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Impact of device resistances in the performance of graphene‑based terahertz photodetectors

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Frontiers of Optoelectronics 2024年第2期17卷 87-97页

作者： O.Castelló Sofía m.López Baptista K.Watanabe t.taniguchi E.Diez j.E.Velázquez-Pérez Y.m.meziani j.m.Caridad j.A.Delgado-Notario Department of Applied Physics University of Salamanca37008 SalamancaSpain Unidad de Excelencia en Luz y materia Estructurada(LUmES) University of Salamanca37008 SalamancaSpain Research Center for Electronic and Optical materials National Institute for Materials Science1-1 NamikiTsukuba 305-0044Japan Research Center for materials Nanoarchitectonics National Institute for Materials Science1-1 NamikiTsukuba 305-0044Japan Nanotechnology Group USAL-NanolabUniversity of Salamanca37008 SalamancaSpain

In recent years,graphene field-effect-transistors(GFEts)have demonstrated an outstanding potential for terahertz(tHz)photodetection due to their fast response and high-sensitivity.Such features are essential to enable emerging tHz applications,including 6G wireless communications,quantum information,bioimaging and security.However,the overall performance of these photodetectors may be utterly compromised by the impact of internal resistances presented in the device,so-called access or parasitic resistances.In this work,we provide a detailed study of the influence of internal device resistances in the photoresponse of high-mobility dual-gate GFEt detectors.Such dual-gate architectures allow us to fine tune(decrease)the internal resistance of the device by an order of magnitude and consequently demonstrate an improved responsivity and noise-equivalent-power values of the photodetector,respectively.Our results can be well understood by a series resistance model,as shown by the excellent agreement found between the experimental data and theoretical calculations.these findings are therefore relevant to understand and improve the overall performance of existing high-mobility graphene photodetectors.

关键词： Graphene tHz Photodetector Field-effect transistor Plasmonic

SmILE soft X-ray Imager flight model CCD370 pre-flight device characterisation

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Earth and Planetary Physics 2024年第1期8卷 25-38页

作者： S.Parsons D.j.Hall O.Hetherington t.W.Buggey t.Arnold m.W.j.Hubbard A.Holland Centre for Electronic Imaging the Open UniversityMilton KeynesMK76AAUK

throughout the SmILE mission the satellite will be bombarded by radiation which gradually damages the focal plane devices and degrades their performance.In order to understand the changes of the CCD370s within the soft X-ray Imager,an initial characterisation of the devices has been carried out to give a baseline performance level.three CCDs have been characterised,the two flight devices and the flight spa re.this has been carried out at the Open University in a bespo ke cleanroom measure ment facility.the results show that there is a cluster of bright pixels in the flight spa re which increases in size with tempe rature.However at the nominal ope rating tempe rature(-120℃) it is within the procure ment specifications.Overall,the devices meet the specifications when ope rating at -120℃ in 6 × 6 binned frame transfer science mode.the se rial charge transfer inefficiency degrades with temperature in full frame mode.However any charge losses are recovered when binning/frame transfer is implemented.

关键词： CCD soft X-ray imager characterisation SmILE

Supposition of graphene stacks to estimate the contact resistance and conductivity of nanocomposites

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Applied mathematics and mechanics(English Edition) 2024年第4期45卷 663-676页

作者： Y.ZARE m.t.mUNIR G.j.WENG K.Y.RHEE Biomaterials and tissue Engineering Research Group Department of Interdisciplinary TechnologiesBreast Cancer Research CenterMotamed Cancer InstituteTehran ***Iran College of Engineering and technology American University of the Middle EastEgaila 54200Kuwait Department of mechanical and Aerospace Engineering Rutgers UniversityNew BrunswickNJ 08903U.S.A. Department of mechanical Engineering(BK21 Four) College of EngineeringKyung Hee UniversityYongin 446701Republic of Korea

In this study,the effects of stacked nanosheets and the surrounding interphase zone on the resistance of the contact region between nanosheets and the tunneling conductivity of samples are evaluated with developed equations superior to those previously reported.the contact resistance and nanocomposite conductivity are modeled by several influencing factors,including stack properties,interphase depth,tunneling size,and contact diameter.the developed model's accuracy is verified through numerous experimental measurements.to further validate the models and establish correlations between parameters,the effects of all the variables on contact resistance and nanocomposite conductivity are analyzed.Notably,the contact resistance is primarily dependent on the polymer tunnel resistivity,contact area,and tunneling size.the dimensions of the graphene nanosheets significantly influence the conductivity,which ranges from 0 S/m to90 S/m.An increased number of nanosheets in stacks and a larger gap between them enhance the nanocomposite's conductivity.Furthermore,the thicker interphase and smaller tunneling size can lead to higher sample conductivity due to their optimistic effects on the percolation threshold and network efficacy.

