In this letter we present the results regarding the electrical and optical characterization of Geiger mode silicon avalanche photodiodes(GMAP) fabricated by silicon standard planar technology. Low dark count rates,neg...In this letter we present the results regarding the electrical and optical characterization of Geiger mode silicon avalanche photodiodes(GMAP) fabricated by silicon standard planar technology. Low dark count rates,negligible afterpulsing effects,good timing resolution and high quantum detection efficiency in all the visible range have been measured. The very good electro-optical performances of our photodiodes make them attractive for the fabrication of arrays with a large number of GMAP to be used both in the commercial and the scientific fields,as telecommunications and nuclear medical imaging.展开更多
Four-dimensional scanning transmission electron microscopy(4-D STEM)is a state-of-the-art image acquisition mode used to reveal high and low mass elements at atomic resolution.The acquisition of the electron momenta a...Four-dimensional scanning transmission electron microscopy(4-D STEM)is a state-of-the-art image acquisition mode used to reveal high and low mass elements at atomic resolution.The acquisition of the electron momenta at each real space probe location allows for various analyses to be performed from a single dataset,including virtual imaging,electric field analysis,as well as analytical or iterative extraction of the object induced phase shift.However,the limiting factor in 4-D STEM is the speed of acquisition which is bottlenecked by the read-out speed of the camera,which must capture a convergent beam electron diffraction(CBED)pattern at each probe position in the scan.Recent developments in sparse sampling and image inpainting(a branch of compressive sensing)for STEM have allowed for real-time recovery of sparsely acquired data from fixed monolithic detectors,Further developments in compressive sensing for 4-D STEM have also demonstrated that acquisition speeds can be increased,i.e.,live video rate 4-D imaging is now possible.In this work,we demonstrate the first practical implementations of compressive 4-D STEM for real-time inference on two different scanning transmission electron microscopes.展开更多
This paper describes our research activity involved in the identification, development and test of a prototype SHM system constituted by optical sensing nodes to measure both temperature and strain on ultra high tempe...This paper describes our research activity involved in the identification, development and test of a prototype SHM system constituted by optical sensing nodes to measure both temperature and strain on ultra high temperature ceramics （UHTC） materials up to 1000℃. Commercially available optic devices can operate up to 550℃. To raise temperature limit up to 1000℃, custom devices, mainly under development for scientific applications, have been identified. A prototype SHM system has been developed adopting a FBG sensor for temperature measurement and an EFPI sensor in sapphire fiber for strain measurement. The preliminary findings from thermo-mechanical tests indicate that former SHM system is capable of accurately measuring strain at elevated temperatures on UHTC materials.展开更多
Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique...Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit.We demonstrate that conventionally doped,hole-selective poly-Si/SiO_(x)contacts that provide poor surface passivation of c-Si can be replaced with Ga-or B-doped contacts based on non-equilibrium doping.We overcome the solid solubility limit for both dopants in poly-Si by rapid cooling and recrystallization over a timescale of∼25 ns.We show an active Ga dopant concentration of∼3×10^(20)cm^(−3)in poly-Si which is six times higher than its solubility limit in c-Si,and a B dopant concentration as high as∼10^(21) cm^(−3).We measure an implied open-circuit voltage of 735 mV for Ga-doped poly-Si/SiO_(x)contacts on Czochralski Si with a low contact resistivity of 35.5±2.4 mΩcm^(2).Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p-n junction that contributes to the low contact resistivity.Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high-efficiency devices.展开更多
