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Secondary electron emission and photoemission from a negative electron affinity semiconductor with large mean escape depth of excited electrons

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Chinese Physics B 2023年第4期32卷 677-690页

作者：谢爱根董红杰刘亦凡 School of Physics and Optoelectronic Engineering Nanjing University of Information Science and TechnologyNanjing 210044China Jiangsu Key Laboratory for Optoelectronic Detection of Atmosphere and Ocean Nanjing University of Information Science&TechnologyNanjing 210044China Jiangsu international Joint Laboratory on Meteorological Photonics and Optoelectronic Detection Nanjing University of Information Science&TechnologyNanjing 210044China

The formulae for parameters of a negative electron affinity semiconductor(NEAS)with large mean escape depth of secondary electrons A(NEASLD)are deduced.The methods for obtaining parameters such asλ,B,E_(pom)and the maximumδandδat 100.0 keV≥E_(po)≥1.0 keV of a NEASLD with the deduced formulae are presented(B is the probability that an internal secondary electron escapes into the vacuum upon reaching the emission surface of the emitter,δis the secondary electron yield,E_(po)is the incident energy of primary electrons and E_(pom)is the E_(po)corresponding to the maximumδ).The parameters obtained here are analyzed,and it can be concluded that several parameters of NEASLDs obtained by the methods presented here agree with those obtained by other authors.The relation between the secondary electron emission and photoemission from a NEAS with large mean escape depth of excited electrons is investigated,and it is concluded that the presented method of obtaining A is more accurate than that of obtaining the corresponding parameter for a NEAS with largeλ_(ph)(λ_(ph)being the mean escape depth of photoelectrons),and that the presented method of calculating B at E_(po)>10.0 keV is more widely applicable for obtaining the corresponding parameters for a NEAS with largeλ_(ph).

关键词： negative electron affinity semiconductor secondary electron emission photoemission the probability secondary electron yield large mean escape depth of excited electrons

Electronic structure of transition metal dichalcogenides PdTe_2 and Cu_(0.05)PdTe_2 superconductors obtained by angle-resolved photoemission spectroscopy

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Chinese Physics B 2015年第6期24卷 100-108页

作者：刘艳赵建洲俞理林成天胡成刘德发彭莹莹谢卓晋何俊峰陈朝宇冯娅伊合绵刘旭赵林何少龙刘国东董晓莉张君陈创天许祖彦翁虹明戴希方忠周兴江 National Laboratory for Superconductivity Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of Sciences Max-Planck-Institut für Festk rperforschung Heisenbergstrasse 170569 StuttgartGermany Technical Institute of Physics and Chemistry Chinese Academy of Sciences Collaborative Innovation Center of Quantum Matter

The layered transition metal chalcogenides have been a fertile land in solid state physics for many decades. Various MX2-type transition metal dichalcogenides, such as WTe2, IrTe2, and MoS2, have triggered great attention recently, either for the discovery of novel phenomena or some extreme or exotic physical properties, or for their potential applications. PdTe2 is a superconductor in the class of transition metal dichalcogenides, and superconductivity is enhanced in its Cu- intercalated form, Cuo.05PdTe2. It is important to study the electronic structures of PdTe2 and its intercalated form in order to explore for new phenomena and physical properties and understand the related superconductivity enhancement mecha- nism. Here we report systematic high resolution angle-resolved photoemission （ARPES） studies on PdTe2 and Cuo.05PdTe2 single crystals, combined with the band structure calculations. We present in detail for the first time the complex multi-band Fermi surface topology and densely-arranged band structure of these compounds. By carefully examining the electronic structures of the two systems, we find that Cu-intercalation in PdTe2 results in electron-doping, which causes the band structure to shift downwards by nearly 16 meV in Cuo.05PdTe2. Our results lay a foundation for further exploration and investigation on PdTe2 and related superconductors.

