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The Diagonal Grid as a Design Method in the Armenian Medieval Architecture

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The Diagonal Grid as a Design Method in the Armenian Medieva...

New Applications of the Noise Spectroscopy for Hydrogen Sensors

作者： hrant Hovsepyan Researcher at the Institute of Arts of the National Academy of Sciences of the Republic of Armenia

Armenian architecture has been a subject of serious studies since the beginning of last century. Numerous medieval constructions have been measured, researched and reconstructed. However, there is a major disagreement among the specialists on the existence of a design stage, preceding the actual phase of construction. The absence of actual data and survived projects, as well as the limited historical information on this issue, are the reasons of this disagreement. That is why the historical evidence on the activity of Trdat the architect, provided by the 10 th century chronicler Asoghik, is of critical importance. In this historical record the chronicler testifies that Trdat had a preliminary idea on the reconstruction of ruined St. Sofia dome. The information provided on Trdat's method is of particular interest, as the latter set an example and prepared a model of the future construction. The Cathedral of Ani was erected by the same architect Trdat in 989. The study of the cathedral's measured materials may shed a light on the issue of existence of preliminary developed drafts with volumetric and spatial solutions of future structures. Here the diagonals drawn by the midpoints of the dome columns are not only the principal lines of the planning, but also a part of a uniform diagonal grid, which underlies the whole plan. The facades fit into a square and all key feature marks are located in horizontal lines, which are set on the peaks of diagonal grid. The slopes of pediment are obtained by connecting the vertices of a smaller grid to each other. The same construction principles were identified as a result of measurement research about Marmashen Cathedral(which was built in the beginning of the 11 th century and is attributed to Trdat) and Noravank(this church is considered to be a masterpiece by the architect Momik of the 14 th century). The studies have helped to come to the conclusion that the diagonal grid as a design method has been continuously used by Armenia

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Journal of Modern Physics 2014年第16期5卷 1662-1669页

作者： Ferdinand Gasparyan hrant Khondkaryan Mikayel Aleksanyan Department of Physics of Semiconductors and Microelectronics Yerevan State University Yerevan Armenia

Peculiarities of the low-frequency noise spectroscopy of hydrogen gas sensors made on MgFeO4 n-type porous semiconductor covered by the palladium catalytic nanosize particles are investigated. Behavior of the low-frequency noise spectral density and its exponent value from sensitive layer thickness in the frequency range 2 - 300 Hz are analyzed. Sensitivity of the sensor calculated by the noise method is several tenth times higher as compared with the resistive method. It is shown that besides of the well-known applications, noise spectroscopy can be also used for definition of the unknown thickness of gas sensitive layer, for definition of the sensitive layer subsurface role in the formation of the low-frequency noises and for definition of the intensity of trapping-detrapping processes of the gas molecules.

关键词： Low-Frequency Noise Hydrogen Sensor Porous Semiconductor

Scattering and Transformation of Waves on Heavy Particles in Magnetized Plasma

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Journal of Modern Physics 2011年第3期2卷 162-173页

作者： Hrachya B. Nersisyan hrant H. Matevosyan 不详

The scattering and transformation of the waves propagating in magnetized plasma on a heavy stationary charged particle located at a plane plasma-vacuum boundary is considered. The scattering (transformation) occurs due to the nonlinear coupling of the incident wave with the polarization (shielding) cloud surrounding the particle. It is shown that the problem is reduced to the determination of the nonlinear (three index) dielectric tensor of magnetized plasma. The angular distribution and the cross section for scattering (transformation) of high-frequency ordinary and extraordinary waves and low-frequency upper-hybrid, low-hybrid, and magnetosonic waves are investigated within a cold plasma (hydrodynamic) model.

