A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity(VHS) near the Fermi level by solving Bogoliubov–de Gennes(Bd G) equations. When the VHS ...A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity(VHS) near the Fermi level by solving Bogoliubov–de Gennes(Bd G) equations. When the VHS lies exactly at the Fermi level and also at the middle of the band, a zero-energy state and other higher-energy states whose energy ratios follow integer numbers emerge. These discrete vortex bound state peaks undergo a splitting behavior when the VHS or Fermi level moves away from the middle of the band. Such splitting behavior will eventually lead to a new arrangement of quantized vortex core states whose energy ratios follow half-odd-integer numbers.展开更多
Fermi level pinning and interface instability have hindered the achievement of field-effect-transistors(FETs)with high performance.Interface passivation and doping engineering technology have become the main driving f...Fermi level pinning and interface instability have hindered the achievement of field-effect-transistors(FETs)with high performance.Interface passivation and doping engineering technology have become the main driving force to solve the issue.Herein,interface chemistry and transport characteristics determination of Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb gate stacks have been achieved by passivation and doping process.X-ray photoelectron spectroscopy characterization and electrical measurements have demonstrated the existence of less intrinsic oxides and elemental Sb at Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb interface with optimized doping content,as well as the minimum leakage current density of 2.23×10^(5)A cm.The energy distribution of interface state based on conductance method has confirmed the achievement of the lowest interface state density of 1.98×10^(13)e Vcm,resulting in Fermi level unpinning.Carrier transport mechanisms of Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb MOS capacitors as a function of temperature have been investigated systematically and some important electrical parameters have been extracted.Comprehensive analyses show that sputtering-derived Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb(x=0.32)gate stack has potential application in future Ga Sbbased metal-oxide-semiconductor field effect transistor(MOSFET)devices.展开更多
On the basis of free-electronic bands, the Fermi energy is calculated by summing the band eigenvalues over Brillouin-zones ,and the results may lead to understand the physical basis of the average-bond-energy model in...On the basis of free-electronic bands, the Fermi energy is calculated by summing the band eigenvalues over Brillouin-zones ,and the results may lead to understand the physical basis of the average-bond-energy model in the calculation of valence-band offsets.展开更多
The dependences of Fermi-level pinning on interface state densities for the metal-dielectric, ploycrystalline silicon-dielectric, and metal silicide-dielectric interfaces are investigated by calculating their effectiv...The dependences of Fermi-level pinning on interface state densities for the metal-dielectric, ploycrystalline silicon-dielectric, and metal silicide-dielectric interfaces are investigated by calculating their effective work functions and their pinning factors. The Fermi-level pinning factors and effective work functions of the metal-dielectric interface are observed to be more susceptible to the increasing interface state densities, differing significantly from that of the ploycrystalline silicon-dielectric interface and the metal silicide-dielectric interface. The calculation results indicate that metal silicide gates with high-temperature resistance and low resistivity are a more promising choice for the design of gate materials in metal-oxide semiconductor（MOS） technology.展开更多
Superconducting SnTe-type topological crystalline insulators(TCIs)are predicted to host multiple Majorana zero modes(MZMs)which can coexist in a single vortex.Fermi level(FL)close to the Dirac points of topological su...Superconducting SnTe-type topological crystalline insulators(TCIs)are predicted to host multiple Majorana zero modes(MZMs)which can coexist in a single vortex.Fermi level(FL)close to the Dirac points of topological surface states is helpful for detecting MZMs.However,the TCI SnTe is a heavily p-type semiconductor which is very difficult to modify to n-type via doping or alloying.In this work,we fabricate the atomically flat Sn_(1-x)Pb_(x)Te/Pb heterostructure by molecular beam epitaxy,and make the p-type Sn_(1-x)Pb_(x)Te become n-type through changing the interface roughness.Using scanning tunnelling microscope,we find the Dirac points of Sn_(1-x)Pb_(x)Te/Pb heterostructure are always above the FL due to the Fermi level pinning(FLP)induced by topological surface states at atomically flat interface.After increasing the interface roughness,the FLP effect is suppressed and then the Dirac points of p-type Sn_(1-x)Pb_(x)Te can be tuned very close to or even below the FL.Our work provides a new method for tuning the FL of SnTe-type TCI which has potential application in novel topological superconductor device.展开更多
