CdTe/CdS quantum dots（QDs） are fabricated on Si nanowires（NWs） substrates with and without Au nanoparticles（NPs）. The formation of Au NPs on Si NWs can be certified as shown in scanning electron microscopy image...CdTe/CdS quantum dots（QDs） are fabricated on Si nanowires（NWs） substrates with and without Au nanoparticles（NPs）. The formation of Au NPs on Si NWs can be certified as shown in scanning electron microscopy images. The optical properties of samples are also investigated. It is interesting to find that the photoluminescence（PL） intensity of Cd Te/Cd S QD films on Si nanowire substrates with Au NPs is significantly increased,which can reach 8-fold higher than that of samples on planar Si without Au NPs. The results of finite-difference time-domain simulation indicate that Au NPs induce stronger localization of electric field and then boost the PL intensity of QDs nearby. Furthermore, the time-resolved luminescence decay curve shows the PL lifetime, which is about 5.5 ns at the emission peaks of QD films on planar, increasing from 1.8 ns of QD films on Si NWs to4.7 ns after introducing Au NPs into Si NWs.展开更多
In order to realize ultralow surface reflectance and broadband antireflection effects which common pyramidal textures and antireflection coatings can't achieve in photovoltaic industry,we used low-cost and easy-ma...In order to realize ultralow surface reflectance and broadband antireflection effects which common pyramidal textures and antireflection coatings can't achieve in photovoltaic industry,we used low-cost and easy-made Ag-catalyzed etching techniques to synthesize silicon nanowires(Si NWs) arrays on the substrate of single-crystalline silicon.The dense vertically-aligned Si NWs arrays are fabricated by local oxidation and selective dissolution of Si in etching solution containing Ag catalyst.The Si NWs arrays with 3 μm in depth make reflectance reduce to less than 3% in the range of 400 to 1000 nm while reflectance gradually reached the optimum value with the increasing of etching time.The antireflection of Si NWs arrays are based on indexgraded mechanism:Si NWs arrays on a subwavelength scale strongly scatter incident light and have graded refractive index that enhance the incidence of light in usable wavelength range.However,surface recombination of Si NWs arrays are deteriorated due to numerous dangling bonds and residual Ag particles.展开更多
Largescale vaporsolid synthesis of ultralong silicon nitride （Si3N4） nanowires was achieved by using simple thermal evaporation of mixture powders of active carbon and monoxide silicon. The products were charac teri...Largescale vaporsolid synthesis of ultralong silicon nitride （Si3N4） nanowires was achieved by using simple thermal evaporation of mixture powders of active carbon and monoxide silicon. The products were charac terized by Xray diffraction, scanning electron microscopy, energydispersive Xray spectroscopy, and transmission electron microscopy. The results suggest that the silicon nitride nanowires have a smooth surface, with lengths of up to several hundreds of microns and diameters of 100300 nm. A detailed study of both the chemical and structural composition was performed. Such ultralong sil icon nitride nanowires demonstrate potential applications as materials for constructing nanoscale devices and as reinforcement in advanced composites.展开更多
We have investigated the optical properties of laterally aligned Si nanowire （SiNW） arrays in order to explore their potential applicability in transparent electronics. The SiNW array exhibited good optical transpar...We have investigated the optical properties of laterally aligned Si nanowire （SiNW） arrays in order to explore their potential applicability in transparent electronics. The SiNW array exhibited good optical transparency in the visible spectral range with a transmittance of -90% for a NW density of -20-25 per 10 μm. In addition, polarization-dependent measurements revealed a variation in transmittance in the range of 80%-95% depending on the angle between the polarization of incident light and the NW axis. Using the SiNWs, we demonstrated that transparent transistors exhibit good optical transparency （greater than 80%） and showed typical p-type SiNW transistor characteristics.展开更多
A facile approach was demonstrated for fabricating high-performance nonvolatile memory devices based on ferroelectric-gate field effect transistors using a p-type Si nanowire coated with omega-shaped gate organic ferr...A facile approach was demonstrated for fabricating high-performance nonvolatile memory devices based on ferroelectric-gate field effect transistors using a p-type Si nanowire coated with omega-shaped gate organic ferroelectric poly(vinylidene fluoride-trifluoroethylene)(P(VDF-Tr FE)). We overcame the interfacial layer problem by incorporating P(VDF-Tr FE) as a ferroelectric gate using a low-temperature fabrication process. Our memory devices exhibited excellent memory characteristics with a low programming voltage of ±5 V, a large modulation in channel conductance between ON and OFF states exceeding 105, a long retention time greater than 3 9 104 s, and a high endurance of over 105 programming cycles while maintaining an ION/IOFFratio higher than 102.展开更多
