Zepeng Lv, Zhenyu Wu, Bo Li, Jianhong Song, Kai Wu, Yonghong Cheng
The surface discharge at metal/insulation/gas (or vacuum) triple junctions (TJs) poses a serious threat to the insulation reliability of high-voltage equipment. An insulation layer was fabricated on the surface of aluminum metal electrodes via microarc oxidation (MAO) to suppress surface discharge at the TJ. The partial discharge inception voltage was effectively increased by up to 54.5% with the MAO layer. At 1.5 kV, the average discharge magnitude per minute at the TJ decreased by up to 66.7% after MAO treatment. The composition of the insulation layer is primarily Al2O3 and Al2SiO5. As the MAO duration and voltage increase, the thickness and surface pore area ratio of the MAO layer increased continuously. The mechanism of partial discharge suppression was investigated by analyzing the layer's composition, resistivity, surface potential decay, and phase-resolved partial discharge spectrum. The analysis indicates that the mechanism primarily involves suppressing the direct or indirect movement of electrons from the metal electrode to the gas. Consequently, this suppression reduces both the number of seed charges for electron avalanches and the probability of avalanche initiation at the microscopic level. At the macro-level, the insulation layer eliminates the traditional TJ, establishing a TJ of insulation/insulation/gas (or vacuum). This work proposes a strategy for suppressing surface discharges at TJs through metal surface modification.
{"title":"Microarc oxidation layer on aluminum surface significantly suppresses partial discharge at triple junction point on insulation surface","authors":"Zepeng Lv, Zhenyu Wu, Bo Li, Jianhong Song, Kai Wu, Yonghong Cheng","doi":"10.1063/5.0310808","DOIUrl":"https://doi.org/10.1063/5.0310808","url":null,"abstract":"The surface discharge at metal/insulation/gas (or vacuum) triple junctions (TJs) poses a serious threat to the insulation reliability of high-voltage equipment. An insulation layer was fabricated on the surface of aluminum metal electrodes via microarc oxidation (MAO) to suppress surface discharge at the TJ. The partial discharge inception voltage was effectively increased by up to 54.5% with the MAO layer. At 1.5 kV, the average discharge magnitude per minute at the TJ decreased by up to 66.7% after MAO treatment. The composition of the insulation layer is primarily Al2O3 and Al2SiO5. As the MAO duration and voltage increase, the thickness and surface pore area ratio of the MAO layer increased continuously. The mechanism of partial discharge suppression was investigated by analyzing the layer's composition, resistivity, surface potential decay, and phase-resolved partial discharge spectrum. The analysis indicates that the mechanism primarily involves suppressing the direct or indirect movement of electrons from the metal electrode to the gas. Consequently, this suppression reduces both the number of seed charges for electron avalanches and the probability of avalanche initiation at the microscopic level. At the macro-level, the insulation layer eliminates the traditional TJ, establishing a TJ of insulation/insulation/gas (or vacuum). This work proposes a strategy for suppressing surface discharges at TJs through metal surface modification.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"25 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393241","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 active control of nonlinear absorption (NLA), particularly the dynamic transition between saturable absorption (SA) and reverse saturable absorption (RSA), is essential for advanced photonics such as all-optical logic gates. However, the mechanisms governing these transitions remain poorly understood, especially concerning the roles of excitonic and defect states. This work systematically investigates the broadband NLA properties of two-dimensional (2D) perovskite (PEA)2PbI4 films from 470 to 1440 nm. Abnormal RSA to SA transition is observed at 470 nm (near the continuous state absorption shoulder) under a low pump intensity of ∼20.5 GW/cm2, attributed to the competition between many-body effect induced above band edge absorption enhancement and bleaching caused by non-thermalized carriers. At 520 nm (near the exciton resonance), SA dominates due to exciton bleaching. In the 560–650 nm range, RSA dominates due to the two-photon absorption, and the coefficient dispersion can be well-described by a two-band model. Notably, a clear transition from SA to RSA appears in the near-infrared region (1240–1440 nm), where defect-state filling induces SA, followed by RSA driven by three-photon absorption. The threshold for this transition is as low as ∼57.5 GW/cm2 at 1340 nm. These findings provide a mechanistic understanding of wavelength-dependent NLA transitions in 2D perovskites, highlighting the potential of (PEA)2PbI4 for multi-band nonlinear photonic applications.
