Amongst all the scientific achievements in the 20th century,no single invention has impacted our lives more profoundly than the transistors,or semiconductors.Since we entered the era of computing in the 1960s,we have ...Amongst all the scientific achievements in the 20th century,no single invention has impacted our lives more profoundly than the transistors,or semiconductors.Since we entered the era of computing in the 1960s,we have witnessed a number of notable transformational shifts such as the transition to personal computers and then mobile era.展开更多
Regioselevtive functionalization of perylene diimides(PDIs)at bay area often requires multistep synthesis and strenuous recrystallization.Direct bromination of perylene diimides only afford the 1,6 and 1,7-regioisomer...Regioselevtive functionalization of perylene diimides(PDIs)at bay area often requires multistep synthesis and strenuous recrystallization.Direct bromination of perylene diimides only afford the 1,6 and 1,7-regioisomers.More importantly,the 1,6-dibromo regioisomers could only be separated by preparative HPLC.Herein,we report a promising strategy for constructing Janus backbone of BN-doped perylene diimide derivatives.This Janus-type configuration results in the unique regioselective functionalization of BN-JPDIs,which yields exclusively the 1,6-regioisomers.Further investigation shows that the Janus-type configuration leads to a net dipole moment of 1.94 D and intramolecular charge transfer,which causes substantial changes on the optoelectronic properties.Moreover,the single crystal organic field-effect transistors based on BN-JPDIs exhibit electron mobilities up to 0.57 cm^(2)V^(-1)s^(-1),showcasing their potential as versatile building block towards high-performance n-type organic semiconductors.展开更多
Flexoelectricity,an electromechanical coupling between strain gradient and electrical polarization in dielectrics or semiconductors,has attracted significant scientific interest.It is reported that large flexoelectric...Flexoelectricity,an electromechanical coupling between strain gradient and electrical polarization in dielectrics or semiconductors,has attracted significant scientific interest.It is reported that large flexoelectric behaviors can be obtained at the nanoscale because of the size effect.However,the flexoelectric responses of centrosymmetric semiconductors(CSs)are extremely weak under a conventional beam-bending approach,owing to weak flexoelectric coefficients and small strain gradients.The flexoelectric-like effect is an enhanced electromechanical effect coupling the flexoelectricity and piezoelectricity.In this paper,a composite structure consisting of piezoelectric dielectric layers and a CS layer is proposed.The electromechanical response of the CS is significantly enhanced via antisymmetric piezoelectric polarization.Consequently,the cross-scale mechanically tuned carrier distribution in the semiconductor is realized.Meanwhile,the significant size dependence of the electromechanical fields in the semiconductor is demonstrated.The flexoelectronics suppression is found when the semiconductor thickness reaches a critical size(0.8μm).In addition,the first-order carrier density of the composite structure under local loads is illustrated.Our results can suggest the structural design for flexoelectric semiconductor devices.展开更多
Doping plays a pivotal role in enhancing the performance of organic semiconductors(OSCs)for advanced optoelectronic and thermoelectric applications.In this study,we systematically investigated the doping performance a...Doping plays a pivotal role in enhancing the performance of organic semiconductors(OSCs)for advanced optoelectronic and thermoelectric applications.In this study,we systematically investigated the doping performance and applicability of the ionic dopant 4-isopropyl-4′-methyldiphenyliodonium tetrakis(penta-fluorophenyl-borate)(DPI-TPFB)as a p-dopant for OSCs.Using the p-type OSC PBBT-2T as a model system,we demonstrated that DPI-TPFB shows significant doping effect,as confirmed by ESR spectra,ultraviolet-visible-near-infrared(UV-vis-NIR)absorption,and work function analysis,and enhances the electronic conductivity of PBBT-2T films by over four orders of magnitude.Furthermore,DPI-TPFB exhibited broad doping applicability,effectively doping various p-type OSCs and even imparting p-type characteristics to the n-type OSC N2200,transforming its intrinsic n-type behavior into p-type.The application of DPI-TPFB-doped PBBT-2T films in organic thermoelectric devices(OTEs)was also explored,achieving a power factor of approximately 10μW·m^(-1)·K^(-2).These findings highlight the potential of DPI-TPFB as a versatile and efficient dopant for integration into organic optoelectronic and thermoelectric devices.展开更多
The optical absorption spectra of the covalent crystals ZnX(X=S,Se) doped with Co 2+ are studied using the double covalency factors,which considers the anisotropic distortion of e g and t 2g orbits for d el...The optical absorption spectra of the covalent crystals ZnX(X=S,Se) doped with Co 2+ are studied using the double covalency factors,which considers the anisotropic distortion of e g and t 2g orbits for d electron.When the paramagnetic g factor is calculated,the contributions of the spin orbit coupling from the ligand ions are taken into account besides that from the central ion,which is the double ξ model.The calculated results indicate that the theoretical values coincide with the experimental values very well.This suggests that the method presented in this paper could be more valid to some strongly covalent crystals.展开更多