关键词： Scattering Transformation Plasma Modes Magnetized Plasmas

Long-Time Relaxation and Residual Conductivity in GaP Irradiated by High-Energy Electrons

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Journal of Modern Physics 2014年第1期5卷 51-54页

作者： hrant yerits.an Norik Grigoryan Vachagan Harutyunyan Eleonora Hakhverdyan Valeriy Baghdasaryan A. Alikhanian National Science Laboratory Yerevan Physics Institute Yerevan Armenia

This paper presents the results of a study of long-time relaxation (LR) and residual conductivity in n-type gallium phosphide (GaP) crystals irradiated by 50 MeV electrons. A manifold increase in photosensitivity and quenching of residual conductivity was found as a result of irradiation. It is shown that LR in GaP is due to disordered regions (generated by electron irradiation) which have conductivity close to self one. The Fermi level in the disordered regions is determined by which is located deep in the forbidden band (Ее - 1.0 eV). LR effect is mainly explained by a spatial separation of electrons and holes, recombination of which is prevented by potential barriers. The observed increase in conductivity is associated with the increase in the concentration of minority carriers as well as with increase of the Hall mobility at the sample illumination.

关键词： Long-Time Relaxation (LR) Residual Conductivity (RC) Photoconductivity Irradiation Gallium Phosphide

The Influence of Different Type Irradiations on the Surface States Parameters of Si-SiO<sub>2</sub>Structures

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Journal of Modern Physics 2015年第11期6卷 1657-1662页

作者： Aram A. Sahakyan hrant N. yerits.an Vachagan V. Harutunyan Hamlet S. Karayan Vahan A. Sahakyan A. I. Alikhanyan National Science Laboratory Yerevan Physics Institute Yerevan Armenia Yerevan State University Yerevan Armenia National Institute of Metrology Yerevan Armenia

The results of experimental research of some effects in metal-insulator-semiconductor (MIS) structures induced by different types of radiation (50 MeV electrons, 12 keV gamma-quanta, 10 and 40 keV arsenic ions) are presented. It is found that there is a significant difference between the characters of radiation surface states (SS) formed by ionization and impact actions of the MIS structure irradiation at the insulator-semiconductor (I-S) interface. It is shown that the SS generation rate is increased in electric fields and depends on the MIS structure field electrode material.

关键词： Metal-Insulator-Semiconductor (MIS) Structures Radiation Effects Surface States (SS) Density Insulator-Semiconductor (I-S) Interface Annealing

Scattering of Conduction Electrons on the Static Deformation Raised by Irradiation in n-GaP Crystals

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Journal of Modern Physics 2015年第13期6卷 1935-1941页

作者： Norik Е. Grigoryan hrant N. yerits.an Vachagan V. Harutyunyan Narek A. Hakobyan Eduard A. Aleksanyan Vahan A. Sahakyan A. Alikhanian National Science Laboratory Yerevan Physics Institute Yerevan Armenia National Institute of Metrology Yerevan Armenia

Study of spectral dependences of absorption coefficient at the region of absorption by free carriers shows that the introduction of radiation defects in n-GaP crystals leads to the appearance of additional scattering besides of traditional ones. A new scattering mechanism on “frozen” phonons (deformation localized near the radiation defects) is suggested and its behavior in experimental and theoretical aspects taking into account Х1с-Х3с transitions at the scattering process has been studied. It was shown that the increase of “frozen” phonons’ concentration results to the growth of this mechanism contribution in the whole scattering and the absorption coefficient by free carriers is described approximately by low α ~ ω-r, where -1/2 ≤ r ≤ 7/2. Suggested scattering mechanism allows explaining qualitatively the decrease of r. It was established that the dis- ordered by irradiation region effectively decreases the concentration of free carriers, but being a region of increased resistivity, it influences the scattering slightly even at the actual quantum region .

关键词： Free Carriers Absorption Irradiation Scattering Mechanism Deformation Potential Phonon Gallium Phosphide

Clusters of Radiation Defects in Silicon Crystals

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Journal of Modern Physics 2015年第9期6卷 1270-1276页

作者： hrant N. yerits.an Aram A. Sahakyan Norair E. Grigoryan Vachagan V. Harutunyan Vahan A. Sahakyan Armenuhi A. Khachatryan A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Yerevan Armenia National Institute of Metrology Yerevan Armenia

While considerable progress has been achieved in radiation influence on the solid states, the quantitative assessment of defect production is very scarce. In this paper radiation defects studies in silicon crystals are briefly reviewed and comprehensively analyzed depending on irradiation energy and dose, paying special attention to electron irradiation in wide energy spectrum when crystal lattice disordered regions (clusters) occur. Electron irradiation, which is a simple way to introduce intrinsic defects, was used as one of the most powerful techniques to study point and cluster defects which affect properties of semiconductors depending on irradiation energy. Fundamental aspects of radiation induced defects are discussed and it is shown that they bring information on the threshold energy for atomic displacement, on the recombination of vacancy—interstitial pair and mainly, on radiation defects cluster formation which essentially influences on the irradiating material properties. The determination of the irradiation critical dose and energy for the formation of homogeneous disordered regions (clusters) are detailed.

