Low-Cost and Biodegradable Thermoelectric Devices Based on van der Waals Semiconductors on Paper Substrates

We present a method to fabricate handcrafted thermoelectric devices on standard office paper substrates.The devices are based on thin films of WS_(2),Te,and BP(P-type semiconductors)and TiS_(3)and TiS_(2)(N-type semiconductors),deposited by simply rubbing powder of these materials against paper.The thermoelectric properties of these semiconducting films revealed maximum Seebeck coefficients of(+1.32±0.27)mV K^(-1)and(-0.82±0.15)mV K^(-1)for WS_(2)and TiS_(3),respectively.Additionally,Peltier elements were fabricated by interconnecting the P-and N-type films with graphite electrodes.A thermopower value up to 6.11 mV K^(-1)was obtained when the Peltier element were constructed with three junctions.The findings of this work show proof-of-concept devices to illustrate the potential application of semiconducting van der Waals materials in future thermoelectric power generation as well as temperature sensing for low-cost disposable electronic devices.

Features of Recombination Radiation of GaAs Type Semiconductors with the Participation of Fine Acceptor Levels in a Magnetic Field

Using the method of Picus and Beer invariants, general expressions are obtained for the total intensity I and the degree of circular polarization Рcirc.of the luminescence of GaAs-type semiconductors with the participation of shallow acceptor levels in a longitudinal magnetic field H. Special cases are analyzed depending on the value and direction of the magnetic field strength, as well as on the constants of the g-factor of the acceptor g1,g2and the conduction band electron ge. In the case of a strong magnetic field H// [100], [111], [110], a numerical calculation of the angular dependence of the quantities I and Рcirc.was performed for some critical values of g2/g1, at which Рcirc.exhibits a sharp anisotropy in the range from −100% to +100%, and the intensity of the crystal radiation along the magnetic field tends to a minimum value.

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.

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.

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.

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.

Ultrafine Vacancy-Rich Nb_(2)O_(5)Semiconductors Confined in Carbon Nanosheets Boost Dielectric Polarization for High-Attenuation Microwave Absorption

The integration of nano-semiconductors into electromagnetic wave absorption materials is a highly desirable strategy for intensifying dielectric polarization loss;achieving high-attenuation microwave absorption and realizing in-depth comprehension of dielectric loss mechanisms remain challenges.Herein,ultrafine oxygen vacancy-rich Nb_(2)O_(5)semiconductors are confined in carbon nanosheets(ov-Nb_(2)O_(5)/CNS)to boost dielectric polarization and achieve high attenuation.The polarization relaxation,electromagnetic response,and impedance matching of the ov-Nb_(2)O_(5)/CNS are significantly facilitated by the Nb_(2)O_(5)semiconductors with rich oxygen vacancies,which consequently realizes an extremely high attenuation performance of-80.8 dB(>99.999999%wave absorption)at 2.76 mm.As a dielectric polarization center,abundant Nb_(2)O_(5)–carbon heterointerfaces can intensify interfacial polarization loss to strengthen dielectric polarization,and the presence of oxygen vacancies endows Nb_(2)O_(5)semiconductors with abundant charge separation sites to reinforce electric dipole polarization.Moreover,the three-dimensional reconstruction of the absorber using microcomputer tomography technology provides insight into the intensification of the unique lamellar morphology regarding multiple reflection and scattering dissipation characteristics.Additionally,ov-Nb_(2)O_(5)/CNS demonstrates excellent application potential by curing into a microwave-absorbing,machinable,and heat-dissipating plate.This work provides insight into the dielectric polarization loss mechanisms of nano-semiconductor/carbon composites and inspires the design of high-performance microwave absorption materials.

p‑Type Two‑Dimensional Semiconductors:From Materials Preparation to Electronic Applications

Two-dimensional(2D)materials are regarded as promising candidates in many applications,including electronics and optoelectronics,because of their superior properties,including atomic-level thickness,tunable bandgaps,large specific surface area,and high carrier mobility.In order to bring 2D materials from the laboratory to industrialized applications,materials preparation is the first prerequisite.Compared to the n-type analogs,the family of p-type 2D semiconductors is relatively small,which limits the broad integration of 2D semiconductors in practical applications such as complementary logic circuits.So far,many efforts have been made in the preparation of p-type 2D semiconductors.In this review,we overview recent progresses achieved in the preparation of p-type 2D semiconductors and highlight some promising methods to realize their controllable preparation by following both the top-down and bottom-up strategies.Then,we summarize some significant application of p-type 2D semiconductors in electronic and optoelectronic devices and their superiorities.In end,we conclude the challenges existed in this field and propose the potential opportunities in aspects from the discovery of novel p-type 2D semiconductors,their controlled mass preparation,compatible engineering with silicon production line,high-κdielectric materials,to integration and applications of p-type 2D semiconductors and their heterostructures in electronic and optoelectronic devices.Overall,we believe that this review will guide the design of preparation systems to fulfill the controllable growth of p-type 2D semiconductors with high quality and thus lay the foundations for their potential application in electronics and optoelectronics.

