scholarly journals Вплив механічної обробки поверхні на діелектричні та фотодіелектричні властивості кристалів AIIBVI

2021 ◽  
pp. 73-78
Author(s):  
Олег Миколайович Чугай ◽  
Сергій Леонідович Абашин ◽  
Сергій Володимирович Олійник ◽  
Ігор Валентинович Луньов
Keyword(s):  
Local Deformation ◽  
Localized States ◽  
Structural Defects ◽  
Dielectric Parameters ◽  
Defective Structure ◽  
Surface Machining ◽  
Elastic Fields ◽  
Elastic Stresses ◽  
Characteristic Effect ◽  
Grinding And Polishing

The subject matter of the study is the dielectric and photodielectric properties of AIIBVI crystals of composition ZnSe and Cd1-хZnхTe, which are grown from the melt, and the structural defects and internal elastic fields associated with these properties. The goal of the article is to study the patterns of influence of surface machining by grinding, polishing, and local loading on the defective structure in the deformation region, and thus on the dielectric and photodielectric properties of AIIBVI crystals of this composition, which is important given the use of these crystals in aerospace engineering. The tasks to be solved are: to investigate the regularities of the influence of grinding, polishing, and local deformation of the chipped surface of ZnSe and Cd1-хZnхTe samples on their defective structure, dielectric and photodielectric properties, including irreversible changes in properties. The problems were solved by the following methods: dielectric and photodielectric properties of crystals were investigated by the capacitive method; scanning photodielectric spectroscopy was used to measure the photoionization energies of localized states of charge carriers in crystals; the distribution of residual elastic stresses in the samples was studied by the polarization-optical method. The following results were obtained. Grinding and polishing cause the transformation of own and impurity maxima of the spectral dependences of the dielectric parameters of AIIBVI crystals, has a characteristic effect on the coordinate dependences of the dielectric parameters of crystals Cd1-хZnхTe. This is due to the transformation of localized states of carriers, which is confirmed by the study of ZnSe crystals. Concentrated deformation of Cd1-хZnхTe crystals significantly affects their dielectric properties, in particular, causes relaxation of dielectric parameters. Conclusions. Mechanical surface treatment of AIIBVI crystals by grinding and polishing, as well as local mechanical loading of Cd1-хZnхTe samples significantly affect their dielectric and photodielectric properties, which is associated with the formation of a system of defects and internal elastic fields in the deformation regions. An explanation of the observed effects is given.

Ion-beam-assisted deposition of nonhydrogenated a-Si:C films

1996 ◽  
Vol 74 (3-4) ◽  
pp. 97-101
Author(s):  
C. D. Tucker ◽  
D. E. Brodie
Keyword(s):  
Electron Cyclotron Resonance ◽  
Defect Density ◽  
Ion Beam ◽  
High Vacuum ◽  
Argon Plasma ◽  
Localized States ◽  
Structural Defects ◽  
Electrical Characteristics ◽  
Ion Beam Assisted Deposition ◽  
Ultra High Purity

Amorphous silicon carbide (a-Si:C) films were prepared by low-energy ion-beam-assisted deposition (IBAD) in an attempt to remove structural defects in the "lattice" and improve the electrical characteristics of the film. The ion beam was generated by electron cyclotron resonance from an ultra-high-purity argon plasma. The deposition environment was first evacuated to a very high vacuum to eliminate all but trace amounts of water vapour and other gases so that improvements in the electrical and (or) structural properties of the film would be attributable to the influence of the densification by ion bombardment and not to contaminants. The IBAD process does improve the film characteristics by reducing the density of localized states at the Fermi level and the porosity of the film. However, even though these films have the best electrical characteristics obtained thus far for these kind of films, none of them exhibited device quality and none were observed to be photoconducting. A large density (≈1 at.%) of implanted argon atoms may be limiting the reduction in the defect density that might otherwise be achievable.

scholarly journals Диэлектрические свойства нанокристаллического оксида вольфрама в области температур 223-293 K