We present the properties and potentialities of light emitting devices based on amorphous Si nanoclusters. Amorphousnanostructures may constitute an interesting alternative to Si nanocrystals for the monolithic integr...We present the properties and potentialities of light emitting devices based on amorphous Si nanoclusters. Amorphousnanostructures may constitute an interesting alternative to Si nanocrystals for the monolithic integration of optical andelectrical functions in Si technology. In fact, they exhibit an intense room temperature electroluminescence (EL). The ELproperties of these devices have been studied as a function of current and of temperature. Moreover, to improve theextraction efficiency of the light, we have integrated the emitting system with a 2D photonic crystal structure opportunelyfabricated by using conventional optical lithography to reduce the total internal reflection of the emitted light. The extractionefficiency in such devices increases by a factor of 4 at a resonance wavelength.展开更多
A dual phase boride and carbide ceramic with the nominal composition(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 and(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C was prepared by reactive synthesis and consolidated by spark plasma sintering.The resul...A dual phase boride and carbide ceramic with the nominal composition(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 and(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C was prepared by reactive synthesis and consolidated by spark plasma sintering.The resulting microstructure contained about 30%(in volume)boride and 70%carbide.Compositional inhomogeneities were observed within single grains that had core-shell structures and preferential accumulation of specific metals in the boride or carbide phases.Specifically,Ti and Nb had higher concentrations in the boride,whereas Hf and Ta in the carbide.The Zr concentration was relatively equally distributed in the two phases.The dual phase ceramic had additional,distinctive features including nanosized inclusions,possibly related to local miscibility gaps and supersaturation,linear defects,and strain due to adjustment of the crystal structure.As a consequence,the fracture mode was transgranular with the crack path deviated by these nanometric microstructure alterations.Nanoindentation under 5 mN measured higher hardness and modulus for the boride,30 GPa and 525 GPa,as compared to the carbide phase,22 GPa and 425 GPa,due to a higher concentration of dislocation tangles and strains deriving from the introduction of metals with different sizes(and properties)in a less compliant hexagonal lattice.展开更多
【目的】微小杆菌属(Exiguobacterium)细菌广泛分布于海洋及非海洋环境中,具有多种代谢途径以适应复杂多样的生境。本研究从能量代谢途径角度出发,探究该属菌株对不同生境的适应能力。【方法】从美国国家生物科技数据中心(National Cent...【目的】微小杆菌属(Exiguobacterium)细菌广泛分布于海洋及非海洋环境中,具有多种代谢途径以适应复杂多样的生境。本研究从能量代谢途径角度出发,探究该属菌株对不同生境的适应能力。【方法】从美国国家生物科技数据中心(National Center for Biotechnology Information, NCBI)数据库中获取146个Exiguobacterium属菌株的基因组,查找并统计光营养、厌氧呼吸和底物代谢等多种能量代谢途径的关键蛋白或关键酶基因在各菌株基因组中的分布,包括光营养型的视紫红质基因、厌氧呼吸营养型的钼辅因子合成蛋白基因,以及底物代谢营养型中乙醛酸分流途径的异柠檬酸裂解酶及苹果酸合酶基因等。根据对应的氨基酸序列构建视紫红质、MoaC和异柠檬酸裂解酶的系统发育树,分析不同能量代谢途径在该属菌株进化过程中的保守性,推测其对于该属菌株的重要性。【结果】Exiguobacterium属中50%的种具有视紫红质基因,其中分离自非海洋生境的菌株更趋向于含有视紫红质基因。本研究所统计的全部非海洋生境菌株中,含有视紫红质基因的菌株占比约为70%,而在海洋生境菌株中该比例仅为19%。Exiguobacterium属约27%的种存在钼辅因子合成蛋白基因,分离自海洋环境的菌株有该类蛋白的可能性更高(32%:21%),具有完整钼辅因子合成途径的菌株集中于进化树同一分支上的少数种。该属约61%的种存在乙醛酸分流途径相关酶基因,这些种隶属进化树的同一分支,且种内所有菌株都具备相关基因,表明乙醛酸分流途径在Exiguobacterium属的分布具有种特异性。【结论】Exiguobacterium属细菌具有多种能量代谢途径相关基因,包括基于视紫红质的光营养型能量代谢途径、基于钼酶的厌氧呼吸型能量代谢途径和底物代谢营养型能量代谢途径中的乙醛酸分流途径。能量代谢途径多样性可能是Exiguobacterium属细菌适应复杂多样生境的机制之一。此外,本研究发现Exiguobacterium属中不同种、同种不同菌株间存在能量代谢途径差异,且能量代谢途径在该属内的分布多不具备种特异性,表明仅通过16S rRNA基因种属鉴定来预测目标菌株的代谢类型可能有较大偏差和局限性。展开更多
Taking the full advantage of the conformal growth characterizing atomic layer deposition(ALD),the possibility to grow Co thin films,with thickness from several tens down to few nanometers on top of a granular topologi...Taking the full advantage of the conformal growth characterizing atomic layer deposition(ALD),the possibility to grow Co thin films,with thickness from several tens down to few nanometers on top of a granular topological insulator(TI)Sb2Tes film,exhibiting a quite high surface roughness(2-5 nm),was demonstrated.To study the Co growth on the Sb2Tes substrate,we performed simultaneous Co depositions also on sputtered Pt substrates for comparison.We conducted a thorough