Md Mazharul Islam, Md Shafayat Hossain, Kathleen E. Hamilton, Ahmedullah Aziz
Oscillators designed to function at cryogenic temperatures play a critical role in superconducting electronics and quantum computing by providing stable, low-noise signals with minimal energy loss. Here, we present a comprehensive numerical study of injection locking and mutual coupling dynamics in superconducting nanowire (ScNW)-based cryogenic oscillators. Using the design space of a standalone ScNW-based oscillator, we investigate two critical mechanisms that govern frequency synchronization and signal coordination in cryogenic computing architectures: (1) injection locking induced by an external AC signal with a frequency near the oscillator's natural frequency, and (2) the mutual coupling dynamics between two ScNW oscillators under varying coupling strengths. We identify key design parameters—such as shunt resistance, nanowire inductance, and coupling strength—that govern the locking range. Additionally, we examine how the amplitude of the injected signal affects the amplitude of the locked oscillation, offering valuable insights for power-aware oscillator synchronization. Furthermore, we analyze mutual synchronization between coupled ScNW oscillators using capacitive and resistive coupling elements. Our results reveal that the phase difference between oscillators can be controlled by tuning the coupling strength, enabling programmable phase-encoded information processing. These findings could enable building ScNW-based oscillatory neural networks, synchronized cryogenic logic blocks, and on-chip cryogenic resonator arrays.
{"title":"Injection locking and coupling dynamics in superconducting nanowire-based cryogenic oscillators","authors":"Md Mazharul Islam, Md Shafayat Hossain, Kathleen E. Hamilton, Ahmedullah Aziz","doi":"10.1063/5.0297721","DOIUrl":"https://doi.org/10.1063/5.0297721","url":null,"abstract":"Oscillators designed to function at cryogenic temperatures play a critical role in superconducting electronics and quantum computing by providing stable, low-noise signals with minimal energy loss. Here, we present a comprehensive numerical study of injection locking and mutual coupling dynamics in superconducting nanowire (ScNW)-based cryogenic oscillators. Using the design space of a standalone ScNW-based oscillator, we investigate two critical mechanisms that govern frequency synchronization and signal coordination in cryogenic computing architectures: (1) injection locking induced by an external AC signal with a frequency near the oscillator's natural frequency, and (2) the mutual coupling dynamics between two ScNW oscillators under varying coupling strengths. We identify key design parameters—such as shunt resistance, nanowire inductance, and coupling strength—that govern the locking range. Additionally, we examine how the amplitude of the injected signal affects the amplitude of the locked oscillation, offering valuable insights for power-aware oscillator synchronization. Furthermore, we analyze mutual synchronization between coupled ScNW oscillators using capacitive and resistive coupling elements. Our results reveal that the phase difference between oscillators can be controlled by tuning the coupling strength, enabling programmable phase-encoded information processing. These findings could enable building ScNW-based oscillatory neural networks, synchronized cryogenic logic blocks, and on-chip cryogenic resonator arrays.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"52 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894032","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}
Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/silicon (Si) heterojunction solar cells (HSCs) have garnered extensive interest owing to their potential for high efficiency and low cost. However, their performance is constrained by a limited open-circuit voltage (VOC). In this manuscript, PEDOT:PSS films endowed with both high conductance and high work function via an alcohol-doping-based molecular engineering strategy were applied to induce strong inversion layers on the n-Si surface and generate large built-in voltage in HSCs. This molecular engineering strategy enables precise modulation of PEDOT:PSS molecular building blocks, achieving a work function tuning range from 4.81 to 4.93 eV while retaining high conductivity exceeding 650 S/cm. A photovoltaic device with alcohol-doped PEDOT:PSS delivers a large VOC of 0.66 V without additional modifications and a power conversion efficiency of 12.80%. This study on the molecular engineering of PEDOT:PSS establishes an effective and simplified pathway for fabricating PEDOT:PSS/Si HSCs with high VOC.