Molecular dynamics simulations with Stillinger-Weber potential are used to study the tensile and melting behavior of single-crystalline silicon nanowires（SiNWs）.The tensile tests show that the tensile behavior of th...Molecular dynamics simulations with Stillinger-Weber potential are used to study the tensile and melting behavior of single-crystalline silicon nanowires（SiNWs）.The tensile tests show that the tensile behavior of the SiNWs is strongly dependent on the simulation temperature,the strain rate,and the diameter of the nanowires.For a given diameter,the critical load significantly decreases as the temperature increases and also as the strain rate decreases.Additionally,the critical load increases as the diameter increases.Moreover,the melting tests demonstrate that both melting temperature and melting heat of the SiNWs decrease with decreasing diameter and length,due to the increase in surface energy.The melting process of SiNWs with increasing temperature is also investigated.展开更多
Integration of molybdenum disulfide （MoS2） onto high surface area photocathod is highly desired to minimize the overpotential for the solar-powered hydrogen evolution reaction （HER）. Semiconductor nanowires （NWs...Integration of molybdenum disulfide （MoS2） onto high surface area photocathod is highly desired to minimize the overpotential for the solar-powered hydrogen evolution reaction （HER）. Semiconductor nanowires （NWs） are beneficial use in photoelectrochemistry because of their large electrochemically availab surface area and inherent ability to decouple light absorption and the transpo of minority carriers. Here, silicon （Si） NW arrays were employed as a mod photocathode system for MoS2 wrapping, and their solar-driven HER activil was evaluated. The photocathode is made up of a well-defined MoSJTiO2/Si coaxial NW heterostructure, which yielded photocurrent density up to 15 mA/cm2 （at 0 V vs. the reversible hydrogen electrode （RHE）） with goo stability under the operating conditions employed. This work reveals the earth-abundant electrocatalysts coupled with high surface area NW electrod~ can provide performance comparable to noble metal catalysts for photocathod hydrogen evolution.展开更多
In this study, we reported the design, fabrication, and characterization of well- ordered arrays of vertically-aligned, epitaxial NiSi2/Si heterostructures and single- crystalline NiSi2 nanowires on （001）Si substrat...In this study, we reported the design, fabrication, and characterization of well- ordered arrays of vertically-aligned, epitaxial NiSi2/Si heterostructures and single- crystalline NiSi2 nanowires on （001）Si substrates. The epitaxial NiSi2 with {111} facets was found to be the first and the only silicide phase formed inside the Si nanowires after annealing at a temperature as low as 300℃. Upon annealing at 500 ℃ for 4 h, the residual parts of Si nanowires were completely consumed and the NiSi2/Si heterostructured nanowires were transformed to fully silicided NiSi2 nanowires. XRD, TEM and SAED analyses indicated that all the NiSi2 nanowires were single crystalline and their axial orientations were parallel to the [001] direction. The obtained vertically-aligned NiSi2 nanowires, owing to their well-ordered arrangement, single-crystalline structure, and low effective work function, exhibit excellent field-emission properties with a very low turn-on field of 1.1 V/m. The surface wettability of the nanowires was found to switch from hydrophobic to hydrophilic after the formation of NiSi2 phase and the measured water contact angle decreased with increasing extent of Ni silicidation. The increased hydrophilicity can be explained by the Wenzel model. The obtained results present the exciting prospect that the new approach proposed here will provide the capability to fabricate other highly-ordered, vertically-aligned fully silicided nanowire arrays and may offer potential applications in constructing vertical silicide-based nanodevices.展开更多
Hydrogen evolution by electrocatalysis clean energy. However, it is challenging is an attractive method of supplying to find cheap and efficient alternatives to rare and expensive platinum based catalysts. Pt provides...Hydrogen evolution by electrocatalysis clean energy. However, it is challenging is an attractive method of supplying to find cheap and efficient alternatives to rare and expensive platinum based catalysts. Pt provides the best hydrogen evolution performance, because it optimally balances the free energies of adsorption and desorption. Appropriate control of these quantities is essential for producing an efficient electrocatalyst. We demonstrate, based on first principles calculations, a stepwise designed Rh-Au-Si ternary catalyst, in which adsorption （the Volmer reaction） and desorption （the Heyrovsky reaction） take place on Rh and Si surfaces, respectively. The intermediate Au surface plays a vital role by promoting hydrogen diffusion from the Rh to the Si surface. Theoretical predictions have been explored extensively and verified by experimental observations. The optimized catalyst （Rh-Au-SiNW-2） has a com- position of 2.2：28.5：69.3 （Rh：Au：Si mass ratio） and exhibits a Tafel slope of 24.0 mV.dec-L Its electrocatalytic activity surpasses that of a commercial 40 wt.% Pt/C catalyst at overpotentials above 0.19 V by exhibiting a current density of greater than 108 mA-cm-2. At 0.3 V overpotential, the turnover frequency of Rh-Au-SiNW-2 is 10.8 times greater than that of 40 wt.% Pt/C. These properties may open new directions in the stepwise design of highly efficient catalysts for the hydrogen evolution reaction （HER）.展开更多
