In the last decade, refrigeration technology based on electrocaloric effect (ECE) has become a research hotspot in the ferroelectric field, profiting from being environmentally friendly and highly efficient. In this paper, we fabricated CoFe2O4/P(VDF-TrFE) multilayer composite films on an fluorine-doped tin oxide glass by integrating CoFe2O4 additives and P(VDF-TrFE) barriers to innovate the structures and ECE performances. As a result, the multilayer composite films showed comprehensive superiorities such as higher crystallization, smaller grain size, more polar phase, smaller coercive fields, and higher polarizations than the reference P(VDF-TrFE) films. The composite films have acceptably low leakage currents far below micrometers at a high electric field of 100 MV m−1. We measured a giant ECE temperature change of 25.9 K and an ECE strength of 0.37 K m MV−1 at a relatively small external field of 70 MV m−1 for ferroelectric polymers, extremely competitive over the reported. The Landau–Devonshire theory ascertained the reliability of the ECE performance by the indirect method and predicted a high ECE temperature change of 54 K under 140 MV m−1 of the multilayer composite films. The giant ECE CoFe2O4/P(VDF-TrFE) multilayer composite films are prospective for solid-state refrigeration.
近十年来，基于电热效应（ECE）的制冷技术以其环保、高效等优点成为铁电领域的研究热点。本文通过将CoFe2O4添加剂和P（VDF-TrFE）阻隔层整合到含氟氧化锡玻璃上，制备了CoFe2O4/P（VDF-TrFE）多层复合薄膜，创新了膜的结构和ECE性能。结果表明，与参考P（VDF-TrFE）薄膜相比，多层复合薄膜具有结晶性高、晶粒尺寸小、极性相多、矫顽力场小、极化率高等综合优势。在100 MV m−1的高电场下，复合薄膜具有可接受的远低于微米的低泄漏电流。我们测量了铁电聚合物在相对较小的70 MV m−1外场下的25.9 K的巨大ECE温度变化和0.37 K m MV−1的ECE强度，与报道的极具竞争力。Landau-Devonshire理论通过间接方法确定了ECE性能的可靠性，并预测多层复合膜在140 MV m−1下的ECE温度变化高达54 K。巨型ECE CoFe2O4/P（VDF-TrFE）多层复合薄膜在固态制冷领域具有广阔的应用前景。
{"title":"Synergism of CoFe2O4 additives and P(VDF-TrFE) barriers in crystallization, polar phase, and electrocaloric effects of multilayer composite thin films","authors":"Jinyan Wang, Ronghua Qin, Lingfang Xu, Xiguang Huang, Tian Liang, Yalong Ge, Changping Yang","doi":"10.1063/5.0272666","DOIUrl":"https://doi.org/10.1063/5.0272666","url":null,"abstract":"In the last decade, refrigeration technology based on electrocaloric effect (ECE) has become a research hotspot in the ferroelectric field, profiting from being environmentally friendly and highly efficient. In this paper, we fabricated CoFe2O4/P(VDF-TrFE) multilayer composite films on an fluorine-doped tin oxide glass by integrating CoFe2O4 additives and P(VDF-TrFE) barriers to innovate the structures and ECE performances. As a result, the multilayer composite films showed comprehensive superiorities such as higher crystallization, smaller grain size, more polar phase, smaller coercive fields, and higher polarizations than the reference P(VDF-TrFE) films. The composite films have acceptably low leakage currents far below micrometers at a high electric field of 100 MV m−1. We measured a giant ECE temperature change of 25.9 K and an ECE strength of 0.37 K m MV−1 at a relatively small external field of 70 MV m−1 for ferroelectric polymers, extremely competitive over the reported. The Landau–Devonshire theory ascertained the reliability of the ECE performance by the indirect method and predicted a high ECE temperature change of 54 K under 140 MV m−1 of the multilayer composite films. The giant ECE CoFe2O4/P(VDF-TrFE) multilayer composite films are prospective for solid-state refrigeration.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"370 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Yi Liang, Sheng Cao, Yuhe Bi, Yusheng Song, Qiuyan Li, Shulin Han, Zhengtuan Chen, Lei Cai, Bingsuo Zou, Jialong Zhao
