Detian Yang, Arjun Subedi, Chao Liu, Haile Ambaye, Valeria Lauter, Peter A. Dowben, Yaohua Liu, Xiaoshan Xu
Understanding intrinsic exchange bias in nominally single-component ferromagnetic or ferrimagnetic materials is crucial for simplifying related device architectures. However, the mechanisms behind this phenomenon and its tunability remain elusive, which hinders the efforts to achieve unidirectional magnetization for widespread applications. Inspired by the high tunability of ferrimagnetic inverse spinel NiCo2O4, the origin of intrinsic exchange bias in NiCo2O4 (111) films deposited on Al2O3 (0001) substrates are investigated. The comprehensive characterizations, including electron diffraction, X-ray reflectometry and spectroscopy, and polarized neutron reflectometry, reveal that intrinsic exchange bias in NiCo2O4 (111)/Al2O3 (0001) arises from a reconstructed antiferromagnetic rock-salt NixCo1-xO layer at the interface between the film and the substrate due to a significant structural mismatch. Remarkably, by engineering the interfacial structure under optimal growth conditions, it can achieve exchange bias larger than coercivity, leading to unidirectional magnetization. Such giant intrinsic exchange bias can be utilized for realistic device applications. This work establishes a new material platform based on NiCo2O4, an emergent spintronics material, to study tunable interfacial magnetic and spintronic properties.
{"title":"Microstructural Underpinnings of Giant Intrinsic Exchange Bias in Epitaxial NiCo2O4 Thin Films","authors":"Detian Yang, Arjun Subedi, Chao Liu, Haile Ambaye, Valeria Lauter, Peter A. Dowben, Yaohua Liu, Xiaoshan Xu","doi":"10.1002/aelm.202400149","DOIUrl":"https://doi.org/10.1002/aelm.202400149","url":null,"abstract":"Understanding intrinsic exchange bias in nominally single-component ferromagnetic or ferrimagnetic materials is crucial for simplifying related device architectures. However, the mechanisms behind this phenomenon and its tunability remain elusive, which hinders the efforts to achieve unidirectional magnetization for widespread applications. Inspired by the high tunability of ferrimagnetic inverse spinel NiCo<sub>2</sub>O<sub>4</sub>, the origin of intrinsic exchange bias in NiCo<sub>2</sub>O<sub>4</sub> (111) films deposited on Al<sub>2</sub>O<sub>3</sub> (0001) substrates are investigated. The comprehensive characterizations, including electron diffraction, X-ray reflectometry and spectroscopy, and polarized neutron reflectometry, reveal that intrinsic exchange bias in NiCo<sub>2</sub>O<sub>4</sub> (111)/Al<sub>2</sub>O<sub>3</sub> (0001) arises from a reconstructed antiferromagnetic rock-salt Ni<i><sub>x</sub></i>Co<sub>1</sub><i><sub>-x</sub></i>O layer at the interface between the film and the substrate due to a significant structural mismatch. Remarkably, by engineering the interfacial structure under optimal growth conditions, it can achieve exchange bias larger than coercivity, leading to unidirectional magnetization. Such giant intrinsic exchange bias can be utilized for realistic device applications. This work establishes a new material platform based on NiCo<sub>2</sub>O<sub>4</sub>, an emergent spintronics material, to study tunable interfacial magnetic and spintronic properties.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"8 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142643230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aditya S. Dutt, Nithin B Pulumati, Kangfa Deng, Jens Wagner, Andreas Brönner, Frank Ellinger, Gabi Schierning, Kornelius Nielsch, Heiko Reith
Micro thermoelectric generators (µTEGs) can harvest waste heat to generate electricity, making them a potential solution to the growing problem of powering autonomous electronics, such as sensors for the Internet of Things. Until now, µTEGs have not been able to provide power for these applications. This is because the output power of µTEGs is limited due to insufficient contacts and poor thermal coupling between the device and the heat source. In this work, the contact resistance as well as the thermal coupling between the heat source and the device through process optimization are improved. The former by improved electrochemical deposition (ECD) conditions, the latter by introducing a thin solder adhesion layer, which smooths the uneven surface of µTEG due to its good wetting properties. Using these improvements in combination with optimized packing density, here the fabrication and characterization of a µTEG with 126 leg pairs connected in series are reported that exhibits an open circuit voltage of 339.2 mV at a temperature difference of 20.6 K and a record-high normalized power density of 25.1 µW cm−2 K−2 for ECD based µTEGs. This µTEG is used to power a temperature sensor, bringing this work one step closer to application.