Discovery of new potential magnetic semiconductors in quaternary Heusler compounds by addition of lanthanides

Magnetic semiconductors have attracted a lot of attention by having both electronic charge and spin degrees of freedom. In this paper, we obtained twenty magnetic semiconductors such as FeVLaSb, FeVPrSb, FeCrTbSi, CoVDySi, and CoVHoSi by adding lanthanides to quaternary Heusler compounds based on the Slater-Pauling law and orbital hybridization theory. The relationship between the lattice constants and energy gaps of the magnetic semiconductors with lanthanide elements is investigated by in-depth analysis. These magnetic semiconductors of quaternary Heusler compounds are promising candidates to find applications as spin filtering materials in spintronics devices.

Valley polarization in transition metal dichalcogenide layered semiconductors:Generation,relaxation,manipulation and transport

In recent years,valleytronics researches based on 2D semiconducting transition metal dichalcogenides have attracted considerable attention.On the one hand,strong spin–orbit interaction allows the presence of spin–valley coupling in this system,which provides spin addressable valley degrees of freedom for information storage and processing.On the other hand,large exciton binding energy up to hundreds of me V enables excitons to be stable carriers of valley information.Valley polarization,marked by an imbalanced exciton population in two inequivalent valleys(+K and-K),is the core of valleytronics as it can be utilized to store binary information.Motivated by the potential applications,we present a thorough overview of the recent advancements in the generation,relaxation,manipulation,and transport of the valley polarization in nonmagnetic transition metal dichalcogenide layered semiconductors.We also discuss the development of valleytronic devices and future challenges in this field.

Two-dimensional transition metal halide PdX_(2)(X=F,Cl,Br,I):A promising candidate of bipolar magnetic semiconductors

Two-dimensional(2D)nanomaterials with bipolar magnetism show great promise in spintronic applications.Manipulating carriers'spin-polarized orientation in bipolar magnetic semiconductor(BMS)requires a gate voltage,but that is volatile.Recently,a new method has been proposed to solve the problem of volatility by introducing a ferroelectric gate with proper band alignment.In this paper,we predict that the PdX_(2)(X=F,Cl,Br,I)monolayers are 2D ferromagnetic BMS with dynamic stability,thermal stability,and mechanical stability by first-principles calculations.The critical temperatures are higher than the boiling point of liquid nitrogen and the BMS characteristics are robust against external strains and electric fields for PdCl_(2) and PdBr_(2).Then,we manipulate the spin-polarization of PdCl_(2) and PdBr_(2) by introducing a ferroelectric gate to enable magnetic half-metal/semiconductor switching and spin-up/down polarization switching control.Two kinds of spin devices(multiferroic memory and spin filter)have been proposed to realize the spin-polarized directions of electrons.These results demonstrate that PdCl_(2) and PdBr_(2) with BMS characters can be widely used as a general material structure for spintronic devices.

A family of flexible two-dimensional semiconductors:MgMX2Y6(M=Ti/Zr/Hf;X=Si/Ge;Y=S/Se/Te)

Inspired by the recently predicted 2D MX_(2)Y_(6)(M=metal element;X=Si/Ge/Sn;Y=S/Se/Te),we explore the possible applications of alkaline earth metal(using magnesium as example)in this family based on the idea of element replacement and valence electron balance.Herein,we report a new family of 2D quaternary compounds,namely MgMX_(2)Y_(6)(M=Ti/Zr/Hf;X=Si/Ge;Y=S/Se/Te)monolayers,with superior kinetic,thermodynamic and mechanical stability.In addition,our results indicate that MgMX_(2)Y_(6)monolayers are all indirect band gap semiconductors with band gap values ranging from 0.870 to 2.500 eV.Moreover,the band edges and optical properties of 2D MgMX_(2)Y_(6)are suitable for constructing multifunctional optoelectronic devices.Furthermore,for comparison,the mechanical,electronic and optical properties of In_(2)X_(2)Y_(6)monolayers have been discussed in detail.The success of introducing Mg into the 2D MX_(2)Y_(6)family indicates that more potential materials,such as Caand Sr-based 2D MX_(2)Y_(6)monolayers,may be discovered in the future.Therefore,this work not only broadens the existing family of 2D semiconductors,but it also provides beneficial results for the future.