{"title":"Nonlinear absorption transition governed by exciton and defect states in 2D (PEA)2PbI4 from visible to near-infrared","authors":"Lili Zhao, Yixuan Zhou, Yanqing Ge, Jiayu Tan, Yayan Xi, Yue Wu, Ying Zhang, Chunhui Lu, Xinlong Xu","doi":"10.1063/5.0315643","DOIUrl":"https://doi.org/10.1063/5.0315643","url":null,"abstract":"The active control of nonlinear absorption (NLA), particularly the dynamic transition between saturable absorption (SA) and reverse saturable absorption (RSA), is essential for advanced photonics such as all-optical logic gates. However, the mechanisms governing these transitions remain poorly understood, especially concerning the roles of excitonic and defect states. This work systematically investigates the broadband NLA properties of two-dimensional (2D) perovskite (PEA)2PbI4 films from 470 to 1440 nm. Abnormal RSA to SA transition is observed at 470 nm (near the continuous state absorption shoulder) under a low pump intensity of ∼20.5 GW/cm2, attributed to the competition between many-body effect induced above band edge absorption enhancement and bleaching caused by non-thermalized carriers. At 520 nm (near the exciton resonance), SA dominates due to exciton bleaching. In the 560–650 nm range, RSA dominates due to the two-photon absorption, and the coefficient dispersion can be well-described by a two-band model. Notably, a clear transition from SA to RSA appears in the near-infrared region (1240–1440 nm), where defect-state filling induces SA, followed by RSA driven by three-photon absorption. The threshold for this transition is as low as ∼57.5 GW/cm2 at 1340 nm. These findings provide a mechanistic understanding of wavelength-dependent NLA transitions in 2D perovskites, highlighting the potential of (PEA)2PbI4 for multi-band nonlinear photonic applications.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"1 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393617","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}
Siyu Liu, Yihao Zhuang, Pengju Cui, Qingyun Xie, Hanlin Xie, Geok Ing Ng
This work investigates the impact of stress-induced effects on the stability of AlN/GaN MIS-HEMTs on Si employing PECVD-SiN as a passivation layer. DC and temperature-dependent C–V/I–V measurements together with technology computer-aided design simulations are used to correlate stress state, defect behavior, and channel transport. As-deposited PECVD-SiN introduces strong inelastic stress that compresses the 2DEG near the GaN surface and drives an anomalous reverse shift of the threshold voltage of ∼−0.3 V between 300 and 475 K, with room-temperature mobility limited to ∼700 cm2 V−1 s−1 by remote scattering. Arrhenius analysis of the drain current yields an activation energy Ea = 0.059 eV, attributed to thermally activated charging and restructuring of bulk and interface defects coupled to the stress field. Post-passivation annealing at 450 °C largely relaxes the inelastic component, broadens the potential well, and reduces Ea to 0.019 eV. The mobility increases to ∼1260 cm2 V−1 s−1 and exhibits a polar optical phonon-like temperature dependence, while the VTH–T behavior changes to a weak positive coefficient. These results offer insights on the temperature stability of stress-induced GaN MIS-HEMTs from a material perspective.
