirmed by measuring the sound pressure level while rotating the lens. The sound pressure level gain was defined to represent the frequency-dependent performance of the lens, and the maximum values were measured at approximately 20 dB and 15 dB in the numerical simulation and the experiment, respectively, at a frequency of 16 kHz. The results suggest that acoustic meta-lenses can be used for acoustic communication, imaging systems, and energy harvesting.
{"title":"Acoustic imaging by three-dimensional acoustic Luneburg meta-lens with lattice columns","authors":"Jung-Woo Kim, Seong-Jin Lee, Jun-Yeong Jo, Semyun Wang, Sang-Hoon Kim","doi":"10.1063/5.0037600","DOIUrl":"https://doi.org/10.1063/5.0037600","url":null,"abstract":"A three-dimensional acoustic Luneburg lens, or acoustic Luneburg ball, has the advantage of refracting sound waves for all incident angles and concentrating higher sound pressure compared to a two-dimensional lens. A lens with a radius of 60 mm was designed with thousands of unit atoms comprising lattice columns to maintain its shape. The focusing performance of the lens was simulated using COMSOL Multiphysics, a finite element analysis program. Acoustic imaging was performed at a frequency of 10 kHz using a microphone, transducer, three-axis linear stage, and LabVIEW-based measurement program for a plastic lens made by a selective laser sintering 3D printer. The omnidirectional property was confirmed by measuring the sound pressure level while rotating the lens. The sound pressure level gain was defined to represent the frequency-dependent performance of the lens, and the maximum values were measured at approximately 20 dB and 15 dB in the numerical simulation and the experiment, respectively, at a frequency of 16 kHz. The results suggest that acoustic meta-lenses can be used for acoustic communication, imaging systems, and energy harvesting.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83346851","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 : 2020-11-23DOI: 10.1103/PHYSREVAPPLIED.15.024064
M. Colangelo, Di Zhu, D. Santavicca, B. Butters, J. Bienfang, K. Berggren
Developing compact, low-dissipation, cryogenic-compatible microwave electronics is essential for scaling up low-temperature quantum computing systems. In this paper, we demonstrate an ultra-compact microwave directional forward coupler based on high-impedance slow-wave superconducting-nanowire transmission lines. The coupling section of the fabricated device has a footprint of $416,mathrm{mu m^2}$. At 4.753 GHz, the input signal couples equally to the through port and forward-coupling port (50:50) at $-6.7,mathrm{dB}$ with $-13.5,mathrm{dB}$ isolation. The coupling ratio can be controlled with DC bias current or temperature by exploiting the dependence of the kinetic inductance on these quantities. The material and fabrication-process are suitable for direct integration with superconducting circuits, providing a practical solution to the signal distribution bottlenecks in developing large-scale quantum computers.
{"title":"Compact and Tunable Forward Coupler Based on High-Impedance Superconducting Nanowires","authors":"M. Colangelo, Di Zhu, D. Santavicca, B. Butters, J. Bienfang, K. Berggren","doi":"10.1103/PHYSREVAPPLIED.15.024064","DOIUrl":"https://doi.org/10.1103/PHYSREVAPPLIED.15.024064","url":null,"abstract":"Developing compact, low-dissipation, cryogenic-compatible microwave electronics is essential for scaling up low-temperature quantum computing systems. In this paper, we demonstrate an ultra-compact microwave directional forward coupler based on high-impedance slow-wave superconducting-nanowire transmission lines. The coupling section of the fabricated device has a footprint of $416,mathrm{mu m^2}$. At 4.753 GHz, the input signal couples equally to the through port and forward-coupling port (50:50) at $-6.7,mathrm{dB}$ with $-13.5,mathrm{dB}$ isolation. The coupling ratio can be controlled with DC bias current or temperature by exploiting the dependence of the kinetic inductance on these quantities. The material and fabrication-process are suitable for direct integration with superconducting circuits, providing a practical solution to the signal distribution bottlenecks in developing large-scale quantum computers.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85962068","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 : 2020-11-20DOI: 10.26434/chemrxiv.13265288.v1
Daniil Bash, Yongqiang Cai, Vijila Chellappan, S. L. Wong, Yang Xu, Pawan Kumar, J. Tan, Anas Abutaha, J. Cheng, Y. Lim, S. Tian, D. Ren, Flore Mekki-Barrada, W. Wong, J. Kumar, Saif A. Khan, Qianxiao Li, T. Buonassisi, K. Hippalgaonkar
Combining high-throughput experiments with machine learning allows quick optimization of parameter spaces towards achieving target properties. In this study, we demonstrate that machine learning, combined with multi-labeled datasets, can additionally be used for scientific understanding and hypothesis testing. We introduce an automated flow system with high-throughput drop-casting for thin film preparation, followed by fast characterization of optical and electrical properties, with the capability to complete one cycle of learning of fully labeled ~160 samples in a single day. We combine regio-regular poly-3-hexylthiophene with various carbon nanotubes to achieve electrical conductivities as high as 1200 S/cm. Interestingly, a non-intuitive local optimum emerges when 10% of double-walled carbon nanotubes are added with long single wall carbon nanotubes, where the conductivity is seen to be as high as 700 S/cm, which we subsequently explain with high fidelity optical characterization. Employing dataset resampling strategies and graph-based regressions allows us to account for experimental cost and uncertainty estimation of correlated multi-outputs, and supports the proving of the hypothesis linking charge delocalization to electrical conductivity. We therefore present a robust machine-learning driven high-throughput experimental scheme that can be applied to optimize and understand properties of composites, or hybrid organic-inorganic materials.
