Synthesizing active and durable cubic ceria catalysts(<6 nm)for fast dehydrogenation of bio-polyols to carboxylic acids coproducing green H_(2)

Dehydrogenation is considered as one of the most important industrial applications for renewable energy.Cubic ceria-based catalysts are known to display promising dehydrogenation performances in this area.Large particle size(>20 nm)and less surface defects,however,hinder further application of ceria materials.Herein,an alternative strategy involving lactic acid(LA)assisted hydrothermal method was developed to synthesize active,selective and durable cubic ceria of<6 nm for dehydrogenation reactions.Detailed studies of growth mechanism revealed that,the carboxyl and hydroxyl groups in LA molecule synergistically manipulate the morphological evolution of ceria precursors.Carboxyl groups determine the cubic shape and particle size,while hydroxyl groups promote compositional transformation of ceria precursors into CeO_(2) phases.Moreover,enhanced oxygen vacancies(Vo)on the surface of CeO_(2) were obtained owing to continuous removal of O species under reductive atmosphere.Cubic CeO_(2) catalysts synthesized by the LA-assisted method,immobilized with bimetallic PtCo clusters,exhibit a record high activity(TOF:29,241 h^(-1))and Vo-dependent synergism for dehydrogenation of bio-derived polyols at 200℃.We also found that quenching Vo defects at air atmosphere causes activity loss of PtCo/CeO_(2) catalysts.To regenerate Vo defects,a simple strategy was developed by irradiating deactivated catalysts using hernia lamp.The outcome of this work will provide new insights into manufacturing durable catalyst materials for aqueous phase dehydrogenation applications.

Regulating the dopant clustering in LiZnAs-based diluted magnetic semiconductor

Tuning of the magnetic interaction plays the vital role in reducing the clustering of magnetic dopant in diluted magnetic semiconductors(DMS).Due to the not well understood magnetic mechanism and the interplay between different magnetic mechanisms,no efficient and universal tuning strategy is proposed at present.Here,the magnetic interactions and formation energies of isovalent-doped(Mn) and aliovalent(Cr)-doped LiZnAs are studied based on density functional theory(DFT).It is found that the dopant–dopant distance-dependent magnetic interaction is highly sensitive to the carrier concentration and carrier type and can only be explained by the interplay between two magnetic mechanisms,i.e.,superexchange and Zener’s p–d exchange model.Thus,the magnetic behavior and clustering of magnetic dopant can be tuned by the interplay between two magnetic mechanisms.The insensitivity of the tuning effect to U parameter suggests that our strategy could be universal to other DMS.

Anomalous bond lengthening in compressed magnetic doped semiconductor Ba(Zn_(0.95)Mn_(0.05))_(2)As_(2)

Applying pressure has been evidenced as an effective method to control the properties of semiconductors,owing to its capability to modify the band configuration around Fermi energy.Correspondingly,structural evolutions under external pres-sures are required to analyze the mechanisms.Herein high-pressure structure of a magnetic doped semiconductor Ba(Zn_(0.95)Mn_(0.05))_(2)As_(2)is studied with combination of in-situ synchrotron X-ray diffractions and diamond anvil cells.The materials become ferromagnetic with Curie temperature of 105 K after further 20%K doping.The title material undergoes an isostruc-tural phase transition at around 19 GPa.Below the transition pressure,it is remarkable to find lengthening of Zn/Mn-As bond within Zn/MnAs layers,since chemical bonds are generally shortened with applying pressures.Accompanied with the bond stretch,interlayer As-As distances become shorter and the As-As dimers form after the phase transition.With further compres-sion,Zn/Mn-As bond becomes shortened due to the recovery of isotropic compression on the Zn/MnAs layers.

Functional Confirmation Using a Medical X-Ray System of a Semiconductor Survey Meter

In recent years, semiconductor survey meters have been developed and are in increasing demand worldwide. This study determined if it is possible to use the X-ray system installed in each medical facility to calculate the time constant of a semiconductor survey meter and confirm the meter’s function. An additional filter was attached to the medical X-ray system to satisfy the standards of N-60 to N-120, more copper plates were added as needed, and the first and second half-value layers were calculated to enable comparisons of the facility’s X-ray system quality with the N-60 to N-120 quality values. Next, we used a medical X-ray system to measure the leakage dose and calculate the time constant of the survey meter. The functionality of the meter was then checked and compared with the energy characteristics of the meter. The experimental results showed that it was possible to use a medical X-ray system to reproduce the N-60 to N-120 radiation quality values and to calculate the time constant from the measured results, assuming actual leakage dosimetry for that radiation quality. We also found that the calibration factor was equivalent to that of the energy characteristics of the survey meter.