{"title":"High Power Density Micro Thermoelectric Generators for Powering IoTs","authors":"Aditya S. Dutt, Nithin B Pulumati, Kangfa Deng, Jens Wagner, Andreas Brönner, Frank Ellinger, Gabi Schierning, Kornelius Nielsch, Heiko Reith","doi":"10.1002/aelm.202400198","DOIUrl":"https://doi.org/10.1002/aelm.202400198","url":null,"abstract":"Micro thermoelectric generators (µTEGs) can harvest waste heat to generate electricity, making them a potential solution to the growing problem of powering autonomous electronics, such as sensors for the Internet of Things. Until now, µTEGs have not been able to provide power for these applications. This is because the output power of µTEGs is limited due to insufficient contacts and poor thermal coupling between the device and the heat source. In this work, the contact resistance as well as the thermal coupling between the heat source and the device through process optimization are improved. The former by improved electrochemical deposition (ECD) conditions, the latter by introducing a thin solder adhesion layer, which smooths the uneven surface of µTEG due to its good wetting properties. Using these improvements in combination with optimized packing density, here the fabrication and characterization of a µTEG with 126 leg pairs connected in series are reported that exhibits an open circuit voltage of 339.2 mV at a temperature difference of 20.6 K and a record-high normalized power density of 25.1 µW cm<sup>−2</sup> K<sup>−2</sup> for ECD based µTEGs. This µTEG is used to power a temperature sensor, bringing this work one step closer to application.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"4 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yang Ye, Jin Ning, Yuan Meng, Yuxin Wang, Peike Wang, Jingjing Luo, Ao Yin, Zhongqi Ren, Haipeng Liu, Xue Qi, Suzhu Yu, Jun Wei
Recently, flexible strain sensors have attracted great attention due to their wide applications in human-machine interface interaction, healthcare, soft robotics, etc. While many reported flexible strain sensors are stretchable, the stability of sensors under long-term deformation is still a significant challenge. In this work, a strain sensor has been fabricated by encapsulating semi-embedded aligned silver nanowires with a PDMS layer, showing a maximum gauge factor of 396.3 at 100% strain and a durability of 3000 cycles stretching. The strain-sensitive material also remains stable after multiple bending and twisting during the 10000 cycles test. Furthermore, the strain sensor is endowed with a triboelectric nanogeneration function based on the triboelectric nanogeneration effect. The device has a maximum output power density of 9.36 mW m−2, allowing it to realize strain sensing while converting the mechanical energy produced by daily activities into electrical power. As proof of demonstration, attaching the device to the finger joint provides accurate real-time strain sensing and stable output of triboelectric power.
