Perforated nitrogen-rich graphene-like carbon nanolayers supported Cu-In catalyst for boosting CO_(2) electroreduction to CO

The combination of a powerful CO_(2)-enriching carrier and robust active component provides a new idea for the construction of efficient catalysts for electrocatalytic CO_(2)reduction.Herein,novel perforated nitrogen-rich graphene-like carbon nanolayers(PNGC)are prepared from biomass derivatives,which promotes the oriented deposition of In-doped Cu_(2)(OH)_(3)(NO_(3))nanosheet patches.A robust Cu-In/PNGC composite catalyst is then obtained via simple in-situ electrochemical reduction.Unsurprisingly,CuIn/PNGC exhibits a CO Faradaic efficiency(FECO)of 91.3%and a remarkable CO partial current density(jCO)of 136.4 m A cm^(-2)at a moderate overpotential of 0.59 V for electrocatalytic CO_(2)reduction reaction(CO_(2)RR).DFT calculations and experimental studies indicate that the strong carrier effect of PNGC makes PNGC carried Cu-In nanosheets improved the adsorption capacity of CO_(2)gas,reconfigured electronic structure,and reduced free energy of key intermediate formation,thereby the CO_(2)activation and conversion are promoted.

Quantum confinement of carriers in the type-I quantum wells structure

Quantum confinement is recognized to be an inherent property in low-dimensional structures.Traditionally,it is believed that the carriers trapped within the well cannot escape due to the discrete energy levels.However,our previous research has revealed efficient carrier escape in low-dimensional structures,contradicting this conventional understanding.In this study,we review the energy band structure of quantum wells along the growth direction considering it as a superposition of the bulk material dispersion and quantization energy dispersion resulting from the quantum confinement across the whole Brillouin zone.By accounting for all wave vectors,we obtain a certain distribution of carrier energy at each quantized energy level,giving rise to the energy subbands.These results enable carriers to escape from the well under the influence of an electric field.Additionally,we have compiled a comprehensive summary of various energy band scenarios in quantum well structures relevant to carrier transport.Such a new interpretation holds significant value in deepening our comprehension of low-dimensional energy bands,discovering new physical phenomena,and designing novel devices with superior performance.

Reanalysis of energy band structure in the type-II quantum wells

Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semiconductor structures and exploring their potential applications in practice. For quantum well structures, the energy of carriers in the well splits into discrete energy levels due to the confinement of barriers in the growth direction. However, the discrete energy levels obtained at a fixed wave vector cannot accurately reflect the actual energy band structure. In this work, the band structure of the type-II quantum wells is reanalyzed. When the wave vectors of the entire Brillouin region(corresponding to the growth direction) are taken into account, the quantized energy levels of the carriers in the well are replaced by subbands with certain energy distributions. This new understanding of the energy bands of low-dimensional structures not only helps us to have a deeper cognition of the structure, but also may overturn many viewpoints in traditional band theories and serve as supplementary to the band theory of low-dimensional systems.

Relation of V/III ratio of AlN interlayer with the polarity of nitride

N-polar GaN film was obtained by using a high-temperature AlN buffer layer.It was found that the polarity could be inverted by a thin low-temperature AlN interlayer with the same V/III ratio as that of the high-temperature AlN layer.Continuing to increase the V/III ratio of the low-temperature AlN interlayer,the Ga-polarity of GaN film was inverted to N-polarity again but the crystal quality and surface roughness of GaN film greatly deteriorated.Finally,we analyzed the chemical environment of the AlN layer by x-ray photoelectron spectroscopy(XPS),which provides a new direction for the control of GaN polarity.

Formulation of Work-Study Combined and Result-Oriented Integrated Curriculum Standards

According to the Annex Technical Regulations for Integrated Curriculum Development(Trial)in Document No.30 of the General Office of the Ministry of Human Resources and Social Security(2012),this paper studies the formulation of the curriculum standards for the integration of Chinese medicinal materials production.We focus on the formulation ideas of the curriculum standards for the integration of Chinese medicinal materials production,the formulation process of the curriculum standards for the integration of Chinese medicinal materials production,including the description of typical work tasks,the determination of curriculum objectives,the analysis of study content,the description of referential study tasks,teaching implementation suggestions,assessment and evaluation suggestions,which can provide a reference for the development and research of other related integrated courses.

