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INVESTIGATION ON THE VALENCE STATE OF Ce ATOMIN BULK AND NANOCRYSTAL CeO_2 BY X-RAY ABSORPTION ANDphotoemission

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Acta Metallurgica Sinica(English Letters) 2001年第6期14卷 511-516页

作者： K. Ibrahim, Z.Y. Wu, J. Zhang, M.I. Abbas, F.Q. Liu and H.J. Qian (Beijing Synchrotron Radiation Laboratory, Institute of High Energy Physics, The Chinese Academy of Sciences, P.O. Box 918, Beijing 100039, China) Beijing Synchrotron Radiat. Lab. Inst. of High Energy Phys. Chinese Acad. of Sci. P.O. Box 918 Beijing 100039 China

Valence band photoemission spectra (PES) for both bulk and nanocrystal CeO2 have been measured on and off resonance of Ce 4d-4f absorption edge. The PES show that the bulk and nanocrystal CeO2 of diameter ranging from 8nm to 50nm exhibit a peak near Fermi edge with binding energy of about 1.8eV. The 1.8eV peak shows a strong dependence on excitation energy, although it looks like the contribution of Ce3+ ion following the data reported in literatures. However, according to the results of resonance photoemission and X-ray absorption spectra at 1s edge, this electronic structure may be associated to the intermediate state charge transfer effects.

关键词： rare earth oxide photoemission electronic structure photoabsorption

Adsorption and reaction of CO and O_2 on the Ag/Pt(110) surface studied by photoemis-sion electron microscopy

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Chinese Science Bulletin 2001年第12期46卷 998-1002页

作者： HUANG Weixin & BAO XinheState Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian China

The Ag/Pt(110) model catalyst was prepared by evaporating silver on Pt(110). Adsorption and reaction of CO and O2 on Ag/Pt(110) surface were studied in situ by photo-emission electron microscopy (PEEM) during the pressure range of 10-5-10-2 Pa at 480 K. The Ag/Pt(110) surface consisted of Pt(110), AgPt interface and Ag area after annealing at 500 K. The dosing pressure of CO and O2 had a larger influence on their adsorption on the Ag area than on the Pt(110) and AgPt interface. Small Pt clusters formed on the Ag area and AgPt interface, which had a stronger ability to adsorb CO than Pt(110) terrace. The existence of Ag had an obvious influence on the kinetic of CO oxidation on Pt(110). No pattern was observed on the AgPt interface under the same condition when the formation of reaction-diffusion waves occurred on Pt(110).

关键词： silver Pt(110) carbon monoxide oxygen adsorption reaction photoemission electron microscopy.

Surface-induced orbital-selective band reconstruction in kagome superconductor CsV_(3)Sb_(5)

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Chinese Physics B 2022年第5期31卷 10-14页

作者：淮琳崴罗洋 Samuel M.L.Teicher Brenden R.Ortiz 王铠泽彭舒婷魏志远沈建昌王冰倩缪宇孙秀鹏欧志鹏 Stephen D.Wilson 何俊峰 CAS Key Laboratory of Strongly-coupled Quantum Matter Physics and Department of Physics University of Science and Technology of ChinaHefei 230026China Materials Department and California Nanosystems Institute University of California Santa BarbaraSanta BarbaraCalifornia 93106USA

The two-dimensional(2 D)kagome superconductor Cs V_(3)Sb_(5) has attracted much recent attention due to the coexistence of superconductivity,charge orders,topology and kagome physics,which manifest themselves as distinct electronic structures in both bulk and surface states of the *** interesting next step is to manipulate the electronic states in this ***,we report angle-resolved photoemission spectroscopy(ARPES)evidence for a surface-induced orbitalselective band reconstruction in Cs V_(3)Sb_(5).A significant energy shift of the electron-like band aroundΓand a moderate energy shift of the hole-like band around M are observed as a function of *** evolution is reproduced in a much shorter time scale by in-situ annealing of the Cs V_(3)Sb_(5) ***-resolved density functional theory(DFT)calculations reveal that the momentum-dependent band reconstruction is associated with different orbitals for the bands aroundΓand M,and the time-dependent evolution points to the change of sample surface that is likely caused by the formation of Cs vacancies on the *** results indicate the possibility of orbital-selective control of the band structure via surface modification,which may open a new avenue for manipulating exotic phenomena in this material system,including superconductivity.