Enhanced magnetic anisotropy and high hole mobility in magnetic semiconductor Ga_(1-x-y)Fe_(x)Ni_(y)Sb

(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,Fe)Sb is below 7.6×10^(3)erg/cm^(3)when Fe concentration is lower than 30%,which is one order of magnitude lower than that of(Ga,Mn)As.To address this issue,we grew Ga_(1-x-y)Fe_(x)Ni_(y)Sb films with almost the same x(≈24%)and different y to characterize their magnetic and electrical transport properties.We found that the magnetic anisotropy of Ga_(0.76-y)Fe_(0.24)Ni_(y)Sb can be enhanced by increasing y,in which Ku is negligible at y=1.7%but increases to 3.8×10^(5)erg/cm^(3)at y=6.1%(T_(C)=354 K).In addition,the hole mobility(μ)of Ga_(1-x-y)Fe_(x)Ni_(y)Sb reaches 31.3 cm^(2)/(V∙s)at x=23.7%,y=1.7%(T_(C)=319 K),which is much higher than the mobility of Ga_(1-x)Fe_(x)Sb at x=25.2%(μ=6.2 cm^(2)/(V∙s)).Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of(Ga,Fe)Sb by using Ni co-doping.

Indentation behavior of a semi-infinite piezoelectric semiconductor under a rigid flat-ended cylindrical indenter

This paper theoretically studies the axisymmetric frictionless indentation of a transversely isotropic piezoelectric semiconductor(PSC)half-space subject to a rigid flatended cylindrical indenter.The contact area and other surface of the PSC half-space are assumed to be electrically insulating.By the Hankel integral transformation,the problem is reduced to the Fredholm integral equation of the second kind.This equation is solved numerically to obtain the indentation behaviors of the PSC half-space,mainly including the indentation force-depth relation and the electric potential-depth relation.The results show that the effect of the semiconductor property on the indentation responses is limited within a certain range of variation of the steady carrier concentration.The dependence of indentation behavior on material properties is also analyzed by two different kinds of PSCs.Finite element simulations are conducted to verify the results calculated by the integral equation technique,and good agreement is demonstrated.

Analysis of piezoelectric semiconductor fibers under gradient temperature changes

Piezoelectric semiconductors(PSs)possess both semiconducting properties and piezoelectric coupling effects,making them optimal building blocks for semiconductor devices.PS fiber-like structures have wide applications in multi-functional semiconductor devices.In this paper,a one-dimensional(1D)theoretical model is established to describe the piezotronic responses of a PS fiber under gradient temperature changes.The theoretical model aims to explain the mechanism behind the resistance change caused by such gradient temperature changes.Numerical results demonstrate that a gradient temperature change significantly affects the physical fields within the PS fiber,and can induce changes in its surface resistance.It provides important theoretical guidance on the development of piezotronic devices that are sensitive to temperature effects.

Identifying the enhancement mechanism of Al/MoO_(3) reactive multilayered films on the ignition ability of semiconductor bridge using a one-dimensional gas-solid two-phase flow model

Energetic Semiconductor bridge(ESCB)based on reactive multilayered films(RMFs)has a promising application in the miniature and intelligence of initiator and pyrotechnics device.Understanding the ignition enhancement mechanism of RMFs on semiconductor bridge(SCB)during the ignition process is crucial for the engineering and practical application of advanced initiator and pyrotechnics devices.In this study,a one-dimensional(1D)gas-solid two-phase flow ignition model was established to study the ignition process of ESCB to charge particles based on the reactivity of Al/MoO_(3) RMFs.In order to fully consider the coupled exothermic between the RMFs and the SCB plasma during the ignition process,the heat release of chemical reaction in RMFs was used as an internal heat source in this model.It is found that the exothermal reaction in RMFs improved the ignition performance of SCB.In the process of plasma rapid condensation with heat release,the product of RMFs enhanced the heat transfer process between the gas phase and the solid charge particle,which accelerated the expansion of hot plasma,and heated the solid charge particle as well as gas phase region with low temperature.In addition,it made up for pressure loss in the gas phase.During the plasma dissipation process,the exothermal chemical reaction in RMFs acted as the main heating source to heat the charge particle,making the surface temperature of the charge particle,gas pressure,and gas temperature rise continuously.This result may yield significant advantages in providing a universal ignition model for miniaturized ignition devices.