Characteristics of AlGaN/GaN high electron mobility transistors on metallic substrate

We have successfully prepared GaN based high electron mobility transistors(HEMTs)on metallic substrates transferred from silicon substrates by electroplating technique.GaN HEMTs on Cu substrates are demonstrated to basically have the same good electric characteristics as the chips on Si substrates.Furthermore,the better heat dissipation of HEMTs on Cu substrates compared to HEMTs on Si substrates is clearly observed by thermoreflectance imaging,showing the promising potential for very high-power and high-temperature operation.This work shows the outstanding ability of HEMT chips on Cu substrates for solving the self-heating effect with the advantages of process simplicity,high yield,and low production requirement.

Absorption Enhancement of Silicon Solar Cell in a Positive-Intrinsic-Negative Junction

Absorption coefficient is a physical parameter to describe electromagnetic energy absorption of materials, which is closely related to solar cells and photodetectors. We grow a series of positive-intrinsic-negative(PIN) structures on silicon wafer by a gas source molecule beam epitaxy system and the investigate the absorption coefficient through the photovoltaic processes in detail. It is found that the absorption coefficient is enhanced by one order and can be tuned greatly through the thickness of the intrinsic layer in the PIN structure, which is also demonstrated by the 730-nm-wavelength laser irradiation. These results cannot be explained by the traditional absorption theory.We speculate that there could be some uncovered mechanism in this system, which will inspire us to understand the absorption process further.

Insight into pyrolysis of hydrophobic silica aerogels:Kinetics,reaction mechanism and effect on the aerogels

Silica aerogels have promising applications in thermal insulation,but their flammability and reaction mechanisms have rarely been investigated.The pyrolysis kinetics and thermodynamics of hydrophobic silica aerogels under N_(2) environment were studied.The kinetic and thermodynamic parameters were obtained by three model-free methods.Based on the calculated kinetic parameters,the pyrolysis mechanism of silica aerogels was discussed by the master plots method.The results indicate that the reactions of the whole pyrolysis phase can be characterized by a random nuclear model.In addition,FTIR test results show that the volatile products of silica aerogel pyrolysis are mainly hydrocarbons generated by the decomposition of hydrophobic groups(methyl groups)on the surface.Finally,the effects of pyrolysis on the properties of silica aerogels Finally,the effects of pyrolysis on the properties of silica aerogels were investigated based on the analysis results of SEM,specific surface area,pore size distribution,X-ray diffraction,XPS and infrared spectroscopy.

Origin of anomalous enhancement of the absorption coefficient in a PN junction

The absorption coefficient is usually considered as a constant for certain materials at the given wavelength.However,recent experiments demonstrated that the absorption coefficient could be enhanced a lot by the PN junction.The absorption coefficient varies with the thickness of the intrinsic layer in a PIN structure.Here,we interpret the anomalous absorption coefficient from the competition between recombination and drift for non-equilibrium carriers.Based on the Fokker-Planck theory,a non-equilibrium statistical model that describes the relationship between absorption coefficient and material thickness has been proposed.It could predict the experimental data well.Our results can give new ideas to design photoelectric devices.

Sphere-shaped SiGe micro/nanostructures with tunable Ge composition and size formed by laser irradiation

SiGe spheres with different diameters are successfully fabricated on a virtual SiGe template using a laser irradiation method.The results from scanning electron microscopy and micro-Raman spectroscopy reveal that the diameter and Ge composition of the SiGe spheres can be well controlled by adjusting the laser energy density.In addition,the transmission electron microscopy results show that Ge composition inside the SiGe spheres is almost uniform in a well-defined,nearly spherical outline.As a convenient method to prepare sphere-shaped SiGe micro/nanostructures with tunable Ge composition and size,this technique is expected to be useful for SiGe-based material growth and micro/optoelectronic device fabrication.