关键词： photoemission kagome superconductor band structure

Experimental evidence of anomalously large superconducting gap on topological surface state of b-Bi2Pd film

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Science Bulletin 2019年第17期64卷 1215-1221页

作者： Jian-Yu Guan Lingyuan Kong Li-Qin Zhou Yi-Gui Zhong Hang Li Hai-Jiang Liu Cen-Yao Tang Da-Yu Yan Fa-Zhi Yang Yao-Bo Huang You-Guo Shi Tian Qian Hong-Ming Weng Yu-Jie Sun Hong Ding Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China School o f Physics University of Chinese Academy of Sciences Beijing 100190 China Shanghai Synchrotron Radiation Facility Shanghai Institute o f Applied Physics Chinese Academy of Sciences Shanghai 201204 China CAS Center for Excellence in Topological Quantum Computation University o f Chinese Academy of Sciences Beijing 100190 China Songshan Lake Materials Laboratory Dongguan 523808 China

Connate topological superconductor(TSC) combines topological surface states with nodeless superconductivity in a single material, achieving effective p-wave pairing without interface complication. By combining angle-resolved photoemission spectroscopy and in-situ molecular beam epitaxy, we studied the momentum-resolved superconductivity in b-Bi2 Pd film. We found that the superconducting gap of topological surface state(DTSS$ 3.8 meV) is anomalously enhanced from its bulk value(Db$ 0.8 meV). The ratio of 2 DTSS/kBTc$ 16.3, is substantially larger than the BCS value. By measuring b-Bi2 Pd bulk single crystal as a comparison, we clearly observed the upward-shift of chemical potential in the film. In addition, a concomitant increasing of surface weight on the topological surface state was revealed by our first principle calculation, suggesting that the Dirac-fermion-mediated parity mixing may cause this anomalous superconducting enhancement. Our results establish b-Bi2 Pd film as a unique case of connate TSCs with a highly enhanced topological superconducting gap, which may stabilize Majorana zero modes at a higher temperature.

关键词： Topological surface state Multiband superconductivity Thin film photoemission spectroscopy

Electronic structure of exfoliated millimeter-sized monolayer WSe2 on silicon wafer

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Nano Research 2019年第12期12卷 3095-3100页

作者： Wenjuan Zhao Yuan Huang Cheng Shen Cong Li Yongqing Cai Yu Xu Hongtao Rong Qiang Gao Yang Wang Lin Zhao Lihong Bao Qingyan Wang Guangyu Zhang Hongjun Gao Zuyan Xu Xingjiang Zhou Guodong Liu Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Technical Institute of Physics and Chemistry Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China Beijing Academy of Quantum Information Sciences Beijing 100193China

The mono layer WSe2 is in teresting and important for future application in nanoelectronics,spintronics and valleytronics devices,because it has the largest spin splitting and Ion gest valley coherence time among all the known monolayer transition-metal dichalcogenides(TMDs).Toobtain the large-area monolayer TMDs'crystal is the first step to manu facture scalable and high-performance electronic *** this letter,we have successfully fabricated millimeter-sized mono layer WSe2 single crystals with very high quality,based on our improved mecha nicalexfoliation *** such superior samples,using standard high resolution angle-resolved photoemission spectroscopy,we didcomprehe nsive electronic band structure measurements on our mono layer *** overall band features point it to be a 1.2 eV direct bandgap semico *** spin splitting of the valence band at K point is found as 460 meV,which is 30 meV less than the corresponding band splitting in its bulk *** effective hole masses of valence bands are determined as 2.344 me atГ,and 0.529 me as well as 0.532 meat K for the upper and lower branch of splitting ban ds,*** screening effect from substrate is shown to substa ntially impact onthe electronic *** results provide importa nt insights into band structure engineering in mono layer *** mono layer WSe2 crystals may constitute a valuable device platform.

关键词： transition-metal dichalcogenides WSe2 monolayer electronic structure angle-resolved photoemission spectroscopy

Ab Initio Comparative Study of Zincblende and Wurtzite ZnO

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Chinese Physics Letters 2007年第4期24卷 1032-1034页

作者：张新宇陈洲文齐彦鹏冯燕赵亮戚力马明臻刘日平王文魁 State Key Laboratory of Metastable Materials Science & Technology Yanshan University Qinhuangdao 066004

By employing the first-principles pseudopotential plane-wave method, the physical properties of zincblende ZnO are investigated in comparison with those of the common wurtzite structure. Zincblende ZnO is predicted to be a direct gap semiconductor. Compared to the wurtzite structure, the zincblende ZnO is characterized by smaller bandgap and pressure coefficient, larger electron effective mass, increasing static dielectric constants and more covalent bonding. Furthermore, the optical properties including dielectric function and energy loss function of zincblende ZnO were obtained and analysed with some features. These aspects reveal promising applications of zincblende ZnO in optoelectronic devices.