{"title":"Flexible and Sensitive Triboelectric Nanogenerator Strain Sensors Made of Semi-Embedded Aligned Silver Nanowires","authors":"Yang Ye, Jin Ning, Yuan Meng, Yuxin Wang, Peike Wang, Jingjing Luo, Ao Yin, Zhongqi Ren, Haipeng Liu, Xue Qi, Suzhu Yu, Jun Wei","doi":"10.1002/aelm.202400426","DOIUrl":"https://doi.org/10.1002/aelm.202400426","url":null,"abstract":"Recently, flexible strain sensors have attracted great attention due to their wide applications in human-machine interface interaction, healthcare, soft robotics, etc. While many reported flexible strain sensors are stretchable, the stability of sensors under long-term deformation is still a significant challenge. In this work, a strain sensor has been fabricated by encapsulating semi-embedded aligned silver nanowires with a PDMS layer, showing a maximum gauge factor of 396.3 at 100% strain and a durability of 3000 cycles stretching. The strain-sensitive material also remains stable after multiple bending and twisting during the 10000 cycles test. Furthermore, the strain sensor is endowed with a triboelectric nanogeneration function based on the triboelectric nanogeneration effect. The device has a maximum output power density of 9.36 mW m<sup>−2</sup>, allowing it to realize strain sensing while converting the mechanical energy produced by daily activities into electrical power. As proof of demonstration, attaching the device to the finger joint provides accurate real-time strain sensing and stable output of triboelectric power.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"154 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Davide Pilati, Fabio Michieletti, Alessandro Cultrera, Carlo Ricciardi, Gianluca Milano
Self-organizing memristive nanowire (NW) networks are promising candidates for neuromorphic-type data processing in a physical reservoir computing framework because of their collective emergent behavior, which enables spatiotemporal signal processing. However, understanding emergent dynamics in multiterminal networks remains challenging. Here experimental spatiotemporal characterization of memristive NW networks dynamics in multiterminal configuration is reported, analyzing the activation and relaxation of network's global and local conductance, as well as the inherent spatial nonlinear transformation capabilities. Emergent effects are analyzed i) during activation, by investigating the spatiotemporal dynamics of the electric field distribution across the network through voltage mapping; ii) during relaxation, by monitoring the evolution of the conductance matrix of the multiterminal system. The multiterminal approach also allowed monitoring the spatial distribution of nonlinear activity, demonstrating the impact of different network areas on the system's information processing capabilities. Nonlinear transformation tasks are experimentally performed by driving the network into different conductive states, demonstrating the importance of selecting proper operating conditions for efficient information processing. This work allows a better understanding of the local nonlinear dynamics in NW networks and their impact on the information processing capabilities, providing new insights for a rational design of self-organizing neuromorphic systems.
{"title":"Emerging Spatiotemporal Dynamics in Multiterminal Neuromorphic Nanowire Networks Through Conductance Matrices and Voltage Maps","authors":"Davide Pilati, Fabio Michieletti, Alessandro Cultrera, Carlo Ricciardi, Gianluca Milano","doi":"10.1002/aelm.202400750","DOIUrl":"https://doi.org/10.1002/aelm.202400750","url":null,"abstract":"Self-organizing memristive nanowire (NW) networks are promising candidates for neuromorphic-type data processing in a physical reservoir computing framework because of their collective emergent behavior, which enables spatiotemporal signal processing. However, understanding emergent dynamics in multiterminal networks remains challenging. Here experimental spatiotemporal characterization of memristive NW networks dynamics in multiterminal configuration is reported, analyzing the activation and relaxation of network's global and local conductance, as well as the inherent spatial nonlinear transformation capabilities. Emergent effects are analyzed <i>i)</i> during activation, by investigating the spatiotemporal dynamics of the electric field distribution across the network through voltage mapping; <i>ii)</i> during relaxation, by monitoring the evolution of the conductance matrix of the multiterminal system. The multiterminal approach also allowed monitoring the spatial distribution of nonlinear activity, demonstrating the impact of different network areas on the system's information processing capabilities. Nonlinear transformation tasks are experimentally performed by driving the network into different conductive states, demonstrating the importance of selecting proper operating conditions for efficient information processing. This work allows a better understanding of the local nonlinear dynamics in NW networks and their impact on the information processing capabilities, providing new insights for a rational design of self-organizing neuromorphic systems.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"11 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142609903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
2D magnetic crystals with atomic thickness exhibit intriguing physical properties, which have attracted considerable research interest in the related materials’ family, both in fundamental research and in developing spintronic devices. The recent discovery of some non-van der Waals 2D magnetic crystals expands the systems. Nevertheless, the relationship between the dimensionality of microscopic magnetic exchange interactions and macroscopic magnetic properties at the 2D limit remains to be fully elucidated. Here, we have fabricated mono-phased continuous ultrathin CrTe2 and Cr3Te4 films by molecular beam epitaxy and elucidated the diverse magnetism tuned by the dimensionality of exchange interactions by a joint study of spin-polarized scanning tunneling microscopy, magnetization, magneto-transport measurements, and density functional theory calculations. The transition from a zigzag-antiferromagnetic order in the monolayer CrTe2 to a ferromagnetic (FM) order in the second-layer CrTe2 is confirmed, which is driven by their varied in-plane lattice constants induced change of 2D exchange interactions. A robust FM state with large perpendicular magnetic anisotropy in Cr3Te4 is observed, originating from its strong 3D exchange interactions. The observed evolution of magnetism demonstrates that the dimensionality of magnetic exchange interactions strongly influences magnetism even at the 2D limit.