We study electromechanical fields near the interface between a circular piezoelectric semiconductor cylinder and another piezoelectric semiconductor in which it is embedded. The cylinder is p-doped. The surrounding ma...We study electromechanical fields near the interface between a circular piezoelectric semiconductor cylinder and another piezoelectric semiconductor in which it is embedded. The cylinder is p-doped. The surrounding material is n-doped. The phenomenological theory of piezoelectric semiconductors consisting of the equations of piezoelectricity and the conservation of charge for holes and electrons is used. The theory is linearized for small carrier concentration perturbations. An analytical solution is obtained, showing the formation of a PN junction near the interface. Various electromechanical fields associated with the junction are calculated. The effects of a few physical parameters are examined.展开更多
The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magne...The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magnetic semiconductor families, including europium chalcogenides, chromium spinels, dilute magnetic semiconductors, dilute ferromagnetic semiconductors and insulators, mentioning also sources of non-uniformities in the magnetization distribution, accounting for an apparent high Curie temperature ferromagnetism in many systems. Our survey is carried out from today's perspective of ferromagnetic and antiferromagnetic spintronics as well as of the emerging fields of magnetic topological materials and atomically thin 2D layers.展开更多
As one branch of spintronics, diluted magnetic semiconductors (DMSs) are extensively investigated due to their fundamental significance and potential application in modern information society. The classical materials ...As one branch of spintronics, diluted magnetic semiconductors (DMSs) are extensively investigated due to their fundamental significance and potential application in modern information society. The classical materials (Ga,Mn)As of III-V group based DMSs has been well studied for its high compatibility with the high-mobility semiconductor GaAs. But the Curie temperature in (Ga,Mn)As film is still far below room temperature because the spin & charge doping is bundled to the same element that makes the fabrication very difficult. Alternatively, the discovery of a new generation DMSs with independent spin and charge doping, such as (Ba,K)(Zn,Mn)2As2 (briefly named BZA), attracted considerable attention due to their unique advantages in physical properties and heterojunction fabrication. In this review we focus on this series of new DMSs including (I) materials in terms of three types of new DMSs, i.e. the "111","122" and "1111" system;(II) the physical properties of BZA;(III) single crystals & prototype device based on BZA. The prospective of new type of DMSs with independent spin and charge doping is briefly discussed.展开更多
The development of two-dimensional(2D)semiconductors has attracted widespread attentions in the scientific community and industry due to their ultra-thin thickness,unique structure,excellent optoelectronic properties ...The development of two-dimensional(2D)semiconductors has attracted widespread attentions in the scientific community and industry due to their ultra-thin thickness,unique structure,excellent optoelectronic properties and novel physics.The excellent flexibility and outstanding mechanical strength of 2D semiconductors provide opportunities for fabricated strain-sensitive devices and utilized strain tuning their electronic and optic–electric performance.The strain-engineered one-dimensional materials have been well investigated,while there is a long way to go for 2D semiconductors.In this review,starting with the fundamental theories of piezoelectric and piezoresistive effect resulted by strain,following we reviewed the recent simulation works of strain engineering in novel 2D semiconductors,such as Janus 2D and 2D-Xene structures.Moreover,recent advances in experimental observation of strain tuning PL spectra and transport behavior of 2D semiconductors are summarized.Furthermore,the applications of strain-engineered 2D semiconductors in sensors,photodetectors and nanogenerators are also highlighted.At last,we in-depth discussed future research directions of strain-engineered 2D semiconductor and related electronics and optoelectronics device applications.展开更多
Diluted magnetic semiconductors (DMSs) that possess both properties of semiconductors and ferromagnetism, have attracted a lot of attentions due to its potential applications for spin-sensitive electronic devices. Rec...Diluted magnetic semiconductors (DMSs) that possess both properties of semiconductors and ferromagnetism, have attracted a lot of attentions due to its potential applications for spin-sensitive electronic devices. Recently, a series of bulk form DMSs isostructural to iron-based superconductors have been reported, which can be readily investigated by microscopic experimental techniques such as nuclear magnetic resonance (NMR) and muon spin rotation (μSR). The measurements have demonstrated that homogeneous ferromagnetism is achieved in these DMSs. In this review article, we summarize experimental evidences from both NMR and μSR measurements. NMR results have shown that carriers facilitate the interactions between distant Mn atoms, while μSR results indicate that these bulk form DMSs and (Ga,Mn)As share a common mechanism for the ferromagnetic exchange interactions.展开更多
