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Propagation of light near the band edge in one-dimensional multilayers
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作者 唐洋 范灵杰 +3 位作者 张彦彬 李同宇 沈唐尧 石磊 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第4期370-373,共4页
Optical systems offer rich modulation in light propagation, but sufficient quantitative descriptions lack when highly complex structures are considered since practical structures contain defects or imperfections. Here... Optical systems offer rich modulation in light propagation, but sufficient quantitative descriptions lack when highly complex structures are considered since practical structures contain defects or imperfections. Here, we utilize a method combining a data-fitting method and a time-resolved system to describe light propagation near the band edges in onedimensional structures. Calculations after optimization of the method show little deviation to the measurements. 展开更多
关键词 light propagation band edge light localization
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Band Edge Model of (101)-Biaxial Strained Si 被引量:1
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作者 宋建军 张鹤鸣 +2 位作者 戴显英 胡辉勇 宣荣喜 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2008年第9期1670-1673,共4页
A band edge model in (101)-biaxial strained Si on relaxed Si1-x Gex alloy,or monoclinic Si (m-Si),is presented using the k · p perturbation method coupled with deformation potential theory. Results show that ... A band edge model in (101)-biaxial strained Si on relaxed Si1-x Gex alloy,or monoclinic Si (m-Si),is presented using the k · p perturbation method coupled with deformation potential theory. Results show that the [001], [001], [100], [100] valleys constitute the conduction band (CB) edge,which moves up in electron energy as the Ge fraction (x) increases. Furthermore,the CB splitting energy is in direct proportion to x and all the valence band (VB) edges move up in electron energy as x increases. In addition, the decrease in the indirect bandgap and the increase in the VB edge splitting energy as x increases are found. The quantitative data from the models supply valuable references for the design of the devices. 展开更多
关键词 strained Si band edge k · p method
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Band Edge Emission Improvement by Energy Transfer in HybridⅢ-Nitride/Organic Semiconductor Nanostructure
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作者 蒋府龙 刘亚莹 +9 位作者 李扬扬 陈鹏 刘斌 谢自力 修向前 华雪梅 韩平 施毅 张荣 郑有炓 《Chinese Physics Letters》 SCIE CAS CSCD 2016年第10期132-135,共4页
GaN nanorods are fabricated using inductively coupled plasma etching with Ni nano-island masks. The poly [2- methoxy-5-(2-ethyl)hexoxy-l,4-phenylenevinylene] (MEH-PPV)/GaN-nanorod hybrid structure is fabricated by... GaN nanorods are fabricated using inductively coupled plasma etching with Ni nano-island masks. The poly [2- methoxy-5-(2-ethyl)hexoxy-l,4-phenylenevinylene] (MEH-PPV)/GaN-nanorod hybrid structure is fabricated by depositing the MEH-PPV film on the GaN nanorods by using the spin-coating process. In the hybrid structure, the spatial separation is minimized to achieve high-emciency non-radiative resonant energy transfer. Optical properties of a novel device consisting of MEH-PPV/GaN-nanorod hybrid structure is studied by analyzing photoluminescenee (PL) spectra. Compared with the pure GaN nanorods, the PL intensity of the band edge emission of GaN in the MEH-PPV/GaN-nanorods is enhanced as much as three times, and the intensity of the yellow band is suppressed slightly. The obtained results are analyzed by energy transfer between the GaN nanorods and the MEH-PPV. An energy transfer model is proposed to explain the phenomenon. 展开更多
关键词 GaN PPV MEH Nitride/Organic Semiconductor Nanostructure band edge Emission Improvement by Energy Transfer in Hybrid by in
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Calculation of band edge levels of strained Si/(111)Si_(1-x)Ge_x
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作者 宋建军 张鹤鸣 +2 位作者 胡辉勇 戴显英 宣荣喜 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2010年第1期1-3,共3页
Calculations were performed on the band edge levels of (111)-biaxially strained Si on relaxed Si1-xGex alloy using the k.p perturbation method coupled with deformation potential theory. The results show that the con... Calculations were performed on the band edge levels of (111)-biaxially strained Si on relaxed Si1-xGex alloy using the k.p perturbation method coupled with deformation potential theory. The results show that the conduction band (CB) edge is characterized by six identicalvalleys, that the valence band (VB) edge degeneracies are partially lifted, and that both the CB and VB edge levels move up in electron energy as the Ge fraction (x) increases. In addition, the dependence of the indirect bandgap and the VB edge splitting energy on x was obtained. Quantitative data from the results supply valuable references for Si-based strained device design. 展开更多