chemical-structural characterization of the Co/Sb2Tes and Co/Pt heterostructures,confirming for both cases,not only an excellent conformality,but also the structural continuity of the Co layers.X-ray diffraction(XRD)and high-resolution transmission electron microscope(HRTEM)analyses evidenced that Co on Sb2Te3 grows preferentially oriented along the[0oe]direction,following the underlying rhombohedric substrate.Differently,Co crystallizes in a cubic phase oriented along the[111]direction when deposited on Pt.This work shows that,in case of deposition of crystalline materials,the ALD surface selectivity and conformality can be extended to the definition of local epitaxy,where in-plane ordering of the crystal structure and mosaicity of the developed crystallized grains are dictated by the underlying substrate.Moreover,a highly sharp and chemically-pure Co/Sb2Tes interface was evidenced,which is promising for the application of this growth process for spintronics.展开更多
Multi-phase ceramics based on ZrB_(2),TiB_(2) and doped with CrB_(2) and SiC were prepared by powder metallurgy and hot pressing to explore the possibility of obtaining multi-scale microstructures by super-saturation ...Multi-phase ceramics based on ZrB_(2),TiB_(2) and doped with CrB_(2) and SiC were prepared by powder metallurgy and hot pressing to explore the possibility of obtaining multi-scale microstructures by super-saturation of complex(Zr,Ti,Cr)B_(2) solid solutions.Core-shell structures formed in TiB_(2) grains,whereas ZrB_(2) appeared to form a homogeneous solid solution with the other metals.Precipitation of nano-inclusions within both micron-sized borides was assessed by transmission electron microscopy and thermodynamics elucidated the preferential formation of boride inclusions due to the specific sintering atmosphere.In addition,atomic size factors explicated the precipitation of CrB_(2) nano-particles into ZrB_(2)-rich grains and of ZrB_(2) nano-particles into TiB_(2)-rich grains.The hardness of the constituent phases measured by nanoindentation ranged from 36 to 43 GPa.展开更多
Despite the considerable effort,fast and highly sensitive photodetection is not widely available at the low-photon-energy range(~meV)of the electromagnetic spectrum,owing to the challenging light funneling into small ...Despite the considerable effort,fast and highly sensitive photodetection is not widely available at the low-photon-energy range(~meV)of the electromagnetic spectrum,owing to the challenging light funneling into small active areas with efficient conversion into an electrical signal.Here,we provide an alternative strategy by efficiently integrating and manipulating at the nanoscale the optoelectronic properties of topological Dirac semimetal PtSe_(2)and its van der Waals heterostructures.Explicitly,we realize strong plasmonic antenna coupling to semimetal states near the skin-depth regime(λ/10^(4)),featuring colossal photoresponse by in-plane symmetry breaking.The observed spontaneous and polarization-sensitive photocurrent are correlated to strong coupling with the nonequilibrium states in PtSe_(2)Dirac semimetal,yielding efficient light absorption in the photon range below 1.24 meV with responsivity exceeding∼0.2 A/W and noise-equivalent power(NEP)less than~38 pW/Hz^(0.5),as well as superb ambient stability.Present results pave the way to efficient engineering of a topological semimetal for high-speed and low-energy photon harvesting in areas such as biomedical imaging,remote sensing or security applications.展开更多
Two-dimensional materials are today a solid reality in condensed matter physics due to the disruptive discoveries about graphene.The class of the X-enes,namely,graphene-like single element artificial crystals,is quick...Two-dimensional materials are today a solid reality in condensed matter physics due to the disruptive discoveries about graphene.The class of the X-enes,namely,graphene-like single element artificial crystals,is quickly emerging driven by the high-momentum generated by silicene.Silicene,in addition to the graphene properties,shows up incidentally at the end of Moore’s law debate in the electronic era.Indeed,silicene occurs as the crafted shrunk version of silicon long yearned by device manufacturers to improve the performances of their chips.Despite the periodic table kinship with graphene,silicene and