Diluted ferromagnetic semiconductors（DMSs） that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic（spintronic） devices. The search for DMS material...Diluted ferromagnetic semiconductors（DMSs） that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic（spintronic） devices. The search for DMS materials exploded after the observation of ferromagnetic ordering in Ⅲ-Ⅴ（Ga,Mn）As films. Recently, a series of DMS compounds isostructural to iron-based superconductors have been reported. Among them, the highest Curie temperature TCo f 230 K has been achieved in（Ba,K）（Zn,Mn）2As2. However, most DMSs, including（Ga,Mn）As, are p-type, i.e., the carriers that mediate the ferromagnetism are holes. For practical applications, DMSs with n-type carriers are also advantageous. Very recently,a new DMS Ba（Zn,Co）2As2 with n-type carriers has been synthesized. Here we summarize the recent progress on this research stream. We will show that the homogeneous ferromagnetism in these bulk form DMSs has been confirmed by microscopic techniques, i.e., nuclear magnetic resonance（NMR） and muon spin rotation（μSR）.展开更多
Two-dimensional(2D)semiconductors isoelectronic to phosphorene have been drawing much attention recently due to their promising applications for next-generation(opt)electronics.This family of 2D materials contains mor...Two-dimensional(2D)semiconductors isoelectronic to phosphorene have been drawing much attention recently due to their promising applications for next-generation(opt)electronics.This family of 2D materials contains more than 400members,including(a)elemental group-V materials,(b)binary III–VII and IV–VI compounds,(c)ternary III–VI–VII and IV–V–VII compounds,making materials design with targeted functionality unprecedentedly rich and extremely challenging.To shed light on rational functionality design with this family of materials,we systemically explore their fundamental band gaps and alignments using hybrid density functional theory(DFT)in combination with machine learning.First,calculations are performed using both the Perdew–Burke–Ernzerhof exchange–correlation functional within the generalgradient-density approximation(GGA-PBE)and Heyd–Scuseria–Ernzerhof hybrid functional(HSE)as a reference.We find this family of materials share similar crystalline structures,but possess largely distributed band-gap values ranging approximately from 0 eV to 8 eV.Then,we apply machine learning methods,including linear regression(LR),random forest regression(RFR),and support vector machine regression(SVR),to build models for the prediction of electronic properties.Among these models,SVR is found to have the best performance,yielding the root mean square error(RMSE)less than 0.15 eV for the predicted band gaps,valence-band maximums(VBMs),and conduction-band minimums(CBMs)when both PBE results and elemental information are used as features.Thus,we demonstrate that the machine learning models are universally suitable for screening 2D isoelectronic systems with targeted functionality,and especially valuable for the design of alloys and heterogeneous systems.展开更多
Recently, amorphous magnetic semiconductors as a new family of magnetic semiconductors have been developed by oxidizing ferromagnetic amorphous metals/alloys. Intriguingly, tuning the relative atomic ratios of Co and ...Recently, amorphous magnetic semiconductors as a new family of magnetic semiconductors have been developed by oxidizing ferromagnetic amorphous metals/alloys. Intriguingly, tuning the relative atomic ratios of Co and Fe in a Co-Fe-Ta-B-O system leads to the formation of an intrinsic magnetic semiconductor. Starting from high Curie-temperature amorphous ferromagnets, these amorphous magnetic semiconductors show Curie temperatures well above room temperature. Among them, one typical example is a p-type Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor, which has an optical bandgap of ~2.4 eV, roomtemperature saturation magnetization of ~433 emu/cm3, and the Curie temperature above 600 K. The amorphous Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor can be integrated with n-type Si to form p-n heterojunctions with a threshold voltage of ~1.6 V, validating its p-type semiconducting character. Furthermore, the demonstration of electric field control of its room-temperature ferromagnetism reflects the interplay between the electricity and ferromagnetism in this material. It is suggested that the carrier density, ferromagnetism and conduction type of an intrinsic magnetic semiconductor are controllable by means of an electric field effect. These findings may pave a new way to realize magnetic semiconductor-based spintronic devices that work at room temperature.展开更多
The electronic and optical properties of zincblende ZnX（X=S, Se, Te） and ZnX：Co are studied from density functional theory （DFT） based first principles calculations. The local crystal structure changes around the...The electronic and optical properties of zincblende ZnX（X=S, Se, Te） and ZnX：Co are studied from density functional theory （DFT） based first principles calculations. The local crystal structure changes around the Co atoms in the lattice are studied after Co atoms are doped. It is shown that the Co-doped materials have smaller lattice constant （about 0.6%-0.9%）. This is mainly due to the shortened Co-X bond length. The （partial） density of states （DOS） is calculated and differences between the pure and doped materials are studied. Results show that for the Co-doped materials, the valence bands are moving upward due to the existence of Co 3d electron states while the conductance bands are moving downward due to the reduced lattice constants. This results in the narrowed band gap of the doped materials. The complex dielectric indices and the absorption coefficients are calculated to examine the influences of the Co atoms on the optical properties. Results show that for the Co-doped materials, the absorption peaks in the high wavelength region are not as sharp and distinct as the undoped materials, and the absorption ranges are extended to even higher wavelength region.展开更多