关键词 strained Si band edge k-p method
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Tunable edge bands and optical properties in black phosphorus nanoribbons under electric field
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作者 Hong Liu 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第12期115-120,共6页
For several types of the applied electric field configuration on the normal-zigzag black phosphorus nanoribbon(nZZ-BPNR)we investigate the band structure and the linear optical absorption spectrum,especially for the e... For several types of the applied electric field configuration on the normal-zigzag black phosphorus nanoribbon(nZZ-BPNR)we investigate the band structure and the linear optical absorption spectrum,especially for the edge states and the corresponding low-energy absorption peaks.The obtained results show that the applied electric field can not only open another band gap at k=0.5 point,but also can change completely the spacial probabilities of edge states in the two edge bands.The strength of electric field can tune the two band gaps at the Γ point and 0.5 point.Further,one remarkable feature is that the forbidden transitionallowed.The lowest-excited-energy linear absorption peakfrom the transition between two edge bands at the Γ point.Finally,in comparison with the lowest-excited-energy peaks among various configurations,the second type of electric field configuration can move this peak blue-shift larger than other configurations. 展开更多
关键词 black phosphorus nanoribbon edge band linear optical absorption spectrum
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Band structure and edge states of star-like zigzag graphene nanoribbons
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作者 刘红 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第11期457-459,共3页
Connecting three zigzag graphene nanoribbons(ZGNRs) together through the sp^3 hybrid bonds forms a star-like ZGNR(S-ZGNR). Its band structure shows that there are four edge states at k = 0.5, in which the three el... Connecting three zigzag graphene nanoribbons(ZGNRs) together through the sp^3 hybrid bonds forms a star-like ZGNR(S-ZGNR). Its band structure shows that there are four edge states at k = 0.5, in which the three electrons distribute at three outside edge sites, and the last electron is shared equally(50%) by two sites near the central site. The lowest conductance step in the valley is 2, two times higher than that of monolayer ZGNR(M-ZGNR). Furthermore, in one quasithree-dimensional hexagonal lattice built, both of the Dirac points and the zero-energy states appear in the band structure along the z-axis for the fixed zero k-point in the x-y plane. In addition, it is an insulator in the x-y plane due to band gap 4 eV, however, for any k-point in the x-y plane the zero-energy states always exist at kz = 0.5. 展开更多
关键词 zigzag graphene nanoribbon band structure edge state
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Phosphorene-Based van der Waals Heterojunction for Solar Water Splitting 被引量:1
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作者 Peng Wang Jie Meng +2 位作者 Jing Huang Jia-jun Wang Qun-xiang Li 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2019年第4期431-436,I0002,共7页
As a clean and renewable future energy source, hydrogen fuel can be produced via solar water splitting. Two-dimensional (2D) black phosphorene (black-P) can harvest visible light due to the desirable band gap, which p... As a clean and renewable future energy source, hydrogen fuel can be produced via solar water splitting. Two-dimensional (2D) black phosphorene (black-P) can harvest visible light due to the desirable band gap, which promises it as a metal-free photocatalyst. However, black-P can be only used to produce hydrogen since the oxidation potential of water locates lower than the position of the valence band maximum. To improve the photocatalytic performance of black-P, here, using black-P and blue phosphorene (blue-P) monolayers, we propose a 2D van der Waals (vdW) heterojunction. Theoretical results, including the band structures, density of states, Bader charge population, charge density di erence, and optical absorption spectra, clearly reveal that the visible light absorption ability is obviously improved, and the band edge alignment of the proposed vdW heterojunction displays a typical type-II feature to effectively separate the photogenerated carriers. At the same time, the built-in interfacial electric field prevents the electron-hole recombination. These predictions suggest that the examined phosphorene-based vdW heterojunction is an efficient photocatalyst for solar water splitting. 展开更多