We present a generic approximate graphical method for determining the equilibrium Fermi level and majority carrier density of a semiconductor with multiple donors and multiple acceptors compensating each other. Simple...We present a generic approximate graphical method for determining the equilibrium Fermi level and majority carrier density of a semiconductor with multiple donors and multiple acceptors compensating each other. Simple and easy-to-follow procedures of the graphical method are described.By graphically plotting two wrapping step functions facing each other,one for the positive hole-ionized donor and one for the negative electron-ionized acceptor,we have the crossing point that renders the Fermi level and majority carrier density.Using the graphical method,new equations are derived,such as the carrier compensation proportional to N;/N;,not the widely quoted N;-N;.Visual insight is offered to view not only the result of graphic determination of Fermi level and majority carrier density but also the dominant and critical pair of donors and acceptors in compensation.The graphical method presented in this work will help to guide the design,adjustment,and improvement of the multiply doped semiconductors.Comparison of this approximate graphical method with previous work on compensation,and with some experimental results,is made.Future work in the field is proposed.展开更多
The photocatalytic performances are highly dependent on the charge separation and surface reaction kinetics of photocatalysts.Aiming at figuring out the effects of co-catalyst with the lower Fermi level on photocataly...The photocatalytic performances are highly dependent on the charge separation and surface reaction kinetics of photocatalysts.Aiming at figuring out the effects of co-catalyst with the lower Fermi level on photocatalytic activity,we tuned the Fermi level of Pt nanoparticles on g-C_(3)N_(4)(GCN)by introducing Co atom.Experimental results show that lowering the Fermi level of co-catalyst does not alter light absorption of GCN due to the invariable structure.Besides,Pt_(3)Co with a lower Fermi level contributes less positive influence on charge separation in GCN due to an opposite effect from the stronger electron-trap ability of Pt_(3)Co and increased band bending in GCN-Pt_(3)Co.The density functional theory(DFT)calculations indicate that GCN-Pt_(3)Co has faster surface reaction kinetics than GCN-Pt,owing to easier dissociation of H_(2)O molecules and faster desorption of H^(*)on Pt_(3)Co.Consequently,GCN-Pt_(3)Co exhibits an excellent H_(2) evolution rate with 2.91 mmol g^(-1)·h^(-1),which 2.67 times that of GCN-Pt.展开更多
For semiconductors with localized intrinsic/impurity defects, intentionally doped or unintentionally incorporated, that have multiple transition energy levels among charge states, the general formulation of the local ...For semiconductors with localized intrinsic/impurity defects, intentionally doped or unintentionally incorporated, that have multiple transition energy levels among charge states, the general formulation of the local charge neutrality condition is given for the determination of the Fermi level and the majority carrier density. A graphical method is used to illustrate the solution of the problem. Relations among the transition energy levels of the multi-level defect are derived using the graphical method. Numerical examples are given for p-doping of the CdTe thin film used in solar panels and semi-insulating Si to illustrate the relevance and importance of the issues discussed in this work.展开更多
Insertion of a C-containing layer in a metal/Ge structure,using a chemical bath,enabled the Schottky barrier height（SBH） to be modulated.Chemical baths with 1-octadecene,1-hexadecene,1-tetradecene,and 1- dodecene we...Insertion of a C-containing layer in a metal/Ge structure,using a chemical bath,enabled the Schottky barrier height（SBH） to be modulated.Chemical baths with 1-octadecene,1-hexadecene,1-tetradecene,and 1- dodecene were used separately with Ge substrates.An ultrathin C-containing layer stops the penetration of free electron wave functions from the metal to the Ge.Metal-induced gap states are alleviated and the pinned Fermi level is released.The SBH is lowered to 0.17 eV.This new formation method is much less complex than traditional ones,and the result is very good.展开更多
A compact model is proposed to derive the charge density of the AlInSb/InSb HEMT devices by con- sidering the variation of Fermi level, the first subband, the second subband and sheet carrier charge density with appli...A compact model is proposed to derive the charge density of the AlInSb/InSb HEMT devices by con- sidering the variation of Fermi level, the first subband, the second subband and sheet carrier charge density with applied gate voltage. The proposed model considers the Fermi level dependence of charge density and vice versa. The analytical results generated by the proposed model are compared and they agree well with the experimental results. The developed model can be used to implement a physics based compact model for an InSb HEMT device in SPICE applications.展开更多