2018 ◽  
Vol 52 (7) ◽  
pp. 745
Author(s):  
С.А. Козюхин ◽  
С.А. Бедин ◽  
П.Г. Рудаковская ◽  
О.С. Иванова ◽  
В.К. Иванов
Keyword(s):  
Heat Treatment ◽  
Charged Particle ◽  
Dielectric Properties ◽  
Localized States ◽  
Structural Defects ◽  
Particle Sizes ◽  
Frequency Range ◽  
Potential Barriers ◽  
Polarization Characteristics ◽  
Frequency Dependences

AbstractThe dielectric properties of nanocrystalline tungsten oxide are studied in the temperature range of 223–293 K and in the frequency range ν = 10^–2–10^6 Hz. Powders of WO_3 with particle sizes of 110, 150, and 200 nm are prepared by the heat treatment of ammonium paratungstate at various temperatures. It is established that the frequency dependences of the conductivity for all samples increase with an increase in frequency, while the polarization characteristics ε'(ν) and ε"(ν) decrease. It is found that the frequency dependences of the conductivity are described by a function of the form ν^ s with an index in the range of (0.83–0.90) ± 0.01, which is characteristic of the “hopping” mechanism of charged-particle motion (complexes) over localized states confined by potential barriers and structural defects.

Research on Surface Grinding and Polishing Process of Precise Hydraulic Couples

2011 ◽  
Vol 487 ◽  
pp. 317-321
Author(s):  
W.H. Wang ◽  
L. Teng ◽  
B.L. Zhao ◽  
Q.Q. Yang ◽  
J.J. Wang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Dead Zone ◽  
Surface Grinding ◽  
Strongly Correlated ◽  
Hydraulic Characteristics ◽  
Surface Machining ◽  
Optimum Parameters ◽  
Geometric Elements ◽  
Grinding And Polishing

Manufacturing of precise couples is the most important key technology for hydraulic products. The hydraulic characteristics are not only strongly correlated with their geometric elements, but also associated with the surface qualities of the couples, including surface roughness and surface texture, and which primarily influence the dead zone, lag rings and friction of the couples. In order to get better surface machining quality of the precise hydraulic couples, the process of surface grinding and polishing was researched. Through process test, the optimum parameters of grinding and polishing processing were found, which made the surface roughness achieved Ra 0.031μm.

scholarly journals Study of vibratory condition of the construction with a structural defect in progressive damage development stages

2016 ◽  
pp. 52-60
Author(s):  
A. M. Kokurov ◽  
I. N. Odintsev
Keyword(s):  
Structural Defects ◽  
Progressive Damage ◽  
Computational Studies ◽  
Practical Application ◽  
Improved Method ◽  
Damage Development ◽  
Defective Structure ◽  
Development Stages ◽  
Structure Vibration ◽  
Propeller Blades

The paper presents an improved method of experimental and computational studies of vibratory condition of the composite constructions with structural defects such as local fibrations. With the proposed approach it is possible to determine the size of the defect and its influence on the inherent forms and structure vibration frequency. In our work we demonstrate practical application of the technique studying the vibration characteristics of the feathering propeller blades with defective structure of the material.

scholarly journals Photoluminescence Emission Induced by Localized States in Halide Passivated Colloidal Two-Dimensional WS2 Nanoflakes

2019 ◽  
Author(s):  
Rosanna Mastria ◽  
Anna Loiudice ◽  
Jan Vávra ◽  
Concetta Nobile ◽  
Riccardo Scarfiello ◽  
...  
Keyword(s):  
Density Functional ◽  
Large Scale ◽  
Colloidal Stability ◽  
Solution Phase ◽  
Localized States ◽  
Structural Defects ◽  
Ambient Atmosphere ◽  
Transition Metal Dichalcogenide ◽  
Two Dimensional ◽  
Photoluminescence Emission