High-efficiency green emission is essential for next-generation quantum dot light-emitting diodes (QLEDs); however, fully solution-processed inverted green QLEDs, particularly cadmium-free devices, are limited by surface defects, non-radiative recombination, and inefficient charge transport. Herein, we report all-solution-processed inverted ZnSeTe green QLEDs enabled by the passivation of ZnSeTe quantum dots (QDs) with the short-chain ligand of NH4PF6. This treatment effectively suppresses surface traps, prolongs photoluminescence lifetimes, and enhances carrier transport, increasing QD film conductivity from 1.42 × 10−6 to 6.15 × 10−5 S m−1 and reducing device recombination resistance from 36.2 to 16.6 kΩ. As a result, the NH4PF6-passivated QLEDs achieve a maximum external quantum efficiency of 7.3%, a peak luminance of 6732.7 cd m−2, and an operational T50 lifetime of 115 h at 100 cd m−2, a 46-fold enhancement compared to devices based on untreated QDs. These findings reveal that NH4PF6 short-chain ligands simultaneously passivate surface defects and accelerate radiative recombination, offering a viable strategy for high-efficiency, environmentally friendly green-emitting inverted QLEDs.
高效绿色发光是下一代量子点发光二极管（qled）的关键。然而，完全溶液处理的倒转绿色qled，特别是无镉器件，受到表面缺陷、非辐射复合和低效电荷输运的限制。在此，我们报道了全溶液处理的倒置ZnSeTe绿色qled，该qled是由ZnSeTe量子点（QDs）与NH4PF6短链配体钝化而实现的。该处理有效地抑制了表面陷阱，延长了光致发光寿命，增强了载流子输运，将QD薄膜的电导率从1.42 × 10−6提高到6.15 × 10−5 S m−1，并将器件重组电阻从36.2降低到16.6 kΩ。结果表明，nh4pf6钝化qled的最大外部量子效率为7.3%，峰值亮度为6732.7 cd m−2，在100 cd m−2下工作T50寿命为115小时，与未经处理的QDs相比，提高了46倍。这些发现表明，NH4PF6短链配体可以同时钝化表面缺陷和加速辐射重组，为高效、环保的绿色发光倒转qled提供了可行的策略。
{"title":"Defect passivation by short-chain ligands in all-solution-processed inverted ZnSeTe green QLEDs","authors":"Yi Liang, Sheng Cao, Yuhe Bi, Yusheng Song, Qiuyan Li, Shulin Han, Zhengtuan Chen, Lei Cai, Bingsuo Zou, Jialong Zhao","doi":"10.1063/5.0303612","DOIUrl":"https://doi.org/10.1063/5.0303612","url":null,"abstract":"High-efficiency green emission is essential for next-generation quantum dot light-emitting diodes (QLEDs); however, fully solution-processed inverted green QLEDs, particularly cadmium-free devices, are limited by surface defects, non-radiative recombination, and inefficient charge transport. Herein, we report all-solution-processed inverted ZnSeTe green QLEDs enabled by the passivation of ZnSeTe quantum dots (QDs) with the short-chain ligand of NH4PF6. This treatment effectively suppresses surface traps, prolongs photoluminescence lifetimes, and enhances carrier transport, increasing QD film conductivity from 1.42 × 10−6 to 6.15 × 10−5 S m−1 and reducing device recombination resistance from 36.2 to 16.6 kΩ. As a result, the NH4PF6-passivated QLEDs achieve a maximum external quantum efficiency of 7.3%, a peak luminance of 6732.7 cd m−2, and an operational T50 lifetime of 115 h at 100 cd m−2, a 46-fold enhancement compared to devices based on untreated QDs. These findings reveal that NH4PF6 short-chain ligands simultaneously passivate surface defects and accelerate radiative recombination, offering a viable strategy for high-efficiency, environmentally friendly green-emitting inverted QLEDs.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"20 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Accurate evaluation of mechanical properties in steels under ageing or service conditions remains a major challenge. We propose a thermo-mechanical coupling framework for nanosecond laser ablation based on energy conservation, which is embedded into a physics-informed neural network (PINN) to enable simultaneous inversion of multiple mechanical properties. A thermo-mechanical coupling coefficient is defined to uniformly describe the dynamic allocation of input laser energy among thermal diffusion, mechanical work, and plasma shielding across different deformation stages under laser irradiation. Furthermore, hard-to-measure physical characteristics in the coupled equation are replaced with experimentally accessible features obtained through the simultaneous acquisition of spectroscopic, shockwave, and surface-wave signals. Using 210 experimental datasets, the framework simultaneously recovers Young's modulus, yield strength, ultimate tensile strength, and micro-Vickers