For photocatalytic materials,the composites formed by metal oxides and heteroatom-doped carbon have outstanding activity.Among them,metal-organic framework(MOF)derived composites,usually composed of metal oxide and ni...For photocatalytic materials,the composites formed by metal oxides and heteroatom-doped carbon have outstanding activity.Among them,metal-organic framework(MOF)derived composites,usually composed of metal oxide and nitrogen-doped carbon,is not only simple to prepare,but also have far-exceeding catalytic performance than homogenous semiconductor.However,the relationship between the structure and performance in the photocatalytic system is still not clear.Here,we explored the tunable nitrogen configurations in sample N-ZnO@NC by controlling the thermal conversion of ZIF-8.Crucially,through exsitu and in-situ XPS characterization,it is found that the ZnO and nitrogen-doped carbon in N-ZnO@NC are connected by C-N-Zn bond,which enhances charge separation efficiency and becomes the origin of superior photocatalytic performance.DFT calculations further reveal the influence of different Zn-bonding nitrogen configurations on the adjusting of Fermi level and electron transfer.This study exhibits that the pyridine-N configuration in MOF-derived material is the main contributor for the improved performance and tunes Fermi level more appropriately than the pyrrolic-N,which can hold the key for future design of next-generation photocatalysts.展开更多
The widely used deep level transient spectroscopy（DLTS） theory and data analysis usually assume that the defect level distribution is uniform through the depth of the depletion region of the n–p junction. In this w...The widely used deep level transient spectroscopy（DLTS） theory and data analysis usually assume that the defect level distribution is uniform through the depth of the depletion region of the n–p junction. In this work we introduce the concept of effective Fermi level of the steady state of semiconductor, by using which deep level transient spectroscopy depth profiling（DLTSDP） is proposed. Based on the relationship of its transition free energy level（TFEL） and the effective Fermi level, the rules of detectivity of the defect levels are listed. Computer simulation of DLTSDP is presented and compared with experimental data. The experimental DLTS data are compared with what the DLTSDP selection rules predicted. The agreement is satisfactory.展开更多
Antibiotics and heavy metals usually co-exist in wastewater and pose serious environmental hazards.Herein,a series of VMo-BMO/O_(v)-BOB S-scheme heterojunctions with double vacancy(Mo vacancy and photoexcited O vacanc...Antibiotics and heavy metals usually co-exist in wastewater and pose serious environmental hazards.Herein,a series of VMo-BMO/O_(v)-BOB S-scheme heterojunctions with double vacancy(Mo vacancy and photoexcited O vacancy)were constructed via an electrostatic assembly method.The removal efficiency of Cr(VI)and tetracycline(TC)over VMo-BMO/O_(v)-BOB-0.3 was 2.47 and 1.13 times than that of a single system,respectively.In-situ EPR demonstrated that the surface O vacancies could be generated under LED light irradiation.These photoexcited O vacancies(P-O_(v))enabled VMo-BMO/O_(v)-BOB composites still exhibit satisfactory activity after five successive cycles and an amplified Fermi level gap.The enhancement could be attributed to the enhanced internal electric field and double-vacancy-induced polarization.Additionally,the density functional theory calculation results suggested that double vacancy induced polarization electric field increases the dipole moment,which was conducive to rapid electron transport.Photoluminescence and time-resolved photoluminescence analysis demonstrated that the introduction of S-scheme heterojunction and double vacancy promoted charge transfer and prolonged the lifetime of carriers.Degradation intermediates and toxicity of products were evaluated.In conclusion,a possible mechanism based on VMo-BMO/O_(v)-BOB S-scheme heterojunction in the simultaneous removal of Cr(VI)and TC was proposed.展开更多
The photoelectrocatalytic(PEC)CO_(2)reduction process includes photogenerated charge transport,multiphase interface,intermediate adsorption,and chemical bonding transformation,all of which are closely associated with ...The photoelectrocatalytic(PEC)CO_(2)reduction process includes photogenerated charge transport,multiphase interface,intermediate adsorption,and chemical bonding transformation,all of which are closely associated with the interface and surface layer on the photocathode.However,it is difficult to design the photocathode with an effective interface and surface active site for realizing the highly selective PEC CO_(2)reduction at ultralow potential.Here,we design a novel semiconductor p-n junction comprising Si nanowires and an indium-edited porphyrin-based metal-organic framework{Al/In-PMOF(Co)}for efficient CO_(2)reduction.The Al/In-PMOF(Co)catalyst containing In and Co metal atoms demonstrates quasidiatomic site behavior,where the introduced In causes