{"title":"Molecular engineering of PEDOT:PSS for enhancing open-circuit voltage in organic/silicon heterojunction solar cells","authors":"Leiming Yu, Rui Yang, Xiangdong Duan, Zhuo Wu, Suicai Zhang, Xiaohui Song, Yurong Jiang, Congxin Xia","doi":"10.1063/5.0306461","DOIUrl":"https://doi.org/10.1063/5.0306461","url":null,"abstract":"Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/silicon (Si) heterojunction solar cells (HSCs) have garnered extensive interest owing to their potential for high efficiency and low cost. However, their performance is constrained by a limited open-circuit voltage (VOC). In this manuscript, PEDOT:PSS films endowed with both high conductance and high work function via an alcohol-doping-based molecular engineering strategy were applied to induce strong inversion layers on the n-Si surface and generate large built-in voltage in HSCs. This molecular engineering strategy enables precise modulation of PEDOT:PSS molecular building blocks, achieving a work function tuning range from 4.81 to 4.93 eV while retaining high conductivity exceeding 650 S/cm. A photovoltaic device with alcohol-doped PEDOT:PSS delivers a large VOC of 0.66 V without additional modifications and a power conversion efficiency of 12.80%. This study on the molecular engineering of PEDOT:PSS establishes an effective and simplified pathway for fabricating PEDOT:PSS/Si HSCs with high VOC.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"56 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894035","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}
Mercury telluride (HgTe) nanocrystals (NCs) are promising materials for infrared photodetection due to their size-tunable band edges and compatibility with colloidal synthesis. While optical studies have established the temperature dependence of their relative bandgaps, the evolution of their absolute electronic spectrum with cooling remains poorly understood, despite its critical role in the device operation. In this work, we investigate in situ the temperature-induced absolute energy shift of HgTe NCs' electronic states with varying band edge energies, using X-ray photoemission spectroscopy. We observe a systematic and reversible rigid shift of core levels toward lower binding energies upon cooling, reaching approximately 80 meV per 100 K, four times larger than the corresponding optical band edge shift (≈20 meV). This behavior is consistent across different NC sizes, making the impact more dramatic for the narrower bandgap NCs. Such absolute energy shifts can significantly alter carrier densities and interfacial band alignments, potentially creating Schottky barriers and reducing extraction efficiency in photodiode architectures. Our findings highlight the necessity of accounting for temperature-induced absolute energy shifts in the design of next-generation HgTe NC-based infrared detectors.
{"title":"Temperature-induced absolute energy shift of the electronic spectrum in HgTe nanocrystals","authors":"Tommaso Gemo, Dario Mastrippolito, Mariarosa Cavallo, Giorgia Strobbia, Albin Colle, Marco Paye, Jiho Roh, Adrien Khalili, Clement Gureghian, Erwan Bossavit, Sandrine Ithurria, Yoann Prado, Sébastien Sauvage, Mathieu G. Silly, Nicolas Péré-Laperne, Debora Pierucci, Emmanuel Lhuillier","doi":"10.1063/5.0308025","DOIUrl":"https://doi.org/10.1063/5.0308025","url":null,"abstract":"Mercury telluride (HgTe) nanocrystals (NCs) are promising materials for infrared photodetection due to their size-tunable band edges and compatibility with colloidal synthesis. While optical studies have established the temperature dependence of their relative bandgaps, the evolution of their absolute electronic spectrum with cooling remains poorly understood, despite its critical role in the device operation. In this work, we investigate in situ the temperature-induced absolute energy shift of HgTe NCs' electronic states with varying band edge energies, using X-ray photoemission spectroscopy. We observe a systematic and reversible rigid shift of core levels toward lower binding energies upon cooling, reaching approximately 80 meV per 100 K, four times larger than the corresponding optical band edge shift (≈20 meV). This behavior is consistent across different NC sizes, making the impact more dramatic for the narrower bandgap NCs. Such absolute energy shifts can significantly alter carrier densities and interfacial band alignments, potentially creating Schottky barriers and reducing extraction efficiency in photodiode architectures. Our findings highlight the necessity of accounting for temperature-induced absolute energy shifts in the design of next-generation HgTe NC-based infrared detectors.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"28 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894037","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. Tatebayashi, T. Yoshimura, K. Sato, S. Ichikawa, Y. Fujiwara
We report the formation and optical/structural characteristics of Tb-doped AlGaN (AlGaN:Tb)/GaN core–shell NWs grown by organometallic vapor phase epitaxy. AlGaN:Tb layers are formed on GaN NWs in a core–shell configuration, as confirmed by cross-sectional transmission electron microscope equipped with energy dispersive x-ray spectroscopy (EDS). Tb3+-related visible photoluminescence (PL) is observed at room temperature simultaneously in the blue (∼490 nm), green (∼550 nm), yellow (∼580 nm), and red (∼620 nm) regions, which are assigned as the 5D4-7F6, 5D4-7F5, 5D4-7F4, and 5D4-7F3 transitions, respectively. The Tb luminescence intensity increases with the Al composition of the AlGaN host, exhibiting the strongest PL peak when Tb3+ ions are doped in the Al0.6Ga0.4N shell layers, whose AlN mole fraction is quantified by EDS elemental mapping.