the X-enes must deal with the twofold problem of their metastable nature,i.e.,the stabilization on a substrate and out of vacuum environment.Synthesis on different substrates and deep characterization through electronic and optical techniques of silicene in the early days have been now following by the tentative steps towards reliable integration of silicene into devices.Here,we review three paradigmatic cases of silicene grown by molecular beam epitaxy showing three different possible applications,aiming at extending the exploitation of silicene out of the nanoelectronics field and thus keeping silicon a key player in nanotechnology,just in a thinner fashion.展开更多
The increasing need for sustainable energy and the transition from a linear to a circular economy pose great challenges to the materials science community.In this view,the chance of producing efficient nanocatalysts f...The increasing need for sustainable energy and the transition from a linear to a circular economy pose great challenges to the materials science community.In this view,the chance of producing efficient nanocatalysts for water splitting using industrial waste as starting material is attractive.Here,we report low-cost processes to convert Mo-based industrial waste powder into efficient catalysts for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).pH controlled hydrothermal processing of Mo-based industrial waste powder leads to pure orthorhombic MoO_(3) nanobelts(50–200 nm wide,10µm long)with promising OER performances at 10 mA·cm^(−2) with an overpotential of 324 mV and Tafel slope of 45 mV·dec^(−1) in alkaline electrolyte.Indeed,MoS_(2)/MoO_(3) nanostructures were obtained after sulfurization during hydrothermal processes of the MoO_(3) nanobelts.HER tests in acidic environment show a promising overpotential of 208 mV at 10 mA·cm^(−2) and a Tafel slope of 94 mV·dec^(−1).OER and HER performances of nanocatalysts obtained from Mo industrial waste powder are comparable or better than Mo-based nanocatalysts obtained from pure commercial Mo reagent.This work shows the great potential of reusing industrial waste for energy applications,opening a promising road to join waste management and efficient and sustainable nanocatalysts for water splitting.展开更多
Though it is well recognized that the space between graphene cover and the metal substrate canact as a two-dimensional(2D)nanoreactor,several issues are still unresolved,including the role of the metal substrate,the m...Though it is well recognized that the space between graphene cover and the metal substrate canact as a two-dimensional(2D)nanoreactor,several issues are still unresolved,including the role of the metal substrate,the mechanisms ruling water intercalation and the identification ofsites at which water is decomposed.Here,we solve these issues by means of density functional theory and high-resolution electron energyloss spectroscopy experiments carried out on graphene grown on(111)-oriented Cu foils.Specifically,we observe decomposition of H2O atroom temperature with only H atoms forming bonds with graphene and with buried OH groups underneath the graphene cover.Ourtheoretical model discloses physicochemical mechanisms ruling the migration and decomposition of water on graphene/Cu.We discover thatthe edge of graphene can be easily saturated by H through decomposition of H2O,which allows H2O to migrate in the subsurface region from thedecoupled edge,where H2O decomposes at room temperature.Hydrogen atoms produced by the decomposition of H2O initially form a chemicalbond with graphene for the lower energy barrier compared with other routes.These findings are essential to exploit graphene/Cu interfaces incatalysis and in energy-related applications.展开更多
文摘In this letter we present the results regarding the electrical and optical characterization of Geiger mode silicon avalanche photodiodes(GMAP) fabricated by silicon standard planar technology. Low dark count rates,negligible afterpulsing effects,good timing resolution and high quantum detection efficiency in all the visible range have been measured. The very good electro-optical performances of our photodiodes make them attractive for the fabrication of arrays with a large number of GMAP to be used both in the commercial and the scientific fields,as telecommunications and nuclear medical imaging.