<p>Engineering physicochemical properties of two-dimensional transition metal dichalcogenide (2D-TMD) materials by surface manipulation is essential for their practical and large-scale application especially for colloidal 2D-TMDs that are plagued by the unintentional formation of structural defects during the synthetic procedure. However, the available methods to manage surface states of 2D-TMDs in solution-phase are still limited hampering the production of high quality colloidal 2D-TMD inks to be straightforwardly assembled into actual devices. Here, we demonstrate an efficient solution-phase strategy to passivate surface defect states of colloidally synthetized WS<sub>2 </sub>nanoflakes with halide ligands, resulting in the activation of the photoluminescence emission. Photophysical investigation and density functional theory calculations suggest that halide atoms enable the suppression of non-radiative recombination through the elimination deep gap trap states, and introduce localized states in the energy band structure from which excitons efficiently recombine. Halide passivated WS<sub>2</sub> nanoflakes importantly preserve colloidal stability and photoluminescence emission after several weeks of storing in ambient atmosphere, corroborating the potential of our developed 2D-TMD inks.</p>

scholarly journals Photoluminescence Emission Induced by Localized States in Halide Passivated Colloidal Two-Dimensional WS2 Nanoflakes

2019 ◽  
Author(s):  
Rosanna Mastria ◽  
Anna Loiudice ◽  
Jan Vávra ◽  
Concetta Nobile ◽  
Riccardo Scarfiello ◽  
...  
Keyword(s):  
Density Functional ◽  
Large Scale ◽  
Colloidal Stability ◽  
Solution Phase ◽  
Localized States ◽  
Structural Defects ◽  
Ambient Atmosphere ◽  
Transition Metal Dichalcogenide ◽  
Two Dimensional ◽  
Photoluminescence Emission

<p>Engineering physicochemical properties of two-dimensional transition metal dichalcogenide (2D-TMD) materials by surface manipulation is essential for their practical and large-scale application especially for colloidal 2D-TMDs that are plagued by the unintentional formation of structural defects during the synthetic procedure. However, the available methods to manage surface states of 2D-TMDs in solution-phase are still limited hampering the production of high quality colloidal 2D-TMD inks to be straightforwardly assembled into actual devices. Here, we demonstrate an efficient solution-phase strategy to passivate surface defect states of colloidally synthetized WS<sub>2 </sub>nanoflakes with halide ligands, resulting in the activation of the photoluminescence emission. Photophysical investigation and density functional theory calculations suggest that halide atoms enable the suppression of non-radiative recombination through the elimination deep gap trap states, and introduce localized states in the energy band structure from which excitons efficiently recombine. Halide passivated WS<sub>2</sub> nanoflakes importantly preserve colloidal stability and photoluminescence emission after several weeks of storing in ambient atmosphere, corroborating the potential of our developed 2D-TMD inks.</p>

scholarly journals The role of annealing temperature on the optical energy gap and Urbach energy of Se:2%Sb thin films

2008 ◽  
Vol 5 (2) ◽  
pp. 249-252
Author(s):  
Baghdad Science Journal
Keyword(s):  
Thin Films ◽  
Annealing Temperature ◽  
Urbach Energy ◽  
Energy Gap ◽  
Localized States ◽  
Structural Defects ◽  
Indirect Transition ◽  
Optical Energy Gap ◽  
Optical Energy

The optical energy gap(Eopt) and the width of the tails of localized states in the band gap (?E) for Se:2%Sb thin films prepared by thermal co-evaporation method as a function of annealing temperature are studied in the photon energy range ( 1 to 5.4)eV.Se2%Sb film was found to be indirect transition with energy gap of (1.973,2.077, 2.096, 2.17) eV at annealing temperature (295,370,445,520)K respectively. The Eopt and ?E of Se:2%Sb films as a function of annealing temperature showed an increase in Eopt and a decrease in ?E with increasing the annealing temperature. This behavior may be related to structural defects and dangling bonds.