redistribution of the electronic structure of the Co 3d states.Besides,the Al/In-PMOF(Co)layer promotes bulk charge transport and interfacial charge transfer of Si photocathode during PEC CO_(2)reduction.The Faradaic efficiency of the Si-Al/In-PMOF(Co)photocathode toward CO could increase to>90%at 0.2 V vs.RHE.Si-Al/In-PMOF(Co)photocathode also achieves a high applied bias solar-to-CO(STC)efficiency of 2.8%,which is at the state-of-the-art level.The enhanced PEC CO_(2)reduction performance is ascribed to the variation of the Fermi level of AlPMOF(Co)after the introduction of In atoms,expediting the charge transport and promoting the shift of potential of Si photocathode.Density functional theory(DFT)calculation also demonstrates that the molecular catalyst layer with quasi-diatomic sites facilitates the^(*)COOH absorption and^(*)CO desorption,thereby accelerating CO production.展开更多
Motivated by the recent discovery of charge density wave(CDW)order in the magnetic kagomémetal Fe Ge,we study the single-orbital t-N-V_(1)-V_(2)model on the kagomélattice,where N,V_(1),and V_(2)are the onsit...Motivated by the recent discovery of charge density wave(CDW)order in the magnetic kagomémetal Fe Ge,we study the single-orbital t-N-V_(1)-V_(2)model on the kagomélattice,where N,V_(1),and V_(2)are the onsite,nearest neighbor,and next-nearest-neighbor Coulomb interactions,respectively.When the Fermi level lies in the flat band,the instability toward ferromagnetic(FM)order gives rise to a FM half-metal at sufficiently large onsite N.Intriguingly,at band filling n=17/24,the Fermi level crosses the van Hove singularity of the spin-minority bands of the half-metal.We show that,due to the unique geometry and sublattice interference on the kagomélattice at van Hove singularity,the inter-site Coulomb interactions V_(1) and V_(2)drive a real and an imaginary bond-ordered 2a_(0)×2a_(0) CDW instability,respectively.The FM loop current CDW with complex bond orders is a spin-polarized Chern insulator exhibiting the quantum anomalous Hall effect.The bond fluctuations are found to be substantially enhanced compared to the corresponding nonmagnetic kagomémetals at van Hove filling,providing a concrete model realization of the bond-ordered CDWs,including the FM loop current CDW,over the onsite charge density ordered states.When the spins are partially polarized at an intermediate N,we find that the interplay of CDW and magnetism enables the formation of real and complex bond-ordered CDWs,and the CDW transition is accompanied by a substantial enhancement in the ordered magnetic moments.These findings provide physical insights for the emergence of 2a_(0)×2a_(0) CDWs and their interplay with magnetism on the kagomélattice,and capture the essential physics observed experimentally in Fe Ge.展开更多
Interfacial solar evaporation,which captures solar energy and localizes the absorbed heat for water evaporation,is considered a promising technology for seawater desalination and solar energy conversion.However,it is ...Interfacial solar evaporation,which captures solar energy and localizes the absorbed heat for water evaporation,is considered a promising technology for seawater desalination and solar energy conversion.However,it is currently limited by its low photothermal conversion efficiency,salt accumulation,and poor reliability.Herein,inspired by human intestinal villi structure,we design and fabricate a novel intestinal villi-like nitrogen-doped carbon nanotubes solar steam generator(N-CNTs SSG)consisting of three-dimensional(3D)hierarchical carbon nanotube matrices for ultrahigh solar evaporation efficiency.The 3D matrices with radial direction nitrogen-doped carbon nanotube clusters achieve ultrahigh surface area,photothermal efficiency,and hydrophilicity,which significantly intensifies the whole interfacial solar evaporation process.The new solar evaporation efficiency reaches as high as 96.8%.Furthermore,our ab initio molecular dynamics simulation reveals that N-doped carbon nanotubes exhibit a greater number of electronic states in close proximity to the Fermi level when compared to pristine carbon nanotubes.The outstanding absorptivity in the full solar spectrum and high solar altitude angles of the 3D hierarchical carbon nanotube matrices offer great potential to enable ultrahigh photothermal conversion under all-day and all-season circumstances.展开更多
基金the National Natural Science Foundation of China (Grant No. 11804154)the Scientific Research Foundation of NJIT (Grant Nos. YKJ201853 and CKJA201807)。
文摘A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity(VHS) near the Fermi level by solving Bogoliubov–de Gennes(Bd G) equations. When the VHS lies exactly at the Fermi level and also at the middle of the band, a zero-energy state and other higher-energy states whose energy ratios follow integer numbers emerge. These discrete vortex bound state peaks undergo a splitting behavior when the VHS or Fermi level moves away from the middle of the band. Such splitting behavior will eventually lead to a new arrangement of quantized vortex core states whose energy ratios follow half-odd-integer numbers.