Electron beam （e-beam） irradiation is an inev- itable, but crucial issue for electron microscopy. Our investigation results show the e-beam-induced in situ structural transformations in silicon （Si） nanowires and ...Electron beam （e-beam） irradiation is an inev- itable, but crucial issue for electron microscopy. Our investigation results show the e-beam-induced in situ structural transformations in silicon （Si） nanowires and zinc oxide （ZnO） nanowires （NWs）, respectively. Crystal to amorphous structure transition was revealed in Si NWs utilizing high resolution electron microscopy and electron energy loss spectroscopy. Reconstruction at the （1010） surface of ZnO NWs was also observed in the transmission electron microscope （TEM） using aberration-corrected electron microscopy. These e-beam-induced in situ struc- tural transformations prove that the electron beam irradi- ation effect is able to be used for the local modification of one-dimensional nanomaterials.展开更多
A 16 channel arrayed waveguide grating demultiplexer with 200 GHz channel spacing based on Si nanowire waveguides is designed. The transmission spectra response simulated by transmission function method shows that the...A 16 channel arrayed waveguide grating demultiplexer with 200 GHz channel spacing based on Si nanowire waveguides is designed. The transmission spectra response simulated by transmission function method shows that the device has channel spacing of 1.6 nm and crosstalk of 31 dB. The device is fabricated by 193 nm deep UV lithography in silicon-on-substrate. The demultiplexing characteristics are observed with crosstalk of 5-8 dB, central channel＇s insertion loss of 2.2 dB, flee spectral range of 24.7 nm and average channel spacing of 1.475 nm. The cause of the spectral distortion is analyzed specifically.展开更多
基金Supported by the Qing Lan Project of the Higher Education Institutions of Jiangsu Province,Qing Lan Project of Yangzhou Polytechnic Institute,the Natural Science Foundation of Yangzhou City under Grant No YZ2016123the National Natural Science Foundation of China under Grant No 61376004
文摘CdTe/CdS quantum dots（QDs） are fabricated on Si nanowires（NWs） substrates with and without Au nanoparticles（NPs）. The formation of Au NPs on Si NWs can be certified as shown in scanning electron microscopy images. The optical properties of samples are also investigated. It is interesting to find that the photoluminescence（PL） intensity of Cd Te/Cd S QD films on Si nanowire substrates with Au NPs is significantly increased,which can reach 8-fold higher than that of samples on planar Si without Au NPs. The results of finite-difference time-domain simulation indicate that Au NPs induce stronger localization of electric field and then boost the PL intensity of QDs nearby. Furthermore, the time-resolved luminescence decay curve shows the PL lifetime, which is about 5.5 ns at the emission peaks of QD films on planar, increasing from 1.8 ns of QD films on Si NWs to4.7 ns after introducing Au NPs into Si NWs.
基金partly supported by Natural Science Foundation of China (No.60876045)Shanghai Leading Basic Research Pro ject (No.09JC1405900)+2 种基金Shanghai Leading Academic Discipline Pro ject (No.S30105)R&D Foundation of SHU-SOENs PV Joint Lab (No.SS-E0700601)supported by Analysis and Testing Center of Shanghai University
文摘In order to realize ultralow surface reflectance and broadband antireflection effects which common pyramidal textures and antireflection coatings can't achieve in photovoltaic industry,we used low-cost and easy-made Ag-catalyzed etching techniques to synthesize silicon nanowires(Si NWs) arrays on the substrate of single-crystalline silicon.The dense vertically-aligned Si NWs arrays are fabricated by local oxidation and selective dissolution of Si in etching solution containing Ag catalyst.The Si NWs arrays with 3 μm in depth make reflectance reduce to less than 3% in the range of 400 to 1000 nm while reflectance gradually reached the optimum value with the increasing of etching time.The antireflection of Si NWs arrays are based on indexgraded mechanism:Si NWs arrays on a subwavelength scale strongly scatter incident light and have graded refractive index that enhance the incidence of light in usable wavelength range.However,surface recombination of Si NWs arrays are deteriorated due to numerous dangling bonds and residual Ag particles.