Cyano substitution is vital to the molecular design of polymer semiconductors toward highly efficient organic solar cells.However,how regioselectivity impacts relevant optoelectronic properties in cyano-substituted bi...Cyano substitution is vital to the molecular design of polymer semiconductors toward highly efficient organic solar cells.However,how regioselectivity impacts relevant optoelectronic properties in cyano-substituted bithiophene systems remain poorly understood.Three regioisomeric cyano-functionalized dialkoxybithiophenes BT_(HH),BT_(HT),and BT_(TT) with headto-head,head-to-tail,and tail-to-tail linkage,respectively,were synthesized and characterized in this work.The resulting polymer semiconductors(PBDTBTs)based on these building blocks were prepared accordingly.The regiochemistry and property relationships of PBDTBTs were investigated in detail.The BTHH moiety has a higher torsional barrier than the analogs BT_(HT) and BT_(TT),and the regiochemistry of dialkoxybithiophenes leads to fine modulation in the optoelectronic properties of these polymers,such as optical absorption,band gap,and energy levels of frontier molecular orbitals.Organic field-effect transistors based on PBDTBT_(HH) had higher hole mobility(4.4×10^(-3) cm^(2)/(V·s))than those(ca.10^(-4) cm^(2)/(V·s))of the other two polymer analogs.Significantly different short-circuit current densities and fill factors were obtained in polymer solar cells using PBDTBTs as the electron donors.Such difference was probed in greater detail by performing space-charge-limited current mobility,thin-film morphology,and transient photocurrent/photovoltage characterizations.The findings highlight that the BTHH unit is a promising building block for the construction of polymer donors for highperformance organic photovoltaic cells.展开更多
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 f...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.展开更多
Simple models are proposed for the calculation of refractive index n and electronic polarizability α of AⅠBⅢC2Ⅵ and AⅡBⅣC2Ⅴ compounds of groups of chalcopyrite semiconductors from their energy gap data. The val...Simple models are proposed for the calculation of refractive index n and electronic polarizability α of AⅠBⅢC2Ⅵ and AⅡBⅣC2Ⅴ compounds of groups of chalcopyrite semiconductors from their energy gap data. The values family and 12 compounds of AⅡBⅣC2Ⅴ family are calculated for the work. The proposed models are applicable for the whole range of energy gap materials. The calculated values are compared with the available experimental and reported values. A fairly good agreement between them is obtained.展开更多
Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room tempera...Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room temperature magnetic semiconductors with strong and controllable s, p-d exchange interaction. With this s, p-d exchange interaction, one can utilize the spin degree of freedom to design applicable spintronics devices with very attractive functions that are not available in conventional semiconductors. Here, we first review the progress in understanding of this particular material and the dilemma to prepare a room temperature magnetic semiconductor. Then we discuss recent experimental progresses to pursue strong s, p-d interaction to realize room temperature magnetic semiconductors, which are achieved by introducing a very high concentration of magnetic atoms by means of low-temperature nonequilibrium growth.展开更多
In this short review,we discuss a few recent advances in calculating the nonradiative decay rates for point defects in semiconductors.We briefly review the debates and connections of using different formalisms to calc...In this short review,we discuss a few recent advances in calculating the nonradiative decay rates for point defects in semiconductors.We briefly review the debates and connections of using different formalisms to calculate the multi-phonon processes.We connect Dr.Huang's formula with Marcus theory formula in the high temperature limit,and point out that Huang's formula provide an analytical expression for the phonon induced electron coupling constant in the Marcus theory formula.We also discussed the validity of 1D formula in dealing with the electron transition processes,and practical ways to correct the anharmonic effects.展开更多
Atomically thin two-dimensional （2D） layered materials have potential applications in nanoelectronics, nanophoton- ics, and integrated optoelectronics. Band gap engineering of these 2D semiconductors is critical for...Atomically thin two-dimensional （2D） layered materials have potential applications in nanoelectronics, nanophoton- ics, and integrated optoelectronics. Band gap engineering of these 2D semiconductors is critical for their broad applications in high-performance integrated devices, such as broad-band photodetectors, multi-color light emitting diodes （LEDs）, and high-efficiency photovoltaic devices. In this review, we will summarize the recent progress on the controlled growth of composition modulated atomically thin 2D semiconductor alloys with band gaps tuned in a wide range, as well as their induced applications in broadly tunable optoelectronic components. The band gap engineered 2D semiconductors could open up an exciting opportunity for probing their fundamental physical properties in 2D systems and may find diverse applications in functional electronic/optoelectronic devices.展开更多
文摘Amongst all the scientific achievements in the 20th century,no single invention has impacted our lives more profoundly than the transistors,or semiconductors.Since we entered the era of computing in the 1960s,we have witnessed a number of notable transformational shifts such as the transition to personal computers and then mobile era.
