Phonon States and Dispersive Spectra of Polar Optical Phonons in Quasi-One-Dimensional Nanowires of Wurtzite ZnO and Zinc-Blend MgO Semiconductors

在宏观的绝缘的连续统模型和 Loudon 的框架以内是单轴的水晶模型， wurtzite/zinc-blende 的声子模式一个维(1D ) 圆柱的 nanowire (NW ) 被导出并且学习。声子模式的分析声子状态被给。在那里存在，这被发现极的声子模式的二种类型，即接口光(IO ) 声子模式并且限制伪(质量管理) 声子模式在 1D wurtzite/zinc-blende NW 存在。经由地量子化的标准过程， Fr ? hlich 电子声子相互作用 Hamiltonians 被获得。wurtzite/zinc-blende ZnO/MgO NW 上的这些声子模式的散行为的数字计算被执行。ZnO/MgO NW 的 IO 和质量管理声子模式的频率范围被分析并且讨论。IO 模式仅仅在一个频率范围存在，这被发现，当质量管理模式可以出现在三个频率范围时。免费波浪数字 kz 和方位角的量数字 m 上的 IO 和质量管理模式的散性质被讨论。这里获得的电子声子相互作用的分析 Hamiltonians 为进一步在 wurtzite/zinc-blende 1D NW 结构的光电子性质上调查声子影响是相当有用的。

Spin gap in quasi-one-dimensional S=3/2 antiferromagnet CoTi2O5

Quasi-one-dimensional(1D)antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra.Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi2O5 with highly ordered Co2+/Ti4+occupation,in which the Co2+ions with S=3/2 form a 1D spin chain along the a-axis.CoTi2O5 undergoes an antiferromagnetic transition at TN~24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region.Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins,by analyzing the specific heat,the thermal conductivity,and the spin-lattice relaxation rate(1/T1)as a function of temperature,we found that a spin gap is opened in the spin-excitation spectrum of CoTi2O5 around TN,manifested by the rapid decrease of magnetic specific heat to zero,the double-peak characteristic in thermal conductivity,and the exponential decay of 1/T1 below TN.Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi2O5,which induces the magnetic anisotropy in CoTi2O5,and then opens the spin gap at low temperature.

Hard Superconducting Gap in Pb Te Nanowires

Semiconductor nanowires coupled to a superconductor provide a powerful testbed for quantum device physics such as Majorana zero modes and gate-tunable hybrid qubits.The performance of these quantum devices heavily relies on the quality of the induced superconducting gap.A hard gap.

Determination of Thermal Properties of Unsmooth Si Nanowires

We estimate the thermal properties of unsmooth Si nanowires,considering key factors such as size(diameter),surface texture(roughness)and quantum size effects(phonon states)at different temperatures.For nanowires with a diameter of less than 20 nm,we highlight the importance of quantum size effects in heat capacity calculations,using dispersion relations derived from the modified frequency equation for the elasticity of a rod.The thermal conductivities of nanowires with diameters of 37,56,and 115nm are predicted using the Fuchs–Sondheimer model and Soffer’s specular parameter.Notably,the roughness parameters are chosen to reflect the technological characteristics of the real surfaces.Our findings reveal that surface texture plays a significant role in thermal conductivity,particularly in the realm of ballistic heat transfer within nanowires.This study provides practical recommendations for developing new thermal management materials.

Diameter-dependent ultra-high thermoelectric performance of ZnO nanowires

Zinc oxide(ZnO)shows great potential in electronics,but its large intrinsic thermal conductivity limits its thermoelectric applications.In this work,we explore the significant carrier transport capacity and diameter-dependent thermoelectric characteristics of wurtzite-ZnO(0001)nanowires based on first-principles and molecular dynamics simulations.Under the synergistic effect of band degeneracy and weak phonon-electron scattering,P-type(ZnO)_(73) nanowires achieve an ultrahigh power factor above 1500μW·cm^(-1)·K^(-2)over a wide temperature range.The lattice thermal conductivity and carrier transport properties of ZnO nanowires exhibit a strong diameter size dependence.When the ZnO nanowire diameter exceeds 12.72A,the carrier transport properties increase significantly,while the thermal conductivity shows a slight increase with the diameter size,resulting in a ZT value of up to 6.4 at 700 K for P-type(ZnO)_(73).For the first time,the size effect is also illustrated by introducing two geometrical configurations of the ZnO nanowires.This work theoretically depicts the size optimization strategy for the thermoelectric conversion of ZnO nanowires.