{"title":"Inelastic-stress-induced threshold instability and mobility degradation in AlN/GaN MIS-HEMTs on Si","authors":"Siyu Liu, Yihao Zhuang, Pengju Cui, Qingyun Xie, Hanlin Xie, Geok Ing Ng","doi":"10.1063/5.0313481","DOIUrl":"https://doi.org/10.1063/5.0313481","url":null,"abstract":"This work investigates the impact of stress-induced effects on the stability of AlN/GaN MIS-HEMTs on Si employing PECVD-SiN as a passivation layer. DC and temperature-dependent C–V/I–V measurements together with technology computer-aided design simulations are used to correlate stress state, defect behavior, and channel transport. As-deposited PECVD-SiN introduces strong inelastic stress that compresses the 2DEG near the GaN surface and drives an anomalous reverse shift of the threshold voltage of ∼−0.3 V between 300 and 475 K, with room-temperature mobility limited to ∼700 cm2 V−1 s−1 by remote scattering. Arrhenius analysis of the drain current yields an activation energy Ea = 0.059 eV, attributed to thermally activated charging and restructuring of bulk and interface defects coupled to the stress field. Post-passivation annealing at 450 °C largely relaxes the inelastic component, broadens the potential well, and reduces Ea to 0.019 eV. The mobility increases to ∼1260 cm2 V−1 s−1 and exhibits a polar optical phonon-like temperature dependence, while the VTH–T behavior changes to a weak positive coefficient. These results offer insights on the temperature stability of stress-induced GaN MIS-HEMTs from a material perspective.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"55 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393242","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}
High-mobility spin-polarized two-dimensional electron gases (2DEGs) hold fundamental importance for the development of next-generation spintronic devices. In this work, we fabricate a high-quality epitaxial Eu2O3/STO (001) heterointerface, which hosts a two-dimensional electron gas exhibiting a high electron mobility of approximately 4.3 × 103 cm2 V−1 s−1 at 2 K. This interface demonstrates robust metallic conductivity, a pronounced Kondo effect, and an observable anomalous Hall effect that persists up to 100 K. Furthermore, magnetic measurements confirm the emergence of ferromagnetic order, which is primarily attributed to the combined effects of the Ti3+ magnetic moments induced by oxygen vacancies on the surface of the STO single crystal and the localized Eu2+ magnetic moments within the thin film. These collective findings support the possible formation of a spin-polarized 2DEG characterized by a high ferromagnetic ordering temperature. Our work underscores the significant potential of Eu-based oxide heterostructures as a promising platform for fundamental research of spin-polarized 2DEG.
{"title":"High-mobility magnetic two-dimensional electron gas with high Curie temperatures at Eu2O3/SrTiO3 interfaces","authors":"Zhao-Cai Wang, Shu-Juan Zhang, Fu-Sheng Luo, Weiyao Zhao, Ren-Kui Zheng","doi":"10.1063/5.0309535","DOIUrl":"https://doi.org/10.1063/5.0309535","url":null,"abstract":"High-mobility spin-polarized two-dimensional electron gases (2DEGs) hold fundamental importance for the development of next-generation spintronic devices. In this work, we fabricate a high-quality epitaxial Eu2O3/STO (001) heterointerface, which hosts a two-dimensional electron gas exhibiting a high electron mobility of approximately 4.3 × 103 cm2 V−1 s−1 at 2 K. This interface demonstrates robust metallic conductivity, a pronounced Kondo effect, and an observable anomalous Hall effect that persists up to 100 K. Furthermore, magnetic measurements confirm the emergence of ferromagnetic order, which is primarily attributed to the combined effects of the Ti3+ magnetic moments induced by oxygen vacancies on the surface of the STO single crystal and the localized Eu2+ magnetic moments within the thin film. These collective findings support the possible formation of a spin-polarized 2DEG characterized by a high ferromagnetic ordering temperature. Our work underscores the significant potential of Eu-based oxide heterostructures as a promising platform for fundamental research of spin-polarized 2DEG.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"88 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393318","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}