hardness with high accuracy (R2 = 0.9927, 0.9912, 0.9916, and 0.9959, respectively), significantly outperforming the baseline method (ultrasonic velocity regression for E, R2 = 0.0012). Comparisons with linear normalization and unconstrained neural networks demonstrate that PINN achieves near-unity accuracy through the embedding of conservation-law constraints. Partial dependency analysis further uncovers the nonlinear coupling laws between input features and mechanical properties. The proposed paradigm, integrating conservation laws, measurable features, and physics-informed learning, offers a universal approach for non-contact, high-precision, and physically consistent multi-to-multi inversion of multiple material properties under nanosecond laser ablation conditions.
{"title":"Measurement of multiple mechanical properties from multi-dimensional signals in nanosecond laser ablation via PINN","authors":"Ying Zhou, Jian Wu, Ziyuan Song, Jinghui Li, Xinyu Guo, Hao Sun, Yuhua Hang, Cuixiang Pei, Xingwen Li","doi":"10.1063/5.0301252","DOIUrl":"https://doi.org/10.1063/5.0301252","url":null,"abstract":"Accurate evaluation of mechanical properties in steels under ageing or service conditions remains a major challenge. We propose a thermo-mechanical coupling framework for nanosecond laser ablation based on energy conservation, which is embedded into a physics-informed neural network (PINN) to enable simultaneous inversion of multiple mechanical properties. A thermo-mechanical coupling coefficient is defined to uniformly describe the dynamic allocation of input laser energy among thermal diffusion, mechanical work, and plasma shielding across different deformation stages under laser irradiation. Furthermore, hard-to-measure physical characteristics in the coupled equation are replaced with experimentally accessible features obtained through the simultaneous acquisition of spectroscopic, shockwave, and surface-wave signals. Using 210 experimental datasets, the framework simultaneously recovers Young's modulus, yield strength, ultimate tensile strength, and micro-Vickers hardness with high accuracy (R2 = 0.9927, 0.9912, 0.9916, and 0.9959, respectively), significantly outperforming the baseline method (ultrasonic velocity regression for E, R2 = 0.0012). Comparisons with linear normalization and unconstrained neural networks demonstrate that PINN achieves near-unity accuracy through the embedding of conservation-law constraints. Partial dependency analysis further uncovers the nonlinear coupling laws between input features and mechanical properties. The proposed paradigm, integrating conservation laws, measurable features, and physics-informed learning, offers a universal approach for non-contact, high-precision, and physically consistent multi-to-multi inversion of multiple material properties under nanosecond laser ablation conditions.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"152 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
The ability to control spin and valley degrees of freedom in two-dimensional materials offers promising prospects for next-generation electronic and spintronic devices. However, achieving tunable valley polarization and intrinsic anomalous Hall effect (AHE) within a single material system without an external magnetic or optical field remains challenging. Here, we present two complementary mechanisms to realize robust valley polarization control in TiInSe3. In the monolayer, electron doping modifies the magnetic easy axis, inducing spontaneous valley polarization. More importantly, in bilayers with specific stacking configurations, intrinsic interlayer charge transfer breaks inversion symmetry, enabling spontaneous valley polarization and a switchable layer-resolved AHE even in the absence of doping. These findings establish fundamental strategies to manipulate spin and valley degrees of freedom through doping and stacking engineering.