ZnO nanowires based degradable high-performance photodetectors for eco-friendly green electronics

Disposable devices designed for single and/or multiple reliable measurements over a short duration have attracted considerable interest recently. However, these devices often use non-recyclable and non-biodegradable materials and wasteful fabrication methods. Herein, we present ZnO nanowires(NWs) based degradable high-performance UV photodetectors(PDs) on flexible chitosan substrate. Systematic investigations reveal the presented device exhibits excellent photo response, including high responsivity(55 A/W), superior specific detectivity(4×10^(14) jones), and the highest gain(8.5×10~(10)) among the reported state of the art biodegradable PDs. Further, the presented PDs display excellent mechanical flexibility under wide range of bending conditions and thermal stability in the measured temperature range(5–50 ℃).The biodegradability studies performed on the device, in both deionized(DI) water(pH≈6) and PBS solution(pH=7.4),show fast degradability in DI water(20 mins) as compared to PBS(48 h). These results show the potential the presented approach holds for green and cost-effective fabrication of wearable, and disposable sensing systems with reduced adverse environmental impact.

Carbon nanotube-hyperbranched polymer core-shell nanowires with highly accessible redox-active sites for fast-charge organic lithium batteries

Organic electrode materials are promising for lithium-ion batteries(LIBs) because of their environmental friendliness and structural diversity.However,they always suffer from limited capacity,poor cycling stability,and rate performance.Herein,hexaazatrinaphthalene-based azo-linked hyperbranched polymer(HAHP) is designed and synthesized as a cathode for LIBs.However,the densely stacked morphology lowers the chance of the active sites participating in the redox reaction.To address this issue,the singlewalled carbon nanotube(SWCNT) template is used to induce the growth of nanosized HAHP on the surface of SWCNTs.The HAHP@SWCNT nanocomposites have porous structures and highly accessible active sites.Moreover,the strong π-π interaction between HAHP and highly conductive SWCNTs effectively endows the HAHP@SWCNT nanocomposites with improved cycling stability and fast charge-discharge rates.As a result,the HAHP@SWCNT nanocomposite cathode shows a high specific capacity(320.4 mA h g^(-1)at 100 mA g^(-1)),excellent cycling stability(800 cycles;290 mA h g^(-1)at 100 mA g^(-1),capacity retained 91%) and outstanding rate performance(235 mA h g^(-1)at 2000 mA g^(-1),76% capacity retention versus 50 mA g^(-1)).This work provides a strategy to combine the macromolecular structural design and micromorphology control of electrode materials for obtaining organic polymer cathodes for high-performance LIBs.

Optimized CeO_(2) Nanowires with Rich Surface Oxygen Vacancies Enable Fast Li-Ion Conduction in Composite Polymer Electrolytes

Low-cost and flexible solid polymer electrolytes are promising in all-solid-state Li-metal batteries with high energy density and safety.However,both the low room-temperature ionic conductivities and the small Li^(+)transference number of these electrolytes significantly increase the internal resistance and overpotential of the battery.Here,we introduce Gd-doped CeO_(2) nanowires with large surface area and rich surface oxygen vacancies to the polymer electrolyte to increase the interaction between Gd-doped CeO_(2) nanowires and polymer electrolytes,which promotes the Li-salt dissociation and increases the concentration of mobile Li ions in the composite polymer electrolytes.The optimized composite polymer electrolyte has a high Li-ion conductivity of 5×10^(-4)4 S cm^(-1) at 30℃ and a large Li+transference number of 0.47.Moreover,the composite polymer electrolytes have excellent compatibility with the metallic lithium anode and high-voltage LiNi_(0.8)Mn _(0.1)Co_(0.1)O_(2)(NMC)cathode,providing the stable cycling of all-solid-state batteries at high current densities.

Periodic transparent nanowires in ITO film fabricated via femtosecond laser direct writing

This paper reports the fabrication of regular large-area laser-induced periodic surface structures(LIPSSs)in indium tin oxide(ITO)films via femtosecond laser direct writing focused by a cylindrical lens.The regular LIPSSs exhibited good properties as nanowires,with a resistivity almost equal to that of the initial ITO film.By changing the laser fluence,the nanowire resistances could be tuned from 15 to 73 kΩ/mm with a consistency of±10%.Furthermore,the average transmittance of the ITO films with regular LIPSSs in the range of 1200-2000 nm was improved from 21%to 60%.The regular LIPSS is promising for transparent electrodes of nano-optoelectronic devices-particularly in the near-infrared band.