{"title":"Formation and optical characteristics of AlGaN:Tb/GaN core–shell nanowires grown by organometallic vapor phase epitaxy","authors":"J. Tatebayashi, T. Yoshimura, K. Sato, S. Ichikawa, Y. Fujiwara","doi":"10.1063/5.0302885","DOIUrl":"https://doi.org/10.1063/5.0302885","url":null,"abstract":"We report the formation and optical/structural characteristics of Tb-doped AlGaN (AlGaN:Tb)/GaN core–shell NWs grown by organometallic vapor phase epitaxy. AlGaN:Tb layers are formed on GaN NWs in a core–shell configuration, as confirmed by cross-sectional transmission electron microscope equipped with energy dispersive x-ray spectroscopy (EDS). Tb3+-related visible photoluminescence (PL) is observed at room temperature simultaneously in the blue (∼490 nm), green (∼550 nm), yellow (∼580 nm), and red (∼620 nm) regions, which are assigned as the 5D4-7F6, 5D4-7F5, 5D4-7F4, and 5D4-7F3 transitions, respectively. The Tb luminescence intensity increases with the Al composition of the AlGaN host, exhibiting the strongest PL peak when Tb3+ ions are doped in the Al0.6Ga0.4N shell layers, whose AlN mole fraction is quantified by EDS elemental mapping.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"114 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894059","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}
D. V. Brazhnikov, V. I. Vishnyakov, M. N. Skvortsov
We study the magnetic-field-induced frequency shift (MFS) of the reference resonance in a coherent population trapping (CPT) microwave atomic clock. It is shown that the use of the Pound–Drever–Hall-like technique for frequency locking provides brilliant opportunities for mitigating the MFS. Using a 0.125 cm3 rubidium vapor cell with a buffer gas, we have measured a residual sensitivity of the reference CPT resonance frequency to be ≈70μHz/mG over ≈6 mG interval. It means that a fractional frequency shift is extremely small (≈1×10−14 mG−1). The results contribute to the development of a new-generation CPT-based miniature atomic clock with improved long-term frequency stability. The proposed method is sufficiently versatile and can be adapted for other excitation schemes in atomic clocks, including those based on Ramsey-like or double-resonance techniques.
{"title":"Mitigation of the magnetic-field-induced frequency shift in coherent-population-trapping atomic clocks","authors":"D. V. Brazhnikov, V. I. Vishnyakov, M. N. Skvortsov","doi":"10.1063/5.0305867","DOIUrl":"https://doi.org/10.1063/5.0305867","url":null,"abstract":"We study the magnetic-field-induced frequency shift (MFS) of the reference resonance in a coherent population trapping (CPT) microwave atomic clock. It is shown that the use of the Pound–Drever–Hall-like technique for frequency locking provides brilliant opportunities for mitigating the MFS. Using a 0.125 cm3 rubidium vapor cell with a buffer gas, we have measured a residual sensitivity of the reference CPT resonance frequency to be ≈70μHz/mG over ≈6 mG interval. It means that a fractional frequency shift is extremely small (≈1×10−14 mG−1). The results contribute to the development of a new-generation CPT-based miniature atomic clock with improved long-term frequency stability. The proposed method is sufficiently versatile and can be adapted for other excitation schemes in atomic clocks, including those based on Ramsey-like or double-resonance techniques.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"21 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894062","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}
Junyeob Song, Ashish Chanana, Emerson G. Melo, William Eshbaugh, Craig R. Copeland, Luca Sapienza, Edward B. Flagg, Jindong Song, Kartik Srinivasan, Marcelo Davanco
Epitaxial III–V semiconductor quantum dots (QDs) integrated with nanophotonic structures are promising on-demand sources of indistinguishable single photons for quantum photonic circuits. Close proximity of QDs to etched sidewalls in such structures, however, may induce excitonic linewidth broadening, reducing photon indistinguishability. Here, we design and demonstrate GaAs photonic crystal cavities based on multimode nanobeam waveguides that maximize QD separation from etched surfaces beyond an empirically determined threshold that suppresses spectral broadening, while enabling QD access through higher-order waveguide modes. Although multimode propagation adds design complexity, simulations predict quality factors Q≈103 and mode volumes V/(λ/n)3≈2 for Purcell radiative rate enhancements of Fp≈100. Fabricated devices containing QD ensembles exhibit resonances consistent with these predictions, and single-QD measurements yield Fp<5 for 11 randomly located emitters. Monte Carlo simulations of spatially dependent Fp distributions indicate that slow carrier capture and relaxation dynamics, rather than QD placement, primarily limit the observation of higher Purcell factors. These results highlight the potential of our cavities for integrating epitaxial QDs while clarifying key constraints on observation of radiative rate enhancement.