关键词 FIRST-PRINCIPLES Phosphorene band edge alignment van der Waals heter-junction Water splitting
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Work Function and Electron Affinity of Semiconductors:Doping Effect and Complication due to Fermi Level Pinning 被引量:1
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作者 Guosheng Shao 《Energy & Environmental Materials》 SCIE EI CAS CSCD 2021年第3期273-276,共4页
Semiconductors are a major category of functional materials essential to various applications to sustain the modern society.Most applied materials or devices utilizing semiconductors are enabled by interfaces or junct... Semiconductors are a major category of functional materials essential to various applications to sustain the modern society.Most applied materials or devices utilizing semiconductors are enabled by interfaces or junctions,such as solar cells,electronic/photonic devices,environmental sensors,and redox hetero-catalysts.Herein,the author provides a critical commentary on photoemission measurement of the work function and,more importantly,the electron affinity of semiconductors essential for energy band diagram of heterojunctions.Particular effort is made towards addressing complications associated with Fermi level pinning due to surficial states of doped semiconductors. 展开更多
关键词 band edges electron affinity Fermi pinning ultraviolet photoelectron spectroscopy work function
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g-C3N4/SnS2 Heterostructure: a Promising Water Splitting Photocatalyst
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作者 Shao-hua Chen Jia-jun Wang +1 位作者 Jing Huang Qun-xiang Li 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2017年第1期36-42,I0001,共8页
Graphite-like carbon nitride (g-C3N4) based heterostrutures has attracted intensive attention due to their prominent photocatalytic performance. Here, we explore the g-CaN4/SnS2 coupling effect on the electronic str... Graphite-like carbon nitride (g-C3N4) based heterostrutures has attracted intensive attention due to their prominent photocatalytic performance. Here, we explore the g-CaN4/SnS2 coupling effect on the electronic structures and optical absorption of the proposed g-CaN4/SnS2 heterostructure through performing extensive hybrid functional calculations. The obtained geometric structure, band structures, band edge positions and optical absorptions clearly reveal that the g-C3N4 monolayer weakly couples to SnS2 sheet, and forms a typical van der Waals heterojunction. The g-C3N4/SnS2 heterostructure can effectively harvest visible light, and its valence band maximum and conduction band minimum locate in energetically favorable positions for both water oxidation and reduction reactions. Remarkably, the charge transfer from the g-C3N4 monolayer to SnS2 sheet leads to the built-in interface polarized electric field, which is desirable for the photogenerated carrier separation. The built-in interface polarized electric field as well as the nice band edge alignment implys that the g-CaN4/SnS2 heterostructure is a promising g-CaN4 based water splitting photocatalyst with good performance. 展开更多
关键词 First-principles calculation Coupling effect Optical absorption band edge alignment Water splitting
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Two-Dimensional GaTe/Bi2Se3 Heterostructure:a Promising Direct Z-scheme Water Splitting Photocatalyst
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作者 Shu-min Tian Jie Meng +1 位作者 Jing Huang Qun-xiang Lia 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2020年第4期427-433,I0001,共8页