{"title":"Tuning the Magnetism in Ultrathin CrxTey Films by Lattice Dimensionality","authors":"Guangyao Miao, Minghui Gu, Haojie Sun, Pan Chen, Jiade Li, Siwei Xue, Nuoyu Su, Zhibin Su, Weiliang Zhong, Zhihan Zhang, Xuetao Zhu, Jiandi Zhang, Yugui Yao, Wei Jiang, Meng Meng, Weihua Wang, Jiandong Guo","doi":"10.1002/aelm.202400720","DOIUrl":"https://doi.org/10.1002/aelm.202400720","url":null,"abstract":"2D magnetic crystals with atomic thickness exhibit intriguing physical properties, which have attracted considerable research interest in the related materials’ family, both in fundamental research and in developing spintronic devices. The recent discovery of some non-van der Waals 2D magnetic crystals expands the systems. Nevertheless, the relationship between the dimensionality of microscopic magnetic exchange interactions and macroscopic magnetic properties at the 2D limit remains to be fully elucidated. Here, we have fabricated mono-phased continuous ultrathin CrTe<sub>2</sub> and Cr<sub>3</sub>Te<sub>4</sub> films by molecular beam epitaxy and elucidated the diverse magnetism tuned by the dimensionality of exchange interactions by a joint study of spin-polarized scanning tunneling microscopy, magnetization, magneto-transport measurements, and density functional theory calculations. The transition from a zigzag-antiferromagnetic order in the monolayer CrTe<sub>2</sub> to a ferromagnetic (FM) order in the second-layer CrTe<sub>2</sub> is confirmed, which is driven by their varied in-plane lattice constants induced change of 2D exchange interactions. A robust FM state with large perpendicular magnetic anisotropy in Cr<sub>3</sub>Te<sub>4</sub> is observed, originating from its strong 3D exchange interactions. The observed evolution of magnetism demonstrates that the dimensionality of magnetic exchange interactions strongly influences magnetism even at the 2D limit.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"43 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142599959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Daniel Binion, Colin A. Mussman, Erik Lier, Thomas H. Hand, Douglas H. Werner
A lens consisting of an anisotropic near-zero index metamaterial (NZIM) is introduced for improving the far-field performance of active electronically scanned arrays (AESA). Several simulation studies demonstrate how the NZIM lens (metalens) can be functionalized to transform the embedded element pattern of an array from a typical cosinusoidal shape to a flat-topped pattern, dramatically reducing the gain at wider angles. This corresponds to reductions in scan loss and suppression of grating lobes in the desired field of view (FOV), especially for arrays with large element spacing (i.e., sparse or thinned arrays). The metalens concept is demonstrated through several simulation studies illustrating the beam shaping capability of NZIM materials. A fabricated metalens demonstrates full suppression of grating lobes and minimal scan loss with a ±10° FOV, which is ideally suited for limited FOV applications such as geosynchronous satellite communications.