基金support from the National Natural Science Foundation of China(Nos.22071007,22020102001,22335002)the National Key R&D Program of China(No.2022YFB3602802)+3 种基金Beijing Natural Science Foundation(No.Z220025)the National Facility for Protein Science in Shanghai,Shanghai Advanced Research Institute,CAS,for providing technical support in X-ray diffraction data collectionthe High-Performance Computing Platform of Peking University for supporting the computational workthe support of BMS Junior Fellow program。
文摘Regioselevtive functionalization of perylene diimides(PDIs)at bay area often requires multistep synthesis and strenuous recrystallization.Direct bromination of perylene diimides only afford the 1,6 and 1,7-regioisomers.More importantly,the 1,6-dibromo regioisomers could only be separated by preparative HPLC.Herein,we report a promising strategy for constructing Janus backbone of BN-doped perylene diimide derivatives.This Janus-type configuration results in the unique regioselective functionalization of BN-JPDIs,which yields exclusively the 1,6-regioisomers.Further investigation shows that the Janus-type configuration leads to a net dipole moment of 1.94 D and intramolecular charge transfer,which causes substantial changes on the optoelectronic properties.Moreover,the single crystal organic field-effect transistors based on BN-JPDIs exhibit electron mobilities up to 0.57 cm^(2)V^(-1)s^(-1),showcasing their potential as versatile building block towards high-performance n-type organic semiconductors.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB2011400)the National Natural Science Foundation of China(Grant No.52375081).
文摘Flexoelectricity,an electromechanical coupling between strain gradient and electrical polarization in dielectrics or semiconductors,has attracted significant scientific interest.It is reported that large flexoelectric behaviors can be obtained at the nanoscale because of the size effect.However,the flexoelectric responses of centrosymmetric semiconductors(CSs)are extremely weak under a conventional beam-bending approach,owing to weak flexoelectric coefficients and small strain gradients.The flexoelectric-like effect is an enhanced electromechanical effect coupling the flexoelectricity and piezoelectricity.In this paper,a composite structure consisting of piezoelectric dielectric layers and a CS layer is proposed.The electromechanical response of the CS is significantly enhanced via antisymmetric piezoelectric polarization.Consequently,the cross-scale mechanically tuned carrier distribution in the semiconductor is realized.Meanwhile,the significant size dependence of the electromechanical fields in the semiconductor is demonstrated.The flexoelectronics suppression is found when the semiconductor thickness reaches a critical size(0.8μm).In addition,the first-order carrier density of the composite structure under local loads is illustrated.Our results can suggest the structural design for flexoelectric semiconductor devices.
基金supported by the Fundamental Research Program of Shanxi Province(Nos.202303021212159 and 202303021222190)the National Natural Science Foundation of China(No.62222403)+2 种基金the Higher Education Institutions Science and Technology Innovation Program of Shanxi Province(No.2023L160)the Scientific Research Fund of Hunan Provincial Education Department(No.23B0842)the Natural Science Foundation of Shanxi Normal University(Nos.JCYJ2024017 and JCYJ2023015)。
文摘Doping plays a pivotal role in enhancing the performance of organic semiconductors(OSCs)for advanced optoelectronic and thermoelectric applications.In this study,we systematically investigated the doping performance and applicability of the ionic dopant 4-isopropyl-4′-methyldiphenyliodonium tetrakis(penta-fluorophenyl-borate)(DPI-TPFB)as a p-dopant for OSCs.Using the p-type OSC PBBT-2T as a model system,we demonstrated that DPI-TPFB shows significant doping effect,as confirmed by ESR spectra,ultraviolet-visible-near-infrared(UV-vis-NIR)absorption,and work function analysis,and enhances the electronic conductivity of PBBT-2T films by over four orders of magnitude.Furthermore,DPI-TPFB exhibited broad doping applicability,effectively doping various p-type OSCs and even imparting p-type characteristics to the n-type OSC N2200,transforming its intrinsic n-type behavior into p-type.The application of DPI-TPFB-doped PBBT-2T films in organic thermoelectric devices(OTEs)was also explored,achieving a power factor of approximately 10μW·m^(-1)·K^(-2).These findings highlight the potential of DPI-TPFB as a versatile and efficient dopant for integration into organic optoelectronic and thermoelectric devices.
文摘The optical absorption spectra of the covalent crystals ZnX(X=S,Se) doped with Co 2+ are studied using the double covalency factors,which considers the anisotropic distortion of e g and t 2g orbits for d electron.When the paramagnetic g factor is calculated,the contributions of the spin orbit coupling from the ligand ions are taken into account besides that from the central ion,which is the double ξ model.The calculated results indicate that the theoretical values coincide with the experimental values very well.This suggests that the method presented in this paper could be more valid to some strongly covalent crystals.
基金supported by the National Natural Science Foundation of China (Nos.11672265,11621062,and 11202182)the Fundamental Research Funds for the Central Universities (Nos.2016QNA4026 and 2016XZZX001-05)the open foundation of Zhejiang Provincial Top Key Discipline of Mechanical Engineering
文摘We study electromechanical fields near the interface between a circular piezoelectric semiconductor cylinder and another piezoelectric semiconductor in which it is embedded. The cylinder is p-doped. The surrounding material is n-doped. The phenomenological theory of piezoelectric semiconductors consisting of the equations of piezoelectricity and the conservation of charge for holes and electrons is used. The theory is linearized for small carrier concentration perturbations. An analytical solution is obtained, showing the formation of a PN junction near the interface. Various electromechanical fields associated with the junction are calculated. The effects of a few physical parameters are examined.
