Photoelectron Diffraction and Band Structure Effects in ARXPS from the Valence Bands of GeS

Angle-resolved photoemission in the soft X-ray region has so far been used to study crystal (surface) structure by using photoelectron diffraction phenomena. In this energy region, the observation of the band structure was considered to be difficult, because the momentum of the incident photon cannot be negligible, the emitted electron is strongly influenced by the electron diffraction effects, and the cross section of the valence band is very small. We have performed the angle-resolved photoemission from the valence bands of highly oriented pyrolytic graphite by using the soft X-ray (hν=980 eV ) and successfully observed the band structure. The appearance of the structures of the band density of state is also discussed. Since the escape depth for the electrons with high kinetic energies is longer than ARUPS, this experimental method is better than the usual ARUPS in order to study the bulk band structures in solids.

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The Highly Uniform Photoresponsivity from Visible to Near IR Light in Sb2Te3 Flakes

Sensors ◽

10.3390/s21041535 ◽

2021 ◽

Vol 21 (4) ◽

pp. 1535

Author(s):

Shiu-Ming Huang ◽

Jai-Lung Hung ◽

Mitch Chou ◽

Chi-Yang Chen ◽

Fang-Chen Liu ◽

...

Keyword(s):

Band Structure ◽

Energy Difference ◽

Experimental Result ◽

Light Illumination ◽

Near Ir ◽

State Band ◽

Valence Bands ◽

Low Dimensional ◽

Low Dimensional Materials ◽

Ir Light

Broadband photosensors have been widely studied in various kinds of materials. Experimental results have revealed strong wavelength-dependent photoresponses in all previous reports. This limits the potential application of broadband photosensors. Therefore, finding a wavelength-insensitive photosensor is imperative in this application. Photocurrent measurements were performed in Sb2Te3 flakes at various wavelengths ranging from visible to near IR light. The measured photocurrent change was insensitive to wavelengths from 300 to 1000 nm. The observed wavelength response deviation was lower than that in all previous reports. Our results show that the corresponding energies of these photocurrent peaks are consistent with the energy difference of the density of state peaks between conduction and valence bands. This suggests that the observed photocurrent originates from these band structure peak transitions under light illumination. Contrary to the most common explanation that observed broadband photocurrent carrier is mainly from the surface state in low-dimensional materials, our experimental result suggests that bulk state band structure is the main source of the observed photocurrent and dominates the broadband photocurrent.

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DICHROISM IN ANGLE-RESOLVED PHOTOEMISSION FROM Pt(111)

Surface Review and Letters ◽

10.1142/s0218625x0200310x ◽

2002 ◽

Vol 09 (02) ◽

pp. 883-888 ◽

Cited By ~ 1

Author(s):

G. H. FECHER ◽

J. BRAUN ◽

A. OELSNER ◽

CH. OSTERTAG ◽

G. SCHÖNHENSE

Keyword(s):

Circular Dichroism ◽

Band Structure ◽

Valence Band ◽

Single Step ◽

Core Level ◽

X Ray ◽

Photoelectron Diffraction ◽

Band Emission ◽

First Results ◽

Circular Dichroïsm

The angular dependence of the circular dichroism in photoemission from Pt(111) was investigated for excitation with VUV and soft X-ray radiation. VUV excitation was used to probe band structure and the circular dichroism for valence band emission. The measurements are compared to full relativistic single step photoemission calculations. XPS was used to investigate the circular dichroism in emission from the 4f core level. In this case, the dichroism is induced by photoelectron diffraction. First results from single step core level calculations are compared to the experimental observations.