{"title":"Machine Learning and High-Throughput Robust Design of P3HT-CNT Composite Thin Films for High Electrical Conductivity","authors":"Daniil Bash, Yongqiang Cai, Vijila Chellappan, S. L. Wong, Yang Xu, Pawan Kumar, J. Tan, Anas Abutaha, J. Cheng, Y. Lim, S. Tian, D. Ren, Flore Mekki-Barrada, W. Wong, J. Kumar, Saif A. Khan, Qianxiao Li, T. Buonassisi, K. Hippalgaonkar","doi":"10.26434/chemrxiv.13265288.v1","DOIUrl":"https://doi.org/10.26434/chemrxiv.13265288.v1","url":null,"abstract":"Combining high-throughput experiments with machine learning allows quick optimization of parameter spaces towards achieving target properties. In this study, we demonstrate that machine learning, combined with multi-labeled datasets, can additionally be used for scientific understanding and hypothesis testing. We introduce an automated flow system with high-throughput drop-casting for thin film preparation, followed by fast characterization of optical and electrical properties, with the capability to complete one cycle of learning of fully labeled ~160 samples in a single day. We combine regio-regular poly-3-hexylthiophene with various carbon nanotubes to achieve electrical conductivities as high as 1200 S/cm. Interestingly, a non-intuitive local optimum emerges when 10% of double-walled carbon nanotubes are added with long single wall carbon nanotubes, where the conductivity is seen to be as high as 700 S/cm, which we subsequently explain with high fidelity optical characterization. Employing dataset resampling strategies and graph-based regressions allows us to account for experimental cost and uncertainty estimation of correlated multi-outputs, and supports the proving of the hypothesis linking charge delocalization to electrical conductivity. We therefore present a robust machine-learning driven high-throughput experimental scheme that can be applied to optimize and understand properties of composites, or hybrid organic-inorganic materials.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90459399","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}
Admittance spectroscopy combined with non-ionizing energy loss (NIEL) analysis is shown to be a powerful tool for analyzing solar cell radiation degradation, not relying on the change of macroscopic cell parameters. GaAs component cells, representative of the middle sub-cell in Ga 0.5 In 0.5 P / GaAs / Ge solar cells, were irradiated with protons and electrons in the 0.5–3 MeV energy range. Four irradiation-induced defects are identified in the p-type base layer. The nature of each defect is assessed by analyzing the dependence of its introduction rate on the NIEL deposited by electrons in the semiconductor. The expected linear relationship is only achieved if a unique threshold energy E d is ascribed to each defect, which ranges from 9 to 38 eV. An electron NIEL with E d = 21 eV, customarily used for GaAs-based solar cell degradation analysis, is an approximation of the relative abundance of these four defects. The 21 eV value is thus a GaAs material-specific parameter, independent of the electrical device design. In addition, the type and energy of the incident particle is correlated with the relative abundance of high E d defects. The impact of each defect on the macroscopic electrical parameters of the cell, namely, the open-circuit voltage V OC, the short-circuit current density J SC, and the recombination current density J 02, is assessed with the help of a Pearson analysis. The different effectiveness of electron and proton irradiation on parameters dominated by recombination in the depleted region, such as V OC or J 02, is attributed in part to the influence of the particle recoil spectra on the defect capture cross section.