{"title":"Valley manipulation in 2D multiferroic TiInSe3: Doping-induced valley polarization and stacking-engineered effects","authors":"Shuhong Li, Yuehua Huangfu, Kexu Ren, Chang Liu, Bing Wang, Xiaodong Zhou","doi":"10.1063/5.0305791","DOIUrl":"https://doi.org/10.1063/5.0305791","url":null,"abstract":"The ability to control spin and valley degrees of freedom in two-dimensional materials offers promising prospects for next-generation electronic and spintronic devices. However, achieving tunable valley polarization and intrinsic anomalous Hall effect (AHE) within a single material system without an external magnetic or optical field remains challenging. Here, we present two complementary mechanisms to realize robust valley polarization control in TiInSe3. In the monolayer, electron doping modifies the magnetic easy axis, inducing spontaneous valley polarization. More importantly, in bilayers with specific stacking configurations, intrinsic interlayer charge transfer breaks inversion symmetry, enabling spontaneous valley polarization and a switchable layer-resolved AHE even in the absence of doping. These findings establish fundamental strategies to manipulate spin and valley degrees of freedom through doping and stacking engineering.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"7 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
The magnetic two-dimensional transition metal dichalcogenides with high Curie temperature play a pivotal role in spintronic devices and exhibit promising application potentials. In this paper, rare earth Dy-doped SnS2 wafers are synthesized through gas–liquid phase deposition and high-temperature, high-pressure processes. The material exhibits comprehensive properties such as ferromagnetism, high Curie temperature (628 K), and large negative magnetoresistance at low magnetic fields over a wide temperature range (55%–4%, 50–350 K). The results of first-principles calculations indicate that it exhibits the half-metallic behavior of electrons with a single spin direction passing through the Fermi level, with a large spin bandgap of 1.7 eV, and a flatband exists near the Fermi level. Therefore, the substitution of Sn with Dy induces a global structural reorganization and disrupts the system's symmetry, resulting in the formation of a flatband near the Fermi level through the occupation of 4f orbital electrons, providing a stable local magnetic moment. Through the orbital hybridization between Dy and S, the ferromagnetic exchange interaction is formed, achieving the ferromagnetism of DyxSn1−xS2. This laid the foundation for the application of magnetoresistive sensors, electromagnetic shielding, and spin field-effect transistors.
{"title":"Realization and regulation of negative magnetoresistance behavior in Dy-doped SnS2 with high Curie temperature","authors":"Yu Tong, Xi Chen, Hongpeng Zhang, Jianyu Ling, Haoqun Zeng, Kewei Zhang, Mingzhe Zhang","doi":"10.1063/5.0288646","DOIUrl":"https://doi.org/10.1063/5.0288646","url":null,"abstract":"The magnetic two-dimensional transition metal dichalcogenides with high Curie temperature play a pivotal role in spintronic devices and exhibit promising application potentials. In this paper, rare earth Dy-doped SnS2 wafers are synthesized through gas–liquid phase deposition and high-temperature, high-pressure processes. The material exhibits comprehensive properties such as ferromagnetism, high Curie temperature (628 K), and large negative magnetoresistance at low magnetic fields over a wide temperature range (55%–4%, 50–350 K). The results of first-principles calculations indicate that it exhibits the half-metallic behavior of electrons with a single spin direction passing through the Fermi level, with a large spin bandgap of 1.7 eV, and a flatband exists near the Fermi level. Therefore, the substitution of Sn with Dy induces a global structural reorganization and disrupts the system's symmetry, resulting in the formation of a flatband near the Fermi level through the occupation of 4f orbital electrons, providing a stable local magnetic moment. Through the orbital hybridization between Dy and S, the ferromagnetic exchange interaction is formed, achieving the ferromagnetism of DyxSn1−xS2. This laid the foundation for the application of magnetoresistive sensors, electromagnetic shielding, and spin field-effect transistors.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"13 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Bio-inspired visuomorphic vision integrates multi-dimensional information (spectrum, spatial, temporal, and so on), providing an effective computational paradigm for sensing a visual scene in the physical world. Using photosensors with multi-dimensional information processing functionality to split complex optical information into visible and ultraviolet channels for separate perception and processing is the basis for constructing tetrachromatic vision systems. Here, by modulating the transport dynamics of photogenerated excitons between pentacene and ZnO thin films, both wavelength-dependent volatile positive photoconductance and non-volatile negative photoconductance characteristics are coupled into a single optoelectronic transistor. Utilizing the optoelectronic transistor as the tetrachromatic sensor, the constructed in-sensor computing system can effectively extract and identify the types of visible objects (99%) and the motion direction of ultraviolet objects (97%). This work provides a foundational hardware platform for intelligent artificial vision systems.