关键词： graphene polymer composite stacked nanosheet tunneling conductivity contact resistance interphase

the CCD instrument background of the SmILE SXI

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Earth and Planetary Physics 2024年第1期8卷 15-24页

作者： m.W.j.Hubbard O.Hetherington D.j.Hall t.W.Buggey S.Parsons t.Arnold A.Holland C.Pagani S.Sembay Centre for Electronic Imaging The Open UniversityMilton KeynesMK76AAUK X-ray and Observational Astronomy Group Department of Physics&AstronomyUniversity of LeicesterLE17RHUK

the ESA and CAS SmILE mission orbit is highly elliptical and will pass through multiple radiation environments.the Soft X-ray Imager(SXI)instrument aboard has a radiation shutter door designed to close when the surrounding radiation flux is high.the shutter door will close when passing below an altitude threshold to protect against trapped particles in the Earth’s Van Allen Belts.therefore,two radiation environments can be approximated based on the shutter door position:open and closed.the instrument background for the CCDs(Charge-Coupled Devices)that form the focal plane array of the SXI were evaluated for the two environments.Due to the correlation of the space environment with the solar cycle,the solar minima and maxima,the background was also evaluated at these two extremes.the results demonstrated that the highest instrument background will occur during solar minima due to the main contributing source being Galactic Cosmic Rays(GCRs).It was also found that the open background was highest for solar minima and that the closed background was highest during solar maxima.this is due to the radiation shutter door acting as a scattering centre and the changes in the energy flux distribution of the GCRs between the two solar extremes.

关键词： instrument background X-ray astronomy space radiation

In situ characterization of particle formation in spray flame synthesis using wide-angle light scattering

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Particuology 2024年第3期86卷 304-312页

作者： Simon Aβmann Franz j.t.Huber Stefan Will Lehrstuhl für technische thermodynamik(Ltt) Friedrich-Alexander-Universitat Erlangen-Nürnberg(FAU)Erlangen91058Germany Erlangen Graduate Schoolin Advanced Optical technologies(SAOt) Friedrich-Alexander-Universitat Erlangen-Nurnberg(FAU)Erlangen91052Germany Competence Unit Engineering of Advanced materials(EAm) Friedrich-Alexander-Universitat Erlangen-Nürnberg(FAU)Erlangen91052Germany

Wide-angle light scattering(WALS)was used for in situ measurements of droplet and nanoparticle size distributions during the synthesis of titania and iron oxide particles from liquid precursor solutions in the standardized SpraySyn burner for spray flame synthesis.titania was synthesized from titanium tetraisopropoxide(ttIP)and iron oxide from iron(II)nitrate nonahydrate(INN)using ethanol(EtOH)as solvent.Scattering images were taken at heights up to 120 mm above the burner surface and classified into droplet and particle scattering.Droplet size distributions were derived from a sequential analysis of scattering data containing the oscillating mie pattern,the lognormal size distribution parameters for spherical and fractal particle fractions from a multivariate approach on averaged particle scattering data.the results show that the precursor addition leads to altered evaporation behavior and even droplet disruption probably induced by puffing or micro-explosions compared to pure EtOH.In the case of ttIP(a hygroscopic alkoxide),the synthesis of a large fraction of spheres was observed,while the nitrate INN leads to the formation of mostly fractal aggregates.

关键词： Spray flame synthesis metal oxide particles Elastic light scattering Droplet size distribution Nanoparticle morphology Particle size distribution

Distribution, health and ecological risk assessments of trace elements in Nigerian oil sands

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Acta Geochimica 2024年第1期43卷 59-71页