基金supported by the Key Program of the National Natural Science Foundation of China(No.19934003)the Grand Program of Natural Science Research of Anhui Education Department(No.ZD2007003-1)+1 种基金the Natural Science Research Program of Universities and Colleges of Anhui Province(No.KJ2008A19ZC)the Opening Program of Cultivating Baseof Anhui Key Laboratory of Spintronics and Nano-materials(No.2012YKF10)
文摘Largescale vaporsolid synthesis of ultralong silicon nitride （Si3N4） nanowires was achieved by using simple thermal evaporation of mixture powders of active carbon and monoxide silicon. The products were charac terized by Xray diffraction, scanning electron microscopy, energydispersive Xray spectroscopy, and transmission electron microscopy. The results suggest that the silicon nitride nanowires have a smooth surface, with lengths of up to several hundreds of microns and diameters of 100300 nm. A detailed study of both the chemical and structural composition was performed. Such ultralong sil icon nitride nanowires demonstrate potential applications as materials for constructing nanoscale devices and as reinforcement in advanced composites.
文摘We have investigated the optical properties of laterally aligned Si nanowire （SiNW） arrays in order to explore their potential applicability in transparent electronics. The SiNW array exhibited good optical transparency in the visible spectral range with a transmittance of -90% for a NW density of -20-25 per 10 μm. In addition, polarization-dependent measurements revealed a variation in transmittance in the range of 80%-95% depending on the angle between the polarization of incident light and the NW axis. Using the SiNWs, we demonstrated that transparent transistors exhibit good optical transparency （greater than 80%） and showed typical p-type SiNW transistor characteristics.
基金supported by Center for BioNano Health-Guardfunded by the Ministry of Science, ICT & Future Planning (MSIP) of Korea as a Global Frontier Project (HGUARD_2013M3A6B2)
文摘A facile approach was demonstrated for fabricating high-performance nonvolatile memory devices based on ferroelectric-gate field effect transistors using a p-type Si nanowire coated with omega-shaped gate organic ferroelectric poly(vinylidene fluoride-trifluoroethylene)(P(VDF-Tr FE)). We overcame the interfacial layer problem by incorporating P(VDF-Tr FE) as a ferroelectric gate using a low-temperature fabrication process. Our memory devices exhibited excellent memory characteristics with a low programming voltage of ±5 V, a large modulation in channel conductance between ON and OFF states exceeding 105, a long retention time greater than 3 9 104 s, and a high endurance of over 105 programming cycles while maintaining an ION/IOFFratio higher than 102.
基金supported by the National Natural Science Foundation of China(No.10772062)
文摘Molecular dynamics simulations with Stillinger-Weber potential are used to study the tensile and melting behavior of single-crystalline silicon nanowires（SiNWs）.The tensile tests show that the tensile behavior of the SiNWs is strongly dependent on the simulation temperature,the strain rate,and the diameter of the nanowires.For a given diameter,the critical load significantly decreases as the temperature increases and also as the strain rate decreases.Additionally,the critical load increases as the diameter increases.Moreover,the melting tests demonstrate that both melting temperature and melting heat of the SiNWs decrease with decreasing diameter and length,due to the increase in surface energy.The melting process of SiNWs with increasing temperature is also investigated.
文摘Integration of molybdenum disulfide （MoS2） onto high surface area photocathod is highly desired to minimize the overpotential for the solar-powered hydrogen evolution reaction （HER）. Semiconductor nanowires （NWs） are beneficial use in photoelectrochemistry because of their large electrochemically availab surface area and inherent ability to decouple light absorption and the transpo of minority carriers. Here, silicon （Si） NW arrays were employed as a mod photocathode system for MoS2 wrapping, and their solar-driven HER activil was evaluated. The photocathode is made up of a well-defined MoSJTiO2/Si coaxial NW heterostructure, which yielded photocurrent density up to 15 mA/cm2 （at 0 V vs. the reversible hydrogen electrode （RHE）） with goo stability under the operating conditions employed. This work reveals the earth-abundant electrocatalysts coupled with high surface area NW electrod~ can provide performance comparable to noble metal catalysts for photocathod hydrogen evolution.
