A new method for fabricating ordered porous silicon is reported. A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres. The ini...A new method for fabricating ordered porous silicon is reported. A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres. The initial diameter and distribution of the holes in the resulting porous silicon layer are determined by the size and distribution of the silica nanospheres. The corrosion time can be used to control the depths of the holes. It is found that the presence of a SiO2 layer, formed by the oxidation of the rough internal surface of the hole, is the primary reason allowing the corrosion to proceed. Ultraviolet reflection and thermal conductivity measurements show that the diameter and distribution of the holes have a great influence on properties of the porous silicon.展开更多
A New method,named atmospheric pressure plasma polishing,for the ultra-smooth machining of the silicon based materials is introduced.By inputting the CF4 gas into the atmospheric pressure plasma flame,high density rea...A New method,named atmospheric pressure plasma polishing,for the ultra-smooth machining of the silicon based materials is introduced.By inputting the CF4 gas into the atmospheric pressure plasma flame,high density reactive radicals will be generated,which will then react with the silicon based materials.The reaction product is the vaporization of the SiF4,which can be easily processed.In this way,the atomic scale material removal can be realized and the defect free ultra-smooth surface can be obtained.An experimental setup is built up,and the SiC polishing experiment is carried out.The AFM test result shows that the finished surface roughness (Ra) can be improved from 4.529 nm to 0.926 nm in 3 minutes.展开更多
A single mode hybrid Ⅲ-Ⅴ/silicon on-chip laser based on the flip-chip bonding technology for on-chip optical interconnection is demonstrated. A single mode Fabry-Perot laser structure with micro-structures on an InP...A single mode hybrid Ⅲ-Ⅴ/silicon on-chip laser based on the flip-chip bonding technology for on-chip optical interconnection is demonstrated. A single mode Fabry-Perot laser structure with micro-structures on an InP ridge waveguide is designed and fabricated on an InP/AIGaInAs multiple quantum well epitaxial layer structure wafer by using i-line lithography. Then, a silicon waveguide platform including a laser mounting stage is designed and fabricated on a silicon-on-insulator substrate. The single mode laser is flip-chip bonded on the laser mounting stage. The lasing light is butt-coupling to the silicon waveguide. The laser power output from a silicon waveguide is 1.3roW, and the threshold is 37mA at room temperature and continuous wave operation.展开更多
We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is ...We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is deter- mined to be a Si 170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300meV, which is a result of the large capacitance of a small silicon quantum dot （-1.8 nm）. This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time.展开更多
This work adopts a multi⁃step etching⁃heat treatment strategy to prepare porous silicon microsphere com⁃posite with Sb⁃Sn surface modification and carbon coating(pSi/Sb⁃Sn@C),using industrial grade SiAl alloy micro⁃sp...This work adopts a multi⁃step etching⁃heat treatment strategy to prepare porous silicon microsphere com⁃posite with Sb⁃Sn surface modification and carbon coating(pSi/Sb⁃Sn@C),using industrial grade SiAl alloy micro⁃spheres as a precursor.pSi/Sb⁃Sn@C had a 3D structure with bimetallic(Sb⁃Sn)modified porous silicon micro⁃spheres(pSi/Sb⁃Sn)as the core and carbon coating as the shell.Carbon shells can improve the electronic conductivi⁃ty and mechanical stability of porous silicon microspheres,which is beneficial for obtaining a stable solid electrolyte interface(SEI)film.The 3D porous core promotes the diffusion of lithium ions,increases the intercalation/delithia⁃tion active sites,and buffers the volume expansion during the intercalation process.The introduction of active met⁃als(Sb⁃Sn)can improve the conductivity of the composite and contribute to a certain amount of lithium storage ca⁃pacity.Due to its unique composition and microstructure,pSi/Sb⁃Sn@C showed a reversible capacity of 1247.4 mAh·g^(-1) after 300 charge/discharge cycles at a current density of 1.0 A·g^(-1),demonstrating excellent rate lithium storage performance and enhanced electrochemical cycling stability.展开更多
A reverse bias silicon p-n junction based on light emitting diode is designed in standard 0.6μm industrial CMOS technology.The mechanism of the light emitting of this device is discussed.The device is simulated by th...A reverse bias silicon p-n junction based on light emitting diode is designed in standard 0.6μm industrial CMOS technology.The mechanism of the light emitting of this device is discussed.The device is simulated by the commercial software.I-V characteristic under forward or reverse bias is simulated utilizing the commercial software.The results between simulation and experiment data are compared.The results show that it is a promising device and may find applications in light linking.展开更多
