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- 实验方案
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Actively tunable mid-infrared Fano resonance in Ge2Sb2Te5-based grating structures
摘要： Dynamic tuning of the resonance wavelength of subwavelength gratings in the mid-infrared (MIR) region via the permittivity change of phase-change material (PCM) has been demonstrated. A large shift in the peak of reflectance can be obtained by intermediate phase states of the Ge2Sb2Te5 (GST) layer. Fano resonance (FR) can be excited and is verified by the rigorous coupled-wave analysis (RCWA) method. Non-volatile tuning of lattice resonances over a range Δλ of about 1.9 μm (10.9 μm–12.8 μm) is achieved. Significant spectral tuning of FR can also be achieved by changing geometrical parameters as well as the angle of incidence. The wide range of the tunable FR in the technologically important MIR region offers a high resolution filter, which is useful for numerous sensing, imaging, and detection applications.
关键词： Fano resonance,Phase change materials,Mid-infrared
更新于2025-09-23 15:22:29
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Persistence of the R3m Phase in Powder GeTe at High Pressure and High Temperature
摘要： As a phase-change material, rhombohedral GeTe (space group R3m) was believed to transform to the cubic rock-salt phase (B1) at 3–4 GPa, associated with the disappearance of a Peierls distortion. However, using a combination of synchrotron X-ray diffraction and theoretical calculations, we found that the R3m phase persists from ambient pressure up to pressures of about 15.8 GPa, in contrast to previous reports. Neither was the B1 phase observed in a heating X-ray powder diffraction experiment. The spurious transformation from R3m to B1 is caused by changes to the compression ratio of lattice parameters in the R3m phase under high pressure/temperature. These findings provide insight into transitions of phase-change materials, relevant to other materials undergoing displacive transitions under high pressure/temperature.
关键词： structural phase transitions,density-functional theory,high pressure,phase-change materials,high temperature,GeTe,synchrotron X-ray diffraction
更新于2025-09-23 15:21:01
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[IEEE 2019 11th International Symposium on Image and Signal Processing and Analysis (ISPA) - Dubrovnik, Croatia (2019.9.23-2019.9.25)] 2019 11th International Symposium on Image and Signal Processing and Analysis (ISPA) - Acknowledgements
摘要： Phase-change materials and devices have received much attention as a potential route to the realization of various types of unconventional computing paradigms. In this letter, we present non-von Neumann arithmetic processing that exploits the accumulative property of phase-change memory (PCM) cells. Using PCM cells with integrated FET access devices, we perform a detailed study of accumulation-based computation. We also demonstrate efficient factorization using PCM cells, a technique that could pave the way for massively parallelized computations.
关键词： neuromorphic computing,Phase-change materials,non-von Neumann,arithmetic computing
更新于2025-09-23 15:21:01
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Thermal management of concentrator photovoltaic systems using nanoa??enhanced phase change materialsa??based heat sink
摘要： Temperature regulation of concentrator photovoltaic systems is essential in reducing operating temperatures with higher system performance. A new nano-enhanced phase change material, with multi-cavity heat sinks, integrated with a concentrator photovoltaic (CPV) system is developed. The multi-cavity heat sink includes a single-, triple-, and quintuple-cavity configuration in both parallel and series pattern filled with n-octadecane PCM and graphene nanoparticle additives with 2% and 5 wt%. Numerical simulations are performed using the developed two-dimensional model for photovoltaic layers integrated with the nano-enhanced phase change material-based heat sink. The predicted results are compared with the available numerical results and measurements. Results indicate that increasing the number of parallel cavities, along with weight fraction of nanoparticles, significantly improves the thermal conductivity, and consequently attains better performance for the CPV system. Using a parallel quintuple-cavity configuration, with 5 wt% NPCM, achieves maximum reduction in the solar cell mean temperature along with the best temperature uniformity compared to other configurations. At a concentration ratio of 20, the thermal efficiency is 65%, the electrical efficiency is about 10%, and the output electrical power of the system is 235 W per m width of the cell. On the contrary, using a series pattern of the heat sink has an unfavorable effect on the mean solar cell temperature, as well as on electrical efficiency and thermal performance of the CPV system. The obtained result can assist in identifying the best possible design of the heat sink in addition to the most appropriate selection of PCM and nanoparticle additives.