基金the National Natural Science Foundation of China(No.11774001)the Anhui Project(No.Z010118169)。
文摘Fermi level pinning and interface instability have hindered the achievement of field-effect-transistors(FETs)with high performance.Interface passivation and doping engineering technology have become the main driving force to solve the issue.Herein,interface chemistry and transport characteristics determination of Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb gate stacks have been achieved by passivation and doping process.X-ray photoelectron spectroscopy characterization and electrical measurements have demonstrated the existence of less intrinsic oxides and elemental Sb at Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb interface with optimized doping content,as well as the minimum leakage current density of 2.23×10^(5)A cm.The energy distribution of interface state based on conductance method has confirmed the achievement of the lowest interface state density of 1.98×10^(13)e Vcm,resulting in Fermi level unpinning.Carrier transport mechanisms of Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb MOS capacitors as a function of temperature have been investigated systematically and some important electrical parameters have been extracted.Comprehensive analyses show that sputtering-derived Hf_(1-x)Yb_(x)O_(y)/Al_(2)O_(3)/GaSb(x=0.32)gate stack has potential application in future Ga Sbbased metal-oxide-semiconductor field effect transistor(MOSFET)devices.
文摘On the basis of free-electronic bands, the Fermi energy is calculated by summing the band eigenvalues over Brillouin-zones ,and the results may lead to understand the physical basis of the average-bond-energy model in the calculation of valence-band offsets.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61376096,61327813,and 11234007)
文摘The dependences of Fermi-level pinning on interface state densities for the metal-dielectric, ploycrystalline silicon-dielectric, and metal silicide-dielectric interfaces are investigated by calculating their effective work functions and their pinning factors. The Fermi-level pinning factors and effective work functions of the metal-dielectric interface are observed to be more susceptible to the increasing interface state densities, differing significantly from that of the ploycrystalline silicon-dielectric interface and the metal silicide-dielectric interface. The calculation results indicate that metal silicide gates with high-temperature resistance and low resistivity are a more promising choice for the design of gate materials in metal-oxide semiconductor（MOS） technology.
基金the Ministry of Science and Technology of China(Grant Nos.2019YFA0308600,and 2020YFA0309000)the National Natural Science Foundation of China(Grant Nos.11861161003,12104293,92365302,22325203,92265105,92065201,12074247,and 12174252)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Science and Technology Commission of Shanghai Municipality(Grant Nos.2019SHZDZX01,19JC1412701,and 20QA1405100)the Innovation program for Quantum Science and Technology(Grant No.2021ZD0302500)the China National Postdoctoral Program for Innovative Talents(Grant No.BX2021185)。
文摘Superconducting SnTe-type topological crystalline insulators(TCIs)are predicted to host multiple Majorana zero modes(MZMs)which can coexist in a single vortex.Fermi level(FL)close to the Dirac points of topological surface states is helpful for detecting MZMs.However,the TCI SnTe is a heavily p-type semiconductor which is very difficult to modify to n-type via doping or alloying.In this work,we fabricate the atomically flat Sn_(1-x)Pb_(x)Te/Pb heterostructure by molecular beam epitaxy,and make the p-type Sn_(1-x)Pb_(x)Te become n-type through changing the interface roughness.Using scanning tunnelling microscope,we find the Dirac points of Sn_(1-x)Pb_(x)Te/Pb heterostructure are always above the FL due to the Fermi level pinning(FLP)induced by topological surface states at atomically flat interface.After increasing the interface roughness,the FLP effect is suppressed and then the Dirac points of p-type Sn_(1-x)Pb_(x)Te can be tuned very close to or even below the FL.Our work provides a new method for tuning the FL of SnTe-type TCI which has potential application in novel topological superconductor device.