Two-dimensional Cr_(2)Cl_(3)S_(3)Janus magnetic semiconductor with large magnetic exchange interaction and high-T_(C)

The two-dimensional(2D)Janus monolayers are promising in spintronic device application due to their enhanced magnetic couplings and Curie temperatures.Van der Waals CrCl_(3) monolayer has been experimentally proved to have an in-plane magnetic easy axis and a low Curie temperature of 17 K,which will limit its application in spintronic devices.In this work,we propose a new Janus monolayer Cr_(2)Cl_(3)S_(3) based on the first principles calculations.The phonon dispersion and elastic constants confirm that Janus monolayer Cr_(2)Cl_(3)S_(3) is dynamically and mechanically stable.Our Monte Carlo simulation results based on magnetic exchange constants reveal that Janus monolayer Cr_(2)Cl_(3)S_(3) is an intrinsic ferromagnetic semiconductor with TC of 180 K,which is much higher than that of CrCl_(3) due to the enhanced ferromagnetic coupling caused by S substitution.Moreover,the magnetic easy axis of Janus Cr_(2)Cl_(3)S_(3) can be tuned to the perpendicular direction with a large magnetic anisotropy energy(MAE)of 142eV/Cr.Furthermore,the effect of biaxial strain on the magnetic property of Janus monolayer Cr_(2)Cl_(3)S_(3) is evaluated.It is found that the Curie temperature is more robust under tensile strain.This work indicates that the Janus monolayer Cr_(2)Cl_(3)S_(3) presents increased Curie temperature and out-of-plane magnetic easy axis,suggesting greater application potential in 2D spintronic devices.

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.

Magneto-Photo-Thermoelastic Excitation Rotating Semiconductor Medium Based on Moisture Diffusivity

In this research,we focus on the free-surface deformation of a one-dimensional elastic semiconductor medium as a function of magnetic field and moisture diffusivity.The problem aims to analyze the interconnection between plasma and moisture diffusivity processes,as well as thermo-elastic waves.The study examines the photothermoelasticity transport process while considering the impact of moisture diffusivity.By employing Laplace’s transformation technique,we derive the governing equations of the photo-thermo-elastic medium.These equations include the equations for carrier density,elastic waves,moisture transport,heat conduction,and constitutive relationships.Mechanical stresses,thermal conditions,and plasma boundary conditions are used to calculate the fundamental physical parameters in the Laplace domain.By employing numerical techniques,the Laplace transform is inverted to get complete time-domain solutions for the primary physical domains under study.Referencemoisture,thermoelastic,and thermoelectric characteristics are employed in conjunction with a graphical analysis that takes into consideration the effects of applied forces on displacement,moisture concentration,carrier density,stress due to forces,and temperature distribution.

Performance of Lateral 4H-SiC Photoconductive Semiconductor Switches by Extrinsic Backside Trigger

Photoconductive semiconductor switch(PCSS)can be applied in pulsed high power systems and microwave techniques.However,reducing the damage and increasing the lifetime of silicon carbide(SiC)PCSS are still faced severe challenges.In this study,PCSSs with various structures were prepared on 4-inch diameter,500μm thick high-purity semi-insulating 4H-SiC substrates and their on-state resistance and damage mechanisms were investigated.It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950℃had a minimum on-state resistance of 6.0Ωat 1 kV bias voltage with a 532 nm and 170 mJ pulsed laser by backside illumination single trigger.The backside illumination single trigger could reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot was larger than the channel length of PCSS.For the 200 s trigger test by a 10 Hz laser,the black branch-like ablation on Au/TiW/Ni PCSS was mainly caused by thermal stress owing to hot carriers.Replacing metal Ni with boron gallium co-doped zinc oxide(BGZO)thin films annealed at 400℃,black branch-like ablation was alleviated while concentric arc damage was obvious at the anode.The major causes of concentric arc are both pulsed laser diffraction and thermal effect.

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.

Semitransparent organic photovoltaics enabled by transparent p-type inorganic semiconductor and near-infrared acceptor

Semitransparent organic photovoltaics(STOPVs)have gained wide attention owing to their promising applications in building-integrated photovoltaics,agrivoltaics,and floating photovoltaics.Organic semiconductors with high charge carrier mobility usually have planar and conjugated structures,thereby showing strong absorption in visible region.In this work,a new concept of incorporating transparent inorganic semiconductors is proposed for high-performance STOPVs.Copper(I)thiocyanate(CuSCN)is a visible-transparent inorganic semiconductor with an ionization potential of 5.45 eV and high hole mobility.The transparency of CuSCN benefits high average visible transmittance(AVT)of STOPVs.The energy levels of CuSCN as donor match those of near-infrared small molecule acceptor BTP-eC9,and the formed heterojunction exhibits an ability of exciton dissociation.High mobility of CuSCN contributes to a more favorable charge transport channel and suppresses charge recombination.The control STOPVs based on PM6/BTP-eC9 exhibit an AVT of 19.0%with a power conversion efficiency(PCE)of 12.7%.Partial replacement of PM6 with CuSCN leads to a 63%increase in transmittance,resulting in a higher AVT of 30.9%and a comparable PCE of 10.8%.