基金the Royal Society for providing funding under grant number EGR10965。
文摘Four-dimensional scanning transmission electron microscopy(4-D STEM)is a state-of-the-art image acquisition mode used to reveal high and low mass elements at atomic resolution.The acquisition of the electron momenta at each real space probe location allows for various analyses to be performed from a single dataset,including virtual imaging,electric field analysis,as well as analytical or iterative extraction of the object induced phase shift.However,the limiting factor in 4-D STEM is the speed of acquisition which is bottlenecked by the read-out speed of the camera,which must capture a convergent beam electron diffraction(CBED)pattern at each probe position in the scan.Recent developments in sparse sampling and image inpainting(a branch of compressive sensing)for STEM have allowed for real-time recovery of sparsely acquired data from fixed monolithic detectors,Further developments in compressive sensing for 4-D STEM have also demonstrated that acquisition speeds can be increased,i.e.,live video rate 4-D imaging is now possible.In this work,we demonstrate the first practical implementations of compressive 4-D STEM for real-time inference on two different scanning transmission electron microscopes.
文摘This paper describes our research activity involved in the identification, development and test of a prototype SHM system constituted by optical sensing nodes to measure both temperature and strain on ultra high temperature ceramics （UHTC） materials up to 1000℃. Commercially available optic devices can operate up to 550℃. To raise temperature limit up to 1000℃, custom devices, mainly under development for scientific applications, have been identified. A prototype SHM system has been developed adopting a FBG sensor for temperature measurement and an EFPI sensor in sapphire fiber for strain measurement. The preliminary findings from thermo-mechanical tests indicate that former SHM system is capable of accurately measuring strain at elevated temperatures on UHTC materials.
基金the National Renewable Energy Laboratory,operated by Alliance for Sustainable Energy,LLC,for the U.S.Department of Energy(DOE)under Contract No.DE-AC36-08GO28308.
文摘Polycrystalline Si(poly-Si)-based passivating contacts are promising candidates for high-efficiency crystalline Si solar cells.We show that nanosecond-scale pulsed laser melting(PLM)is an industrially viable technique to fabricate such contacts with precisely controlled dopant concentration profiles that exceed the solid solubility limit.We demonstrate that conventionally doped,hole-selective poly-Si/SiO_(x)contacts that provide poor surface passivation of c-Si can be replaced with Ga-or B-doped contacts based on non-equilibrium doping.We overcome the solid solubility limit for both dopants in poly-Si by rapid cooling and recrystallization over a timescale of∼25 ns.We show an active Ga dopant concentration of∼3×10^(20)cm^(−3)in poly-Si which is six times higher than its solubility limit in c-Si,and a B dopant concentration as high as∼10^(21) cm^(−3).We measure an implied open-circuit voltage of 735 mV for Ga-doped poly-Si/SiO_(x)contacts on Czochralski Si with a low contact resistivity of 35.5±2.4 mΩcm^(2).Scanning spreading resistance microscopy and Kelvin probe force microscopy show large diffusion and drift current in the p-n junction that contributes to the low contact resistivity.Our results suggest that PLM can be extended for hyperdoping of other semiconductors with low solubility atoms to enable high-efficiency devices.
基金This work has been partially supported by MIUR through the proj- ects FIRB and D.D.1105.
文摘We present the properties and potentialities of light emitting devices based on amorphous Si nanoclusters. Amorphousnanostructures may constitute an interesting alternative to Si nanocrystals for the monolithic integration of optical andelectrical functions in Si technology. In fact, they exhibit an intense room temperature electroluminescence (EL). The ELproperties of these devices have been studied as a function of current and of temperature. Moreover, to improve theextraction efficiency of the light, we have integrated the emitting system with a 2D photonic crystal structure opportunelyfabricated by using conventional optical lithography to reduce the total internal reflection of the emitted light. The extractionefficiency in such devices increases by a factor of 4 at a resonance wavelength.
基金by the NATO Science for Peace and Security Programme under grant MYP-G5767(SUSPENCE)by the US AFOSR through the grant no.FA9550-21-1-0399(NACREOUS)+1 种基金funded by the Spanish Science and Innovation Ministry though grant PID2021-126614OBI00supported by the Office of Naval Research through a Multidisciplinary University Research Initiative(MURI)program under project number N00014-21-1-2515.