Among various photocatalytic materials,Z-scheme photocatalysts have drawn tremendous research interest due to high photocatalytic performance in solar water splitting.Here,we perform extensive hybrid density functiona... Among various photocatalytic materials,Z-scheme photocatalysts have drawn tremendous research interest due to high photocatalytic performance in solar water splitting.Here,we perform extensive hybrid density functional theory calculations to explore electronic structures,interfacial charge transfer,electrostatic potential profile,optical absorption properties,and photocatalytic properties of a proposed two-dimensional(2D)small-lattice-mismatched GaTe/Bi2Se3 heterostructure.Theoretical results clearly reveal that the examined heterostructure with a small direct band gap can effectively harvest the broad spectrum of the incoming sunlight.Due to the relative strong interfacial built-in electric field in the heterostructure and the small band gap between the valence band maximum of Ga Te monolayer and the conduction band minimum of Bi2Se3 nanosheet with slight band edge bending,these photogenerated carriers transfer via Z-scheme pathway,which results in the photogenerated electrons and holes effectively separating into the Ga Te monolayer and the Bi2Se3 nanosheet for the hydrogen and oxygen evolution reactions,respectively.Our results imply that the artificial 2D GaTe/Bi2Se3 is a promising Z-scheme photocatalyst for overall solar water splitting. 展开更多
关键词 Z-scheme photocatalyst Interfacial built-in electric field band edge alignment Water splitting
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Edge induced band bending in van der Waals heterojunctions:A first principle study 被引量:1
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作者 Yang Ou Zhuo Kang +2 位作者 Qingliang Liao Zheng Zhang Yue Zhang 《Nano Research》 SCIE EI CAS CSCD 2020年第3期701-708,共8页
The dangling bond free nature of two-dimensional(2D)material surface/interface makes van der Waals(vdW)heterostructure attractive for novel electronic and optoelectronic applications.But in practice,edge is unavoidabl... The dangling bond free nature of two-dimensional(2D)material surface/interface makes van der Waals(vdW)heterostructure attractive for novel electronic and optoelectronic applications.But in practice,edge is unavoidable and could cause band bending at 2D material edge analog to surface/interface band bending in conventional three-dimensional(3D)materials.Here,we report a first principle simulation on edge band bending of free standing MoS2/WS2 vdW heterojunction.Due to the imbalance charges at edge,S terminated edge causes upward band bending while Mo/W terminated induces downward bending in undoped case.The edge band bending is comparable to band gap and could obviously harm electronic and optoelectronic properties.We also investigate the edge band bending of electrostatic doped heterojunction.N doping raises the edge band whereas p doping causes a decline of edge band.Heavy n doping even reverses the downward edge band bending at Mo/W terminated edge.In contrast,heavy p doping doesn’t invert the upward bending to downward.Comparing with former experiments,the expected band gap narrowing introduced by interlayer potential gradient at edge is not observed in our free-standing structures and suggests substrate’s important role in this imbalance charge induced phenomenon. 展开更多
关键词 edge band bending imbalance charge electrostatic doping transition metal dichalcogenides(TMDCs)van der Waals(vdW)heterojunction first principle
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Atomically Precise Pd Species Accelerating CO_(2) Hydrodeoxygenation into CH_(4) with 100%Selectivity
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作者 Kai Zheng Siying Liu +14 位作者 Bangwang Li Juncheng Zhu Xiaojing Zhang Mingyu Wu Li Li Shan Zhu Wenxiu Liu Jun Hu Chengyuan Liu Minghui Fan Ming Zuo Junfa Zhu Yang Pan Yongfu Sun Yi Xie 《Precision Chemistry》 2023年第9期530-537,共8页
High-rate CO_(2)-to-CH_(4)photoreduction with high selectivity is highly attractive,which is a win-win strategy for mitigating the greenhouse effect and the energy crisis.However,the poor photocatalytic activity and l... High-rate CO_(2)-to-CH_(4)photoreduction with high selectivity is highly attractive,which is a win-win strategy for mitigating the greenhouse effect and the energy crisis.However,the poor photocatalytic activity and low product selectivity hinder the practical application.To precisely tailor the product selectivity and realize high-rate CO_(2)photoreduction,we design atomically precise Pd species supported on In_(2)O_(3)nanosheets.Taking the synthetic 1.30Pd/In_(2)O_(3)nanosheets as an example,the aberration-correction high-angle annular dark-field scanning transmission electron microscopy image displayed the Pd species atomically dispersed on the In_(2)O_(3)nanosheets.Raman spectra and X-ray photoelectron spectra established that the strong interaction between the Pd species and the In_(2)O_(3)substrate drove electron transfer from In to Pd species,resulting in electron-enriched Pd sites for CO_(2)activation.Synchrotronradiation photoemission spectroscopy