关键词： electrical efficiency,graphene nanoparticles,concentrator photovoltaic system,multi-cavity heat sink,nano-enhanced phase change materials
更新于2025-09-23 15:21:01
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Electronic Structures of Ge <sub/>2</sub> Sb <sub/>2</sub> Te <sub/>5</sub> /Co <sub/>2</sub> FeX (X: Al, Si) Interfaces for Phase Change Spintronics
摘要： Phase change materials (PCMs), such as Ge2Sb2Te5, are highly attractive in modern electronics and photonics. However, their spintronic applications remain largely unexplored. Here, we propose a tentative modality of phase change spintronic devices based on the ferromagnet/PCM/ferromagnet structure. The electrically tunable properties of a PCM interlayer give rise to new possibilities of manipulating spin transport through phase change, adding new functionalities and modes of operation to the spintronic devices. As the first step toward realizing such phase change spintronic devices, we calculate the electronic structures of the interfaces of c-Ge2Sb2Te5 and half-metallic ferromagnetic Co2FeX (X: Al, Si). The interfaces are found not to be genuine half-metallic, indicating room for improvement. The band alignments are largely determined by the termination of c-Ge2Sb2Te5. Two types of band alignments are found for c-Ge2Sb2Te5/Co2FeX interfaces. Considering c-Ge2Sb2Te5 as heavily p-type-doped, interfaces with Te termination are generally suitable such that they offer low contact resistance for hole injection from Co2FeX to c-Ge2Sb2Te5 in the majority spin channel; at the same time, they naturally form tunneling barriers, alleviating the degradation of spin injection efficiency because of occasional hole injection in the minority spin channel. This work provides important insights into this proposed phase change spintronic framework.
关键词： Spintronics,Electronic structures,Co2FeX,Interface,Phase change materials,Ge2Sb2Te5
更新于2025-09-23 15:21:01
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Modeling Electrical Switching of Nonvolatile Phase-Change Integrated Nanophotonic Structures with Graphene Heaters
摘要： Progress in integrated nanophotonics has enabled large-scale programmable photonic integrated circuits (PICs) for general-purpose electronic-photonic systems on a chip. Relying on the weak, volatile thermo-optic or electro-optic effects, such systems usually exhibit limited reconfigurability along with high energy consumption and large footprints. These challenges can be addressed by resorting to chalcogenide phase-change materials (PCMs) such as Ge2Sb2Te5 (GST) that provide substantial optical contrast in a self-holding fashion upon phase transitions. However, current PCM-based integrated photonic applications are limited to single devices or simple PICs due to the poor scalability of the optical or electrical self-heating actuation approaches. Thermal-conduction heating via external electrical heaters, instead, allows large-scale integration and large-area switching, but fast and energy-efficient electrical control is yet to show. Here, we model electrical switching of GST-clad integrated nanophotonic structures with graphene heaters based on the programmable GST-on-silicon platform. Thanks to the ultra-low heat capacity and high in-plane thermal conductivity of graphene, the proposed structures exhibit a high switching speed of ~80 MHz and high energy efficiency of 19.2 aJ/nm3 (6.6 aJ/nm3) for crystallization (amorphization) while achieving complete phase transitions to ensure strong attenuation (~6.46 dB/μm) and optical phase (~0.28 π/μm at 1550 nm) modulation. Compared with indium tin oxide and silicon p-i-n heaters, the structures with graphene heaters display two orders of magnitude higher figure of merits for heating and overall performance. Our work facilitates the analysis and understanding of the thermal-conduction heating-enabled phase transitions on PICs and supports the development of the future large-scale PCM-based electronic-photonic systems.