关键词： Clusters of Radiation Defects Point Radiation Defects Irradiation Dose Irradiation Energy Semiconductors Silicon

<i>In-Situ</i>Study of Non-Equilibrium Charge Carriers’ Behavior under Ultra-Short Pulsed Electrons Irradiation in Silicon Crystal

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Journal of Modern Physics 2019年第9期10卷 1125-1133页

作者： hrant N. yerits.an Aram A. Sahakyan Norair E. Grigoryan Vachagan V. Harutyunyan Vika V. Arzumanyan Vasili M. Tsakanov Bagrat A. Grigoryan Gayane A. Amatuni A. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Department of Applied Physics Yerevan Armenia CANDLE Synchrotron Research Institute Yerevan Armenia

The recombination processes for charge carriers have been studied in n-type silicon crystals which were irradiated by pico-second duration pulse electrons with energy of 3.5 MeV (ultrafast irradiation), and maximum dose of 3.3 × 1013 el/cm2. In-situ measurements were carried out under artificial conditions simulating natural environment (space, semiconductor detectors, etc.). The observed phenomena were investigated experimentally in-situ using a high-speed oscilloscope equipped with a special preamplifier. Following irradiation to particular doses, some peculiarities of the recovery time of the semiconductor equilibrium condition (“characteristic time”), were obtained. Thus, it was found that the value of the “characteristic time” differs by an order of magnitude from the lifetime of the non-equilibrium (minority) charge carrier measured in an ex-situ regime. However, their behavior, as a function of irradiation dose, is similar and decreases with dose increase. Investigations of the dependencies of electro-physical parameters on irradiation dose, using Hall effect measurements, showed that at particular doses the radiation defects thus created, have an insignificant influence on the concentration of the charge carriers, but change their scattering properties appreciably, which affects the time parameters for the recombination of the semiconductor charge carriers. This investigation uses a novel approach to solid-state radiation physics, where in situ measurements were conducted in addition to conventional pre- and post-irradiation.

关键词： Silicon Crystal Irradiation Recombination Non-Equilibrium State Carrier Lifetime

Quasi-Chemical Reactions in Irradiated Silicon Crystals with Regard to Ultrafast Irradiation

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Journal of Modern Physics 2018年第6期9卷 1271-1280页

作者： hrant N. yerits.an Aram A. Sahakyan Norair E. Grigoryan Vachagan V. Harutyunyan Bagrat A. Grigoryan Gayane A. Amatuni Arsham S. Yeremyan Christopher J. Rhodes Department of Applied Physics Yerevan Physics Institute Yerevan Armenia CANDLE Synchrotron Research Institute Yerevan Armenia Fresh-Lands Environmental Actions Caversham UK

This paper reports results from an investigation of the interaction of displaced Si-self atoms (I) and their vacancies (V), with impurities in crystalline silicon (Si), as induced by micro-second pulse duration irradiation with electrons at different energies: 3.5, 14, 25 and 50 MeV and pico-second pulse duration with energy 3.5 MeV. V-V, I-impurity atom and V-impurity atom interactions are analyzed both experimentally and as modeled using computer simulations. A process of divacancy (V2) accumulation in the dose-dependent linear region is investigated. The effect of impurities on recombination of correlated divacancies, and I-atoms that had become displaced from regular lattice points is estimated by computer modeling of an appropriate diffusion-controlled process. It is concluded that the experimental results can be interpreted quantitatively in terms of a strongly anisotropic quasi-one-dimensional diffusion of displaced I-atoms. In addition, a significant difference is found between the effects of pico-second duration electron beam irradiation, which causes the formation of A-centre (V + Oxygen) clusters, while when the beam is applied on a micro-second timescale, divacancies are created instead, although the electrons have the same energy in both cases.

关键词： Silicon Crystal Electron Irradiation Divacancy Radiation Defects Introduction Rate Impurity Atom