High temperature oxidation behavior of two kinds of nitride bonded SiC based refractories wtls bwestigated at I 100-1 .500℃ by means of X-ray di[fractometer, scanning electronic microscopy and thermogravimetry. The r...High temperature oxidation behavior of two kinds of nitride bonded SiC based refractories wtls bwestigated at I 100-1 .500℃ by means of X-ray di[fractometer, scanning electronic microscopy and thermogravimetry. The results show that ： （1） with the temperature im＇reasing, the oxidation mass increment rote of the specimen increases.first and then. decreases, and oxidation passi＇va tion occttrs; （2） the oxidation resistance of SiAION bonded SiC refractories is superior to that of Si3N4 botlded SiC refractories ; （3） high temperature oxidtttion resuits itt the increase of compressive strength at room temperature of SiC based refractoviesiaes comlmred with specimen before oxidatiotl; the compressive strength of SIMON bonded SiC specimens oxidized at high temperatures decreases with the increase of the temperature as a result of formation amt burst of surfhce bubble, while the decrease of compressive strength of Sign4 bonded SiC specimens oxidized at high temperatures is owitng to the bwrease of the consistency of netlike crack assoeiated with cristobalite transfornuttion during cooling.展开更多
The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite （w（MgO）=95%） as starting material, SiO2 micro-powder as binder, 0.3%, 4% and 5% β-Si3N4 powder replacing the...The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite （w（MgO）=95%） as starting material, SiO2 micro-powder as binder, 0.3%, 4% and 5% β-Si3N4 powder replacing the equal addition of magnesia powder respectively. The slag resistance test was carried out at 1550℃ for 3h using Baosteel tundish slag and static crucible method. The result indicates that： introducing Si3N4 could obviously improve the slag resistance of MgO based castable, which increased with increasing Si3N4. Dense SiO2 sintered layer formed on the surface of magnesia based castable because of the oxidation of Si3N4 addition, which can prevent the further slag penetration. In the deep inner of castable, the partial-pressure of oxygen was very low, so Si3N4 can exist stably. Meanwhile in reducing atmosphere, Si3N4 was hard to be sintered, which resulted in the loose interior structure of MgO based castable.展开更多
The observation of the low-energyγ-ray(0.1 to 30 MeV)sky has been significantly limited since the COMPTEL instrument aboard the Compton Gamma Ray Observatory(CGRO)satellite was decommissioned in 2000.The exploration...The observation of the low-energyγ-ray(0.1 to 30 MeV)sky has been significantly limited since the COMPTEL instrument aboard the Compton Gamma Ray Observatory(CGRO)satellite was decommissioned in 2000.The exploration ofγ-ray photons within this energy band,often referred to as the MeV gap,is crucial to address numerous unresolved mysteries in high-energy and multi-messenger astrophysics.Although several large MeVγ-ray missions have been proposed(e.g.,e-ASTROGAM,AMEGO,and COSI),most of these are in the planning phase,with launches not expected until the next decade,at the earliest.Recently,there has been a surge in proposed CubeSat missions as cost-effective and rapidly implementable pathfinder alternatives.An MeV CubeSat dedicated toγ-ray astronomy could serve as a valuable demonstrator for large-scale future MeV payloads.This paper proposes aγ-ray payload design with a silicon-based tracker and a cesium iodide-based calorimeter.We report the results of a simulation study to assess the performance of this payload concept and compare the results with those of previousγ-ray instruments.As part of the performance assessment and comparison,we show that with our proposed payload design,a sensitivity better than IBIS can be achieved for energies between 0.1 and 10 MeV,and for energies up to around 1 MeV,the achieved sensitivity is comparable to COMPTEL,therefore opening up a window toward cost-effective observational astronomy with comparable performance to past missions.展开更多
Hydrogenated amorphous silicon carbide （a-SixC1-x：H） films were grown on Si substrate by plasma-enhanced chemical vapor deposition. Fixed flow rate of H2 and different flow ratio of SiHJCH4 were used. Er-doped a-Si...Hydrogenated amorphous silicon carbide （a-SixC1-x：H） films were grown on Si substrate by plasma-enhanced chemical vapor deposition. Fixed flow rate of H2 and different flow ratio of SiHJCH4 were used. Er-doped a-SixC1-x ： H （a-SixC1-x-H ：Er） films were prepared by implanting Er into the a- Si,C1-x-H host materials followed by annealing at different temperatures. The structure properties of the films were characterized by X-ray photoelectron spectroscopy （XPS）, Raman spectra. infrared absorption Photoluminescence spectra （IR） and （PL） intensities depending on flow rates and annealing temperatures were studied. High annealing temperature is not favorable for PL because of C-surface segregation. It is shown that thermal quenching of this material is small by comparing the PL intensities of a-SixC1-x-H： Er at room temperature and low temperature.展开更多
We propose and experimentally demonstrate a 2×2 thermo-optic(TO) crossbar switch implemented by dual photonic crystal nanobeam(PCN)cavities within a silicon-on-insulator(SOI)platform.By thermally tuning the refra...We propose and experimentally demonstrate a 2×2 thermo-optic(TO) crossbar switch implemented by dual photonic crystal nanobeam(PCN)cavities within a silicon-on-insulator(SOI)platform.By thermally tuning the refractive index of silicon,the resonance wavelength of the PCN cavities can be red-shifted.With the help of the ultrasmall mode volumes of the PCN cavities,only～0.16 mW power is needed to change the switching state.With a spectral passband of 0.09 nm at the 1583.75 nm operation wavelength,the insertion loss(IL)and crosstalk(CT)performances were measured as IL(bar)=-0.2 dB,CT(bar)=-15 dB,IL(cross)=-1.5 dB,and CT(cross)=-15 dB.Furthermore,the thermal tuning efficiency of the fabricated device is as high as1.23 nm/mW.展开更多