{"title":"Multimode nanobeam photonic crystal cavities for Purcell enhanced quantum dot emission","authors":"Junyeob Song, Ashish Chanana, Emerson G. Melo, William Eshbaugh, Craig R. Copeland, Luca Sapienza, Edward B. Flagg, Jindong Song, Kartik Srinivasan, Marcelo Davanco","doi":"10.1063/5.0288948","DOIUrl":"https://doi.org/10.1063/5.0288948","url":null,"abstract":"Epitaxial III–V semiconductor quantum dots (QDs) integrated with nanophotonic structures are promising on-demand sources of indistinguishable single photons for quantum photonic circuits. Close proximity of QDs to etched sidewalls in such structures, however, may induce excitonic linewidth broadening, reducing photon indistinguishability. Here, we design and demonstrate GaAs photonic crystal cavities based on multimode nanobeam waveguides that maximize QD separation from etched surfaces beyond an empirically determined threshold that suppresses spectral broadening, while enabling QD access through higher-order waveguide modes. Although multimode propagation adds design complexity, simulations predict quality factors Q≈103 and mode volumes V/(λ/n)3≈2 for Purcell radiative rate enhancements of Fp≈100. Fabricated devices containing QD ensembles exhibit resonances consistent with these predictions, and single-QD measurements yield Fp&lt;5 for 11 randomly located emitters. Monte Carlo simulations of spatially dependent Fp distributions indicate that slow carrier capture and relaxation dynamics, rather than QD placement, primarily limit the observation of higher Purcell factors. These results highlight the potential of our cavities for integrating epitaxial QDs while clarifying key constraints on observation of radiative rate enhancement.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"10 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894116","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}
Chi Xie, Zi-Ying Huang, Zhan-Yuan Huang, Ying-Guo Yang, Chao Xu, Ye Zhu, Zhiming Wu, Ming Li, David Wei Zhang, Hong-Liang Lu
In this study, gallium oxide (Ga2O3) insertion layers (ILs) of varying thicknesses were embedded within Hf0.5Zr0.5O2 (HZO) films using atomic layer deposition (ALD). Devices with Ga2O3 ILs grown for fewer than 4 ALD Ga2O3 cycles exhibit a reduction in both remnant polarization (Pr) and coercive field (Ec). Notably, the device incorporating a IL with 2 ALD Ga2O3 cycles demonstrates strong performance, achieving a 2Pr of 47.0 μC/cm2 and an Ec of 0.92 MV/cm. In contrast, for devices with ILs exceeding 8 ALD Ga2O3 cycles, the 2Pr value remains near 18 μC/cm2, while Ec increases significantly. These divergent behaviors can be attributed to the different diffusion states of the insertion IL. For a low number of ALD Ga2O3 cycles, it is the diffusion of Ga3+ ions into the HZO region adjacent to the IL that results in a reduced Ec. Conversely, with higher ALD Ga2O3 cycles, the IL forms a continuous layer that physically divides the 10 nm HZO film into two sections, which leads to a further decrease in Pr and an increase in Ec. Furthermore, the progressive disruption of vertical grain boundaries by the growing insertion layer (IL) leads to a continuous decrease in leakage current. This work demonstrates the effective modulation of HZO devices via a Ga2O3 insertion layer, offering a methodology and data reference for enhancing device reliability.