The room temperature ferromagnetism in highly strained twodimensional magnetic semiconductors

In spintronics,it is still a challenge in experiments to realize the ferromagnetic semiconductors with Curie temperature Tc above room temperature.In 2017,the successful synthesis of two-dimensional(2D)van der Waals ferromagnetic semiconductors,including the monolayer CrI3 with Tc=45 K[1]and the bilayer Cr2Ge2Te6 with Tc=28 K[2]in experiments,has attracted extensive attention in the 2D ferromagnetic semiconductors.One of the key problems is to find suitable 2D magnetic semiconductors,which can have room-temperature operation as required in applications.

Electrospun Semiconductor-Based Nano-Heterostructures for Photocatalytic Energy Conversion and Environmental Remediation:Opportunities and Challenges

Harvesting solar energy to drive the semiconductor photocatalysis offers a promising tactic to address ever-growing challenges of both energy shortage and environmental pollution.Design and synthesis of nano-heterostructure photocatalysts with controllable components and morphologies are the key factors for achieving highly efficient photocatalytic processes.Onedimensional(1D)semiconductor nanofibers produced by electrospinning possess a large ratio of length to diameter,high ratio of surface to volume,small grain sizes,and high porosity,which are ideally suited for photocatalytic reactions from the viewpoint of structure advantage.After the secondary treatment of these nanofibers through the solvothermal,gas reduction,in situ doping,or assembly methods,the multi-component nanofibers with hierarchical nano-heterostructures can be obtained to further enhance their light absorption and charge carrier separation during the photocatalytic processes.In recent years,the electrospun semiconductorbased nano-heterostructures have become a“hot topic”in the fields of photocatalytic energy conversion and environmental remediation.This review article summarizes the recent progress in electrospinning synthesis of various kinds of high-performance semiconductor-based nano-heterostructure photocatalysts for H2 production,CO_(2) reduction,and decomposition of pollutants.The future perspectives of these materials are also discussed.

Application and prospect of semiconductor biosensors in detection of viral zoonoses

The rapid spread of viral zoonoses can cause severe consequences,including huge economic loss,public health problems or even global crisis of society.Clinical detection technology plays a very important role in the prevention and control of such zoonoses.The rapid and accurate detection of the pathogens of the diseases can directly lead to the early report and early successful control of the diseases.With the advantages of being easy to use,fast,portable,multiplexing and cost-effective,semiconductor biosensors are kinds of detection devices that play an important role in preventing epidemics,and thus have become one of the research hotspots.Here,we summarized the advances of semiconductor biosensors in viral zoonoses detection.By discussing the major principles and applications of each method for different pathogens,this review proposed the directions of designing semiconductor biosensors for clinical application and put forward perspectives in diagnostic of viral zoonoses.

Pinning energies of organic semiconductors in high-efficiency organic solar cells

With the emergence of new materials for high-efficiency organic solar cells(OSCs),understanding and finetuning the interface energetics become increasingly important.Precise determination of the so-called pinning energies,one of the critical characteristics of the material to predict the energy level alignment(ELA)at either electrode/organic or organic/organic interfaces,are urgently needed for the new materials.Here,pinning energies of a wide variety of newly developed donors and nonfullerene acceptors(NFAs)are measured through ultraviolet photoelectron spectroscopy.The positive pinning energies of the studied donors and the negative pinning energies of NFAs are in the same energy range of 4.3−4.6 eV,which follows the design rules developed for fullerene-based OSCs.The ELA for metal/organic and inorganic/organic interfaces follows the predicted behavior for all of the materials studied.For organic-organic heterojunctions where both the donor and the NFA feature strong intramolecular charge transfer,the pinning energies often underestimate the experimentally obtained interface vacuum level shift,which has consequences for OSC device performance.

