Anti-Reflection Characteristics of Si Nanowires for Enhanced Photoluminescence from CdTe/CdS Quantum Dots

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.

Fabrication and Optical Properties of Silicon Nanowires Arrays by Electroless Ag-catalyzed Etching

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.

Synthesis of ultralong Si_3N_4 nanowires by a simple thermal evaporation method

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.

Low-Programmable-Voltage Nonvolatile Memory Devices Based on Omega-shaped Gate Organic Ferroelectric P(VDF-TrFE) Field Effect Transistors Using p-type Silicon Nanowire Channels

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.

Atomistic simulations of the tensile and melting behavior of silicon nanowires

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.

A stepwise-designed Rh-Au-Si nanocomposite that surpasses Pt/C hydrogen evolution activity at high overpotentials

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）.

16 channel 200 GHz arrayed waveguide grating based on Si nanowire waveguides

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.

A 45-channel 100 GHz AWG based on Si nanowire waveguides

A 45-channel 100 GHz arrayed waveguide grating(AWG) based on Si nanowire waveguides is designed, simulated and fabricated. Transfer function method is used in the spectrum simulation. The simulated results show that the central wavelength and channel spacing are 1 562.1 nm and 0.8 nm, respectively, which are in accord with the designed values, and the crosstalk is about-23 dB. The device is fabricated on silicon-on-insulator(SOI) substrate by deep ultraviolet lithography(DUV) and inductively coupled plasma(ICP) etching technologies. The 45-channel 100 GHz AWG exhibits insertion loss of 6.5 dB and crosstalk of-8 dB.

Ternary nanoarray electrode with corn-inspired hierarchical design for synergistic lithium storage

Single-component anode materials can barely satisfy the growing demand for next-generation Li-ion batteries with higher capacity and cyclability. Thus developing multi-component synergistic electrodes has become a critical issue. Herein, inspired by natural corn, a ternary hierarchical self-supported array design is proposed. Based on a sequential transformation route, Si/C-modified C0304 nanowire arrays are constructed on 3D Ni foams to form a binder-free integrated electrode. Specifically, an ionic liquid-assisted electrodeposition strategy is employed to prepare discrete ultrafine Si nanoparticles on nanoscale array substrates, which follow the Volmer-Weber island growth mode. In this corn-mimetic system, kernel-like Si nanoparticles and a husk-like carbon coating layer function as enhancing and protecting units, respectively, to improve the capacity and stability of the cobalt oxide basic unit. Taking advantage of a synergistic effect, the ternary nanoarray anode achieves a significant performance enhancement compared to pristine Co304, showing a special capacity as high as -1,000 mAh·g^-1 at 100 mA·g^-1. By extending this corn-mimetic hierarchical array design to other basic, enhancing, and protecting units, new ideas for constructing synergistic nano-architectures for energy conversion and storage field are developed.