{"title":"Thin Ga2O3 insertion layer for phase structure and electrical property evolutions in ferroelectric Hf0.5Zr0.5O2 capacitors","authors":"Chi Xie, Zi-Ying Huang, Zhan-Yuan Huang, Ying-Guo Yang, Chao Xu, Ye Zhu, Zhiming Wu, Ming Li, David Wei Zhang, Hong-Liang Lu","doi":"10.1063/5.0301196","DOIUrl":"https://doi.org/10.1063/5.0301196","url":null,"abstract":"In this study, gallium oxide (Ga2O3) insertion layers (ILs) of varying thicknesses were embedded within Hf0.5Zr0.5O2 (HZO) films using atomic layer deposition (ALD). Devices with Ga2O3 ILs grown for fewer than 4 ALD Ga2O3 cycles exhibit a reduction in both remnant polarization (Pr) and coercive field (Ec). Notably, the device incorporating a IL with 2 ALD Ga2O3 cycles demonstrates strong performance, achieving a 2Pr of 47.0 μC/cm2 and an Ec of 0.92 MV/cm. In contrast, for devices with ILs exceeding 8 ALD Ga2O3 cycles, the 2Pr value remains near 18 μC/cm2, while Ec increases significantly. These divergent behaviors can be attributed to the different diffusion states of the insertion IL. For a low number of ALD Ga2O3 cycles, it is the diffusion of Ga3+ ions into the HZO region adjacent to the IL that results in a reduced Ec. Conversely, with higher ALD Ga2O3 cycles, the IL forms a continuous layer that physically divides the 10 nm HZO film into two sections, which leads to a further decrease in Pr and an increase in Ec. Furthermore, the progressive disruption of vertical grain boundaries by the growing insertion layer (IL) leads to a continuous decrease in leakage current. This work demonstrates the effective modulation of HZO devices via a Ga2O3 insertion layer, offering a methodology and data reference for enhancing device reliability.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"21 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894070","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}
Bin Zhang, Lijuan Shi, Lingrui Chu, Lingqi Li, Saulius Juodkazis, Feng Chen
We report on laser-induced periodic surface structures (LIPSS) on few-layer platinum diselenide (PtSe2) with a thickness of ∼5 nm, which has been realized by femtosecond laser pulse irradiation. Both low spatial frequency LIPSS (LSFL) and high spatial frequency LIPSS (HSFL) have been observed in our experiment. The LSFL period (∼1 μm) is near a central wavelength (1031 nm) of the femtosecond laser, which is much larger than the HSFL period (about 80–120 nm). Under specific laser-irradiation parameters, HSFL grooves can reach a depth of 5 nm below the PtSe2 surface, meaning that PtSe2 could be completely erased at these grooves. The confocal micro-Raman (μ-Raman) spectroscopy indicates that an intensity decrease of ∼25% of both the Eg (at ∼176 cm−1) and A1g (at ∼205 cm−1) vibrations has been observed in PtSe2 LIPSS, where there is an ∼0.27 cm−1 spectral redshift at the Eg Raman peak and an obvious spectral blueshift (∼0.89 cm−1) at the A1g Raman peak. Our work provides a convenient approach to fabricate periodic micro/nanostructures on a few-layer PtSe2, facilitating the development of functional photonic and optoelectronic devices based on two-dimensional (2D) materials.
{"title":"Periodic micro/nanostructures on few-layer PtSe2 irradiated by femtosecond laser pulses","authors":"Bin Zhang, Lijuan Shi, Lingrui Chu, Lingqi Li, Saulius Juodkazis, Feng Chen","doi":"10.1063/5.0300232","DOIUrl":"https://doi.org/10.1063/5.0300232","url":null,"abstract":"We report on laser-induced periodic surface structures (LIPSS) on few-layer platinum diselenide (PtSe2) with a thickness of ∼5 nm, which has been realized by femtosecond laser pulse irradiation. Both low spatial frequency LIPSS (LSFL) and high spatial frequency LIPSS (HSFL) have been observed in our experiment. The LSFL period (∼1 μm) is near a central wavelength (1031 nm) of the femtosecond laser, which is much larger than the HSFL period (about 80–120 nm). Under specific laser-irradiation parameters, HSFL grooves can reach a depth of 5 nm below the PtSe2 surface, meaning that PtSe2 could be completely erased at these grooves. The confocal micro-Raman (μ-Raman) spectroscopy indicates that an intensity decrease of ∼25% of both the Eg (at ∼176 cm−1) and A1g (at ∼205 cm−1) vibrations has been observed in PtSe2 LIPSS, where there is an ∼0.27 cm−1 spectral redshift at the Eg Raman peak and an obvious spectral blueshift (∼0.89 cm−1) at the A1g Raman peak. Our work provides a convenient approach to fabricate periodic micro/nanostructures on a few-layer PtSe2, facilitating the development of functional photonic and optoelectronic devices based on two-dimensional (2D) materials.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"6 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894115","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}
Harmonic Hall measurements were performed on a series of ferromagnetic metal/heavy metal (FM/HM) bilayers consisting of Permalloy (Py) as the FM and β-tungsten (W) as the HM, and the efficiencies of the two orthogonal components of the spin–orbit torque were extracted. Two sets of Hall bar-shaped devices, differing in the aspect ratio of the voltage pickup linewidth and the current channel width, were studied. Within each set, the resistivity of the W layer was systematically varied over a wide range (approximately 150–1000 μΩ cm). To account for geometry-induced variations in current distribution, numerical simulations were performed, and a correction protocol was developed to normalize the torque efficiencies obtained from the conventional analysis. After applying the correction, the Slonczewski-like (anti-damping, in-plane) torque efficiency exhibited a consistent dependence on W-resistivity across both device sets. In contrast, the field-like (out-of-plane) torque efficiency remained largely independent of W-resistivity, reinforcing its interfacial character.