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Intrinsic Carrier Concentration in Strained Si1-XGex/(101)Si

Materials Science Forum ◽

10.4028/www.scientific.net/msf.663-665.470 ◽

2010 ◽

Vol 663-665 ◽

pp. 470-472 ◽

Cited By ~ 1

Author(s):

Jian Jun Song ◽

He Ming Zhang ◽

Hui Yong Hu ◽

Xian Ying Dai ◽

Rong Xi Xuan

Keyword(s):

Band Structure ◽

Carrier Concentration ◽

Device Physics ◽

Strained Si ◽

Intrinsic Carrier Concentration ◽

Materials Properties ◽

Densities Of States ◽

Valence Bands

The intrinsic carrier concentration is the important parameter for researching strained Si1-xGex materials properties and evaluating Si-based strained devices parameters. In this paper, at the beginning of analyzing the band structure of strained Si1-xGex/(101)Si, the dependence of its effective densities of states for the conduction and valence bands (Nc, Nv) and its intrinsic carrier concentration (ni) on Ge fraction (x) and temperature were obtained. The results show that ni increases significantly due to the effect of strain in strained Si1-xGex/(101)Si. Furthermore, Nc and Nv decrease with increasing Ge fraction (x). In addition, it is also found that as the temperature becomes higher, the increase in Nc and Nv occurs. The results can provide valuable references to the understanding on the Si-based strained device physics and its design.

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Direct time-domain observation of attosecond final-state lifetimes in photoemission from solids

Science ◽

10.1126/science.aaf6793 ◽

2016 ◽

Vol 353 (6294) ◽

pp. 62-67 ◽

Cited By ~ 115

Author(s):

Zhensheng Tao ◽

Cong Chen ◽

Tibor Szilvási ◽

Mark Keller ◽

Manos Mavrikakis ◽

...

Keyword(s):

Band Structure ◽

Strong Dependence ◽

Emission Angle ◽

Spectroscopic Techniques ◽

Final State ◽

Band Dispersion ◽

Electron Escape ◽

State Band ◽

The Difference ◽

Valence Bands

Attosecond spectroscopic techniques have made it possible to measure differences in transport times for photoelectrons from localized core levels and delocalized valence bands in solids. We report the application of attosecond pulse trains to directly and unambiguously measure the difference in lifetimes between photoelectrons born into free electron–like states and those excited into unoccupied excited states in the band structure of nickel (111). An enormous increase in lifetime of 212 ± 30 attoseconds occurs when the final state coincides with a short-lived excited state. Moreover, a strong dependence of this lifetime on emission angle is directly related to the final-state band dispersion as a function of electron transverse momentum. This finding underscores the importance of the material band structure in determining photoelectron lifetimes and corresponding electron escape depths.

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Photoemission Spectroscopy of Single Crystal HTSC Materials: A Fermi Liquid Electronic Structure

MRS Proceedings ◽

10.1557/proc-156-159 ◽

1989 ◽

Vol 156 ◽

Author(s):

A. J. Arko ◽

R. S. List ◽

R. J. Bartlett ◽

S. W. Cheong ◽

C. G. Olson ◽

...

Keyword(s):

Electronic Structure ◽

Band Structure ◽

Single Crystal ◽

Fermi Liquid ◽

Wide Band ◽

Photoemission Spectroscopy ◽

Correlation Effects ◽

Band Dispersion ◽

Valence Bands ◽

Orbital Character

ABSTRACTPhotoemission spectra from HTSC materials ( primarily 123 -type ), cleaved and measured at 20K, reveal a rich DOS structure which compares favorably with a calculated band structure, except for a residual 0.5 eV shift which may reflect some correlation effects. Band dispersion is observed throughout the valence bands, with clear evidence for a 0.2 eV wide band dispersing through EF. The orbital character at EF is a mix of Cu-3d and O-2p. There is unambiguous evidence for a large BCS-like gap (2Δ≥ 4kTc).

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High Resolution Optical Spectroscopy of Free Exciton and Electronic Band Structure near the Fundamental Gap in 4H SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.924.239 ◽

2018 ◽

Vol 924 ◽

pp. 239-244 ◽

Cited By ~ 2

Author(s):

Walter M. Klahold ◽

Wolfgang J. Choyke ◽

Robert P. Devaty

Keyword(s):

Absorption Spectrum ◽

Band Structure ◽

Density Functional ◽

Electronic Band Structure ◽

Free Exciton ◽

Electron Mass ◽

Electronic Band ◽

Wavelength Resolution ◽

Primary Origin ◽

Valence Bands

We use thick, relatively high purity 4H SiC boule material to measure the wavelength modulated absorption spectrum with improved wavelength resolution and sensitivity with respect to previous work. We observe several small 0.6 ± 0.1 meV splittings, which we attribute to electron mass anisotropy and electron-hole exchange interaction. In addition, we identify several features in the absorption spectrum as signatures of nonparabolicity in the free exciton dispersion relations, the primary origin of which is likely the nonparabolic energy dispersion of the valence bands, as revealed by published band structure calculations based on density functional theory.