{"title":"Tetrachromatic optoelectronic transistor with multi-dimensional information processing functionality for in-sensor motion perception","authors":"Wanxin Huang, Yiru Wang, Shanshuo Liu, Jianyu Ming, Yannan Xie, Li Gao, Linghai Xie, Haifeng Ling","doi":"10.1063/5.0303796","DOIUrl":"https://doi.org/10.1063/5.0303796","url":null,"abstract":"Bio-inspired visuomorphic vision integrates multi-dimensional information (spectrum, spatial, temporal, and so on), providing an effective computational paradigm for sensing a visual scene in the physical world. Using photosensors with multi-dimensional information processing functionality to split complex optical information into visible and ultraviolet channels for separate perception and processing is the basis for constructing tetrachromatic vision systems. Here, by modulating the transport dynamics of photogenerated excitons between pentacene and ZnO thin films, both wavelength-dependent volatile positive photoconductance and non-volatile negative photoconductance characteristics are coupled into a single optoelectronic transistor. Utilizing the optoelectronic transistor as the tetrachromatic sensor, the constructed in-sensor computing system can effectively extract and identify the types of visible objects (99%) and the motion direction of ultraviolet objects (97%). This work provides a foundational hardware platform for intelligent artificial vision systems.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"46 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Achieving fully electrical and easily integrated programmable spin logic within a single device using spin–orbit torque (SOT)-driven perpendicular magnetization switching (PMS) remains a key challenge for realizing scalable and energy-efficient spin logic-in-memory computing. Here, we demonstrate controllable field-free SOT-driven PMS by the geometric asymmetry of current distribution in a “T-shaped” Pt/CoPt architecture. Deterministic clockwise/counterclockwise PMS is observed when applying current pulses along the left/right arms of the T-architecture, which has been attributed to the combined effect of geometrically curved current channel-induced Oersted field and inhomogeneous spatial distribution of spin currents. Furthermore, by implementing a three-step sequential pulsing scheme that precisely controls channel selection, an initial control current pulse, and two subsequent control pulses, we demonstrate the complete set of 16 Boolean logic functions within a single device. This simple material-agnostic and integration-friendly approach provides a pathway for developing fully electrical controllable SOT-based spin logic and in-memory computing devices.
{"title":"Geometric symmetry breaking of current distribution enables field-free programmable spin logic in T-shaped architecture","authors":"Zhenxing Wang, Qian Wang, Dong Wang, Xiang Han, Chuanwei Feng, Xinglong Ye, Lihui Bai, Shishen Yan, Yufeng Tian","doi":"10.1063/5.0295548","DOIUrl":"https://doi.org/10.1063/5.0295548","url":null,"abstract":"Achieving fully electrical and easily integrated programmable spin logic within a single device using spin–orbit torque (SOT)-driven perpendicular magnetization switching (PMS) remains a key challenge for realizing scalable and energy-efficient spin logic-in-memory computing. Here, we demonstrate controllable field-free SOT-driven PMS by the geometric asymmetry of current distribution in a “T-shaped” Pt/CoPt architecture. Deterministic clockwise/counterclockwise PMS is observed when applying current pulses along the left/right arms of the T-architecture, which has been attributed to the combined effect of geometrically curved current channel-induced Oersted field and inhomogeneous spatial distribution of spin currents. Furthermore, by implementing a three-step sequential pulsing scheme that precisely controls channel selection, an initial control current pulse, and two subsequent control pulses, we demonstrate the complete set of 16 Boolean logic functions within a single device. This simple material-agnostic and integration-friendly approach provides a pathway for developing fully electrical controllable SOT-based spin logic and in-memory computing devices.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"3 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Michael T. Hatzon, Eugene N. Ivanov, Aaron Quiskamp, Michael E. Tobar
We report high-resolution measurements of thermal fluctuations in microwave and mechanical resonators using a dual-channel readout system. The latter comprises a low-noise amplifier, an I/Q-mixer, and a cross-correlator. We discovered that, under certain conditions, the intrinsic fluctuations of the low-noise amplifier, which are common to both channels of the readout system, are averaged out when computing the voltage noise cross-spectrum between the mixer's outputs. The suppression of the amplifier's technical fluctuations significantly improves the contrast of the thermal noise peaks exhibited by the resonators. Thus, for the room-temperature-stabilized 9 GHz sapphire-loaded cavity resonator, we observed more than 16 dB improvement in the thermal noise peak contrast relative to the single-channel measurements. The ability of the dual-channel readout system to discriminate between the broad- and narrow-band fluctuations may benefit the search for dark matter, which relies on the use of cryogenic microwave resonators.