关键词： ELECTRONIC-STRUCTURE OPTICAL-PROPERTIES photoemission PRESSURE PSEUDOPOTENTIALS SEMICONDUCTORS STATES ALLOY FILMS

Electronic Structure of Eu6C60

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Chinese Physics Letters 2009年第1期26卷 252-255页

作者：王晓雄李宏年徐亚伯王鹏张文华徐法强 Department of Physics Zhejiang University Hangzhou 310027 College of Science Nanjing University of Science and Technolog3/ Nanjing 210094 National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei 230029

We study the valence band of Eu-intercalated C6o by synchrotron radiation photoelectron spectroscopy to understand the ferromagnetism （FM） and the giant magnetoresistance （GMR） of Eus C60. The results revea/ the semiconducting property and the remarkable 5d6s-π hybridization. Eu-C60 bonding has both ionic and covalent contributions. No more than half the 5d6s electrons transfer from Eu to the LUMO derived band of C60, and the LUMO＋1 derived band is not filled. The remaining valence electrons of Eu, together with some π （LUMO, HOMO and HOMO-1） electrons, constitute the covalent bond. The electronic structure implies that the magnetic coupling in Eu6 C60 should be through the intra-atomic f-sd exchange and the medium of the π electrons. The possibility of the GMR being tunnelling magnetoresistance is ruled out.

关键词： DOPED C-60 MAGNETIC-PROPERTIES FULLERIDES photoemission BAND MONOLAYER FULLERENE

Broadband electroluminescence from reverse breakdown in individual suspended carbon nanotube pn-junctions

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Nano Research 2020年第10期13卷 2857-2861页

作者： Bo Wang Sisi Yang Yu Wang Younghee Kim Ragib Ahsan Rehan K.apadia Stephen KDoorn Han Htoon Stephen B.Cronin Department of Physics and Astronormy University of Southern CalforniaLos AngelesCA 90089USA Ming Hsieh Department of Electrical Engineering University of Southern CaliforniaLos AngelesCA 90089USA Mork Farmily Department of Chemical Engineering and Materials Science University of Southern CaliforniaLos AngelesCA 90089USA Center for Integrated Nanotechnologies Materials Physics and Applications DivisionLos Alamos National LaboratoryLos AlamosNM 87545USA

There are various mechanisms of light emission in carbon nanotubes (CNTs), which give rise to a wide range of spectral emission characteristics that provide important information regarding the underlying physical processes that lead to photon emission. Here, we report spectra obtained from individual suspended CNT dual-gate field effect transistor (FET) devices under different gate and bias conditions. By applying opposite voltages to the gate electrodes (i.e., Vg1 = –Vg2), we are able to create a pn-junction within the suspended region of the CNT. Under forward bias conditions, the spectra exhibit a peak corresponding to E11 exciton emission via thermal (i.e., blackbody) emission occurring at electrical powers around 8 μW, which corresponds to a power density of approximately 0.5 MW/cm2. On the other hand, the spectra observed under reverse bias correspond to impact ionization and avalanche emission, which occurs at electrical powers of ~ 10 nW and exhibits a featureless flat spectrum extending from 1,600 nm to shorter wavelengths up to 600 nm. Here, the hot electrons generated by the high electric fields (~ 0.5 MV/cm) are able to produce high energy photons far above the E11 (ground state) energy. It is somewhat surprising that these devices do not exhibit light emission by the annihilation of electrons and holes under forward bias, as in a light emitting diode (LED). Possible reasons for this are discussed, including Auger recombination.

关键词： ballistic avalanche high-field band-to-band photoemission

Polarization Measurement of Spin-Polarized Electrons by Optical Electron Polarimeter

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Chinese Physics Letters 2005年第10期22卷 2546-2548页

作者：丁海兵庞文宁刘义保尚仁成 Department of Physics Tsinghua University Beijing 100084

The polarization of spin-polarized electrons, produced from a new GaAs spin-polarized electron source, is determined by an optical electron polarimeter. The He 3^3p→2^3S1 （388.9nm） transition is used for the optical electron polarimetry. The structure and performance of the experimental setup of spin-polarized electron source and optical electron polarimeter are described. The result of polarization of 30.8% averaged spin-up and spindown polarized electrons is obtained and presented.

关键词： photoemission GAAS EXCITATION ENERGY IMPACT