{"title":"Decoupling of spin–orbit torque components in Py/W bilayers unveiled through variation of W-resistivity","authors":"Abu Bakkar Miah, Harekrishna Bhunia, Dhananjaya Mahapatra, Soumik Aon, Partha Mitra","doi":"10.1063/5.0295015","DOIUrl":"https://doi.org/10.1063/5.0295015","url":null,"abstract":"Harmonic Hall measurements were performed on a series of ferromagnetic metal/heavy metal (FM/HM) bilayers consisting of Permalloy (Py) as the FM and β-tungsten (W) as the HM, and the efficiencies of the two orthogonal components of the spin–orbit torque were extracted. Two sets of Hall bar-shaped devices, differing in the aspect ratio of the voltage pickup linewidth and the current channel width, were studied. Within each set, the resistivity of the W layer was systematically varied over a wide range (approximately 150–1000 μΩ cm). To account for geometry-induced variations in current distribution, numerical simulations were performed, and a correction protocol was developed to normalize the torque efficiencies obtained from the conventional analysis. After applying the correction, the Slonczewski-like (anti-damping, in-plane) torque efficiency exhibited a consistent dependence on W-resistivity across both device sets. In contrast, the field-like (out-of-plane) torque efficiency remained largely independent of W-resistivity, reinforcing its interfacial character.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"386 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894045","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}
R. Tartaglia, A. F. Lima, N. Prasai, A. B. Christian, J. J. Neumeier, J. L. Cohn, E. Granado
Ta-based trirutiles of the series ATa2O6 (A = Ni, Co) reportedly present suppressed thermal conductivity (κ) values compared to their Sb-based counterparts. Particularly, the κ values at room temperature for Ta-based samples are in the range observed in materials already employed as thermoelectric devices, suggesting they are potential candidates as a starting point for thermoelectric applications. Here, we investigate their phonon dynamics through a combination of Raman scattering measurements with density functional theory (DFT) calculations. For the Ta-based compounds only, our results reveal the presence of an Eg low-energy optical phonon that softens by ∼10 cm−1 upon cooling from 300 to 15 K, indicating this is a zone-center soft mode associated with an unrealized structural phase transition. The soft mode enhances the phonon density of states at low energies, as directly manifested in the second-order Raman scattering data and also captured by DFT phonon calculations. These results provide insights into the low κ-values of Ta-based trirutiles and place zone-center soft phonons as a key ingredient for the development of novel thermoelectric materials.
{"title":"Soft phonon mode as the origin of the reduced thermal conductivity in Ta-based trirutiles","authors":"R. Tartaglia, A. F. Lima, N. Prasai, A. B. Christian, J. J. Neumeier, J. L. Cohn, E. Granado","doi":"10.1063/5.0306933","DOIUrl":"https://doi.org/10.1063/5.0306933","url":null,"abstract":"Ta-based trirutiles of the series ATa2O6 (A = Ni, Co) reportedly present suppressed thermal conductivity (κ) values compared to their Sb-based counterparts. Particularly, the κ values at room temperature for Ta-based samples are in the range observed in materials already employed as thermoelectric devices, suggesting they are potential candidates as a starting point for thermoelectric applications. Here, we investigate their phonon dynamics through a combination of Raman scattering measurements with density functional theory (DFT) calculations. For the Ta-based compounds only, our results reveal the presence of an Eg low-energy optical phonon that softens by ∼10 cm−1 upon cooling from 300 to 15 K, indicating this is a zone-center soft mode associated with an unrealized structural phase transition. The soft mode enhances the phonon density of states at low energies, as directly manifested in the second-order Raman scattering data and also captured by DFT phonon calculations. These results provide insights into the low κ-values of Ta-based trirutiles and place zone-center soft phonons as a key ingredient for the development of novel thermoelectric materials.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"253 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894073","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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