{"title":"A Near-Zero Index Metamaterial Lens for Reduced Complexity and High-Performance Active Electronically Scanned Arrays","authors":"J. Daniel Binion, Colin A. Mussman, Erik Lier, Thomas H. Hand, Douglas H. Werner","doi":"10.1002/aelm.202400224","DOIUrl":"https://doi.org/10.1002/aelm.202400224","url":null,"abstract":"A lens consisting of an anisotropic near-zero index metamaterial (NZIM) is introduced for improving the far-field performance of active electronically scanned arrays (AESA). Several simulation studies demonstrate how the NZIM lens (metalens) can be functionalized to transform the embedded element pattern of an array from a typical cosinusoidal shape to a flat-topped pattern, dramatically reducing the gain at wider angles. This corresponds to reductions in scan loss and suppression of grating lobes in the desired field of view (FOV), especially for arrays with large element spacing (i.e., sparse or thinned arrays). The metalens concept is demonstrated through several simulation studies illustrating the beam shaping capability of NZIM materials. A fabricated metalens demonstrates full suppression of grating lobes and minimal scan loss with a ±10° FOV, which is ideally suited for limited FOV applications such as geosynchronous satellite communications.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"34 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142599958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Masthead: (Adv. Electron. Mater. 11/2024)","authors":"","doi":"10.1002/aelm.202470038","DOIUrl":"https://doi.org/10.1002/aelm.202470038","url":null,"abstract":"Click on the article title to read more.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"34 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142597844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ned E. Dreamer, Dimitrios A. Koutsouras, Morteza Hassanpour Amiri, Paschalis Gkoupidenis, Kamal Asadi
The existing device models for organic electrochemical transistors (OECTs) fail to provide any device design guidelines for optimized performance parameters such as transconductance that are pivotal for the applications OECTs in sensing. Moreover, the current models are based on the questionable assumption of a homogenous organic semiconductor layer, and all predict a linear behavior of the resistance with the OECT channel length. Consequently, the experimentally observed nonlinear resistance behavior in OECTs has been overlooked thus far. Here, an OECT device model is developed that accurately describes the nonlinear behavior of the OECT channel resistance and offers the first guidelines for maximizing transconductance. The model is inherently nonlinear and the nonlinearity stem from the non‐monolithic capacitance of the organic semiconductor layer. Moreover, the model provides a consistent and reliable estimations for the contact resistance in OECTs. The success of the model in accurately describing and providing predictions of the OECT operation by relating the device's geometrical parameters with electrochemical parameters of the semiconductor layer paves the way toward unlocking OECT potentials in diverse applications, from biosensing to neuromorphic computing and flexible electronics.
{"title":"The Impact of Non‐Monolithic Semiconductor Capacitance on Organic Electrochemical Transistors Performance and Design","authors":"Ned E. Dreamer, Dimitrios A. Koutsouras, Morteza Hassanpour Amiri, Paschalis Gkoupidenis, Kamal Asadi","doi":"10.1002/aelm.202400373","DOIUrl":"https://doi.org/10.1002/aelm.202400373","url":null,"abstract":"The existing device models for organic electrochemical transistors (OECTs) fail to provide any device design guidelines for optimized performance parameters such as transconductance that are pivotal for the applications OECTs in sensing. Moreover, the current models are based on the questionable assumption of a homogenous organic semiconductor layer, and all predict a linear behavior of the resistance with the OECT channel length. Consequently, the experimentally observed nonlinear resistance behavior in OECTs has been overlooked thus far. Here, an OECT device model is developed that accurately describes the nonlinear behavior of the OECT channel resistance and offers the first guidelines for maximizing transconductance. The model is inherently nonlinear and the nonlinearity stem from the non‐monolithic capacitance of the organic semiconductor layer. Moreover, the model provides a consistent and reliable estimations for the contact resistance in OECTs. The success of the model in accurately describing and providing predictions of the OECT operation by relating the device's geometrical parameters with electrochemical parameters of the semiconductor layer paves the way toward unlocking OECT potentials in diverse applications, from biosensing to neuromorphic computing and flexible electronics.","PeriodicalId":110,"journal":{"name":"Advanced Electronic Materials","volume":"24 1","pages":""},"PeriodicalIF":6.2,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142596668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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