关键词： graphene,nonvolatile,reconfigurable photonics,phase-change materials,silicon photonics,integrated nanophotonic structures
更新于2025-09-23 15:19:57
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Photovoltaic Cooling Utilizing Phase Change Materials
摘要： A theoretical analysis based on mathematical formulations and experimental test to a photovoltaic system cooled by Phase Change Material (PCM) is carried out and documented. The PCM is attached to the back of the PV panel to control the temperature of cells in the PV panel. The experimental tests were done to solar systems with and without using PCM for comparison purposes. A PCM of paraffin graphite panels of thickness15 mm has covered the back of the panel. This layer was covered with an aluminum sheet fixed tightly to the panel frame. In the experimental test, it was found that when the average cell temperature exceeds the melting point temperature of the PCM, the efficiency of the system increases. However, when the cell temperature did not exceed the melting temperature of the PCM, the use of the PCM will affect negatively the system efficiency.
关键词： Photovoltaic Cooling,PCM melting point,PV panel efficiency,Phase Change Materials
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE Conference on Antenna Measurements & Applications (CAMA) - Kuta, Bali, Indonesia (2019.10.23-2019.10.25)] 2019 IEEE Conference on Antenna Measurements & Applications (CAMA) - 60GHz Substrate Integrated Waveguide Balun
摘要： Phase-change materials and devices have received much attention as a potential route to the realization of various types of unconventional computing paradigms. In this letter, we present non-von Neumann arithmetic processing that exploits the accumulative property of phase-change memory (PCM) cells. Using PCM cells with integrated FET access devices, we perform a detailed study of accumulation-based computation. We also demonstrate efficient factorization using PCM cells, a technique that could pave the way for massively parallelized computations.
关键词： neuromorphic computing,non-von Neumann,Phase-change materials,arithmetic computing
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE SENSORS - Montreal, QC, Canada (2019.10.27-2019.10.30)] 2019 IEEE SENSORS - A 2x2 Pixel Array Camera based on a Backside Illuminated Ge-on-Si Photodetector
摘要： Phase-change materials and devices have received much attention as a potential route to the realization of various types of unconventional computing paradigms. In this letter, we present non-von Neumann arithmetic processing that exploits the accumulative property of phase-change memory (PCM) cells. Using PCM cells with integrated FET access devices, we perform a detailed study of accumulation-based computation. We also demonstrate efficient factorization using PCM cells, a technique that could pave the way for massively parallelized computations.
关键词： neuromorphic computing,non-von Neumann,Phase-change materials,arithmetic computing
更新于2025-09-23 15:19:57
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Nanofibrous Kevlar Aerogel Films and Their Phase-Change Composites for Highly Efficient Infrared Stealth
摘要： Infrared (IR) stealth is essential not only in high technology and modern military but also in fundamental material science. However, effectively hiding targets and rendering them invisible to thermal infrared detectors have been great challenges in past decades. Herein, flexible, foldable, and robust Kevlar nanofiber aerogel (KNA) films with high porosity and specific surface area were fabricated first. The KNA films display excellent thermal insulation performance and can be employed to incorporate with phase-change materials (PCMs), such as polyethylene glycol, to fabricate KNA/PCM composite films. The KNA/PCM films with high thermal management capability and infrared emissivity comparable to that of various backgrounds demonstrate high performance in IR stealth in outdoor environments with solar illumination variations. To further realize hiding hot targets from IR detection, combined structures constituted of thermal insulation layers (KNA films) and ultralow IR transmittance layers (KNA/PCM) are proposed. A hot target covered with this combined structure becomes completely invisible in infrared images. Such KNA/PCM films and KNA?KNA/PCM combined structures hold great promise for broad applications in infrared thermal stealth.
关键词： thermal management,aerogel,phase-change materials,free-standing films,Kevlar nanofibers,infrared stealth
更新于2025-09-19 17:15:36