{"title":"The study of thermal fluctuations in microwave and mechanical resonators","authors":"Michael T. Hatzon, Eugene N. Ivanov, Aaron Quiskamp, Michael E. Tobar","doi":"10.1063/5.0305008","DOIUrl":"https://doi.org/10.1063/5.0305008","url":null,"abstract":"We report high-resolution measurements of thermal fluctuations in microwave and mechanical resonators using a dual-channel readout system. The latter comprises a low-noise amplifier, an I/Q-mixer, and a cross-correlator. We discovered that, under certain conditions, the intrinsic fluctuations of the low-noise amplifier, which are common to both channels of the readout system, are averaged out when computing the voltage noise cross-spectrum between the mixer's outputs. The suppression of the amplifier's technical fluctuations significantly improves the contrast of the thermal noise peaks exhibited by the resonators. Thus, for the room-temperature-stabilized 9 GHz sapphire-loaded cavity resonator, we observed more than 16 dB improvement in the thermal noise peak contrast relative to the single-channel measurements. The ability of the dual-channel readout system to discriminate between the broad- and narrow-band fluctuations may benefit the search for dark matter, which relies on the use of cryogenic microwave resonators.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"107 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145759840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Yiwen Song, Eungkyun Kim, Jimy Encomendero, Seokjun Kim, Daniel C. Shoemaker, Yu-Hsin Chen, Debdeep Jena, Huili Grace Xing, Sukwon Choi
AlN/GaN/AlN high electron mobility transistors (HEMTs) have demonstrated exceptional potential for surpassing the electrical limitations of conventional AlGaN/GaN HEMTs. This study investigates the thermal performance of two types of AlN/GaN/AlN HEMTs with homoepitaxial AlN buffer layers grown on AlN substrates: an AlN/GaN/AlN single-crystal HEMT (AlN XHEMT) featuring a pseudomorphic/thin GaN channel and a conventional structure with a relaxed/thick GaN channel. Frequency- and time-domain thermoreflectance measurements reveal bulk-like thermal conductivity in the homoepitaxial AlN buffer layer, with negligible thermal boundary resistance at the AlN buffer/substrate interface. Consequently, Raman thermometry demonstrates that the AlN XHEMT with a thin (∼20 nm) pseudomorphically strained GaN channel exhibits better thermal performance than identical HEMT layer structures grown on a 4H-SiC substrate, despite 4H-SiC possessing a higher thermal conductivity. In addition, the AlN XHEMT exhibits a 22% lower channel temperature under 14 W/mm power density than the AlN/GaN/AlN-on-AlN HEMT that employs a thick (275 nm) relaxed GaN channel. These findings highlight that AlN XHEMTs offer not only electrical but also thermal advantages for high-power and high-frequency applications.