关键词： transition metal dichalcogenides PdTe2 superconductor photoemission

Studies on the electronic structures of three-dimensional topological insulators by angle resolved photoemission spectroscopy

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Frontiers of physics 2012年第2期7卷 175-192页

作者： Yulin Chen (1) (2) (3) 1. Department of Physics University of Oxford Clarendon Laboratory Parks Road Oxford OX1 3PU UK2. Stanford Institute for Materials and Energy Sciences SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo Park CA 94025 USA3. Geballe Laboratory for Advanced Materials Departments of Physics and Applied Physics Stanford University Stanford CA 94305 USA

Three-dimensional （3D） topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. The unusual surface states of topological insulators rise from the nontrivial topology of their electronic structures as a result of strong spin-orbital coupling. In this review, we will briefly introduce the concept of topological insu- lators and the experimental method that can directly probe their unique electronic structure： angle resolved photoemission spectroscopy （ARPES）. A few examples are then presented to demonstrate the unique band structures of different families of topological insulators and the unusual properties of the topological surface states. Finally, we will briefly discuss the future development of topological quantum materials.

关键词： topological insulator （TI） photoemission ARPES

Generation of multiple charged ions: photoemission electron impact ionization

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Science China Chemistry 1998年第5期41卷 525-534页

作者：王利李海洋白吉玲吕日昌 State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical Physics Dalian China

Delayed pulsed electric field was used to investigate the generation mechanism of multiple charged ions produced in the interaction of laser, metal surface and electric field on time_of_flight mass spectrometer (TOF MS). A special photoelectron generator was designed to control the energy and timing of the photoelectron beam. This modification made it possible to separate the photoionization process from photoelectron impact ionization. The experiment showed that the multiple charged ions could be produced only by the photoelectron impact, ionized step by step. A design of dual ionization configuration was presented, which could be used to study either multiphoton ionization or photoemission electron impact ionization.

关键词： multiple charged ions photoemission electron electron impact ionization time_of_flight mass spectrometer.

RESONANT photoemission OF BULK CeO_(2) AND NANO-CeO_(2) FILMS

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Acta Metallurgica Sinica(English Letters) 2001年第6期14卷 539-543页

作者： M.I. Abbas, K. Ibrahim, Z.Y. Wu, J. Zhang, 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

photoemission behaviors of nano-CeO2 films with particle sizes ranging from 8 nm to 50 nm and bulk CeO2 in Ce 4 d-4 f absorption region have been investigated. Resonant enhancements of Ce 4 f valance band and Ce 5 p bands for nano film and bulk material have been observed. The variation of electron density of states in valance bands of nano and bulk structures of CeO2 is discussed in terms of Ce 4 d-4 f resonance.

关键词： Nanostructured materials Optical films Oxides photoemission Resonance

Laser induced photoemission electron and the generation of high Rydberg states of atoms and molecules

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Chinese Science Bulletin 1998年第19期43卷 1616-1620页

作者： Li Wang Haiyang Li Jiling Bai Richang Lu Acad Sinica Dalian Inst Chem Phys State Key Lab Mol React Dynam Dalian 116023 Peoples R China

Laser induced photoemission electron was produced by directing 532 nm and/or 355 nm onto stainless steel plate on a time of flight mass spectrometer. Multiple charged ions and high Rydberg states of atoms or molecules were successfully generated by impacts of the photoemission electrons. The high Rydberg states ( n ～40-100) thus produced were separated from ions, produced by direct electron impact ionization, by a 3 V DC electric field and then ionized by a delayed pulsed HV electric field in a ZEKE-PFI manner. Relationship between generation/property of high Rydberg states of atoms/molecules and experimental conditions could be investigated. Relationship between the electron accelerating voltage and high Rydberg states of Ar was described.

关键词： photoemission electron multiple charged ions high Rydberg states.

Hybridization Effects Revealed by Angle-Resolved photoemission Spectroscopy in Heavy-Fermion Ce2IrIn8

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Chinese Physics Letters 2019年第9期36卷 36-40页

作者：刘海江徐远骥钟益桂关剑宇孔令元马均章黄耀波陈秋云陈根富史明杨义峰丁洪 Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 School of Physics University of Chinese Academy of Sciences Beijing 100190 Swiss Light Source Paul Scherrer Institute CH-5232 Villigen PSI Switzerland Shanghai Synchrotron Radiation Facility Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201204 Science and Technology on Surface Physics and Chemistry Laboratory Mianyang 621908 Songshan Lake Materials Laboratory Dongguan 523808

We utilize high-resolution resonant angle-resolved photoemission spectroscopy(ARPES)to study the band structure and hybridization effect of the heavy-fermion compound Ce2 IrIn8.We observe a nearly flat band at the binding energy of 7 meV below the coherent temperature Tcoh^40 K,which characterizes the electrical resistance maximum and indicates the onset temperature of hybridization.However,the Fermi vector and the Fermi surface volume have little change around Tcoh,which challenges the widely believed evolution from a hightemperature small Fermi surface to a low-temperature large Fermi surface.Our experimental results of the band structure fit well with the density functional theory plus dynamic mean-field theory calculations.