All-optical integrators are key devices for the realization of ultra-fast passive photonic networks, and, despite their broad applicability range(e.g., photonic bit counting, optical memory units, analogue computing, ...All-optical integrators are key devices for the realization of ultra-fast passive photonic networks, and, despite their broad applicability range(e.g., photonic bit counting, optical memory units, analogue computing, etc.), their realization in an integrated form is still a challenge. In this work, an all-optical integrator based on a silicon photonic phase-shifted Bragg grating is proposed and experimentally demonstrated, which shows a wide operation bandwidth of 750 GHz and integration time window of 9 ps. The integral operation for single pulse, inphase pulses, and π-shifted pulses with different delays has been successfully achieved.展开更多
We propose and experimentally demonstrate compact on-chip 1×2 wavelength selective switches(WSSs) based on silicon microring resonators(MRRs) with nested pairs of subrings(NPSs). Owing to the resonance splitting ...We propose and experimentally demonstrate compact on-chip 1×2 wavelength selective switches(WSSs) based on silicon microring resonators(MRRs) with nested pairs of subrings(NPSs). Owing to the resonance splitting induced by the inner NPSs, the proposed devices are capable of performing selective channel routing at certain resonance wavelengths of the outer MRRs. System demonstration of dynamic channel routing using fabricated devices with one and two NPSs is carried out for 10 Gb∕s non-return-to-zero signal. The experimental results verify the effectiveness of the fabricated devices as compact on-chip WSSs.展开更多
A novel scheme for the design of an ultra-compact and high-performance optical switch is proposed and investigated numerically. Based on a standard silicon(Si) photonic stripe waveguide, a section of hyperbolic metama...A novel scheme for the design of an ultra-compact and high-performance optical switch is proposed and investigated numerically. Based on a standard silicon(Si) photonic stripe waveguide, a section of hyperbolic metamaterials(HMM) consisting of 20-pair alternating vanadium dioxide (VO_2)∕Si thin layers is inserted to realize the switching of fundamental TE mode propagation. Finite-element-method simulation results show that, with the help of an HMM with a size of 400 nm × 220 nm × 200 nm(width × height × length), the ON/OFF switching for fundamental TE mode propagation in an Si waveguide can be characterized by modulation depth(MD) of5.6 d B and insertion loss(IL) of 1.25 dB. It also allows for a relatively wide operating bandwidth of 215 nm maintaining MD > 5 dB and IL < 1.25 dB. Furthermore, we discuss that the tungsten-doped VO_2 layers could be useful for reducing metal-insulator-transition temperature and thus improving switching performance. In general, our findings may provide some useful ideas for optical switch design and application in an on-chip all-optical communication system with a demanding integration level.展开更多
The electrical nonlinearity of silicon modulators based on reversed PN junctions was found to severely limit the linearity of the modulators.This effect,however,was inadvertently neglected in previous studies.Consider...The electrical nonlinearity of silicon modulators based on reversed PN junctions was found to severely limit the linearity of the modulators.This effect,however,was inadvertently neglected in previous studies.Considering the electrical nonlinearity in simulation,a 32.2 dB degradation in the CDR3(i.e.,the suppression ratio between the fundamental signal and intermodulation distortion)of the modulator was observed at a modulation speed of 12 GHz,and the spurious free dynamic range was simultaneously degraded by 17.4 dB.It was also found that the linearity of the silicon modulator could be improved by reducing the series resistance of the PN junction.The frequency dependence of the linearity due to the electrical nonlinearity was also investigated.展开更多
Two types of 1×2 multi-mode interference （MMI） splitters with splitting ratios of 85：15 and 72：28 are designed. On the basis of a numerical simulation, an optimal length of the MMI section is obtained. Subseq...Two types of 1×2 multi-mode interference （MMI） splitters with splitting ratios of 85：15 and 72：28 are designed. On the basis of a numerical simulation, an optimal length of the MMI section is obtained. Subsequently, the devices are fabricated and tested. The footprints of the rectangular MMI regions are only 3×18.2 and 3×14.3 （#m）. The minimum excess losses are 1.4 and 1.1 dB. The results of the test on the splitting ratios are consistent with designed values. The devices can be applied in ultra-compact photonic integrated circuits to realize the ＂tap＂ function.展开更多
In recent years,artificial intelligence(AI)has achieved tremendous development,akin to a significant leap,similar to progressing from 1 to 100.However,a significant gap still exists between current machine intelligenc...In recent years,artificial intelligence(AI)has achieved tremendous development,akin to a significant leap,similar to progressing from 1 to 100.However,a significant gap still exists between current machine intelligence and human wisdom:machine intelligence is constrained to post hoc inference based on existing data,lacking the ability for genuine exploratory innovation and possessing no prospective reasoning inherent to human wisdom.Drawing inspiration from human wisdom,this article presents conjectures for overcoming the four dilemmas faced by machine intelligence:neglect of silicon-based cognition,lack of artistry,pitfall of perfectionism,and obsession with uniformity.These conjectures aim to propel machine intelligence toward machine wisdom,achieving a great leap from 1 to i.展开更多