Quasi-one-dimensional characters in topological semimetal TaNiTe_(5)

One-dimensional(1D)topological insulators are superior for low-dissipation applications owing to the 1D character of surface states where scatterings other than prohibited backscattering are further restricted.Among the proposed candidates for 1D topological materials,TaNiTe_(5)has attracted intensive attention for its quasi-one-dimensional(quasi-1D)crystalline structure.In this study,we identify the chain-like construction and anisotropic electronic states on TaNiTe_5 surface with scanning tunneling microscopy.The electron scatterings are largely suppressed even with chromium impurities deposited on the surface and magnetic field applied normal to the surface,which endows TaNiTe_5 great potential for low-dissipation spintronic applications.

A simulation study of polarization characteristics of ultrathin CsPbBr3 nanowires with different cross-section shapes and sizes

The polarization characteristics of ultrathin CsPbBr3nanowires are investigated. Especially, for the height of crosssection of nanowires between 2 nm and 25 nm, the normalized intensity and polarization ratio ρ of CsPbBr3nanowires with triangular, square and hexagonal cross-section shapes are compared. The results show that, along with the increase of the height of cross-section, the polarization ratios of these three nanowires decrease until T = 15 nm, and increase afterwards.Also, along with the increase of the cross-section area up to 100 nm~2, the polarization ratios of these three nanowires increase too. In general, for the same height or area, the polarization ratio ρ of these nanowires follows ρhexagon> ρsquare>ρtriangle. Therefore, the nanowire with the hexagonal cross-section should be chosen, where for a cross-section height of 2 nm and a length-height ratio of 20 : 1, the maximal polarization ratio is 0.951 at the longitudinal center of the NW. Further,for the hexagonal NW with a cross-section height of 10 nm, the hexagonal NW with a length-height ratio of 45 : 1 exhibits the maximal polarization ratio at the longitudinal center of the NW. These simulation results predict the feasible size and shape of CsPbBr3nanowire devices with high polarization ratios.

Coral-like and binder-free carbon nanowires for potassium dual-ion batteries with superior rate capability and long-term cycling life

Owing to the advantages of high operating voltage,environmental benignity,and low cost,potassium-based dual-ion batteries(KDIBs)have been considered as a potential candidate for large-scale energy storage.However,KDIBs generally suffer from poor cycling performance and unsatisfied capacity,and inactive components of conductive agents,binders,and current collector further lower their overall capacity.Herein,we prepare coral-like carbon nanowres(CCNWs)doped with nitrogen as a binder-free anode material for K^(+)-ion storage,in which the unique coral-like porous nanostructure and amorphous/short-range-ordered composite feature are conducive to enhancing the structural stability,to facilitating the ion transfer and to boosting the full utilization of active sites during potassiation/de-potassiation process.As a result,the CCNW anode possesses a hybrid K^(+)-storage mechanism of diffusive behavior and capacitive adsorption,and stably delivers a high capacity of 276 mAh g^(-1)at 50 mA g^(-1),good rate capability up to 2 A g^(-1),and long-term cycling stability with 93%capacity retention after 2000 cycles at 1 A g^(-1).Further,assembling this CCNW anode with an environmentally benign expanded graphite(EG)cathode yields a proof-of-concept KDIB,which shows a high specific capacity of 134.4 mAh g^(-1)at 100 mA g^(-1),excellent rate capability of 106.5 mAh g^(-1)at 1 A g^(-1),and long-term cycling stability over 1000 cycles with negligible capacity loss.This study provides a feasible approach to developing high-performance anodes for potassium-based energy storage devices.