导纳光谱与非电离能量损失(NIEL)分析相结合是分析太阳电池辐射退化的有力工具，不依赖于电池宏观参数的变化。采用质子和电子在0.5 ~ 3 MeV的能量范围内辐照GaAs组件电池，作为Ga 0.5 in 0.5 P / GaAs / Ge太阳能电池中间亚电池的代表。在p型基层中发现了四个辐照缺陷。每个缺陷的性质是通过分析其引入率对半导体中电子沉积的NIEL的依赖来评估的。期望的线性关系只有在将一个唯一的阈值能量E d归因于每个缺陷时才能实现，其范围从9到38 eV。ed = 21 eV的电子NIEL通常用于gaas基太阳能电池的降解分析，是这四种缺陷相对丰度的近似值。因此，21 eV值是GaAs材料特定的参数，与电气器件设计无关。此外，入射粒子的类型和能量与高能谱缺陷的相对丰度有关。通过Pearson分析，评估了各缺陷对电池宏观电参数的影响，即开路电压V OC、短路电流密度jsc和复合电流密度j02。电子和质子辐照对贫区以复合为主的参数(如V OC或j02)的不同效果部分归因于粒子反冲谱对缺陷捕获截面的影响。
{"title":"Defect spectroscopy and non-ionizing energy loss analysis of proton and electron irradiated p-type GaAs solar cells","authors":"C. Pellegrino, A. Gagliardi, C. Zimmermann","doi":"10.1063/5.0028029","DOIUrl":"https://doi.org/10.1063/5.0028029","url":null,"abstract":"Admittance spectroscopy combined with non-ionizing energy loss (NIEL) analysis is shown to be a powerful tool for analyzing solar cell radiation degradation, not relying on the change of macroscopic cell parameters. GaAs component cells, representative of the middle sub-cell in Ga 0.5 In 0.5 P / GaAs / Ge solar cells, were irradiated with protons and electrons in the 0.5–3 MeV energy range. Four irradiation-induced defects are identified in the p-type base layer. The nature of each defect is assessed by analyzing the dependence of its introduction rate on the NIEL deposited by electrons in the semiconductor. The expected linear relationship is only achieved if a unique threshold energy E d is ascribed to each defect, which ranges from 9 to 38 eV. An electron NIEL with E d = 21 eV, customarily used for GaAs-based solar cell degradation analysis, is an approximation of the relative abundance of these four defects. The 21 eV value is thus a GaAs material-specific parameter, independent of the electrical device design. In addition, the type and energy of the incident particle is correlated with the relative abundance of high E d defects. The impact of each defect on the macroscopic electrical parameters of the cell, namely, the open-circuit voltage V OC, the short-circuit current density J SC, and the recombination current density J 02, is assessed with the help of a Pearson analysis. The different effectiveness of electron and proton irradiation on parameters dominated by recombination in the depleted region, such as V OC or J 02, is attributed in part to the influence of the particle recoil spectra on the defect capture cross section.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73477838","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}
The phenomenon of selective diffraction is extended to in-plane elastic waves and we design surface corrugated periodic laminates that incorporate crystal momentum transfer which, due to the rich physics embedded within the vector elastic system, results in frequency, angle and wave-type selective diffraction. The resulting devices are elastic grating couplers, with additional capabilities as compared to analogous scalar electromagnetic couplers, in that the elastic couplers possess the ability to split and independently redirect, through selective negative refraction, the two body waves present in the vector elastic system: compressional (P) and shear-vertical (SV) elastic waves. The design paradigm, and interpretation, is aided by obtaining isofrequency contours via a non-dimensionalised transfer matrix method.
{"title":"Surface corrugated laminates as elastic grating couplers: Splitting of SV- and P-waves by selective diffraction","authors":"G. Chaplain, R. Craster","doi":"10.1063/5.0037804","DOIUrl":"https://doi.org/10.1063/5.0037804","url":null,"abstract":"The phenomenon of selective diffraction is extended to in-plane elastic waves and we design surface corrugated periodic laminates that incorporate crystal momentum transfer which, due to the rich physics embedded within the vector elastic system, results in frequency, angle and wave-type selective diffraction. The resulting devices are elastic grating couplers, with additional capabilities as compared to analogous scalar electromagnetic couplers, in that the elastic couplers possess the ability to split and independently redirect, through selective negative refraction, the two body waves present in the vector elastic system: compressional (P) and shear-vertical (SV) elastic waves. The design paradigm, and interpretation, is aided by obtaining isofrequency contours via a non-dimensionalised transfer matrix method.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90877502","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 : 2020-11-12DOI: 10.1103/PHYSREVAPPLIED.15.014058
Shuaifeng Li, Jinkyu Yang
Elastic valley metamaterials offer an excellent platform to manipulate elastic waves and have potential applications in energy harvesting and elastography. Here we introduce a series of strategies to realize topological transition in spiral elastic valley metamaterials by parameter modulations. We show the evolution of Berry curvature and valley Chern number as a function of inherent parameters of spiral, which further results in a general scheme to achieve topological valley edge states. Our strategy leverages multiple degrees of freedom in spiral elastic valley metamaterials to provide enhanced opportunities for desired topological states.
{"title":"Topological Transition in Spiral Elastic Valley Metamaterials","authors":"Shuaifeng Li, Jinkyu Yang","doi":"10.1103/PHYSREVAPPLIED.15.014058","DOIUrl":"https://doi.org/10.1103/PHYSREVAPPLIED.15.014058","url":null,"abstract":"Elastic valley metamaterials offer an excellent platform to manipulate elastic waves and have potential applications in energy harvesting and elastography. Here we introduce a series of strategies to realize topological transition in spiral elastic valley metamaterials by parameter modulations. We show the evolution of Berry curvature and valley Chern number as a function of inherent parameters of spiral, which further results in a general scheme to achieve topological valley edge states. Our strategy leverages multiple degrees of freedom in spiral elastic valley metamaterials to provide enhanced opportunities for desired topological states.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85663579","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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