Atomic layer deposition for nanoscale oxide semiconductor thin film transistors:review and outlook

Since the first report of amorphous In–Ga–Zn–O based thin film transistors,interest in oxide semiconductors has grown.They offer high mobility,low off-current,low process temperature,and wide flexibility for compositions and processes.Unfortunately,depositing oxide semiconductors using conventional processes like physical vapor deposition leads to problematic issues,especially for high-resolution displays and highly integrated memory devices.Conventional approaches have limited process flexibility and poor conformality on structured surfaces.Atomic layer deposition(ALD)is an advanced technique which can provide conformal,thickness-controlled,and high-quality thin film deposition.Accordingly,studies on ALD based oxide semiconductors have dramatically increased recently.Even so,the relationships between the film properties of ALD-oxide semiconductors and the main variables associated with deposition are still poorly understood,as are many issues related to applications.In this review,to introduce ALD-oxide semiconductors,we provide:(a)a brief summary of the history and importance of ALD-based oxide semiconductors in industry,(b)a discussion of the benefits of ALD for oxide semiconductor deposition(in-situ composition control in vertical distribution/vertical structure engineering/chemical reaction and film properties/insulator and interface engineering),and(c)an explanation of the challenging issues of scaling oxide semiconductors and ALD for industrial applications.This review provides valuable perspectives for researchers who have interest in semiconductor materials and electronic device applications,and the reasons ALD is important to applications of oxide semiconductors.

Multi-field coupling and free vibration of a sandwiched functionally-graded piezoelectric semiconductor plate

Sandwiched functionally-graded piezoelectric semiconductor(FGPS)plates possess high strength and excellent piezoelectric and semiconductor properties,and have significant potential applications in micro-electro-mechanical systems.The multi-field coupling and free vibration of a sandwiched FGPS plate are studied,and the governing equation and natural frequency are derived with the consideration of electron movement.The material properties in the functionally-graded layers are assumed to vary smoothly,and the first-order shear deformation theory is introduced to derive the multi-field coupling in the plate.The total strain energy of the plate is obtained,and the governing equations are presented by using Hamilton’s principle.By introducing the boundary conditions,the coupling physical fields are solved.In numerical examples,the natural frequencies of sandwiched FGPS plates under different geometrical and physical parameters are discussed.It is found that the initial electron density can be used to modulate the natural frequencies and vibrational displacement of sandwiched FGPS plates in the case of nano-size.The effects of the material properties of FGPS layers on the natural frequencies are also examined in detail.

Nonlinear free vibration of piezoelectric semiconductor doubly-curved shells based on nonlinear drift-diffusion model

In this paper, the nonlinear free vibration behaviors of the piezoelectric semiconductor(PS) doubly-curved shell resting on the Pasternak foundation are studied within the framework of the nonlinear drift-diffusion(NLDD) model and the first-order shear deformation theory. The nonlinear constitutive relations are presented, and the strain energy, kinetic energy, and virtual work of the PS doubly-curved shell are derived.Based on Hamilton's principle as well as the condition of charge continuity, the nonlinear governing equations are achieved, and then these equations are solved by means of an efficient iteration method. Several numerical examples are given to show the effect of the nonlinear drift current, elastic foundation parameters as well as geometric parameters on the nonlinear vibration frequency, and the damping characteristic of the PS doublycurved shell. The main innovations of the manuscript are that the difference between the linearized drift-diffusion(LDD) model and the NLDD model is revealed, and an effective method is proposed to select a proper initial electron concentration for the LDD model.

Advanced semiconductor catalyst designs for the photocatalytic reduction of CO_(2)

Using clean solar energy to reduce CO_(2)into value-added products not only consumes the over-emitted CO_(2)that causes environmental problems,but also generates fuel chemicals to alleviate energy crises.The photocatalytic CO_(2)reduction reaction(PCO_(2)RR)relies on the semiconductor photocatalysts that suffer from high recombination rate of the photo-generated carriers,low light harvesting capability,and low stability.This review explores the recent discoveries on the novel semiconductors for PCO_(2)RR,focusing on the rational catalyst design strategies(such as surface engineering,band engineering,hierarchical structure construction,single-atom catalysts,and biohybrid catalysts)that promote the catalytic performance of semiconductor catalysts on PCO_(2)RR.The advanced characterization techniques that contribute to understanding the intrinsic properties of the photocatalysts are also discussed.Lastly,the perspectives on future challenges and possible solutions for PCO_(2)RR are presented.