文摘A dual phase boride and carbide ceramic with the nominal composition(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 and(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C was prepared by reactive synthesis and consolidated by spark plasma sintering.The resulting microstructure contained about 30%(in volume)boride and 70%carbide.Compositional inhomogeneities were observed within single grains that had core-shell structures and preferential accumulation of specific metals in the boride or carbide phases.Specifically,Ti and Nb had higher concentrations in the boride,whereas Hf and Ta in the carbide.The Zr concentration was relatively equally distributed in the two phases.The dual phase ceramic had additional,distinctive features including nanosized inclusions,possibly related to local miscibility gaps and supersaturation,linear defects,and strain due to adjustment of the crystal structure.As a consequence,the fracture mode was transgranular with the crack path deviated by these nanometric microstructure alterations.Nanoindentation under 5 mN measured higher hardness and modulus for the boride,30 GPa and 525 GPa,as compared to the carbide phase,22 GPa and 425 GPa,due to a higher concentration of dislocation tangles and strains deriving from the introduction of metals with different sizes(and properties)in a less compliant hexagonal lattice.
文摘【目的】微小杆菌属(Exiguobacterium)细菌广泛分布于海洋及非海洋环境中,具有多种代谢途径以适应复杂多样的生境。本研究从能量代谢途径角度出发,探究该属菌株对不同生境的适应能力。【方法】从美国国家生物科技数据中心(National Center for Biotechnology Information, NCBI)数据库中获取146个Exiguobacterium属菌株的基因组,查找并统计光营养、厌氧呼吸和底物代谢等多种能量代谢途径的关键蛋白或关键酶基因在各菌株基因组中的分布,包括光营养型的视紫红质基因、厌氧呼吸营养型的钼辅因子合成蛋白基因,以及底物代谢营养型中乙醛酸分流途径的异柠檬酸裂解酶及苹果酸合酶基因等。根据对应的氨基酸序列构建视紫红质、MoaC和异柠檬酸裂解酶的系统发育树,分析不同能量代谢途径在该属菌株进化过程中的保守性,推测其对于该属菌株的重要性。【结果】Exiguobacterium属中50%的种具有视紫红质基因,其中分离自非海洋生境的菌株更趋向于含有视紫红质基因。本研究所统计的全部非海洋生境菌株中,含有视紫红质基因的菌株占比约为70%,而在海洋生境菌株中该比例仅为19%。Exiguobacterium属约27%的种存在钼辅因子合成蛋白基因,分离自海洋环境的菌株有该类蛋白的可能性更高(32%:21%),具有完整钼辅因子合成途径的菌株集中于进化树同一分支上的少数种。该属约61%的种存在乙醛酸分流途径相关酶基因,这些种隶属进化树的同一分支,且种内所有菌株都具备相关基因,表明乙醛酸分流途径在Exiguobacterium属的分布具有种特异性。【结论】Exiguobacterium属细菌具有多种能量代谢途径相关基因,包括基于视紫红质的光营养型能量代谢途径、基于钼酶的厌氧呼吸型能量代谢途径和底物代谢营养型能量代谢途径中的乙醛酸分流途径。能量代谢途径多样性可能是Exiguobacterium属细菌适应复杂多样生境的机制之一。此外,本研究发现Exiguobacterium属中不同种、同种不同菌株间存在能量代谢途径差异,且能量代谢途径在该属内的分布多不具备种特异性,表明仅通过16S rRNA基因种属鉴定来预测目标菌株的代谢类型可能有较大偏差和局限性。
基金We acknowledge the MP1402-Hooking together the European research in atomic layer deposition(HERALD)COST action and the Horizon 2020 project SKYTOP"Skyrmion-Topological Insulator and Weyl Semimetal Technology"(FETPROACT-2018-01,n.824123)Efforts at Wayne State University were supported by the U.S.National Science Foundation(Grant No.CHE-1607973)and EMD Performance Materials.
