scholarly journals Спектры пропускания квантовых ям и пленок на основе HgTe в дальнем ИК-диапазоне

2018 ◽  
Vol 60 (4) ◽  
pp. 774
Author(s):  
М.Л. Савченко ◽  
Н.Н. Васильев ◽  
А.С. Ярошевич ◽  
Д.А. Козлов ◽  
З.Д. Квон ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Surface States ◽  
Far Infrared ◽  
Infrared Range ◽  
Optical Transitions ◽  
Interband Transitions ◽  
New Class ◽  
Transmission And Reflection Spectra ◽  
Bulk Band ◽  
Transmission And Reflection

AbstractStrained 80-nm-thick HgTe films belong to a new class of materials referred to as three-dimensional topological insulators (i.e., they have a bulk band gap and spin-nondegenerate surface states). Though there are a number of studies devoted to analysis of the properties of surface states using both transport and magnetooptical techniques in the THz range, the information about direct optical transitions between bulk and surface bands in these systems has not been reported. This study is devoted to the analysis of transmission and reflection spectra of HgTe films of different thicknesses in the far-infrared range recorded in a wide temperature range in order to detect the above interband transitions. A peculiarity at 15 meV, which is sensitive to a change in the temperature, is observed in spectra of both types. Detailed analysis of the data obtained revealed that this feature is related to absorption by HgTe optical phonons, while the interband optical transitions are suppressed.

scholarly journals Особенности спектров примесной фотопроводимости эпитаксиальных пленок PbSnTe(In) при изменении температуры

2019 ◽  
Vol 53 (9) ◽  
pp. 1303
Author(s):  
А.В. Иконников ◽  
В.И. Черничкин ◽  
В.C. Дудин ◽  
Д.А. Акопян ◽  
А.Н. Акимов ◽  
...  
Keyword(s):  
Far Infrared ◽  
Epitaxial Films ◽  
Infrared Range ◽  
Fourier Spectroscopy ◽  
Interband Transitions ◽  
Defect States ◽  
Impurity Defect ◽  
Additional Illumination

AbstractThe photoconductivity spectra of PbSnTe(In) epitaxial films are investigated by Fourier spectroscopy in the far infrared range at temperatures from 4.2 to 32.4 K. In addition to interband transitions, subgap features associated with the excitation of impurity-defect states are found in the spectra. The evolution of the spectra with temperature and additional illumination is traced.

MAGNETO-SPECTROSCOPY OF EPITAXIAL GRAPHENE

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1145-1154 ◽  
Author(s):  
M. L. SADOWSKI ◽  
G. MARTINEZ ◽  
M. POTEMSKI ◽  
C. BERGER ◽  
W. A. DE HEER
Keyword(s):  
Magnetic Field ◽  
Cyclotron Resonance ◽  
Far Infrared ◽  
Theoretical Models ◽  
Epitaxial Graphene ◽  
Landau Levels ◽  
Perpendicular Magnetic Field ◽  
Dirac Fermions ◽  
Optical Transitions ◽  
Interband Transitions

We present a far infrared investigation of the optical transitions in epitaxial graphene subjected to a perpendicular magnetic field. Cyclotron-resonance-like transitions between adjacent electron Landau levels are observed, as well as interband transitions. The results are discussed in terms of existing theoretical models of Dirac fermions in graphene, and the relevant optical selection rules.

Two Dimensional Photonic Crystal Modes and Resonances in Three-dimensional Structures

2001 ◽  
Vol 694 ◽  
Author(s):  
Shanhui Fan ◽  
J. D. Joannopoulos
Keyword(s):  
Spectral Properties ◽  
Three Dimensional ◽  
Reflection Spectra ◽  
Two Dimensional ◽  
Quality Factors ◽  
Transmission And Reflection Spectra ◽  
General Physical ◽  
Two Dimensional Photonic Crystal ◽  
Index Modulation ◽  
Transmission And Reflection

AbstractWe present three-dimensional analysis of two-dimensional guided resonances in photonic crystalslab structures. This analysis leads to a new understanding of the complex spectral properties of such systems. Specifically, we calculate the dispersion diagrams, the modal patterns, and transmission and reflection spectra of these resonances. From these calculations, a key observation emerges involving the presence of two temporal pathways for transmission and eflection processes. Using this insight, we introduce a general physical model that explains the essential features of complex spectral properties. Finally, we show that the quality factors of these resonances are strongly influenced by the symmetry of the modes, and the strength ofthe index modulation.