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Angle-Resolved Photoemission Study on the Band Structure of Organic Single Crystals

Crystals ◽

10.3390/cryst10090773 ◽

2020 ◽

Vol 10 (9) ◽

pp. 773

Author(s):

Ke Wang ◽

Ben Ecker ◽

Yongli Gao

Keyword(s):

Band Structure ◽

Single Crystals ◽

Organic Semiconductors ◽

Electronic Band Structure ◽

Inorganic Materials ◽

Strong Electron ◽

Electronic Band ◽

Valence Bands ◽

Energy And Momentum ◽

Photoemission Study

Angle-resolved photoemission spectroscopy (ARPES) is a vital technique, collecting data from both the energy and momentum of photoemitted electrons, and is indispensable for investigating the electronic band structure of solids. This article provides a review on ARPES studies of the electronic band structure of organic single crystals, including organic charge transfer conductors; organic semiconductors; and organo-metallic perovskites. In organic conductors and semiconductors, band dispersions are observed that are highly anisotropic. The Van der Waals crystal nature, the weak electron wavefunction overlap, as well as the strong electron-phonon coupling result in many organic crystals having indiscernible dispersion. In comparison, organo-metallic perovskite halides are characterized by strong s-p orbitals from the metal and halide at the top of the valence bands, with dispersions similar to those in inorganic materials.

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Exploring Complex Chalcogenides for Thermoelectric Applications

MRS Proceedings ◽

10.1557/proc-626-z7.6 ◽

2000 ◽

Vol 626 ◽

Cited By ~ 1

Author(s):

Ying C. Wang ◽

Francis J. DiSalvo

Keyword(s):

Band Structure ◽

Physical Properties ◽

Thermoelectric Properties ◽

Thermoelectric Materials ◽

Crystal Symmetry ◽

Synthesis And Characterization ◽

Conduction Bands ◽

Valence Bands ◽

Binary Compounds

ABSTRACTOur research on ternary / quaternary chalcogenides for thermoelectric applications has lead to the identification of new interesting compounds and better understanding of the chemistry and physical properties of complex chalcogenides. The chemical, geometric, electronic diversity and flexibility has been well demonstrated in BaBiSe3 and Sr4Bi6Se13 type compounds. This presents both a challenge and more opportunity in controlling and optimizing the thermoelectric properties of these complex chalcogenides, compared with elemental and binary compounds. The importance of multivalley band structure in thermoelectric materials is emphasized. Only compounds with high crystal symmetry have the possibility of having a large number of degenerate valleys in the conduction bands or peaks in the valence bands, respectively. However, most of the complex chalcogenides crystallize in low crystal symmetry. An Edisonian method of exploratory synthesis and characterization may be the working approach to find good thermoelectric materials with ZT higher than 4.

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Effective Densities of States in Conduction and Valence Bands in a-Si

MRS Proceedings ◽

10.1557/proc-297-363 ◽

1993 ◽

Vol 297 ◽

Cited By ~ 3

Author(s):

JoŽE Furlan ◽

Franc Smole ◽

Pavle PopoviĆ

Keyword(s):

Band Structure ◽

Valence Band ◽

Computer Simulations ◽

Gaussian Distribution ◽

Transport Equations ◽

Densities Of States ◽

Extended States ◽

Valence Bands

Effective densities of states in conduction and valence band, Nc and Nv, are usually set to a fixed value of 1019 to 1020 cm−3 in all computer simulations of a-Si structures. In this contribution the densities Nc and Nv are analytically expressed for different selected extended states distributions. The derivatives d(lnNc)/dx and d(lnNv)/dx, representing specific terms in transport equations, are expressed as function of position dependent band structure. The effect of an increased disorder in heterojunction is simulated by Gaussian distribution of states in a linearly graded heterojunction region.

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