文摘We present a generic approximate graphical method for determining the equilibrium Fermi level and majority carrier density of a semiconductor with multiple donors and multiple acceptors compensating each other. Simple and easy-to-follow procedures of the graphical method are described.By graphically plotting two wrapping step functions facing each other,one for the positive hole-ionized donor and one for the negative electron-ionized acceptor,we have the crossing point that renders the Fermi level and majority carrier density.Using the graphical method,new equations are derived,such as the carrier compensation proportional to N;/N;,not the widely quoted N;-N;.Visual insight is offered to view not only the result of graphic determination of Fermi level and majority carrier density but also the dominant and critical pair of donors and acceptors in compensation.The graphical method presented in this work will help to guide the design,adjustment,and improvement of the multiply doped semiconductors.Comparison of this approximate graphical method with previous work on compensation,and with some experimental results,is made.Future work in the field is proposed.
基金supported by the National Key Research and Development Program of China(No.2017YFE0193900)the National Natural Science Foundation of China(No.51802255)+4 种基金the Natural Science Foundation of Shaanxi Province(Nos.2021GXLH-Z-O and 2020JZ-02)the project of Innovative Team of Shaanxi Province(2020TD-001)the China Fundamental Research Funds for the Central Universitiesthe World-Class Universities(Disciplines)the Characteristic Development Guidance Funds for the Central Universities.
文摘The photocatalytic performances are highly dependent on the charge separation and surface reaction kinetics of photocatalysts.Aiming at figuring out the effects of co-catalyst with the lower Fermi level on photocatalytic activity,we tuned the Fermi level of Pt nanoparticles on g-C_(3)N_(4)(GCN)by introducing Co atom.Experimental results show that lowering the Fermi level of co-catalyst does not alter light absorption of GCN due to the invariable structure.Besides,Pt_(3)Co with a lower Fermi level contributes less positive influence on charge separation in GCN due to an opposite effect from the stronger electron-trap ability of Pt_(3)Co and increased band bending in GCN-Pt_(3)Co.The density functional theory(DFT)calculations indicate that GCN-Pt_(3)Co has faster surface reaction kinetics than GCN-Pt,owing to easier dissociation of H_(2)O molecules and faster desorption of H^(*)on Pt_(3)Co.Consequently,GCN-Pt_(3)Co exhibits an excellent H_(2) evolution rate with 2.91 mmol g^(-1)·h^(-1),which 2.67 times that of GCN-Pt.
文摘For semiconductors with localized intrinsic/impurity defects, intentionally doped or unintentionally incorporated, that have multiple transition energy levels among charge states, the general formulation of the local charge neutrality condition is given for the determination of the Fermi level and the majority carrier density. A graphical method is used to illustrate the solution of the problem. Relations among the transition energy levels of the multi-level defect are derived using the graphical method. Numerical examples are given for p-doping of the CdTe thin film used in solar panels and semi-insulating Si to illustrate the relevance and importance of the issues discussed in this work.
基金supported by the Chinese National Key Basic Research Program(No.2011CBA00602)the National Key Scientific and Technological Projects,China(Nos.2009ZX02035-004-02,2011ZX02708-002)
文摘Insertion of a C-containing layer in a metal/Ge structure,using a chemical bath,enabled the Schottky barrier height（SBH） to be modulated.Chemical baths with 1-octadecene,1-hexadecene,1-tetradecene,and 1- dodecene were used separately with Ge substrates.An ultrathin C-containing layer stops the penetration of free electron wave functions from the metal to the Ge.Metal-induced gap states are alleviated and the pinned Fermi level is released.The SBH is lowered to 0.17 eV.This new formation method is much less complex than traditional ones,and the result is very good.
基金Project supported by the Council of Scientific & Industrial Research(CSIR),India under the Senior Research Fellowship Scheme(No.08/237(0005)/2012-EMR-I)
文摘A compact model is proposed to derive the charge density of the AlInSb/InSb HEMT devices by con- sidering the variation of Fermi level, the first subband, the second subband and sheet carrier charge density with applied gate voltage. The proposed model considers the Fermi level dependence of charge density and vice versa. The analytical results generated by the proposed model are compared and they agree well with the experimental results. The developed model can be used to implement a physics based compact model for an InSb HEMT device in SPICE applications.