Effect of Pt Interlayer on Low Resistivity Ohmic Contact to p-InP Layer and Its Optimization

The contact characteristic between p-InP and metal plays an important role in InP-related optoelectronic and microelectronic device applications.We investigate the low-resistance Au/Pt/Ni and Au/Ni ohmic contacts to p-InP based on the solid phase regrowth principle.The lowest specific contact resistivity of Au(100 nm)/Pt(115 nm)/Ni(50 nm)can reach 2.64×10^(-6)Ω·cm^(2) after annealing at 380℃ for 1 min,while the contact characteristics of Au/Ni deteriorated after annealing from 340℃ to 480℃ for 1 min.The results of scanning electron microscopy,atomic force microscopy and x-ray photoelectron spectroscopy show that the Pt layer is an important factor in improving the contact characteristics.The Pt layer prevents the diffusion of In and Au,inhibits the formation of Au3In metal compounds,and prevents the deterioration of the ohmic contact.The metal structures and optimized annealing process is expected to be helpful for obtaining high-performance InP-related devices.

Hierarchically porous carbon/red phosphorus composite for high-capacity sodium-ion battery anode

Red phosphorus has received remarkable attention as a promising anode material for sodium ion batteries(NIBs) due to its high theoretical capacity. However, its practical application has been impeded by its intrinsic low electronic conductivity and large volume variations during sodiation/desodiation process. Here, we design a composite to confine nanosized red phosphorus into the hierarchically porous carbon(HPC) walls by a vaporization-condensation strategy. The mass loading of P in the HPC/P composite is optimized to deliver a reversible specific capacity of 2,202 m Ah/gpbased on the mass of red P(836 m Ah/gcompositebased on the total composite mass), a high capacity retention over 77% after100 cycles, and excellent rate performance of 929 m Ah/gpat 2 C. The hierarchical porous carbon serves as the conductive networks, downsize the red phosphorus to nanoscale, and provide free space to accommodate the large volume expansions. The suppressed mechanical failure of the red phosphorus also enhances the stability of solid-electrolyte interface(SEI) layer, which is confirmed by the microscopy and impedance spectroscopy after the cycling tests. Our studies provide a feasible approach for potentially viable high-capacity NIB anode.

Self-powered electrochromic devices with tunable infrared intensity

Triboelectric nanogenerator （TENG） is an efficient way to convert ambient mechanical energy into electricity to power up portable electronics. In this work, a flexible inflared electrochromical device （IR-ECD） with stable performances was assembled with a TENG for building self-powered infrared detector with tunable intensity. As driven by TENG, the electrochromic device could be operated in the mid-lR region due to the reversible electrochromic reactions. An average infrared reflectance contrast of 46% was achieved in 8-14 μm regions and as well a clear thermal image change can be observed. This work indicates that the TENG-driven infrared electrochromical device has potential for use in self-powered camouflage and tbermal control.

Hybrid nano-scale Au with ITO structure for a high-performance near-infrared silicon-based photodetector with ultralow dark current

An internal photoemission-based silicon photodetector detects light below the silicon bandgap at room temperature and can exhibit spectrally broad behavior,making it potentially suited to meet the need for a near-infrared pure Si photodetector.In this work,the implementation of a thin Au insertion layer into an ITO/n-Si Schottky photodetector can profoundly affect the barrier height and significantly improve the device performance.By fabricating a nanoscale thin Au layer and an ITO electrode on a silicon substrate,we achieve a well-behaved ITO/Au/n-Si Schottky diode with a record dark current density of 3.7×10^(−7) A/cm^(2) at−1 V and a high rectification ratio of 1.5×10^(8) at±1 V.Furthermore,the responsivity has been obviously improved without sacrificing the dark current performance of the device by decreasing the Au thickness.Such a silicon-based photodetector with an enhanced performance could be a promising strategy for the realization of a monolithic integrated pure silicon photodetector in optical communication.