Transmission electron microscopy of composite materials

1988 ◽  
Vol 46 ◽  
pp. 1012-1015
Author(s):  
K.P.D. Lagerlof
Keyword(s):  
Composite Materials ◽  
Physical Properties ◽  
Structural Defects ◽  
Structural Composites ◽  
Multiphase Materials ◽  
Structural Reinforcement ◽  
Transmission Electron ◽  
Reinforced Fiber ◽  
Particulate Reinforced Composites ◽  
Definition Of

Although most materials contain more than one phase, and thus are multiphase materials, the definition of composite materials is commonly used to describe those materials containing more than one phase deliberately added to obtain certain desired physical properties. Composite materials are often classified according to their application, i.e. structural composites and electronic composites, but may also be classified according to the type of compounds making up the composite, i.e. metal/ceramic, ceramic/ceramie and metal/semiconductor composites. For structural composites it is also common to refer to the type of structural reinforcement; whisker-reinforced, fiber-reinforced, or particulate reinforced composites [1-4].For all types of composite materials, it is of fundamental importance to understand the relationship between the microstructure and the observed physical properties, and it is therefore vital to properly characterize the microstructure. The interfaces separating the different phases comprising the composite are of particular interest to understand. In structural composites the interface is often the weakest part, where fracture will nucleate, and in electronic composites structural defects at or near the interface will affect the critical electronic properties.

Searching for the causes why some of the paintings by Mihaly Munkacsy are darkening

1990 ◽  
Vol 48 (2) ◽  
pp. 204-205
Author(s):  
Imre Pozsgai ◽  
Klara Erdöhalmi-Torok
Keyword(s):  
Electron Beam ◽  
Cross Section ◽  
Polyester Resin ◽  
National Gallery ◽  
X Ray ◽  
Art Historians ◽  
Made In ◽  
Grinding And Polishing

The paintings by the great Hungarian master Mihaly Munkacsy (1844-1900) made in an 8-9 years period of his activity are deteriorating. The most conspicuous sign of the deterioration is an intensive darkening. We have made an attempt by electron beam microanalysis to clarify the causes of the darkening. The importance of a study like this is increased by the fact that a similar darkening can be observed on the paintings by Munkacsy’s contemporaries e.g Courbet and Makart. A thick brown mass the so called bitumen used by Munkacsy for grounding and also as a paint is believed by the art historians to cause the darkening.For this study, paint specimens were taken from the following paintings: “Studio”, “Farewell” and the “Portrait of the Master’s Wife”, all of them are the property of the Hungarian National Gallery. The paint samples were embedded in a polyester resin “Poly-Pol PS-230” and after grinding and polishing their cross section was used for x-ray mapping.

High-angle electron scattering from amorphous silicon

1995 ◽  
Vol 53 ◽  
pp. 162-163
Author(s):  
M. Libera ◽  
J.A. Ott ◽  
K. Siangchaew ◽  
L. Tsung
Keyword(s):  
Electron Scattering ◽  
Amorphous Material ◽  
Structural Defects ◽  
Constant Thickness ◽  
High Angle ◽  
Fast Electrons ◽  
Angle Scattering ◽  
Stem Image ◽  
Amorphous Si ◽  
Thermal Vibrations

Channeling occurs when fast electrons follow atomic strings in a crystal where there is a minimum in the potential energy (1). Channeling has a strong effect on high-angle scattering. Deviations in atomic position along a channel due to structural defects or thermal vibrations increase the probability of scattering (2-5). Since there are no extended channels in an amorphous material the question arises: for a given material with constant thickness, will the high-angle scattering be higher from a crystal or a glass?Figure la shows a HAADF STEM image collected using a Philips CM20 FEG TEM/STEM with inner and outer collection angles of 35mrad and lOOmrad. The specimen (6) was a cross section of singlecrystal Si containing: amorphous Si (region A), defective Si containing many stacking faults (B), two coherent Ge layers (CI; C2), and a contamination layer (D). CBED patterns (fig. lb), PEELS spectra, and HAADF signals (fig. lc) were collected at 106K and 300K along the indicated line.

Sign in / Sign up

Export Citation Format

Share Document