For a practical photodetector, fast switching speed and high on-off ratio areessential, and more importantly, the integration capability of the device finallydetermines its application level. In this work, the judicio...For a practical photodetector, fast switching speed and high on-off ratio areessential, and more importantly, the integration capability of the device finallydetermines its application level. In this work, the judiciously engineered Si3N4/Sidetector with an open-circuit voltage of 0.41 V is fabricated by chemical vapordeposition methods, and exhibits good performance with repeatability. Theadvanced integration technology of Si3N4 and Si is the foundation for imagingfunctions in the near future. Compare to the current commercial Si p-i-nphotodiodes, the detector cuts off the long-wavelength UV light over 260 nm,realizing the spectrum selectivity without filters or complexed accessories. Thestability of this detector is further characterized by cycling response, temperature andlight intensity dependence tests. In addition, we also analyze and explain theinherent mechanisms that govern the different operations of two types of Si3N4/Siphotodetectors.展开更多
Integration of graphene in silicon-based micro-/nanoelectromechanical systems(MEMS/NEMS)marries the robustness of silicon-based materials with the exceptional physical properties of graphene,drastically enhancing the ...Integration of graphene in silicon-based micro-/nanoelectromechanical systems(MEMS/NEMS)marries the robustness of silicon-based materials with the exceptional physical properties of graphene,drastically enhancing the system’s regulation performance which now is key for many advanced applications in nanotechnology.Here,we experimentally demonstrate and theoretically analyze a powerful on-chip integration principle consisting of a hybrid graphene/silicon nitride membrane with metallic leads on top that enables an extremely large static and dynamic parameter regulation.When a static voltage is applied to the leads of the integrated structure,a spatially confined localized electrothermomechanical(ETM)effect results in ultra-wide frequency tuning,deformation(buckling transition)and regulation of the mechanical properties.Moreover,by injecting an alternating voltage to the leads,we can excite the resonator vibrating even far beyond its linear regime without a complex and space consuming actuation system.Our results prove that the scheme provides a compact integrated system possessing mechanical robustness,high controllability,and fast response.It not only expands the limit of the application range of MEMS/NEMS devices,but also enables the further miniaturization of the device.展开更多
Silicon offers a high theoretical specific capacity for anodic lithium storage.However,its applications are hindered by the electrode instability caused by the sharp volume change,and the limited rate performance resu...Silicon offers a high theoretical specific capacity for anodic lithium storage.However,its applications are hindered by the electrode instability caused by the sharp volume change,and the limited rate performance resulted from the insulating property.Herein,we introduce a facile and fast method of preparing honeycomb‐like silicon‐based anodes(MXene‐Si@C)with porous structure using MXene and carbon‐coated silicon.The dual protection from both the surface coating and as‐formed interlayered vacant spaces ameliorate the volume expansion of the silicon and thus reinforce the mechanical stability of the electrode.In addition,the highly conducting MXene and the surface carbon coating form a hierarchical and consecutive electron‐conducting network with evidently reduced resistance.With this proposed composite,a high average Coulombic efficiency of 99.73%and high capacity retention of 82.4%after 300 cycles at 1 A/g can be achieved even with an areal loading around 1.5 mg/cm^(2).Coupled with an NCM523 cathode,the proof‐of‐concept full cell delivers a high capacity of 164.2mAh/g with an extremely high energy density of 574Wh/kg(based on the mass of the electrode materials)at 0.2 C and an excellent cyclability at 0.5 C of 100 cycles with decent capacity retention(80.28%).展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 10804026 and 51101049the Natural Science Foundation of Hebei Province under Grant Nos A2013205101 and A2014205051the Hebei Talent Cultivation Foundation under Grant No A201400119
文摘A new method for fabricating ordered porous silicon is reported. A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres. The initial diameter and distribution of the holes in the resulting porous silicon layer are determined by the size and distribution of the silica nanospheres. The corrosion time can be used to control the depths of the holes. It is found that the presence of a SiO2 layer, formed by the oxidation of the rough internal surface of the hole, is the primary reason allowing the corrosion to proceed. Ultraviolet reflection and thermal conductivity measurements show that the diameter and distribution of the holes have a great influence on properties of the porous silicon.