关键词： ARPES Hybridization Effects Revealed by Angle-Resolved photoemission Spectroscopy in Heavy-Fermion Ce2IrIn8 Ce

photoemission and NEXAFS Studies of PTCDA on Sn/Si（111）-2√3×2√3

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Photoemission and NEXAFS Studies of PTCDA on Sn/Si（111）-2...

Angle-Resolved and Resonant photoemission Study of the Valence Bands of α-La(0001) on W(110)

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作者： L.K.E. Ericsson L.S.O. Johansson Department of Physics Karlstad University

Interface interactions between organic molecules and semiconductor substrates are especially important since they affect the electronic structure and modify its growth mode of molecular films. The planar perylene derivative 3,4,9,10-tetracarboxylic dianhydride （PTCDA） has been widely used as a model compound for organic thin films since it has promising electronic and optical properties for organic electronic applications. In this context, a detailed understanding of the interface interactions between PTCDA molecules and semiconductor surfaces may therefore be used to optimize organic-inorganic devices. A series of coverages （0.3-10 monolayer （ML）） of PTCDA were deposited on the Sn/Si（111）-2√3×2√3 surface at room temperature. As shown by O 1s core-level spectra, at low coverage there are two major peaks located at binding energies of 530.3 and 532.6 eV. According to the previous studies [1,2], these two O 1s components should be O atoms in the carboxylic and anhydride groups. At 10 ML, the O 1s spectrum shows a line shape similar with the ones from PTCDA thick films on the H-terminated Si（111） and Ag/Si（111）-√3×√3 surfaces [1,2]. But at low coverages （0.3-1.0 ML） the O 1s spectra also resemble the bulk one, which is very different from other cases. This is a clear evidence of non-chemical interaction between PTCDA O atoms and the Sn/Si（111）-2√3×2√3 substrate. High-resolution C 1s core-level spectra have also been recorded from the same surfaces. At 10 ML the C 1s spectrum looks like a bulk one in a similar way as the O 1s spectrum. There is a strong peak at 284 eV, which originates from the perylene core of the PTCDA molecule. The second peak is located at 288.1 eV, which has previously been assigned to the carboxylic C. The other two small features at 286 eV and 289 eV in the 10 ML spectrum are mainly due to shake-up effects. Interestingly, at 0.3 ML there is an extra peak located at a binding energy of 286.8 eV. The extra peak is well-defined and becomes saturated around 1 ML coverage. Judged from its line-shap

关键词： PTCDA Sn/Si（111）-2√3×2√3 photoemission NEXAFS

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World Journal of Condensed Matter Physics 2016年第1期6卷 17-26页

作者： Yoshiharu Enta Osamu Morimoto Hiroo Kato Yasuo Sakisaka Graduate School of Science and Technology Hirosaki University Hirosaki Japan Spring-8 Service Co. Ltd. Tatsuno Japan

We report a photoelectron spectroscopic study of the valence bands of double hexagonal-close-packed (dhcp) α-La(0001) films epitaxially grown on W(110) at room temperature. The La 5d photoemission cross section in the photon energy region from 20 eV to 130 eV was obtained and the valence-band structure of α-La was determined. Except for 4f-related structures, the valence-band structures of dhcp α-La and dhcp β-Ce were found to resemble each other. From the band structure, the crystal structure of the La film was confirmed. No evidence for the existence of a 5d-like surface state near the Fermi energy at the point of the surface Brillouin zone was obtained and a 6s band bottom was identified.

关键词： Lanthanum Thin Film Electronic Structure Valence Band Tungsten Surface photoemission Angle-Resolved Spectroscopy