基金supported by the Foundation for Polish Science through the IRA Programme financed by EU within SG OP Programmesupport by the Austrian Science Foundation-FWF (P31423 and P26830)the Austrian Exchange Service (OAD) Project PL-01/2017
文摘The interplay of magnetic and semiconducting properties has been in the focus for more than a half of the century. In this introductory article we briefly review the key properties and functionalities of various magnetic semiconductor families, including europium chalcogenides, chromium spinels, dilute magnetic semiconductors, dilute ferromagnetic semiconductors and insulators, mentioning also sources of non-uniformities in the magnetization distribution, accounting for an apparent high Curie temperature ferromagnetism in many systems. Our survey is carried out from today's perspective of ferromagnetic and antiferromagnetic spintronics as well as of the emerging fields of magnetic topological materials and atomically thin 2D layers.
基金financially supported by Ministry of Science and Technology of China (Nos. 2018YFA03057001, and 2017YFB0405703)National Natural Science Foundation of China through the research projects (No. 11534016)
文摘As one branch of spintronics, diluted magnetic semiconductors (DMSs) are extensively investigated due to their fundamental significance and potential application in modern information society. The classical materials (Ga,Mn)As of III-V group based DMSs has been well studied for its high compatibility with the high-mobility semiconductor GaAs. But the Curie temperature in (Ga,Mn)As film is still far below room temperature because the spin & charge doping is bundled to the same element that makes the fabrication very difficult. Alternatively, the discovery of a new generation DMSs with independent spin and charge doping, such as (Ba,K)(Zn,Mn)2As2 (briefly named BZA), attracted considerable attention due to their unique advantages in physical properties and heterojunction fabrication. In this review we focus on this series of new DMSs including (I) materials in terms of three types of new DMSs, i.e. the "111","122" and "1111" system;(II) the physical properties of BZA;(III) single crystals & prototype device based on BZA. The prospective of new type of DMSs with independent spin and charge doping is briefly discussed.
基金supported by the National Natural Science Foundation of China(51572025,51627801,61435010 and 51702219)the State Key Research Development Program of China(2019YFB2203503)+3 种基金Guangdong Basic and Applied Basic Research Foundation(2019A1515110209)the Science and Technology Innovation Commission of Shenzhen(JCYJ20170818093453105,JCYJ20180305125345378)National Foundation of China(41422050303)Beijing Municipal Science&Technology Commission and the Fundamental Research Funds for Central Universities.
文摘The development of two-dimensional(2D)semiconductors has attracted widespread attentions in the scientific community and industry due to their ultra-thin thickness,unique structure,excellent optoelectronic properties and novel physics.The excellent flexibility and outstanding mechanical strength of 2D semiconductors provide opportunities for fabricated strain-sensitive devices and utilized strain tuning their electronic and optic–electric performance.The strain-engineered one-dimensional materials have been well investigated,while there is a long way to go for 2D semiconductors.In this review,starting with the fundamental theories of piezoelectric and piezoresistive effect resulted by strain,following we reviewed the recent simulation works of strain engineering in novel 2D semiconductors,such as Janus 2D and 2D-Xene structures.Moreover,recent advances in experimental observation of strain tuning PL spectra and transport behavior of 2D semiconductors are summarized.Furthermore,the applications of strain-engineered 2D semiconductors in sensors,photodetectors and nanogenerators are also highlighted.At last,we in-depth discussed future research directions of strain-engineered 2D semiconductor and related electronics and optoelectronics device applications.
基金supported by MOST (No. 2016YFA0300402)NSF of China (No. 11574265)the Fundamental Research Funds for the Central Universities
文摘Diluted magnetic semiconductors (DMSs) that possess both properties of semiconductors and ferromagnetism, have attracted a lot of attentions due to its potential applications for spin-sensitive electronic devices. Recently, a series of bulk form DMSs isostructural to iron-based superconductors have been reported, which can be readily investigated by microscopic experimental techniques such as nuclear magnetic resonance (NMR) and muon spin rotation (μSR). The measurements have demonstrated that homogeneous ferromagnetism is achieved in these DMSs. In this review article, we summarize experimental evidences from both NMR and μSR measurements. NMR results have shown that carriers facilitate the interactions between distant Mn atoms, while μSR results indicate that these bulk form DMSs and (Ga,Mn)As share a common mechanism for the ferromagnetic exchange interactions.