文摘A New method,named atmospheric pressure plasma polishing,for the ultra-smooth machining of the silicon based materials is introduced.By inputting the CF4 gas into the atmospheric pressure plasma flame,high density reactive radicals will be generated,which will then react with the silicon based materials.The reaction product is the vaporization of the SiF4,which can be easily processed.In this way,the atomic scale material removal can be realized and the defect free ultra-smooth surface can be obtained.An experimental setup is built up,and the SiC polishing experiment is carried out.The AFM test result shows that the finished surface roughness (Ra) can be improved from 4.529 nm to 0.926 nm in 3 minutes.
基金Supported by the National Basic Research Program of China under Grant No 2012CB933501the National Natural Science Foundation of China under Grant Nos 61307033,61274070,61137003 and 61321063
文摘A single mode hybrid Ⅲ-Ⅴ/silicon on-chip laser based on the flip-chip bonding technology for on-chip optical interconnection is demonstrated. A single mode Fabry-Perot laser structure with micro-structures on an InP ridge waveguide is designed and fabricated on an InP/AIGaInAs multiple quantum well epitaxial layer structure wafer by using i-line lithography. Then, a silicon waveguide platform including a laser mounting stage is designed and fabricated on a silicon-on-insulator substrate. The single mode laser is flip-chip bonded on the laser mounting stage. The lasing light is butt-coupling to the silicon waveguide. The laser power output from a silicon waveguide is 1.3roW, and the threshold is 37mA at room temperature and continuous wave operation.
基金Supported by the National Key Research and Development Program of China under Grant No 2017YFA0303200the National Natural Science Foundation of China under Grant Nos U1732273,U1732159,91421109,91622115,11522432,11574217 and 61774133the Natural Science Foundation of Jiangsu Province under Grant No BK20160659
文摘We demonstrate the fabrication of a single electron transistor device based on a single ultra-small silicon quantum dot connected to a gold break junction with a nanometer scale separation. The gold break junction is created through a controllable electromigration process and the individual silicon quantum dot in the junction is deter- mined to be a Si 170 cluster. Differential conductance as a function of the bias and gate voltage clearly shows the Coulomb diamond which confirms that the transport is dominated by a single silicon quantum dot. It is found that the charging energy can be as large as 300meV, which is a result of the large capacitance of a small silicon quantum dot （-1.8 nm）. This large Coulomb interaction can potentially enable a single electron transistor to work at room temperature. The level spacing of the excited state can be as large as 10meV, which enables us to manipulate individual spin via an external magnetic field. The resulting Zeeman splitting is measured and the g factor of 2.3 is obtained, suggesting relatively weak electron-electron interaction in the silicon quantum dot which is beneficial for spin coherence time.
文摘This work adopts a multi⁃step etching⁃heat treatment strategy to prepare porous silicon microsphere com⁃posite with Sb⁃Sn surface modification and carbon coating(pSi/Sb⁃Sn@C),using industrial grade SiAl alloy micro⁃spheres as a precursor.pSi/Sb⁃Sn@C had a 3D structure with bimetallic(Sb⁃Sn)modified porous silicon micro⁃spheres(pSi/Sb⁃Sn)as the core and carbon coating as the shell.Carbon shells can improve the electronic conductivi⁃ty and mechanical stability of porous silicon microspheres,which is beneficial for obtaining a stable solid electrolyte interface(SEI)film.The 3D porous core promotes the diffusion of lithium ions,increases the intercalation/delithia⁃tion active sites,and buffers the volume expansion during the intercalation process.The introduction of active met⁃als(Sb⁃Sn)can improve the conductivity of the composite and contribute to a certain amount of lithium storage ca⁃pacity.Due to its unique composition and microstructure,pSi/Sb⁃Sn@C showed a reversible capacity of 1247.4 mAh·g^(-1) after 300 charge/discharge cycles at a current density of 1.0 A·g^(-1),demonstrating excellent rate lithium storage performance and enhanced electrochemical cycling stability.