Recent progress on ambipolar 2D semiconductors in emergent reconfigurable electronics and optoelectronics

In these days,the increasing massive data are being produced and demanded to be processed with the rapid growth of information technology.It is difficult to rely solely on the shrinking of semiconductor devices and scale-up of the integrated circuits(ICs)again in the foreseeable future.Exploring new materials,new-principle semiconductor devices and new computing architectures is becoming an urgent topic in this field.Ambipolar two-dimensional(2D)semiconductors,possessing excellent electrostatic field controllability and flexibly modulated major charge carriers,offer a possibility to construct reconfigurable devices and enable the ICs with new functions,showing great potential in computing capacity,energy efficiency,time delay and cost.This review focuses on the recent significant advancements in reconfigurable electronic and optoelectronic devices of ambipolar 2D semiconductors,and demonstrates their potential approach towards ICs,like reconfigurable circuits and neuromorphic chips.It is expected to help readers understand the device design principle of ambipolar 2D semiconductors,and push forward exploring more new-principle devices and new-architecture computing circuits,and even their product applications.

Crystal and electronic structure of a quasi-two-dimensional semiconductor Mg_(3)Si_(2)Te_(6)

We report the synthesis and characterization of a Si-based ternary semiconductor Mg_(3)Si_(2)Te_(6),which exhibits a quasitwo-dimensional structure,where the trigonal Mg_(3)Si_(2)Te_(6)layers are separated by Mg ions.Ultraviolet-visible absorption spectroscopy and density functional theory calculations were performed to investigate the electronic structure.The experimentally determined direct band gap is 1.39 eV,consistent with the value of the density function theory calculations.Our results reveal that Mg_(3)Si_(2)Te_(6)is a direct gap semiconductor,which is a potential candidate for near-infrared optoelectronic devices.

Comparative coherence between layered and traditional semiconductors: unique opportunities for heterogeneous integration

As Moore’s law deteriorates,the research and development of new materials system are crucial for transitioning into the post Moore era.Traditional semiconductor materials,such as silicon,have served as the cornerstone of modern technologies for over half a century.This has been due to extensive research and engineering on new techniques to continuously enrich silicon-based materials system and,subsequently,to develop better performed silicon-based devices.Meanwhile,in the emerging post Moore era,layered semiconductor materials,such as transition metal dichalcogenides(TMDs),have garnered considerable research interest due to their unique electronic and optoelectronic properties,which hold great promise for powering the new era of next generation electronics.As a result,techniques for engineering the properties of layered semiconductors have expanded the possibilities of layered semiconductor-based devices.However,there remain significant limitations in the synthesis and engineering of layered semiconductors,impeding the utilization of layered semiconductor-based devices for mass applications.As a practical alternative,heterogeneous integration between layered and traditional semiconductors provides valuable opportunities to combine the distinctive properties of layered semiconductors with well-developed traditional semiconductors materials system.Here,we provide an overview of the comparative coherence between layered and traditional semiconductors,starting with TMDs as the representation of layered semiconductors.We highlight the meaningful opportunities presented by the heterogeneous integration of layered semiconductors with traditional semiconductors,representing an optimal strategy poised to propel the emerging semiconductor research community and chip industry towards unprecedented advancements in the coming decades.

Enhancement of Carrier Mobility in Semiconductor Nanostructures by Carrier Distribution Engineering

Two-dimensional(2D)van der Waals semiconductors are appealing for low-power transistors.Here,we show the feasibility in enhancing carrier mobility in 2D semiconductors through engineering the vertical distribution of carriers confined inside ultrathin channels via symmetrizing gate configuration or increasing channel thickness.Through self-consistently solving the Schr¨odinger–Poisson equations,the shapes of electron envelope functions are extensively investigated by clarifying their relationship with gate configuration,channel thickness,dielectric permittivity,and electron density.The impacts of electron distribution variation on various carrier scattering matrix elements and overall carrier mobility are insightfully clarified.It is found that the carrier mobility can be generally enhanced in the dual-gated configuration due to the centralization of carrier redistribution in the nanometer-thick semiconductor channels and the rate of increase reaches up to 23%in Hf O2 dual-gated 10-layer MoS_(2) channels.This finding represents a viable strategy for performance optimization in transistors consisting of 2D semiconductors.