J. D. Pei, L. F. Wang, Y. Zhou, Y. P. Wang, X. L. Chai, M. Huang, Y. H. Zhu, Z. M. Liang, Z. C. Xu, J. X. Chen
This study reports a mid-infrared interband cascade superluminescent diode (ICSLD). By controlling the proportion of amplified spontaneous emission in the spectrum, we have achieved spectral width tuning from 1358 to 44 nm. Benefiting from the optical field confinement effect of the waveguide structure, the radiant exitance of the device reaches 77 W/cm2 at 78 K and 5.04 W/cm2 at 300 K, which is an order of magnitude higher than that of the surface-emitting LEDs based on the same material. A five-stage cascaded InAs/GaAsSb interband cascade structure is employed as the active region. The maximum output power-to-length ratio of the ICSLDs at 78 K is close to the state-of-the-art, while the injection current and device length are only 20% of those of quantum cascade superluminescent diodes. The interband cascade structure exhibits a longer nonradiative lifetime than the quantum cascade structure, which is the key to realizing low power consumption. A theoretical model for superluminescent diodes is developed, which reveals that variations in device size and operating conditions typically cause the output power and spectral width to vary inversely. Furthermore, the device functions as an edge-illuminated mesa photodiode at zero bias. It shows a responsivity of 2.6 A/W at 78 K, which is an order of magnitude higher than that of the top-illuminated mesa photodiode fabricated from the same epitaxial wafer. We demonstrate the generation and detection of optical signals on the same epitaxial wafer using ICSLDs.
本研究报道了一种中红外波段间级联超发光二极管（ICSLD）。通过控制放大自发辐射在光谱中的比例，我们实现了光谱宽度从1358到44 nm的调谐。得益于波导结构的光场约束效应，器件的辐射出口在78 K时达到77 W/cm2，在300 K时达到5.04 W/cm2，比基于相同材料的表面发光led高出一个数量级。采用五级级联InAs/GaAsSb带间级联结构作为有源区。在78 K时，icsld的最大输出功率与长度比接近最先进水平，而注入电流和器件长度仅为量子级联超发光二极管的20%。带间级联结构比量子级联结构具有更长的非辐射寿命，这是实现低功耗的关键。建立了超发光二极管的理论模型，揭示了器件尺寸和工作条件的变化通常会导致输出功率和光谱宽度呈反比变化。此外，该器件在零偏置下作为边缘照明台面光电二极管。它在78 K时的响应率为2.6 a /W，比用相同外延片制作的顶照台面光电二极管的响应率高一个数量级。我们演示了使用icsld在同一外延片上产生和检测光信号。
{"title":"Mid-infrared interband cascade superluminescent diode with tunable spectral-width and monolithically integrated detector","authors":"J. D. Pei, L. F. Wang, Y. Zhou, Y. P. Wang, X. L. Chai, M. Huang, Y. H. Zhu, Z. M. Liang, Z. C. Xu, J. X. Chen","doi":"10.1063/5.0315833","DOIUrl":"https://doi.org/10.1063/5.0315833","url":null,"abstract":"This study reports a mid-infrared interband cascade superluminescent diode (ICSLD). By controlling the proportion of amplified spontaneous emission in the spectrum, we have achieved spectral width tuning from 1358 to 44 nm. Benefiting from the optical field confinement effect of the waveguide structure, the radiant exitance of the device reaches 77 W/cm2 at 78 K and 5.04 W/cm2 at 300 K, which is an order of magnitude higher than that of the surface-emitting LEDs based on the same material. A five-stage cascaded InAs/GaAsSb interband cascade structure is employed as the active region. The maximum output power-to-length ratio of the ICSLDs at 78 K is close to the state-of-the-art, while the injection current and device length are only 20% of those of quantum cascade superluminescent diodes. The interband cascade structure exhibits a longer nonradiative lifetime than the quantum cascade structure, which is the key to realizing low power consumption. A theoretical model for superluminescent diodes is developed, which reveals that variations in device size and operating conditions typically cause the output power and spectral width to vary inversely. Furthermore, the device functions as an edge-illuminated mesa photodiode at zero bias. It shows a responsivity of 2.6 A/W at 78 K, which is an order of magnitude higher than that of the top-illuminated mesa photodiode fabricated from the same epitaxial wafer. We demonstrate the generation and detection of optical signals on the same epitaxial wafer using ICSLDs.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"80 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393611","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}