文摘A reverse bias silicon p-n junction based on light emitting diode is designed in standard 0.6μm industrial CMOS technology.The mechanism of the light emitting of this device is discussed.The device is simulated by the commercial software.I-V characteristic under forward or reverse bias is simulated utilizing the commercial software.The results between simulation and experiment data are compared.The results show that it is a promising device and may find applications in light linking.
文摘High temperature oxidation behavior of two kinds of nitride bonded SiC based refractories wtls bwestigated at I 100-1 .500℃ by means of X-ray di[fractometer, scanning electronic microscopy and thermogravimetry. The results show that ： （1） with the temperature im＇reasing, the oxidation mass increment rote of the specimen increases.first and then. decreases, and oxidation passi＇va tion occttrs; （2） the oxidation resistance of SiAION bonded SiC refractories is superior to that of Si3N4 botlded SiC refractories ; （3） high temperature oxidtttion resuits itt the increase of compressive strength at room temperature of SiC based refractoviesiaes comlmred with specimen before oxidatiotl; the compressive strength of SIMON bonded SiC specimens oxidized at high temperatures decreases with the increase of the temperature as a result of formation amt burst of surfhce bubble, while the decrease of compressive strength of Sign4 bonded SiC specimens oxidized at high temperatures is owitng to the bwrease of the consistency of netlike crack assoeiated with cristobalite transfornuttion during cooling.
文摘The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite （w（MgO）=95%） as starting material, SiO2 micro-powder as binder, 0.3%, 4% and 5% β-Si3N4 powder replacing the equal addition of magnesia powder respectively. The slag resistance test was carried out at 1550℃ for 3h using Baosteel tundish slag and static crucible method. The result indicates that： introducing Si3N4 could obviously improve the slag resistance of MgO based castable, which increased with increasing Si3N4. Dense SiO2 sintered layer formed on the surface of magnesia based castable because of the oxidation of Si3N4 addition, which can prevent the further slag penetration. In the deep inner of castable, the partial-pressure of oxygen was very low, so Si3N4 can exist stably. Meanwhile in reducing atmosphere, Si3N4 was hard to be sintered, which resulted in the loose interior structure of MgO based castable.
基金supported by HKU-RMGS Funds (207300301 and 207301033principal investigator: Q.A.P.)+1 种基金The research of P.S.P. is partially supported by a General Research Fund (GRF) grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (HKU Project 17304920principal investigator: S. C. Y. Ng).
文摘The observation of the low-energyγ-ray(0.1 to 30 MeV)sky has been significantly limited since the COMPTEL instrument aboard the Compton Gamma Ray Observatory(CGRO)satellite was decommissioned in 2000.The exploration ofγ-ray photons within this energy band,often referred to as the MeV gap,is crucial to address numerous unresolved mysteries in high-energy and multi-messenger astrophysics.Although several large MeVγ-ray missions have been proposed(e.g.,e-ASTROGAM,AMEGO,and COSI),most of these are in the planning phase,with launches not expected until the next decade,at the earliest.Recently,there has been a surge in proposed CubeSat missions as cost-effective and rapidly implementable pathfinder alternatives.An MeV CubeSat dedicated toγ-ray astronomy could serve as a valuable demonstrator for large-scale future MeV payloads.This paper proposes aγ-ray payload design with a silicon-based tracker and a cesium iodide-based calorimeter.We report the results of a simulation study to assess the performance of this payload concept and compare the results with those of previousγ-ray instruments.As part of the performance assessment and comparison,we show that with our proposed payload design,a sensitivity better than IBIS can be achieved for energies between 0.1 and 10 MeV,and for energies up to around 1 MeV,the achieved sensitivity is comparable to COMPTEL,therefore opening up a window toward cost-effective observational astronomy with comparable performance to past missions.
文摘Hydrogenated amorphous silicon carbide （a-SixC1-x：H） films were grown on Si substrate by plasma-enhanced chemical vapor deposition. Fixed flow rate of H2 and different flow ratio of SiHJCH4 were used. Er-doped a-SixC1-x ： H （a-SixC1-x-H ：Er） films were prepared by implanting Er into the a- Si,C1-x-H host materials followed by annealing at different temperatures. The structure properties of the films were characterized by X-ray photoelectron spectroscopy （XPS）, Raman spectra. infrared absorption Photoluminescence spectra （IR） and （PL） intensities depending on flow rates and annealing temperatures were studied. High annealing temperature is not favorable for PL because of C-surface segregation. It is shown that thermal quenching of this material is small by comparing the PL intensities of a-SixC1-x-H： Er at room temperature and low temperature.