基金Project supported by the Chinese Ministry of Science and Technology(Grant No.2016YFA0300402)the National Natural Science Foundation of China(Grant No.11574265)+1 种基金the Natural Science Foundation of Zhejiang Province,China(Grant Nos.LR15A040001 and LY14A040007)the Fundamental Research Funds for the Central Universities,China
文摘Diluted ferromagnetic semiconductors（DMSs） that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic（spintronic） devices. The search for DMS materials exploded after the observation of ferromagnetic ordering in Ⅲ-Ⅴ（Ga,Mn）As films. Recently, a series of DMS compounds isostructural to iron-based superconductors have been reported. Among them, the highest Curie temperature TCo f 230 K has been achieved in（Ba,K）（Zn,Mn）2As2. However, most DMSs, including（Ga,Mn）As, are p-type, i.e., the carriers that mediate the ferromagnetism are holes. For practical applications, DMSs with n-type carriers are also advantageous. Very recently,a new DMS Ba（Zn,Co）2As2 with n-type carriers has been synthesized. Here we summarize the recent progress on this research stream. We will show that the homogeneous ferromagnetism in these bulk form DMSs has been confirmed by microscopic techniques, i.e., nuclear magnetic resonance（NMR） and muon spin rotation（μSR）.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0206301)。
文摘Two-dimensional(2D)semiconductors isoelectronic to phosphorene have been drawing much attention recently due to their promising applications for next-generation(opt)electronics.This family of 2D materials contains more than 400members,including(a)elemental group-V materials,(b)binary III–VII and IV–VI compounds,(c)ternary III–VI–VII and IV–V–VII compounds,making materials design with targeted functionality unprecedentedly rich and extremely challenging.To shed light on rational functionality design with this family of materials,we systemically explore their fundamental band gaps and alignments using hybrid density functional theory(DFT)in combination with machine learning.First,calculations are performed using both the Perdew–Burke–Ernzerhof exchange–correlation functional within the generalgradient-density approximation(GGA-PBE)and Heyd–Scuseria–Ernzerhof hybrid functional(HSE)as a reference.We find this family of materials share similar crystalline structures,but possess largely distributed band-gap values ranging approximately from 0 eV to 8 eV.Then,we apply machine learning methods,including linear regression(LR),random forest regression(RFR),and support vector machine regression(SVR),to build models for the prediction of electronic properties.Among these models,SVR is found to have the best performance,yielding the root mean square error(RMSE)less than 0.15 eV for the predicted band gaps,valence-band maximums(VBMs),and conduction-band minimums(CBMs)when both PBE results and elemental information are used as features.Thus,we demonstrate that the machine learning models are universally suitable for screening 2D isoelectronic systems with targeted functionality,and especially valuable for the design of alloys and heterogeneous systems.
基金sponsored by the National Key R&D Program of China (Grant No. 2017YFB0405704)the National Natural Science Foundation of China (Grant No. 51471091)
文摘Recently, amorphous magnetic semiconductors as a new family of magnetic semiconductors have been developed by oxidizing ferromagnetic amorphous metals/alloys. Intriguingly, tuning the relative atomic ratios of Co and Fe in a Co-Fe-Ta-B-O system leads to the formation of an intrinsic magnetic semiconductor. Starting from high Curie-temperature amorphous ferromagnets, these amorphous magnetic semiconductors show Curie temperatures well above room temperature. Among them, one typical example is a p-type Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor, which has an optical bandgap of ~2.4 eV, roomtemperature saturation magnetization of ~433 emu/cm3, and the Curie temperature above 600 K. The amorphous Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor can be integrated with n-type Si to form p-n heterojunctions with a threshold voltage of ~1.6 V, validating its p-type semiconducting character. Furthermore, the demonstration of electric field control of its room-temperature ferromagnetism reflects the interplay between the electricity and ferromagnetism in this material. It is suggested that the carrier density, ferromagnetism and conduction type of an intrinsic magnetic semiconductor are controllable by means of an electric field effect. These findings may pave a new way to realize magnetic semiconductor-based spintronic devices that work at room temperature.
基金Project supported by the National Natural Science Foundation of China （Grant No 10564002） and the 0pen Foundations of Key Laboratory for 0pto-electronics of Jiangxi Province, China （Grant Nos 2004003 and 2004008）, the Natural Science Foundation of Jiangxi Province, China （Grant No 0512017） and the Youth Science Program of Jiangxi Normal University, China（Grant No 1075）.
文摘The electronic and optical properties of zincblende ZnX（X=S, Se, Te） and ZnX：Co are studied from density functional theory （DFT） based first principles calculations. The local crystal structure changes around the Co atoms in the lattice are studied after Co atoms are doped. It is shown that the Co-doped materials have smaller lattice constant （about 0.6%-0.9%）. This is mainly due to the shortened Co-X bond length. The （partial） density of states （DOS） is calculated and differences between the pure and doped materials are studied. Results show that for the Co-doped materials, the valence bands are moving upward due to the existence of Co 3d electron states while the conductance bands are moving downward due to the reduced lattice constants. This results in the narrowed band gap of the doped materials. The complex dielectric indices and the absorption coefficients are calculated to examine the influences of the Co atoms on the optical properties. Results show that for the Co-doped materials, the absorption peaks in the high wavelength region are not as sharp and distinct as the undoped materials, and the absorption ranges are extended to even higher wavelength region.