Monodispersed ultrathin twisty PdBi alloys nanowires assemblies with tensile strain enhance C_(2+)alcohols electrooxidation

Direct alcohol fuel cells(DAFCs)are powered by the alcohol electro-oxidation reaction(AOR),where an electrocatalyst with an optimal electronic structure can accelerate the sluggish AOR.Interestingly,strain engineering in hetero-catalysis offers a promising route to boost their catalytic activity.Herein,we report on a class of monodispersed ultrathin twisty PdBi alloy nanowires(TNWs)assemblies with face-centered structures that drive AORs.These thin nanowire structures expose a large number of reactive sites.Strikingly,Pd_(6)Bi_(1)TNWs show an excellent current density of 2066,3047,and 1231 mA mg_(Pd)^(-1)for oxidation of ethanol,ethylene glycol,and glycerol,respectively.The“volcano-like”behaviors observed on PdBi TNWs for AORs indicate that the maximum catalytic mass activity is a well balance between active intermediates and blocking species at the interface.This study offers an effective and universal method to build novel nanocatalysts in various applications by rationally designing highly efficient catalysts with specific strain.

Pick-up strategies for and electrical characterization of ZnO nanowires with a SEM-based nanomanipulator

Because of their unique mechanical and electrical properties,zinc oxide(ZnO)nanowires are used widely in microscopic and nanoscopic devices and structures,but characterizing them remains challenging.In this paper,two pick-up strategies are proposed for characterizing the electrical properties of ZnO nanowires using SEM equipped with a nanomanipulator.To pick up nanowires efficiently,direct sampling is compared with electrification fusing,and experiments show that direct sampling is more stable while electrification fusing is more efficient.ZnO nanowires have cut-off properties,and good Schottky contact with the tungsten probes was established.In piezoelectric experiments,the maximum piezoelectric voltage generated by an individual ZnO nanowire was 0.07 V,and its impedance decreased with increasing input signal frequency until it became stable.This work offers a technical reference for the pick-up and construction of nanomaterials and nanogeneration technology.

Fluxless bonding with silver nanowires aerogel in die-attached interconnection

The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention for high conduction and low density. However,the noble metal aerogels with outstanding solderability were rarely studied. This work has successfully synthesized an aerogel derived from silver nanowires(AgNWs) using a liquid phase reduction method. It is found that the noble metal aerogels can be made into diverse aerogel preformed soldering sheets. The influence of bonding temperature(150-300 ℃), time(2-20 min), and pressure(5-20 MPa) on the joint strength of the AgNWs aerogel affixed to electroless nickel/silver copper plates were investigated. Additionally, the AgNWs aerogel displays almost the same shear strength for substrates of various sizes. In a word, this study presents a flux-free, high-strength, and adaptable soldering structural material.

Pt-Te alloy nanowires towards formic acid electrooxidation reaction

The high-performance anodic electrocatalysts is pivotal for realizing the commercial application of the direct formic acid fuel cells.In this work,a simple polyethyleneimine-assisted galvanic replacement reaction is applied to synthesize the high-quality PtTe alloy nanowires(PtTe NW)by using Te NW as an efficient sacrificial template.The existence of Te atoms separates the continuous Pt atoms,triggering a direct reaction pathway of formic acid electrooxidation reaction(FAEOR)at PtTe NW.The one-dimensional architecture and highly active sites have enabled PtTe NW to reveal outstanding electrocatalytic activity towards FAEOR with the mass/specific activities of 1091.25 mA mg^(-1)/45.34 A m^(-2)at 0.643 V potential,which are 44.72/23.16 and 20.26/11.75 times bigger than those of the commercial Pt and Pd nanoparticles,respectively.Density functional theory calculations reveal that Te atoms optimize the electronic structure of Pt atoms,which decreases the adsorption capacity of CO intermediate and simultaneously improves the durability of PtTe NW towards FAEOR.This work provides the valuable insights into the synthesis and design of efficient Pt-based alloy FAEOR electrocatalysts.