基金National Natural Science Foundation of China(NSFC)(61235007,61505104,61605112)Science and Technology Commission of Shanghai Municipality(15ZR1422800,16XD1401400)National Key R&D Program of China(2016YFB0402501)
文摘We propose and experimentally demonstrate a 2×2 thermo-optic(TO) crossbar switch implemented by dual photonic crystal nanobeam(PCN)cavities within a silicon-on-insulator(SOI)platform.By thermally tuning the refractive index of silicon,the resonance wavelength of the PCN cavities can be red-shifted.With the help of the ultrasmall mode volumes of the PCN cavities,only～0.16 mW power is needed to change the switching state.With a spectral passband of 0.09 nm at the 1583.75 nm operation wavelength,the insertion loss(IL)and crosstalk(CT)performances were measured as IL(bar)=-0.2 dB,CT(bar)=-15 dB,IL(cross)=-1.5 dB,and CT(cross)=-15 dB.Furthermore,the thermal tuning efficiency of the fabricated device is as high as1.23 nm/mW.
基金National Natural Science Foundation of China(NSFC)(61475052,61622502)
文摘All-optical integrators are key devices for the realization of ultra-fast passive photonic networks, and, despite their broad applicability range(e.g., photonic bit counting, optical memory units, analogue computing, etc.), their realization in an integrated form is still a challenge. In this work, an all-optical integrator based on a silicon photonic phase-shifted Bragg grating is proposed and experimentally demonstrated, which shows a wide operation bandwidth of 750 GHz and integration time window of 9 ps. The integral operation for single pulse, inphase pulses, and π-shifted pulses with different delays has been successfully achieved.
基金supported in part by the National Natural Science Foundation of China under Grant 61125504/61235007in part by the 863 High-Tech Program under Grant 2013AA013402
文摘We propose and experimentally demonstrate compact on-chip 1×2 wavelength selective switches(WSSs) based on silicon microring resonators(MRRs) with nested pairs of subrings(NPSs). Owing to the resonance splitting induced by the inner NPSs, the proposed devices are capable of performing selective channel routing at certain resonance wavelengths of the outer MRRs. System demonstration of dynamic channel routing using fabricated devices with one and two NPSs is carried out for 10 Gb∕s non-return-to-zero signal. The experimental results verify the effectiveness of the fabricated devices as compact on-chip WSSs.
基金Ministry of Science and Technology of the People's Republic of China(MOST)(2016YFA0301300)National Natural Science Foundation of China(NSFC)(61275201,61372037)+2 种基金Beijing University of Posts and Telecommunications(BUPT)Excellent Ph.D.Students Foundation(CX2016204)Fundamental Research Funds for the Central Universities(2016RC24)Beijing Excellent Ph.D.Thesis Guidance Foundation(20131001301)
文摘A novel scheme for the design of an ultra-compact and high-performance optical switch is proposed and investigated numerically. Based on a standard silicon(Si) photonic stripe waveguide, a section of hyperbolic metamaterials(HMM) consisting of 20-pair alternating vanadium dioxide (VO_2)∕Si thin layers is inserted to realize the switching of fundamental TE mode propagation. Finite-element-method simulation results show that, with the help of an HMM with a size of 400 nm × 220 nm × 200 nm(width × height × length), the ON/OFF switching for fundamental TE mode propagation in an Si waveguide can be characterized by modulation depth(MD) of5.6 d B and insertion loss(IL) of 1.25 dB. It also allows for a relatively wide operating bandwidth of 215 nm maintaining MD > 5 dB and IL < 1.25 dB. Furthermore, we discuss that the tungsten-doped VO_2 layers could be useful for reducing metal-insulator-transition temperature and thus improving switching performance. In general, our findings may provide some useful ideas for optical switch design and application in an on-chip all-optical communication system with a demanding integration level.
基金National Natural Science Foundation of China(NSFC)(61575189,61635011)
文摘The electrical nonlinearity of silicon modulators based on reversed PN junctions was found to severely limit the linearity of the modulators.This effect,however,was inadvertently neglected in previous studies.Considering the electrical nonlinearity in simulation,a 32.2 dB degradation in the CDR3(i.e.,the suppression ratio between the fundamental signal and intermodulation distortion)of the modulator was observed at a modulation speed of 12 GHz,and the spurious free dynamic range was simultaneously degraded by 17.4 dB.It was also found that the linearity of the silicon modulator could be improved by reducing the series resistance of the PN junction.The frequency dependence of the linearity due to the electrical nonlinearity was also investigated.
基金supported in part by the National Natural Science Foundation of China (No. 60977050)the National "973" Program of China (Nos. 2009CB320302 and 2011CB301704)
文摘Two types of 1×2 multi-mode interference （MMI） splitters with splitting ratios of 85：15 and 72：28 are designed. On the basis of a numerical simulation, an optimal length of the MMI section is obtained. Subsequently, the devices are fabricated and tested. The footprints of the rectangular MMI regions are only 3×18.2 and 3×14.3 （#m）. The minimum excess losses are 1.4 and 1.1 dB. The results of the test on the splitting ratios are consistent with designed values. The devices can be applied in ultra-compact photonic integrated circuits to realize the ＂tap＂ function.