作者： Odunayo t.Ore Festus m.Adebiyi Department of Chemistry Obafemi Awolowo UniversityIle-Ife 220005Nigeria Department of Chemical Sciences Achievers UniversityOwoNigeria

the Nigerian oil sands represent the largest oil sand deposit in Africa, yet there is little published information on the distribution and potential health and ecological risks of trace elements in the oil resource. In the present study, we investigated the distribution pattern of 18trace elements(including biophile and chalcophile elements) as well as the estimated risks associated with exposure to these elements. the results of the study indicated that Fe was the most abundant element, with a mean concentration of 22,131 mg/kg while Br had the lowest mean concentration of 48 mg/kg. the high occurrence of Fe and ti suggested a possible occurrence of ilmenite(Fe tiO_(3)) in the oil sands. Source apportionment using positive matrix factorization showed that the possible sources of detected elements in the oil sands were geogenic, metal production, and crustal. the contamination factor, geo-accumulation index, modified degree of contamination, pollution load index, and Nemerow pollution index indicated that the oil sands are heavily polluted by the elements. Health risk assessment showed that children were relatively more susceptible to the potentially toxic elements in the oil sands principally via ingestion exposure route(HQ > 1E-04). Cancer risks from inhalation are unlikely due to CR t ingestion and dermal contact pose severe risks(CR > 1E-04). the high concentrations of the elements pose serious threats due to the potential for atmospheric transport, bioaccessibility, and bioavailability.

关键词： Biophile Chalcophile Oil sand Risk assessment trace element

Ground-based and additional science support for SmILE

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Earth and Planetary Physics 2024年第1期8卷 275-298页

作者： j.A.Carter m.Dunlop C.Forsyth K.Oksavik E.Donovon A.Kavanagh S.E.milan t.Sergienko R.C.Fear D.G.Sibeck m.Connors t.Yeoman X.tan m.G.G.t.taylor K.mcWilliams j.Gjerloev R.Barnes D.D.Billet G.Chisham A.Dimmock m.P.Freeman D.-S.Han m.D.Hartinger S.-Y.W.Hsieh Z.-j.Hu m.K.james L.juusola K.Kauristie E.A.Kronberg m.Lester j.manuel j.matzka I.mcCrea Y.miyoshi j.Rae L.Ren F.Sigernes E.Spanswick K.Sterne A.Steuwer t.Sun m.-t.Walach B.Walsh C.Wang j.Weygand j.Wild j.Yan j.Zhang Q.-H.Zhang Planetary Sciences Group School of Physics and AstronomyUniversity of LeicesterUniversity RoadLeicesterLE17RHUK Rutherford Appleton Laboratory Space Science Technology Facilities CouncilOxfordshireUK School of Space and Environment Beihang UniversityBeijing 100191China Key Laboratory of Space Environment monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing 100017China Department of Space and Climate Physics UCLMullard Space Science LaboratoryHolmbury St.MaryDorkingSurreyRH56NTUK Birkeland Centre for Space Science Department of Physics and Technology.University of BergenBergenNorway Department of Physics and Astronomy University of Calgary2500 University DriveCalgaryAlbertaCanada T2N 1N4 British Antarctic Survey CambridgeUK Swedish Institute of Space Physics KirunaSweden West Highfield Campus University of SouthamptonUniversity RoadSO171BJUK Goddard Space Flight Center NASAGreenbeltMarylandUSA Athabasca University AthabascaCanada EStEC European Space AgencyNetherlands University of Saskatchewan SaskatoonCanada the johns Hopkins University Applied Physics Laboratory LaurelMarylandUSA Swedish Institude of Space Physics UppsalaSE 75121Sweden tongji University Shanghai 200092China Center for Space Plasma Physics Space Science Institute4765 Walnut Street Suite BBoulderColorado80301USA Polar Research Institute of China Shanghai 200136China Finnish meteorological Institute(FmI) Finland Department of Earth and Environmental Sciences(Geophysics) Ludwig Maximilian University of Munich(LMU)MunichTheresienstr.41MunichD-80333Germany Canadian Space Agency MontrealCanada GFZ German Research Centre for Geosciences PotsdamGermany Nagoya University Institute for Space Earth Environment ResearchCenter for Integrated Data ScienceNagoyaAichiJP 464-8601 Northumbria University Newcastle upon TyneTyne and WearUK NE18ST National Space Science Center Chinese Academy SciencesBeijing 100190China Arctic Geophysics University Centre in Svalbard

the joint European Space Agency and Chinese Academy of Sciences Solar wind magnetosphere Ionosphere Link Explorer(SmILE)mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions,and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere.Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SmILE mission.Here,we describe current community efforts to prepare for SmILE,and the benefits and context various experiments that have explicitly expressed support for SmILE can offer.A dedicated group of international scientists representing many different experiment types and geographical locations,the Ground-based and Additional Science Working Group,is facilitating these efforts.Preparations include constructing an online SmILE Data Fusion Facility,the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar,and the consideration of particular observing strategies and spacecraft conjunctions.We anticipate growing interest and community engagement with the SmILE mission,and we welcome novel ideas and insights from the solar-terrestrial community.