基金financially supported by National Natural Science Foundation of China(Nos.U20A20246 and 51872108)Fundamental Research Funds for the Central Universities(No.CCNU20TS006)。
文摘For photocatalytic materials,the composites formed by metal oxides and heteroatom-doped carbon have outstanding activity.Among them,metal-organic framework(MOF)derived composites,usually composed of metal oxide and nitrogen-doped carbon,is not only simple to prepare,but also have far-exceeding catalytic performance than homogenous semiconductor.However,the relationship between the structure and performance in the photocatalytic system is still not clear.Here,we explored the tunable nitrogen configurations in sample N-ZnO@NC by controlling the thermal conversion of ZIF-8.Crucially,through exsitu and in-situ XPS characterization,it is found that the ZnO and nitrogen-doped carbon in N-ZnO@NC are connected by C-N-Zn bond,which enhances charge separation efficiency and becomes the origin of superior photocatalytic performance.DFT calculations further reveal the influence of different Zn-bonding nitrogen configurations on the adjusting of Fermi level and electron transfer.This study exhibits that the pyridine-N configuration in MOF-derived material is the main contributor for the improved performance and tunes Fermi level more appropriately than the pyrrolic-N,which can hold the key for future design of next-generation photocatalysts.
基金the China Triumph International Engineering Company (CTIEC), Shanghai, China, which offered generous financial support for this work
文摘The widely used deep level transient spectroscopy（DLTS） theory and data analysis usually assume that the defect level distribution is uniform through the depth of the depletion region of the n–p junction. In this work we introduce the concept of effective Fermi level of the steady state of semiconductor, by using which deep level transient spectroscopy depth profiling（DLTSDP） is proposed. Based on the relationship of its transition free energy level（TFEL） and the effective Fermi level, the rules of detectivity of the defect levels are listed. Computer simulation of DLTSDP is presented and compared with experimental data. The experimental DLTS data are compared with what the DLTSDP selection rules predicted. The agreement is satisfactory.
文摘Antibiotics and heavy metals usually co-exist in wastewater and pose serious environmental hazards.Herein,a series of VMo-BMO/O_(v)-BOB S-scheme heterojunctions with double vacancy(Mo vacancy and photoexcited O vacancy)were constructed via an electrostatic assembly method.The removal efficiency of Cr(VI)and tetracycline(TC)over VMo-BMO/O_(v)-BOB-0.3 was 2.47 and 1.13 times than that of a single system,respectively.In-situ EPR demonstrated that the surface O vacancies could be generated under LED light irradiation.These photoexcited O vacancies(P-O_(v))enabled VMo-BMO/O_(v)-BOB composites still exhibit satisfactory activity after five successive cycles and an amplified Fermi level gap.The enhancement could be attributed to the enhanced internal electric field and double-vacancy-induced polarization.Additionally,the density functional theory calculation results suggested that double vacancy induced polarization electric field increases the dipole moment,which was conducive to rapid electron transport.Photoluminescence and time-resolved photoluminescence analysis demonstrated that the introduction of S-scheme heterojunction and double vacancy promoted charge transfer and prolonged the lifetime of carriers.Degradation intermediates and toxicity of products were evaluated.In conclusion,a possible mechanism based on VMo-BMO/O_(v)-BOB S-scheme heterojunction in the simultaneous removal of Cr(VI)and TC was proposed.