文摘Taking the full advantage of the conformal growth characterizing atomic layer deposition(ALD),the possibility to grow Co thin films,with thickness from several tens down to few nanometers on top of a granular topological insulator(TI)Sb2Tes film,exhibiting a quite high surface roughness(2-5 nm),was demonstrated.To study the Co growth on the Sb2Tes substrate,we performed simultaneous Co depositions also on sputtered Pt substrates for comparison.We conducted a thorough chemical-structural characterization of the Co/Sb2Tes and Co/Pt heterostructures,confirming for both cases,not only an excellent conformality,but also the structural continuity of the Co layers.X-ray diffraction(XRD)and high-resolution transmission electron microscope(HRTEM)analyses evidenced that Co on Sb2Te3 grows preferentially oriented along the[0oe]direction,following the underlying rhombohedric substrate.Differently,Co crystallizes in a cubic phase oriented along the[111]direction when deposited on Pt.This work shows that,in case of deposition of crystalline materials,the ALD surface selectivity and conformality can be extended to the definition of local epitaxy,where in-plane ordering of the crystal structure and mosaicity of the developed crystallized grains are dictated by the underlying substrate.Moreover,a highly sharp and chemically-pure Co/Sb2Tes interface was evidenced,which is promising for the application of this growth process for spintronics.
基金sponsored by the NATO Science for Peace and Security Programme under grant MYP-G5767 (SUSPENCE)by the US AFOSR through the grant no.FA9550-21-1-0399 (NACREOUS)with Dr.Ming-Jen Pan as contract monitor+1 种基金supply of laboratory facilities.NG acknowledges the support received by JECS Trust for a mobility grant (ref.2020240)of three months at UPC,SpainNanoindentation tests were funded through The Spanish Ministry of Science,Innovation and Universities through grant PGC-2018-096855-B-C41.S.Guicciardi (CNR-ISMAR)is acknowledged for discussion on nanoindentation.
文摘Multi-phase ceramics based on ZrB_(2),TiB_(2) and doped with CrB_(2) and SiC were prepared by powder metallurgy and hot pressing to explore the possibility of obtaining multi-scale microstructures by super-saturation of complex(Zr,Ti,Cr)B_(2) solid solutions.Core-shell structures formed in TiB_(2) grains,whereas ZrB_(2) appeared to form a homogeneous solid solution with the other metals.Precipitation of nano-inclusions within both micron-sized borides was assessed by transmission electron microscopy and thermodynamics elucidated the preferential formation of boride inclusions due to the specific sintering atmosphere.In addition,atomic size factors explicated the precipitation of CrB_(2) nano-particles into ZrB_(2)-rich grains and of ZrB_(2) nano-particles into TiB_(2)-rich grains.The hardness of the constituent phases measured by nanoindentation ranged from 36 to 43 GPa.
基金This work was supported by the National Key R&D Program of China(No.2021YFB2800702)the National Natural Science Foundation of China(Nos.61521005,61875217,91850208)+4 种基金the STCSM Grants(Nos.1859078100,19590780100)The project was funded by State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,Donghua University(KF1809)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Zhejiang Lab(No.2021MB0AB01)the Natural Science Foundation of Shanghai(No.21ZR1402200).
文摘Despite the considerable effort,fast and highly sensitive photodetection is not widely available at the low-photon-energy range(~meV)of the electromagnetic spectrum,owing to the challenging light funneling into small active areas with efficient conversion into an electrical signal.Here,we provide an alternative strategy by efficiently integrating and manipulating at the nanoscale the optoelectronic properties of topological Dirac semimetal PtSe_(2)and its van der Waals heterostructures.Explicitly,we realize strong plasmonic antenna coupling to semimetal states near the skin-depth regime(λ/10^(4)),featuring colossal photoresponse by in-plane symmetry breaking.The observed spontaneous and polarization-sensitive photocurrent are correlated to strong coupling with the nonequilibrium states in PtSe_(2)Dirac semimetal,yielding efficient light absorption in the photon range below 1.24 meV with responsivity exceeding∼0.2 A/W and noise-equivalent power(NEP)less than~38 pW/Hz^(0.5),as well as superb ambient stability.Present results pave the way to efficient engineering of a topological semimetal for high-speed and low-energy photon harvesting in areas such as biomedical imaging,remote sensing or security applications.