Valeriy I. Kondratyev, Vanik Shahnazaryan, Mikhail Tyugaev, Tatyana V. Ivanova, Ivan E. Kalantaevskii, Dmitry V. Permyakov, Ivan V. Iorsh, Anton K. Samusev, Vasily Kravtsov
Layered van der Waals materials offer promising opportunities for on-chip waveguiding and the development of integrated photonic circuits. In the strong light–matter coupling regime, their nonlinear response can be significantly enhanced, which is crucial for developing active photonic devices. However, probing the nonlinearity of waveguide modes in subwavelength-thick structures is challenging as they are not directly accessible from far-field. Here, we apply a nonlinear spectroscopic technique based on evanescent-wave coupling through a GaP solid immersion lens and femtosecond laser excitation to study nonlinearity of guided modes in monolayer WS2 encapsulated in hBN under the strong light–matter coupling regime. We reveal the formation of exciton-polaritons with a ∼50 meV Rabi splitting and demonstrate sensitive optical control of the light–matter coupling strength. Our results show that exciton resonance saturation and broadening lead to an efficient nonlinear response of guided polaritons, which can be employed for developing compact van der Waals photonic switches and modulators.
{"title":"Nonlinear guided exciton-polaritons in a van der Waals layered waveguide","authors":"Valeriy I. Kondratyev, Vanik Shahnazaryan, Mikhail Tyugaev, Tatyana V. Ivanova, Ivan E. Kalantaevskii, Dmitry V. Permyakov, Ivan V. Iorsh, Anton K. Samusev, Vasily Kravtsov","doi":"10.1063/5.0309067","DOIUrl":"https://doi.org/10.1063/5.0309067","url":null,"abstract":"Layered van der Waals materials offer promising opportunities for on-chip waveguiding and the development of integrated photonic circuits. In the strong light–matter coupling regime, their nonlinear response can be significantly enhanced, which is crucial for developing active photonic devices. However, probing the nonlinearity of waveguide modes in subwavelength-thick structures is challenging as they are not directly accessible from far-field. Here, we apply a nonlinear spectroscopic technique based on evanescent-wave coupling through a GaP solid immersion lens and femtosecond laser excitation to study nonlinearity of guided modes in monolayer WS2 encapsulated in hBN under the strong light–matter coupling regime. We reveal the formation of exciton-polaritons with a ∼50 meV Rabi splitting and demonstrate sensitive optical control of the light–matter coupling strength. Our results show that exciton resonance saturation and broadening lead to an efficient nonlinear response of guided polaritons, which can be employed for developing compact van der Waals photonic switches and modulators.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"7 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393245","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 development of efficient electrochromic materials is critical for advancing energy-efficient smart windows and next-generation display systems. In this study, three-coordinated heteroleptic Cu(I) complexes [Cu(Sphos)(cmdf)]PF6 (1) and [Cu(Xphos)(cmdf)]PF6 (2), incorporating bulky phosphine ligands, have been synthesized to design energy-efficient electrochromic smart devices. Complex 1 exhibits the structural robustness along with reversible and stable redox performance, making it suitable for device integration. Both rigid and flexible devices constructed using 1 demonstrate excellent electrochromic performance. Complex 1 delivers reproducible and high-contrast switching, demonstrating a color contrast as high as 42% and a coloration efficiency of 690 cm2/C. These results highlight the potential of Cu(I) complexes as viable alternatives to traditional electrochromic materials.