基金supported by the National Natural Science Foundation of China(NSFC72421002,72025405,and 62206303)+2 种基金the Science and Technology Innovation Program of Hunan Province(2023RC3009)the Science and Technology Project for Young andMiddle-aged Talents of Hunan(2023TJ-Z03)the Scientific Project ofNUDT(23-ZZCX-JDZ-28 and JS24-05).
文摘In recent years,artificial intelligence(AI)has achieved tremendous development,akin to a significant leap,similar to progressing from 1 to 100.However,a significant gap still exists between current machine intelligence and human wisdom:machine intelligence is constrained to post hoc inference based on existing data,lacking the ability for genuine exploratory innovation and possessing no prospective reasoning inherent to human wisdom.Drawing inspiration from human wisdom,this article presents conjectures for overcoming the four dilemmas faced by machine intelligence:neglect of silicon-based cognition,lack of artistry,pitfall of perfectionism,and obsession with uniformity.These conjectures aim to propel machine intelligence toward machine wisdom,achieving a great leap from 1 to i.
基金supported by the National Natural Science Foundation of China(61427901,61604178,91833301 and U1505252).
文摘For a practical photodetector, fast switching speed and high on-off ratio areessential, and more importantly, the integration capability of the device finallydetermines its application level. In this work, the judiciously engineered Si3N4/Sidetector with an open-circuit voltage of 0.41 V is fabricated by chemical vapordeposition methods, and exhibits good performance with repeatability. Theadvanced integration technology of Si3N4 and Si is the foundation for imagingfunctions in the near future. Compare to the current commercial Si p-i-nphotodiodes, the detector cuts off the long-wavelength UV light over 260 nm,realizing the spectrum selectivity without filters or complexed accessories. Thestability of this detector is further characterized by cycling response, temperature andlight intensity dependence tests. In addition, we also analyze and explain theinherent mechanisms that govern the different operations of two types of Si3N4/Siphotodetectors.
基金financial support from the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)through Project-ID 425217212(SFB 1432)and project 510766045the major program in digital intelligence,Shapingba,Chongqing(Grant No.20240204)the Wisconsin Alumni Research Foundation(WARF)via the Accelerator Program.
文摘Integration of graphene in silicon-based micro-/nanoelectromechanical systems(MEMS/NEMS)marries the robustness of silicon-based materials with the exceptional physical properties of graphene,drastically enhancing the system’s regulation performance which now is key for many advanced applications in nanotechnology.Here,we experimentally demonstrate and theoretically analyze a powerful on-chip integration principle consisting of a hybrid graphene/silicon nitride membrane with metallic leads on top that enables an extremely large static and dynamic parameter regulation.When a static voltage is applied to the leads of the integrated structure,a spatially confined localized electrothermomechanical(ETM)effect results in ultra-wide frequency tuning,deformation(buckling transition)and regulation of the mechanical properties.Moreover,by injecting an alternating voltage to the leads,we can excite the resonator vibrating even far beyond its linear regime without a complex and space consuming actuation system.Our results prove that the scheme provides a compact integrated system possessing mechanical robustness,high controllability,and fast response.It not only expands the limit of the application range of MEMS/NEMS devices,but also enables the further miniaturization of the device.
基金supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.T23‐601/17‐R).
文摘Silicon offers a high theoretical specific capacity for anodic lithium storage.However,its applications are hindered by the electrode instability caused by the sharp volume change,and the limited rate performance resulted from the insulating property.Herein,we introduce a facile and fast method of preparing honeycomb‐like silicon‐based anodes(MXene‐Si@C)with porous structure using MXene and carbon‐coated silicon.The dual protection from both the surface coating and as‐formed interlayered vacant spaces ameliorate the volume expansion of the silicon and thus reinforce the mechanical stability of the electrode.In addition,the highly conducting MXene and the surface carbon coating form a hierarchical and consecutive electron‐conducting network with evidently reduced resistance.With this proposed composite,a high average Coulombic efficiency of 99.73%and high capacity retention of 82.4%after 300 cycles at 1 A/g can be achieved even with an areal loading around 1.5 mg/cm^(2).Coupled with an NCM523 cathode,the proof‐of‐concept full cell delivers a high capacity of 164.2mAh/g with an extremely high energy density of 574Wh/kg(based on the mass of the electrode materials)at 0.2 C and an excellent cyclability at 0.5 C of 100 cycles with decent capacity retention(80.28%).