基金The authors acknowledge the funding support from H2020 European Research Council CoG 2017 Grant N.772261“XFab”Fondazione CARIPLO-Regione Lombardia for the project“CrystEL,”Grant N.2016-0978.
文摘Two-dimensional materials are today a solid reality in condensed matter physics due to the disruptive discoveries about graphene.The class of the X-enes,namely,graphene-like single element artificial crystals,is quickly emerging driven by the high-momentum generated by silicene.Silicene,in addition to the graphene properties,shows up incidentally at the end of Moore’s law debate in the electronic era.Indeed,silicene occurs as the crafted shrunk version of silicon long yearned by device manufacturers to improve the performances of their chips.Despite the periodic table kinship with graphene,silicene and the X-enes must deal with the twofold problem of their metastable nature,i.e.,the stabilization on a substrate and out of vacuum environment.Synthesis on different substrates and deep characterization through electronic and optical techniques of silicene in the early days have been now following by the tentative steps towards reliable integration of silicene into devices.Here,we review three paradigmatic cases of silicene grown by molecular beam epitaxy showing three different possible applications,aiming at extending the exploitation of silicene out of the nanoelectronics field and thus keeping silicon a key player in nanotechnology,just in a thinner fashion.
基金Funding note:Open access funding provided by the CRUI-CARE Agreement.
文摘The increasing need for sustainable energy and the transition from a linear to a circular economy pose great challenges to the materials science community.In this view,the chance of producing efficient nanocatalysts for water splitting using industrial waste as starting material is attractive.Here,we report low-cost processes to convert Mo-based industrial waste powder into efficient catalysts for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER).pH controlled hydrothermal processing of Mo-based industrial waste powder leads to pure orthorhombic MoO_(3) nanobelts(50–200 nm wide,10µm long)with promising OER performances at 10 mA·cm^(−2) with an overpotential of 324 mV and Tafel slope of 45 mV·dec^(−1) in alkaline electrolyte.Indeed,MoS_(2)/MoO_(3) nanostructures were obtained after sulfurization during hydrothermal processes of the MoO_(3) nanobelts.HER tests in acidic environment show a promising overpotential of 208 mV at 10 mA·cm^(−2) and a Tafel slope of 94 mV·dec^(−1).OER and HER performances of nanocatalysts obtained from Mo industrial waste powder are comparable or better than Mo-based nanocatalysts obtained from pure commercial Mo reagent.This work shows the great potential of reusing industrial waste for energy applications,opening a promising road to join waste management and efficient and sustainable nanocatalysts for water splitting.
基金This work was supported by the National Natural Science Foundation of China(Nos.21676232 and 21673206).A.P.thanks Danil W.Boukhvalov for scientific discussions and Vito Fabio for technical support for the HREELS experiments.D.F.acknowledges financial support from the Spanish Ministry of Economy and Competitiveness,through the Maria de Maeztu Programme for Units of Excellence in R&D(No.MDM-2014-0377)and MINECO project MAT2015-65356-C3-3-R.
文摘Though it is well recognized that the space between graphene cover and the metal substrate canact as a two-dimensional(2D)nanoreactor,several issues are still unresolved,including the role of the metal substrate,the mechanisms ruling water intercalation and the identification ofsites at which water is decomposed.Here,we solve these issues by means of density functional theory and high-resolution electron energyloss spectroscopy experiments carried out on graphene grown on(111)-oriented Cu foils.Specifically,we observe decomposition of H2O atroom temperature with only H atoms forming bonds with graphene and with buried OH groups underneath the graphene cover.Ourtheoretical model discloses physicochemical mechanisms ruling the migration and decomposition of water on graphene/Cu.We discover thatthe edge of graphene can be easily saturated by H through decomposition of H2O,which allows H2O to migrate in the subsurface region from thedecoupled edge,where H2O decomposes at room temperature.Hydrogen atoms produced by the decomposition of H2O initially form a chemicalbond with graphene for the lower energy barrier compared with other routes.These findings are essential to exploit graphene/Cu interfaces incatalysis and in energy-related applications.