{"title":"Three-coordinated Cu(I) complexes for electrochromic devices with high coloration efficiency","authors":"Laxman Sarjerao Kharabe, Bhumika Sahu, Rajesh Kumar, Abhinav Raghuvanshi","doi":"10.1063/5.0301911","DOIUrl":"https://doi.org/10.1063/5.0301911","url":null,"abstract":"The development of efficient electrochromic materials is critical for advancing energy-efficient smart windows and next-generation display systems. In this study, three-coordinated heteroleptic Cu(I) complexes [Cu(Sphos)(cmdf)]PF6 (1) and [Cu(Xphos)(cmdf)]PF6 (2), incorporating bulky phosphine ligands, have been synthesized to design energy-efficient electrochromic smart devices. Complex 1 exhibits the structural robustness along with reversible and stable redox performance, making it suitable for device integration. Both rigid and flexible devices constructed using 1 demonstrate excellent electrochromic performance. Complex 1 delivers reproducible and high-contrast switching, demonstrating a color contrast as high as 42% and a coloration efficiency of 690 cm2/C. These results highlight the potential of Cu(I) complexes as viable alternatives to traditional electrochromic materials.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"61 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393249","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}
We apply an approach that uses x-ray diffraction (XRD) and dynamical scattering theory to determine the resulting elemental compositions of a Ge1−ySny/Ge1−xSnx superlattice after growth by simulating not just peak location but also the intensity modulation of the satellite peaks of the XRD profile. Analysis of the intensity modulation of the satellite peaks of the XRD profile of a Ge1−ySny/Ge1−xSnx superlattice determined the Sn composition, strain, and layer thickness, revealing a significant exchange of Sn in each layer. The superlattice structure was additionally confirmed by transmission electron microscopy, validating the XRD approach as applicable to superlattices more generally.
{"title":"Determination of composition, strain, and layer thickness of germanium-tin superlattices using x-ray diffraction","authors":"Hryhorii Stanchu, Nirosh M. Eldose, Mourad Benamara, Serhii Kryvyi, Oleksii Liubchenko, Diandian Zhang, Dinesh Baral, Wei Du, Shui-Qing Yu, Gregory Salamo","doi":"10.1063/5.0308927","DOIUrl":"https://doi.org/10.1063/5.0308927","url":null,"abstract":"We apply an approach that uses x-ray diffraction (XRD) and dynamical scattering theory to determine the resulting elemental compositions of a Ge1−ySny/Ge1−xSnx superlattice after growth by simulating not just peak location but also the intensity modulation of the satellite peaks of the XRD profile. Analysis of the intensity modulation of the satellite peaks of the XRD profile of a Ge1−ySny/Ge1−xSnx superlattice determined the Sn composition, strain, and layer thickness, revealing a significant exchange of Sn in each layer. The superlattice structure was additionally confirmed by transmission electron microscopy, validating the XRD approach as applicable to superlattices more generally.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"87 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393246","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}
Yan Cao, Yitong Hou, Haoran Cui, Linna Zhu, Haiyang Xie, Huanhuan Ma, Yunge Hu, Qiushi Yang, Shuting Lin, Hong Jia, Xuming Wu
Fe3GeTe2 is a representative two-dimensional (2D) magnetic material whose lattice dynamics are highly sensitive to reduced dimensionality and external perturbations. Here, we present a systematic Raman spectroscopy study of Fe3GeTe2 from the monolayer to multilayer regimes, focusing on the effects of environmental oxidation and optical excitation. Our results demonstrate a pronounced thickness-dependent evolution of phonon modes, as well as oxidation-induced shifts in Raman features, indicating reduced symmetry and lattice distortion. In addition, continuous laser irradiation leads to pronounced changes in phonon frequencies, linewidths, and relative intensities, with the response primarily governed by the combined effects of oxidation state and optical excitation rather than purely thermal effects. These results reveal a close interplay between lattice dynamics, surface chemistry, and optical excitation in Fe3GeTe2, providing insight into the environmental stability and optical responsiveness of 2D magnetic materials.