Two Dimensional Photonic Crystal Modes and Resonances in Three-dimensional Structures

2001 ◽  
Vol 692 ◽  
Author(s):  
Shanhui Fan ◽  
J. D. Joannopoulos
Keyword(s):  
Photonic Crystal ◽  
Spectral Properties ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Quality Factors ◽  
Photonic Crystal Slab ◽  
Transmission And Reflection Spectra ◽  
General Physical ◽  
Two Dimensional Photonic Crystal ◽  
Transmission And Reflection

AbstractWe present three-dimensional analysis of two-dimensional guided resonances in photonic crystal slab structures. This analysis leads to a new understanding of the complex spectral properties of such systems. Specifically, we calculate the dispersion diagrams, the modal patterns, and transmission and reflection spectra of these resonances. From these calculations, a key observation emerges involving the presence of two temporal pathways for transmission and reflection processes. Using this insight, we introduce a general physical model that explains the essential features of complex spectral properties. Finally, we show that the quality factors of these resonances are strongly influenced by the symmetry of the modes, and the strength of the index modulation.

ELECTRONIC STRUCTURE OF Ag THIN FILMS ON A Ge(001) SURFACE

2002 ◽  
Vol 09 (02) ◽  
pp. 681-686 ◽  
Author(s):  
K. NAKATSUJI ◽  
M. YAMADA ◽  
S. OHNO ◽  
Y. NAITOH ◽  
T. IIMORI ◽  
...  
Keyword(s):  
Thin Films ◽  
Electronic Structure ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Recent Observation ◽  
Three Dimensional ◽  
Surface States ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Bulk Band

We have studied the electronic structure of Ag thin films of monoatomic height grown on a Ge(001) surface at 95 K by using photoelectron spectroscopy. All the surface states on the clean Ge surface vanished and Ag 5s derived state appeared in the bulk band gap just below the Fermi level. These suggest a strong interaction with the substrate. On the other hand, on three-dimensional (3D) islands formed on a room temperature substrate, small changes were found in Ge 3d spectrum from the clean surface. Each of the Ag 3D islands already had bulklike feature in the valence band structure. The results are consistent with recent observation by scanning tunneling microscopy.

A Peptoid with Extended Shape in Water

2019 ◽  
Author(s):  
Jumpei Morimoto ◽  
Yasuhiro Fukuda ◽  
Takumu Watanabe ◽  
Daisuke Kuroda ◽  
Kouhei Tsumoto ◽  
...  
Keyword(s):  
Spectroscopic Analysis ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Biomolecular Recognition ◽  
Biological Application ◽  
New Class ◽  
Proteolytic Resistance ◽  
Pharmacokinetic Properties ◽  
Optically Pure ◽  
Three Dimensional Space

<div> <div> <div> <p>“Peptoids” was proposed, over decades ago, as a term describing analogs of peptides that exhibit better physicochemical and pharmacokinetic properties than peptides. Oligo-(N-substituted glycines) (oligo-NSG) was previously proposed as a peptoid due to its high proteolytic resistance and membrane permeability. However, oligo-NSG is conformationally flexible and is difficult to achieve a defined shape in water. This conformational flexibility is severely limiting biological application of oligo-NSG. Here, we propose oligo-(N-substituted alanines) (oligo-NSA) as a new peptoid that forms a defined shape in water. A synthetic method established in this study enabled the first isolation and conformational study of optically pure oligo-NSA. Computational simulations, crystallographic studies and spectroscopic analysis demonstrated the well-defined extended shape of oligo-NSA realized by backbone steric effects. The new class of peptoid achieves the constrained conformation without any assistance of N-substituents and serves as an ideal scaffold for displaying functional groups in well-defined three-dimensional space, which leads to effective biomolecular recognition. </p> </div> </div> </div>

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