关键词： magnetosphere ionosphere magnetosphere-ionosphere coupling ground-based experimentation SmILE conjunctions missions

Frequency-dependent viscoelasticity effects on the wave attenuation performance of multi-layered periodic foundations

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Applied mathematics and mechanics(English Edition) 2024年第3期45卷 407-424页

作者： m.SAFI m.VAKILIFARD m.j.mAHmOODI Faculty of Civil Water&Environmental EngineeringShahid Beheshti UniversityTehran ***Iran Faculty of mechanical and Energy Engineering Shahid Beheshti UniversityTehran ***Iran

In this paper,layered periodic foundations(LPFs)are numerically examined for their responses to longitudinal and transverse modes in the time and frequency domains.three different unit-cells,i.e.,2-layer,4-layer,and 6-layer unit-cells,comprising concrete/rubber,concrete/rubber/steel/rubber,and concrete/rubber/steel/rubber/lead/rubber materials,respectively,are taken into account.Also,the viscoelasticity behavior of the rubber is modeled with two factors,i.e.,a frequency-independent(FI)loss factor and a linear frequency-dependent(FD)loss factor.Following the extraction of the complex dispersion curves and the identification of the band gaps(BGs),the simulations of wave transmission in the time and frequency domains are performed using the COmSOL software.Subsequent parametric studies evaluate the effects of the rubber viscoelasticity models on the dispersion curves and the wave transmission for the longitudinal and transverse modes.the results show that considering the rubber viscoelasticity enhances the wave attenuation performance.moreover,the transverse-mode damping is more sensitive to the viscoelasticity model than its longitudinal counterpart.the 6-layer unit-cell LPF exhibits the lowest BG,ranging from 4.8 Hz to 6.5 Hz.

关键词： layered metamaterial periodic foundation complex dispersion curve wave transmission diagram

the secondary injury cascade after spinal cord injury: an analysis of local cytokine/chemokine regulation

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Neural Regeneration Research 2024年第6期19卷 1308-1317页

作者： Daniel j.Hellenbrand Charles m.Quinn Zachariah j.Piper Ryan t.Elder Raveena R.mishra taylor L.marti Phoebe m.Omuro Rylie m.Roddick jae Sung Lee William L.murphy Amgad S.Hanna Department of Neurosurgery University of Wisconsin-Madison School of Medicine and Public Health Department of Biomedical Engineering University of Wisconsin-Madison Department of Orthopedics and Rehabilitation University of Wisconsin-Madison Department of materials Science and Engineering University of Wisconsin-Madison Forward BIO Institute University of Wisconsin-Madison

After spinal cord injury, there is an extensive infiltration of immune cells, which exacerbates the injury and leads to further neural degeneration. therefore, a major aim of current research involves targeting the immune response as a treatment for spinal cord injury. Although much research has been performed analyzing the complex inflammatory process following spinal cord injury, there remain major discrepancies within previous literature regarding the timeline of local cytokine regulation. the objectives of this study were to establish an overview of the timeline of cytokine regulation for 2 weeks after spinal cord injury, identify sexual dimorphisms in terms of cytokine levels, and determine local cytokines that significantly change based on the severity of spinal cord injury. Rats were inflicted with either a mild contusion, moderate contusion, severe contusion, or complete transection, 7 mm of spinal cord centered on the injury was harvested at varying times post-injury, and tissue homogenates were analyzed with a Cytokine/Chemokine 27-Plex assay. Results demonstrated pro-inflammatory cytokines including tumor necrosis factor α, interleukin-1β, and interleukin-6 were all upregulated after spinal cord injury, but returned to uninjured levels within approximately 24 hours post-injury, while chemokines including monocyte chemoattractant protein-1 remained upregulated for days post-injury. In contrast, several anti-inflammatory cytokines and growth factors including interleukin-10 and vascular endothelial growth factor were downregulated by 7 days post-injury. After spinal cord injury, tissue inhibitor of metalloproteinase-1, which specifically affects astrocytes involved in glial scar development, increased more than all other cytokines tested, reaching 26.9-fold higher than uninjured rats. After a mild injury, 11 cytokines demonstrated sexual dimorphisms; however, after a severe contusion only leptin levels were different between female and male rats. In conclusion, pro-inflammatory cytokines initiate the inf

关键词： astrocytes chemokines cytokines inflammation macrophages microglia secondary damage spinal cord injury