{"title":"Enhanced thermal performance of AlN/GaN/AlN XHEMTs on bulk AlN by suppression of phonon-boundary scattering","authors":"Yiwen Song, Eungkyun Kim, Jimy Encomendero, Seokjun Kim, Daniel C. Shoemaker, Yu-Hsin Chen, Debdeep Jena, Huili Grace Xing, Sukwon Choi","doi":"10.1063/5.0305053","DOIUrl":"https://doi.org/10.1063/5.0305053","url":null,"abstract":"AlN/GaN/AlN high electron mobility transistors (HEMTs) have demonstrated exceptional potential for surpassing the electrical limitations of conventional AlGaN/GaN HEMTs. This study investigates the thermal performance of two types of AlN/GaN/AlN HEMTs with homoepitaxial AlN buffer layers grown on AlN substrates: an AlN/GaN/AlN single-crystal HEMT (AlN XHEMT) featuring a pseudomorphic/thin GaN channel and a conventional structure with a relaxed/thick GaN channel. Frequency- and time-domain thermoreflectance measurements reveal bulk-like thermal conductivity in the homoepitaxial AlN buffer layer, with negligible thermal boundary resistance at the AlN buffer/substrate interface. Consequently, Raman thermometry demonstrates that the AlN XHEMT with a thin (∼20 nm) pseudomorphically strained GaN channel exhibits better thermal performance than identical HEMT layer structures grown on a 4H-SiC substrate, despite 4H-SiC possessing a higher thermal conductivity. In addition, the AlN XHEMT exhibits a 22% lower channel temperature under 14 W/mm power density than the AlN/GaN/AlN-on-AlN HEMT that employs a thick (275 nm) relaxed GaN channel. These findings highlight that AlN XHEMTs offer not only electrical but also thermal advantages for high-power and high-frequency applications.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"7 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145729104","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
The ScAlN film has a large electromechanical coupling and low mechanical loss, enabling RF filters with wide bandwidth, low insertion loss, and a steep filter skirt. In order to meet the growing demand for RF filters operating above 5 GHz, the use of polarization inverted multilayers is continuously being proposed. This Perspective discusses the advantages of overtone mode operation in polarization inverted multilayers for high-frequency bulk acoustic wave (BAW) filter applications: high parallel resonance Qp, high series resonance Qs, high electromechanical coupling, high power capability, and better acoustic isolation from the electrode and supporting medium. Three potential approaches for ScAlN polarization inverted multilayers: film transfer technique, unusual N-polar growth, and external DC voltage application are overviewed. This Perspective includes an experimental demonstration of an acoustic isolation of polarization inverted 30-layer resonators as well as frequency switching between the fundamental mode and the third overtone mode in the currently commercial frequency range of 1.3–3.5 GHz. This article provides a metrics of Q and electromechanical coupling coefficient of recently reported BAW and Lamb wave resonators above 5 GHz, along with experimental data on the elastic tensor, dielectric constant, electromechanical coupling coefficient, temperature coefficient of frequency, and relative Q values in ScxAl1−xN films with varying Sc concentration.
{"title":"A perspective and review of polarization inverted multilayer BAW resonators based on ScAlN piezoelectric films","authors":"Takahiko Yanagitani","doi":"10.1063/5.0281181","DOIUrl":"https://doi.org/10.1063/5.0281181","url":null,"abstract":"The ScAlN film has a large electromechanical coupling and low mechanical loss, enabling RF filters with wide bandwidth, low insertion loss, and a steep filter skirt. In order to meet the growing demand for RF filters operating above 5 GHz, the use of polarization inverted multilayers is continuously being proposed. This Perspective discusses the advantages of overtone mode operation in polarization inverted multilayers for high-frequency bulk acoustic wave (BAW) filter applications: high parallel resonance Qp, high series resonance Qs, high electromechanical coupling, high power capability, and better acoustic isolation from the electrode and supporting medium. Three potential approaches for ScAlN polarization inverted multilayers: film transfer technique, unusual N-polar growth, and external DC voltage application are overviewed. This Perspective includes an experimental demonstration of an acoustic isolation of polarization inverted 30-layer resonators as well as frequency switching between the fundamental mode and the third overtone mode in the currently commercial frequency range of 1.3–3.5 GHz. This article provides a metrics of Q and electromechanical coupling coefficient of recently reported BAW and Lamb wave resonators above 5 GHz, along with experimental data on the elastic tensor, dielectric constant, electromechanical coupling coefficient, temperature coefficient of frequency, and relative Q values in ScxAl1−xN films with varying Sc concentration.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"81 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145729102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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