demonstrated that the Pd species can tailor the conduction band edge of In_(2)O_(3)nanosheets to match the CO_(2)-to-CH_(4)pathway,instead of the CO_(2)-to-CO pathway,which theoretically accounts for the high CH_(4)selectivity.Moreover,in situ X-ray photoelectron spectroscopy unveiled that the catalytically active sites had a change from In species to Pd species over the 1.30Pd/In_(2)O_(3)nanosheets.In situ FTIR and EPR spectra reveal the atomically precise Pd species with rich electrons prefer to adsorb the electrophilic protons for accelerating the*COOH intermediates hydrogenation into CH_(4).Consequently,the 1.30Pd/In_(2)O_(3)nanosheets reached CO_(2)-to-CH_(4)photoconversion with 100%selectivity and 81.2μmol g^(−1)h^(−1)productivity. 展开更多
关键词 CO_(2)-to-CH_(4)pathway atomically precise Pd species conduction band edge CH4 selectivity photoelectrons transfer
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Photoluminescence and structural analysis of wurtzite(ZnO)1-x(V2O5)x composite
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作者 Amjid Iqbal Arshad Mahmood +5 位作者 Q. Raza A. Shah Rashad Rashid Zahid Ali A. Malik U. Aziz 《Journal of Semiconductors》 EI CAS CSCD 2018年第8期6-9,共4页
This paper demonstrates the structural, vibrational and photoluminescence characteristics of(ZnO)(VO)(x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffra... This paper demonstrates the structural, vibrational and photoluminescence characteristics of(ZnO)(VO)(x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffraction(XRD) studies show that(ZnO)(VO)composites have the poly crystalline wurtzite structure of hexagonal Zn O. It is found from the XRD results that the lattice constants and the crystallite size increase while the dislocation density decreases with increase in doping concentration. The existence of E1(TO) and E2(high) Raman modes show that the Zn O still preserve wurtzite structure after doping vanadium oxide, which is in agreement with XRD results. Room temperature photoluminescence(PL) exhibit near band edge and broad deep level emission while indicating the suppression of deep level emission with the incorporation of VOup to a certain concentration(x < 9). Moreover, the optical band gap increase with doping, which is accompanied by the blue shift of the NBE emission. 展开更多
关键词 Raman modes dislocation density band edge emission (ZnO)_(1-x)(V_2O_5)_x LUMINESCENCE
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Photophysical,optical,and photocatalytic hydrogen production properties of layered-type BaNb_(2-x)Ta_(x)P_(2)O_(11)(x=0,0.5,1.0,1.5,and 2.0)compounds
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作者 Min Je Kang Gill Sang Han In Sun Cho 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2022年第3期26-32,共7页
Layered-type metal phosphates of BaNb_(2-x)Ta_(x)P_(2)O_(11)(x=0,0.5,1.0,1.5,and 2.0)were synthesized using a solid-state reaction method.The photophysical,optical,and photocatalytic hydrogen production properties of ... Layered-type metal phosphates of BaNb_(2-x)Ta_(x)P_(2)O_(11)(x=0,0.5,1.0,1.5,and 2.0)were synthesized using a solid-state reaction method.The photophysical,optical,and photocatalytic hydrogen production properties of the resulting powders were investigated for the first time.Phase-pure and homogeneous powders with irregular morphologies were obtained at a calcination temperature of 1200℃.As the Ta content increased,the interlayer distance along the c-axis increased by up to 0.14%.Additionally,the optical bandgap values increased from 3.32 to 3.59 eV.The energy band positions were estimated from the Mott–Schottky measurements.BaNb_(2)P_(2)O_(11)(x=0)exhibited the lowest conduction band edge position(-0.14 V vs.the normal hydrogen electrode,NHE),which is located above the water reduction potential(0.0 V vs.NHE).In comparison,BaTa_(2)P_(2)O_(11)(x=2.0)exhibited the highest conduction band edge position(-0.29 V vs.NHE),comparable to that of TiO_(2).The photocatalytic activity for hydrogen produced from splitting water was measured under ultraviolet light irradiation.Notably,BaTa_(2)P_(2)O_(11)exhibited the highest activity(7.3μmol/h),which was 15 and 10 times larger than BaNb_(2)P_(2)O_(11)(0.5μmol/h)and nano-TiO_(2)(0.7μmol/h),respectively.The activity of BaTa_(2)P_(2)O_(11)increased to 24.4μmol/h after deposition of the NiO_(x)co-catalyst(1 wt.%),which remained stable during continuous operation(~35 h). 展开更多
关键词 BaNb_(2)P_(2)O_(11) BaTa_(2)P_(2)O_(11) Layered crystal structure bandgap band edge positions Photocatalytic hydrogen production
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