Multi-segmented nanowires for vortex magnetic domain wall racetrack memory

A vortex domain wall's(VW) magnetic racetrack memory's high performance depends on VW structural stability,high speed, low power consumption and high storage density. In this study, these critical parameters were investigated in magnetic multi-segmented nanowires using micromagnetic simulation. Thus, an offset magnetic nanowire with a junction at the center was proposed for this purpose. This junction was implemented by shifting one portion of the magnetic nanowire horizontally in the x-direction(l) and vertically(d) in the y-direction. The VW structure became stable by manipulating magnetic properties, such as magnetic saturation(M_(4)) and magnetic anisotropy energy(K_(u)). In this case, increasing the values of M_(4) ≥ 800 kA/m keeps the VW structure stable during its dynamics and pinning and depinning in offset nanowires,which contributes to maintenance of the storage memory's lifetime for a longer period. It was also found that the VW moved with a speed of 500 m/s, which is desirable for VW racetrack memory devices. Moreover, it was revealed that the VW velocity could be controlled by adjusting the offset area dimensions(l and d), which helps to drive the VW by using low current densities and reducing the thermal-magnetic spin fluctuations. Further, the depinning current density of the VW(J_(d)) over the offset area increases as d increases and l decreases. In addition, magnetic properties, such as the M_(4) and K_(u),can affect the depinning process of the VW through the offset area. For high storage density, magnetic nanowires(multisegmented) with four junctions were designed. In total, six states were found with high VW stability, which means three bits per cell. Herein, we observed that the depinning current density(J_(d)) for moving the VW from one state to another was highly influenced by the offset area geometry(l and d) and the material's magnetic properties, such as the M_(4) and K_(u).

Restructuring of 4H Phase Au Nanowires and its Catalytic Behavior toward CO Electro-oxidation

Au nanowires in 4H crystalline phase(4H Au NWs)are synthesized by colloid solution methods.The crys-talline phase and surface structure as well as its performance toward electrochemical oxidation of CO be-fore and after removing adsorbed oleylamine molecules(OAs)intro-duced from its synthesis are evaluat-ed by high-resolution transmission electron microscopy(HR-TEM),X-ray diffraction(XRD),underpoten-tial deposition of Pb(Pb-upd)and cyclic voltammetry.Different methods,i.e.acetic acid cleaning,electrochemical oxidation cleaning,and diethylamine replacement,have been tried to remove the adsorbed OAs.For all methods,upon the removal of the adsorbed OAs,the morphology of 4H gold nanoparticles is found to gradually change from nanowires to large dumbbell-shaped nanoparticles,accompanying with a transition from the 4H phase to the face-centered cubic phase.On the other hand,the Pb-upd results show that the sample sur-faces have almost the same facet composition before and after removal of the adsorbed OAs.After electrochemical cleaning with continuous potential scans up to 1.3 V,CO electro-oxida-tion activity of the 4H Au sample is significantly improved.The CO electro-oxidation activi-ty is compared with results on the three basel Au single crystalline surfaces reported in the lit-erature,possible origins for its enhancement are discussed.

Exploring reservoir computing:Implementation via double stochastic nanowire networks

Neuromorphic computing,inspired by the human brain,uses memristor devices for complex tasks.Recent studies show that self-organizing random nanowires can implement neuromorphic information processing,enabling data analysis.This paper presents a model based on these nanowire networks,with an improved conductance variation profile.We suggest using these networks for temporal information processing via a reservoir computing scheme and propose an efficient data encoding method using voltage pulses.The nanowire network layer generates dynamic behaviors for pulse voltages,allowing time series prediction analysis.Our experiment uses a double stochastic nanowire network architecture for processing multiple input signals,outperforming traditional reservoir computing in terms of fewer nodes,enriched dynamics and improved prediction accuracy.Experimental results confirm the high accuracy of this architecture on multiple real-time series datasets,making neuromorphic nanowire networks promising for physical implementation of reservoir computing.

基于Pd-Ni/Si Nanowires电极室内甲醛实时监测处理装置

研究设计一种室内甲醛气体实时监测和处理一体化装置。首先,通过电化学方法刻蚀大面积硅纳米线阵列并通过无电镀技术制备镍/硅纳米线(Ni/Si Nanowires)和钯-镍/硅纳米线(Pd-Ni/Si Nanowires)阵列电极,Pd-Ni/Si Nanowires阵列电极对甲醛有很强电化学催化氧化作用,以其为电化学甲醛传感器工作阳极,以Ni/Si Nanowires阵列为对电极,Ag/AgCl为参考电极,循环伏安技术测试结果显示该传感器对甲醛浓度灵敏度高达0.265 mA/(mmol/L),三倍信噪比检测限为2μmol/L。其次,利用STC12C5410AD单片机产生三角波扫描电压模拟循环伏安原理,可利用回路中因催化氧化产生的峰电流值来监测室内甲醛浓度,并进一步通过恒压电催化将甲醛处理。该设计方案新颖、成本低廉、便于携带,具有较大实际应用价值。