文摘In this study, we reported the design, fabrication, and characterization of well- ordered arrays of vertically-aligned, epitaxial NiSi2/Si heterostructures and single- crystalline NiSi2 nanowires on （001）Si substrates. The epitaxial NiSi2 with {111} facets was found to be the first and the only silicide phase formed inside the Si nanowires after annealing at a temperature as low as 300℃. Upon annealing at 500 ℃ for 4 h, the residual parts of Si nanowires were completely consumed and the NiSi2/Si heterostructured nanowires were transformed to fully silicided NiSi2 nanowires. XRD, TEM and SAED analyses indicated that all the NiSi2 nanowires were single crystalline and their axial orientations were parallel to the [001] direction. The obtained vertically-aligned NiSi2 nanowires, owing to their well-ordered arrangement, single-crystalline structure, and low effective work function, exhibit excellent field-emission properties with a very low turn-on field of 1.1 V/m. The surface wettability of the nanowires was found to switch from hydrophobic to hydrophilic after the formation of NiSi2 phase and the measured water contact angle decreased with increasing extent of Ni silicidation. The increased hydrophilicity can be explained by the Wenzel model. The obtained results present the exciting prospect that the new approach proposed here will provide the capability to fabricate other highly-ordered, vertically-aligned fully silicided nanowire arrays and may offer potential applications in constructing vertical silicide-based nanodevices.
文摘Hydrogen evolution by electrocatalysis clean energy. However, it is challenging is an attractive method of supplying to find cheap and efficient alternatives to rare and expensive platinum based catalysts. Pt provides the best hydrogen evolution performance, because it optimally balances the free energies of adsorption and desorption. Appropriate control of these quantities is essential for producing an efficient electrocatalyst. We demonstrate, based on first principles calculations, a stepwise designed Rh-Au-Si ternary catalyst, in which adsorption （the Volmer reaction） and desorption （the Heyrovsky reaction） take place on Rh and Si surfaces, respectively. The intermediate Au surface plays a vital role by promoting hydrogen diffusion from the Rh to the Si surface. Theoretical predictions have been explored extensively and verified by experimental observations. The optimized catalyst （Rh-Au-SiNW-2） has a com- position of 2.2：28.5：69.3 （Rh：Au：Si mass ratio） and exhibits a Tafel slope of 24.0 mV.dec-L Its electrocatalytic activity surpasses that of a commercial 40 wt.% Pt/C catalyst at overpotentials above 0.19 V by exhibiting a current density of greater than 108 mA-cm-2. At 0.3 V overpotential, the turnover frequency of Rh-Au-SiNW-2 is 10.8 times greater than that of 40 wt.% Pt/C. These properties may open new directions in the stepwise design of highly efficient catalysts for the hydrogen evolution reaction （HER）.
基金supported by the NationalBasic Research Program of China(2009CB623701)the National Natural Science Foundation of China(11374174,51390471)
文摘Electron beam （e-beam） irradiation is an inev- itable, but crucial issue for electron microscopy. Our investigation results show the e-beam-induced in situ structural transformations in silicon （Si） nanowires and zinc oxide （ZnO） nanowires （NWs）, respectively. Crystal to amorphous structure transition was revealed in Si NWs utilizing high resolution electron microscopy and electron energy loss spectroscopy. Reconstruction at the （1010） surface of ZnO NWs was also observed in the transmission electron microscope （TEM） using aberration-corrected electron microscopy. These e-beam-induced in situ struc- tural transformations prove that the electron beam irradi- ation effect is able to be used for the local modification of one-dimensional nanomaterials.
基金Project supported by the National High Technology Research and Development Program of China(No.2006AA03Z420)the National Natural Science Foundation of China(Nos.60776057,60837001,60776057)
文摘A 16 channel arrayed waveguide grating demultiplexer with 200 GHz channel spacing based on Si nanowire waveguides is designed. The transmission spectra response simulated by transmission function method shows that the device has channel spacing of 1.6 nm and crosstalk of 31 dB. The device is fabricated by 193 nm deep UV lithography in silicon-on-substrate. The demultiplexing characteristics are observed with crosstalk of 5-8 dB, central channel＇s insertion loss of 2.2 dB, flee spectral range of 24.7 nm and average channel spacing of 1.475 nm. The cause of the spectral distortion is analyzed specifically.