{"title":"Experimental Raman investigation of thickness-dependent and oxidation-induced lattice dynamics in 2D Fe3GeTe2","authors":"Yan Cao, Yitong Hou, Haoran Cui, Linna Zhu, Haiyang Xie, Huanhuan Ma, Yunge Hu, Qiushi Yang, Shuting Lin, Hong Jia, Xuming Wu","doi":"10.1063/5.0318754","DOIUrl":"https://doi.org/10.1063/5.0318754","url":null,"abstract":"Fe3GeTe2 is a representative two-dimensional (2D) magnetic material whose lattice dynamics are highly sensitive to reduced dimensionality and external perturbations. Here, we present a systematic Raman spectroscopy study of Fe3GeTe2 from the monolayer to multilayer regimes, focusing on the effects of environmental oxidation and optical excitation. Our results demonstrate a pronounced thickness-dependent evolution of phonon modes, as well as oxidation-induced shifts in Raman features, indicating reduced symmetry and lattice distortion. In addition, continuous laser irradiation leads to pronounced changes in phonon frequencies, linewidths, and relative intensities, with the response primarily governed by the combined effects of oxidation state and optical excitation rather than purely thermal effects. These results reveal a close interplay between lattice dynamics, surface chemistry, and optical excitation in Fe3GeTe2, providing insight into the environmental stability and optical responsiveness of 2D magnetic materials.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"8 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393240","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}
Optical technologies based on two-photon absorption can provide high resolution and deep tissue penetration but require very high peak power intensities because of the extremely small absorption cross sections associated with this phenomenon. The use of quantum-entangled photon pairs has been reported to increase the two-photon absorption rate compared with that obtainable using classical coherent laser sources. However, the enhancement that can possibly be obtained using entangled two-photon absorption (ETPA) has thus far been realized only at low photon rates, typically ranging from 107 (on the pW level) to 1013 (on the μW level) photons/s. For this reason, ETPA has been regarded as impractical. The present work demonstrates an experimental evaluation of ETPA-excited fluorescence at both low (μW) and relatively high (mW) pump power levels, using a high-gain parametric down-conversion source. Both an increase in the absorption rate and a linear correlation between rate and power were observed within both power ranges. This work also compared quantum and coherent sources. Assessments of the crossover photon flux suggest that the larger spatial-mode diameter of the present quantum source at the focal point (relative to values used in prior research) may have contributed to the rate enhancement seen at high-power levels. The results presented herein are expected to provide a new route to the mitigation of damage often associated with two-photon imaging and photodynamic therapies.
{"title":"Experimental observation of enhanced quantum-entangled two-photon absorption fluorescence at milliwatt pump power levels","authors":"Tadashi Kasamatsu, Kengo Hisamatsu, Masahiro Toida","doi":"10.1063/5.0316664","DOIUrl":"https://doi.org/10.1063/5.0316664","url":null,"abstract":"Optical technologies based on two-photon absorption can provide high resolution and deep tissue penetration but require very high peak power intensities because of the extremely small absorption cross sections associated with this phenomenon. The use of quantum-entangled photon pairs has been reported to increase the two-photon absorption rate compared with that obtainable using classical coherent laser sources. However, the enhancement that can possibly be obtained using entangled two-photon absorption (ETPA) has thus far been realized only at low photon rates, typically ranging from 107 (on the pW level) to 1013 (on the μW level) photons/s. For this reason, ETPA has been regarded as impractical. The present work demonstrates an experimental evaluation of ETPA-excited fluorescence at both low (μW) and relatively high (mW) pump power levels, using a high-gain parametric down-conversion source. Both an increase in the absorption rate and a linear correlation between rate and power were observed within both power ranges. This work also compared quantum and coherent sources. Assessments of the crossover photon flux suggest that the larger spatial-mode diameter of the present quantum source at the focal point (relative to values used in prior research) may have contributed to the rate enhancement seen at high-power levels. The results presented herein are expected to provide a new route to the mitigation of damage often associated with two-photon imaging and photodynamic therapies.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"54 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147393244","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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