基金supported by the National Natural Science Foundation of China(Nos.52173172,52173171,and 21801124)the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province(2021B1515020027)+6 种基金Guangdong Basic and Applied Basic Research Foundation(2021A1515110892)China Postdoctoral Science Foundation(2021M700062)the Shenzhen Science and Technology Innovation Commission(JCYJ202103243104813035 and JCYJ20180504165709042)the Open Fund of the State Key Laboratory of Luminescent Materials and Devices(South China University of Technology)financial support from the Songshan Lake Materials Laboratory(2021SLABFK03)financial support from the NRF of Korea(2016M1A2A2940911,2017K2A9A2A12000315)supported by the Center for Computational Science and Engineering of Southern University of Science and Technology。
文摘Cyano substitution is vital to the molecular design of polymer semiconductors toward highly efficient organic solar cells.However,how regioselectivity impacts relevant optoelectronic properties in cyano-substituted bithiophene systems remain poorly understood.Three regioisomeric cyano-functionalized dialkoxybithiophenes BT_(HH),BT_(HT),and BT_(TT) with headto-head,head-to-tail,and tail-to-tail linkage,respectively,were synthesized and characterized in this work.The resulting polymer semiconductors(PBDTBTs)based on these building blocks were prepared accordingly.The regiochemistry and property relationships of PBDTBTs were investigated in detail.The BTHH moiety has a higher torsional barrier than the analogs BT_(HT) and BT_(TT),and the regiochemistry of dialkoxybithiophenes leads to fine modulation in the optoelectronic properties of these polymers,such as optical absorption,band gap,and energy levels of frontier molecular orbitals.Organic field-effect transistors based on PBDTBT_(HH) had higher hole mobility(4.4×10^(-3) cm^(2)/(V·s))than those(ca.10^(-4) cm^(2)/(V·s))of the other two polymer analogs.Significantly different short-circuit current densities and fill factors were obtained in polymer solar cells using PBDTBTs as the electron donors.Such difference was probed in greater detail by performing space-charge-limited current mobility,thin-film morphology,and transient photocurrent/photovoltage characterizations.The findings highlight that the BTHH unit is a promising building block for the construction of polymer donors for highperformance organic photovoltaic cells.
文摘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.
文摘Simple models are proposed for the calculation of refractive index n and electronic polarizability α of AⅠBⅢC2Ⅵ and AⅡBⅣC2Ⅴ compounds of groups of chalcopyrite semiconductors from their energy gap data. The values family and 12 compounds of AⅡBⅣC2Ⅴ family are calculated for the work. The proposed models are applicable for the whole range of energy gap materials. The calculated values are compared with the available experimental and reported values. A fairly good agreement between them is obtained.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11434006, and 51871112)the National Basic Research Program of China (Grant No. 2015CB921502)+1 种基金the 111 Project (Grant No. B13029)Shandong Provincial Natural Science Foundation (Grant No. ZR2018MA035)
文摘Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room temperature magnetic semiconductors with strong and controllable s, p-d exchange interaction. With this s, p-d exchange interaction, one can utilize the spin degree of freedom to design applicable spintronics devices with very attractive functions that are not available in conventional semiconductors. Here, we first review the progress in understanding of this particular material and the dilemma to prepare a room temperature magnetic semiconductor. Then we discuss recent experimental progresses to pursue strong s, p-d interaction to realize room temperature magnetic semiconductors, which are achieved by introducing a very high concentration of magnetic atoms by means of low-temperature nonequilibrium growth.
基金supported by the Director, Office of Science (SC), Basic Energy Science (BES)/Materials Science and Engineering Division (MSED) of the U.S. Department of Energy (DOE) under the Contract No. DE-AC02-05CH11231 through the Theory of Material project
文摘In this short review,we discuss a few recent advances in calculating the nonradiative decay rates for point defects in semiconductors.We briefly review the debates and connections of using different formalisms to calculate the multi-phonon processes.We connect Dr.Huang's formula with Marcus theory formula in the high temperature limit,and point out that Huang's formula provide an analytical expression for the phonon induced electron coupling constant in the Marcus theory formula.We also discussed the validity of 1D formula in dealing with the electron transition processes,and practical ways to correct the anharmonic effects.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374092,61474040,61574054,and 61505051)the Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province,Chinathe Science and Technology Department of Hunan Province,China(Grant No.2014FJ2001)
文摘Atomically thin two-dimensional （2D） layered materials have potential applications in nanoelectronics, nanophoton- ics, and integrated optoelectronics. Band gap engineering of these 2D semiconductors is critical for their broad applications in high-performance integrated devices, such as broad-band photodetectors, multi-color light emitting diodes （LEDs）, and high-efficiency photovoltaic devices. In this review, we will summarize the recent progress on the controlled growth of composition modulated atomically thin 2D semiconductor alloys with band gaps tuned in a wide range, as well as their induced applications in broadly tunable optoelectronic components. The band gap engineered 2D semiconductors could open up an exciting opportunity for probing their fundamental physical properties in 2D systems and may find diverse applications in functional electronic/optoelectronic devices.