基金supported by the National Natural Science Foundation of Hunan Province(2025JJ60094)the Hunan Provincial Natural Science Foundation for Distinguished Young Scholars(2025JJ20019)the National Natural Science Foundation of China(22078368)。
文摘The photoelectrocatalytic(PEC)CO_(2)reduction process includes photogenerated charge transport,multiphase interface,intermediate adsorption,and chemical bonding transformation,all of which are closely associated with the interface and surface layer on the photocathode.However,it is difficult to design the photocathode with an effective interface and surface active site for realizing the highly selective PEC CO_(2)reduction at ultralow potential.Here,we design a novel semiconductor p-n junction comprising Si nanowires and an indium-edited porphyrin-based metal-organic framework{Al/In-PMOF(Co)}for efficient CO_(2)reduction.The Al/In-PMOF(Co)catalyst containing In and Co metal atoms demonstrates quasidiatomic site behavior,where the introduced In causes redistribution of the electronic structure of the Co 3d states.Besides,the Al/In-PMOF(Co)layer promotes bulk charge transport and interfacial charge transfer of Si photocathode during PEC CO_(2)reduction.The Faradaic efficiency of the Si-Al/In-PMOF(Co)photocathode toward CO could increase to>90%at 0.2 V vs.RHE.Si-Al/In-PMOF(Co)photocathode also achieves a high applied bias solar-to-CO(STC)efficiency of 2.8%,which is at the state-of-the-art level.The enhanced PEC CO_(2)reduction performance is ascribed to the variation of the Fermi level of AlPMOF(Co)after the introduction of In atoms,expediting the charge transport and promoting the shift of potential of Si photocathode.Density functional theory(DFT)calculation also demonstrates that the molecular catalyst layer with quasi-diatomic sites facilitates the^(*)COOH absorption and^(*)CO desorption,thereby accelerating CO production.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403800 and 2023YFA1407300)the National Natural Science Foundation of China(Grant Nos.12374153,12447101,and 11974362)supported by the U.S.Department of Energy,Basic Energy Sciences(Grant No.DE-FG02-99ER45747)。
文摘Motivated by the recent discovery of charge density wave(CDW)order in the magnetic kagomémetal Fe Ge,we study the single-orbital t-N-V_(1)-V_(2)model on the kagomélattice,where N,V_(1),and V_(2)are the onsite,nearest neighbor,and next-nearest-neighbor Coulomb interactions,respectively.When the Fermi level lies in the flat band,the instability toward ferromagnetic(FM)order gives rise to a FM half-metal at sufficiently large onsite N.Intriguingly,at band filling n=17/24,the Fermi level crosses the van Hove singularity of the spin-minority bands of the half-metal.We show that,due to the unique geometry and sublattice interference on the kagomélattice at van Hove singularity,the inter-site Coulomb interactions V_(1) and V_(2)drive a real and an imaginary bond-ordered 2a_(0)×2a_(0) CDW instability,respectively.The FM loop current CDW with complex bond orders is a spin-polarized Chern insulator exhibiting the quantum anomalous Hall effect.The bond fluctuations are found to be substantially enhanced compared to the corresponding nonmagnetic kagomémetals at van Hove filling,providing a concrete model realization of the bond-ordered CDWs,including the FM loop current CDW,over the onsite charge density ordered states.When the spins are partially polarized at an intermediate N,we find that the interplay of CDW and magnetism enables the formation of real and complex bond-ordered CDWs,and the CDW transition is accompanied by a substantial enhancement in the ordered magnetic moments.These findings provide physical insights for the emergence of 2a_(0)×2a_(0) CDWs and their interplay with magnetism on the kagomélattice,and capture the essential physics observed experimentally in Fe Ge.
基金Funding information National Natural Science Foundation of China,Grant/Award Numbers:52476072,51936005Young Talent Support Project of Guangzhou Association for Science and Technology+1 种基金Guangdong Basic and Applied Basic Research Foundation(No.2024A1515030035)Guangdong Pro vincial University Innovation Team Project(No.2023KCXTD038)。
文摘Interfacial solar evaporation,which captures solar energy and localizes the absorbed heat for water evaporation,is considered a promising technology for seawater desalination and solar energy conversion.However,it is currently limited by its low photothermal conversion efficiency,salt accumulation,and poor reliability.Herein,inspired by human intestinal villi structure,we design and fabricate a novel intestinal villi-like nitrogen-doped carbon nanotubes solar steam generator(N-CNTs SSG)consisting of three-dimensional(3D)hierarchical carbon nanotube matrices for ultrahigh solar evaporation efficiency.The 3D matrices with radial direction nitrogen-doped carbon nanotube clusters achieve ultrahigh surface area,photothermal efficiency,and hydrophilicity,which significantly intensifies the whole interfacial solar evaporation process.The new solar evaporation efficiency reaches as high as 96.8%.Furthermore,our ab initio molecular dynamics simulation reveals that N-doped carbon nanotubes exhibit a greater number of electronic states in close proximity to the Fermi level when compared to pristine carbon nanotubes.The outstanding absorptivity in the full solar spectrum and high solar altitude angles of the 3D hierarchical carbon nanotube matrices offer great potential to enable ultrahigh photothermal conversion under all-day and all-season circumstances.
